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Journal articles on the topic 'Flow visualisation experiments'
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1
Scobie, James A., Carl M. Sangan, and Gary D. Lock. "Flow Visualisation Experiments on Sports Balls." Procedia Engineering 72 (2014): 738–43. http://dx.doi.org/10.1016/j.proeng.2014.06.125.
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Coat, C. A., and G. D. Lock. "Flow visualisation experiments for turbine film cooling." Aeronautical Journal 108, no. 1086 (August 2004): 403–9. http://dx.doi.org/10.1017/s000192400000021x.
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Abstract Flow visualisation experiments related to turbine film cooling have been conducted. These investigated the fluid mechanics of coolant ejection using a large-scale, flat-plate model at engine-representative Reynolds numbers in a low-speed tunnel with ambient-temperature mainstream flow. The coolant trajectories were captured using a fine nylon mesh covered with thermochromic liquid crystals, allowing measurement of gas temperature contours in planes perpendicular to the flow. Three injection geometries were assessed: cylindrical holes with stream-wise injection, cylindrical holes with cross-stream injection, and fan-shaped holes. The data demonstrated that the cylindrical holes produced discrete jets, which lifted off the surface at high coolant-to-mainstream momentum flux ratios; these jets were characterised by the kidney-shaped stream-tubes expected for injection into cross-flow. The jets injected with cross-stream momentum exhibited a more obvious kidney-shaped cross-section, which rotated with distance downstream of injection. The jets from the fan-shaped holes were attached to the surface even at high momentum flux ratios, were more diffuse, and exhibited two cores of high temperature. The trajectory visualisation data were used to interpret the adiabatic cooling effectiveness measured at the surface.
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Davard, F., and D. Dupuis. "Flow visualisation experiments in a blade coating process." Journal of Non-Newtonian Fluid Mechanics 93, no. 1 (September 2000): 17–28. http://dx.doi.org/10.1016/s0377-0257(00)00101-4.
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Scaperdas, A., A. G. Robins, and R. N. Colville. "Flow visualisation and tracer dispersion experiments at street canyon intersections." International Journal of Environment and Pollution 14, no. 1/2/3/4/5/6 (2000): 526. http://dx.doi.org/10.1504/ijep.2000.000576.
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Horwatitsch, Dieter, Jonas Müller, Helmut Kilian, Martin Brandecker, and Arne Wahlen. "Validation of Simulated Material Flow in Aluminium Hot Extrusion with a Novel Visualisation Method." Materials Science Forum 794-796 (June 2014): 15–20. http://dx.doi.org/10.4028/www.scientific.net/msf.794-796.15.
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Commonly used visualisation methods for observing material flow during extrusion are either labor intensive, prone to loss of the tracer pattern or subject to different flow behaviour than occurs in practice. A novel visualisation method using a copper mesh inlay and computer tomography was developed and used to visualise the flow behaviour of partially extruded EN AW-6082 aluminum billets. In parallel with the physical experiments, a finite element (FE) model was developed and compared with the experiments. The material flow was readily observable from the computer tomography images and the FE model data closely matched the experimental results.
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Nathan, N. D., and R. B. Green. "Flow visualisation of the helicopter brown-out phenomenon." Aeronautical Journal 113, no. 1145 (July 2009): 467–78. http://dx.doi.org/10.1017/s0001924000003134.
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Abstract Quantitative and qualitative results of a series of experiments conducted on a rotor in ground effect at low forward speeds are presented. The velocity over a wide area of the ground effect wake was measured using particle image velocimetry, and the evolution of the flow is described as the forward speed increases. The formation of a dust cloud leading to so-called helicopter brown-out was simulated through a series of flow visualisation experiments. The technique involved sprinkling a fine dust on the ground below and ahead of the rotor. Larger dust clouds were observed at lower forward speed, and the dust cloud penetrated into the areas of the flow including those where vorticity levels were of low magnitude and occasional velocity fluctuations from the mean were large.
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Rónaföldi, Arnold, Jenő Kovács, and András Roósz. "Visualisation of the Melt Flow under Rotating Magnetic Field." Materials Science Forum 537-538 (February 2007): 591–98. http://dx.doi.org/10.4028/www.scientific.net/msf.537-538.591.
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Experiments were performed for visual observation and investigation of liquid Gallium flow at a temperature of 40oC in a rotating magnetic field. Two different measuring methods were developed to determine the revolution number of rotating melt. In both cases the frequency of magnetic induction was 50, 100 and 150 Hz and the values of magnetic induction could be changed between 0 and 70 mT. The magnetic Taylor number changed between 0 and 3.54x107 during the experiments.
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Karásek, Matěj, Mustafa Percin, Torbjørn Cunis, Bas W. van Oudheusden, Christophe De Wagter, Bart DW Remes, and Guido CHE de Croon. "Accurate position control of a flapping-wing robot enabling free-flight flow visualisation in a wind tunnel." International Journal of Micro Air Vehicles 11 (January 2019): 175682931983368. http://dx.doi.org/10.1177/1756829319833683.
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Flow visualisations are essential to better understand the unsteady aerodynamics of flapping wing flight. The issues inherent to animal experiments, such as poor controllability and unnatural flapping when tethered, can be avoided by using robotic flyers that promise for a more systematic and repeatable methodology. Here, we present a new flapping-wing micro air vehicle (FWMAV)-specific control approach that, by employing an external motion tracking system, achieved autonomous wind tunnel flight with a maximum root-mean-square position error of 28 mm at low speeds (0.8–1.2 m/s) and 75 mm at high speeds (2–2.4 m/s). This allowed the first free-flight flow visualisation experiments to be conducted with an FWMAV. Time-resolved stereoscopic particle image velocimetry was used to reconstruct the three-dimensional flow patterns of the FWMAV wake. A good qualitative match was found in comparison to a tethered configuration at similar conditions, suggesting that the obtained free-flight measurements are reliable and meaningful.
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Stewart, Robert Logan, Ilija Denis Šutalo, and Petar Liovic. "Perceptive communicating capsules for fluid flow measurement and visualisation." Robotica 35, no. 1 (February 18, 2015): 143–65. http://dx.doi.org/10.1017/s0263574715000041.
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SUMMARYA new approach to flow measurement and visualisation in fluid dynamics based on a group of perceptive communicating capsules has been developed. Experiments were carried out with fluid-mobilised and stationary capsules deployed in a fluid flow test rig (raceway pond). Each capsule contains a microcontroller, battery, infra-red and visible LEDs and other electronics. Using optical communications, capsules can record encounters with one another. From the resulting interaction patterns, fluid flow speed and path-frequency measurements were obtained. Additionally, the capsules have shown the capacity for distributed sensing, and their streaklines provide a valuable means of external visualisation.
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ROY, CLÉMENT, THOMAS LEWEKE, MARK C. THOMPSON, and KERRY HOURIGAN. "Experiments on the elliptic instability in vortex pairs with axial core flow." Journal of Fluid Mechanics 677 (April 11, 2011): 383–416. http://dx.doi.org/10.1017/jfm.2011.91.
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Results are presented from an experimental study on the dynamics of pairs of vortices, in which the axial velocity within each core differs from that of the surrounding fluid. Co- and counter-rotating vortex pairs at moderate Reynolds numbers were generated in a water channel from the tips of two rectangular wings. Measurement of the three-dimensional velocity field was accomplished using stereoscopic particle image velocimetry, revealing significant axial velocity deficits in the cores. For counter-rotating pairs, the long-wavelength Crow instability, involving symmetric wavy displacements of the vortices, could be clearly observed using dye visualisation. Measurements of both the axial wavelength and the growth rate of the unstable perturbation field were found to be in good agreement with theoretical predictions based on the full experimentally measured velocity profile of the vortices, including the axial flow. The dye visualisations further revealed the existence of a short-wavelength core instability. Proper orthogonal decomposition of the time series of images from high-speed video recordings allowed a precise characterisation of the instability mode, which involves an interaction of waves with azimuthal wavenumbers m = 2 and m = 0. This combination of waves fulfils the resonance condition for the elliptic instability mechanism acting in strained vortical flows. A numerical three-dimensional stability analysis of the experimental vortex pair revealed the same unstable mode, and a comparison of the wavelength and growth rate with the values obtained experimentally from dye visualisations shows good agreement. Pairs of co-rotating vortices evolve in the form of a double helix in the water channel. For flow configurations that do not lead to merging of the two vortices over the length of the test section, the same type of short-wave perturbations were observed. As for the counter-rotating case, quantitative measurements of the wavelength and growth rate, and comparison with previous theoretical predictions, again identify the instability as due to the elliptic mechanism. Importantly, the spatial character of the short-wave instability for vortex pairs with axial flow is different from that previously found in pairs without axial flow, which exhibit an azimuthal variation with wavenumber m = 1.
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Melnikov, V. I., V. N. Khokhlov, V. V. Ivanov, V. V. Kontelev, V. R. Zoi, and A. A. Zavinov. "First experiments on visualisation of two-phase high pressure and temperature flows using an ultrasonic mesh sensor." Kerntechnik 68, no. 3 (June 1, 2003): 102–5. http://dx.doi.org/10.1515/kern-2003-0049.
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Abstract A novel device for fast visualisation of gas-liquid two-phase flows was developed and tested during loss-off-coolant accident simulations at the thermal hydraulic test facility PSBVVER, a 1 : 300 integral model of the VVER-1000. The device is an ultrasonic mesh sensor. It consists of a metallic frame where transmitter and receiver wave-guides are fixed, that form two grids inside the measurement cross section. Ultrasonic pulses are transmitted into the fluid by the 8 wave-guides of the first plane. A second plane of another 8 wave-guides, that cross the ones of the first plane under an angle of 90 deg, serves as receives. The measurement is based on the acoustic conductivity of the two-phase mixture at the locations where the wave-guides cross. The sampling frequency is 250 frames per second. This allows both void fraction measurements and a fast flow visualisation. The sensor is applicable to high pressures and temperatures. All parts and surfaces that are in contact with the fluid are manufactured from stainless steel. During the tests at PSB-VVER the flow pattern in the hot leg of the primary circuit model was visualised for the first time.
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Das, R., and J. Kurian. "Supersonic flow over three dimensional cavities." Aeronautical Journal 117, no. 1188 (February 2013): 175–92. http://dx.doi.org/10.1017/s0001924000007934.
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AbstractThis work presents a study of acoustic oscillations generated and the wave structure associated with supersonic flow past wall mounted 3D open cavities of varying length-to-width (L/W) ratio. Experiments were conducted to investigate the acoustic signature generated by the cavities at freestream Mach number of 1·7. The effect ofL/Wratio of the cavity on the dominant modes of the acoustic signature registered on different walls of the cavities is investigated for anL/Wrange of 0·83-4. Shift in the dominant acoustic mode is observed asL/Wratio changes from 3 to 4. Statistical analysis of pressure data showed existence of acoustic waves and spreading of acoustic energy over different modes with change in cavity width. Time averaged schlieren visualisation indicated variation of shock and shear layer structure in the mainstream for the different cavities. Acoustic waves generated by the presence of the cavity and the dynamic behaviour of the shear layer were observed during instantaneous shadowgraph visualisation. Numerical simulation was done to make a prior assessment of the flow structure and the results are in good agreement with those from experiments. Ratio of mass exchange between cavity and mainflow and the cavity volume was observed to have profound effect on the magnitude of pressure oscillations generated by the cavities.
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von Larcher, Th, and C. Egbers. "Experiments on transitions of baroclinic waves in a differentially heated rotating annulus." Nonlinear Processes in Geophysics 12, no. 6 (December 20, 2005): 1033–41. http://dx.doi.org/10.5194/npg-12-1033-2005.
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Abstract. Experiments of baroclinic waves in a rotating, baroclinic annulus of fluid are presented for two gap widths. The apparatus is a differentially heated cylindrical gap, rotated around its vertical axis of symmetry, cooled from within, with a free surface, and filled with de-ionised water as working fluid. The surface flow was observed with visualisation technique while thermographic measurements gave a detailed understanding of the temperature distribution and its time-dependent behaviour. We focus in particular on transitions between different flow regimes. Using a wide gap, the first transition from axisymmetric flow to the regular wave regime was characterised by complex flows. The transition to irregular flows was smooth, where a coexistence of the large-scale jet-stream and small-scale vortices was observed. Furthermore, temperature measurements showed a repetitive separation of cold vortices from the inner wall. Experiments using a narrow gap showed no complex flows but strong hysteresis in the steady wave regime, with up to five different azimuthal wave modes as potential steady and stable solutions.
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Said, M., M. Imai, S. Mat, M. N. Dahalan, S. Mansor, M. N. Mohd Nasir, and N. A. R. Nik Mohd. "Tuft Flow Visualisation on UTM-LST VFE-2 Delta Wing Model Configuration at High Angle of Attacks." International Journal of Automotive and Mechanical Engineering 17, no. 3 (October 7, 2020): 8214–23. http://dx.doi.org/10.15282/ijame.17.3.2020.15.0619.
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This paper reports on flow visualisation and surface pressure measurements over the upper surface of a blunt-edged delta wing model at high angles of attack. The flow structure above the upper surface of the blunt-edged delta wing was found to be different compared to delta wing with sharp leading edge. The flow becomes more complicated especially in the leading edge region of the wing. Currently, there is no data available to verify if the primary vortex could reach the apex of the wing when the angle of attack is further increased. Most prior experiments were performed at the angles of attack, α, below 23° with only a few experiments that had gone to α = 27°. These prior experiments and some CFD works stipulated that the attached flow continue to exist in the apex region of the delta wing even at very high angles of attack above 23°. In order to verify this hypothesis, several experiments at high angles of attack were conducted in Universiti Teknologi Malaysia Low Speed wind Tunnel (UTM–LST), using a specially constructed VFE2 wing model equipped with blunt leading edges. This series of experiments employed two measurement techniques; the first was the long tuft flow visualisation method, followed by surface pressure measurements. The experiments were performed at Reynolds numbers of 1.0×106 and 1.5×106. During these experiments, several interesting flow characteristics were observed at high angles of attack, mainly that the flow became more sensitive to changes in Reynolds number and the angles of attack of the wing. When the Reynolds number increased from 1×106 to 1.5×106, the upstream progression of the initial point of the main vortex was relatively delayed compared to the sharp-edged delta wing. The experiments also showed that the flow continued to be attached in the apex region up to α = 27º.
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Mohammed-Taifour, A., Q. Schwaab, J. Pioton, and J. Weiss. "A new wind tunnel for the study of pressure-induced separating and reattaching flows." Aeronautical Journal 119, no. 1211 (January 2015): 91–108. http://dx.doi.org/10.1017/s0001924000010265.
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AbstractThe design, construction, and validation of a new academic wind tunnel is described in detail. The wind tunnel is of a classical, blow-down type and generates a pressure-induced, turbulent separation bubble on a flat test surface by a combination of adverse and favorable pressure gradients. The Reynolds number, based on momentum thickness just upstream of separation, is Reθ≃ 5,000 at a free-stream velocity ofUref= 25ms−1. The length of the separation bubble is estimated at 0°42 ± 0°02m by three different methods. Results of a numerical simulation demonstrate the absence of flow separation in the wind-tunnel contraction. This results in a turbulence level of about 0·05% in the test section. Oil-film visualisation experiments show that the flow near the wall is strongly three-dimensional in the recirculating region and that the topology of the limiting streamlines is consistent with experiments performed on configurations with fixed separation. Finally, spatial variations of the forward-flow fraction have been documented using a thermal-tuft probe and are shown to compare well with the results of the oil-film visualisation.
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Hu, Yu, Ling Li, Haolai Tian, Zhibing Liu, Qiulan Huang, Yi Zhang, Hao Hu, and Fazhi Qi. "Daisy: Data analysis integrated software system for X-ray experiments." EPJ Web of Conferences 251 (2021): 04020. http://dx.doi.org/10.1051/epjconf/202125104020.
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Daisy (Data Analysis Integrated Software System) has been designed for the analysis and visualisation of X-ray experiments. To address the requirements of the Chinese radiation facilities community, spanning an extensive range from purely algorithmic problems to scientific computing infrastructure, Daisy sets up a cloud-native platform to support on-site data analysis services with fast feedback and interaction. Furthermore, the plug-in based application is convenient to process the expected high throughput data flow in parallel at next-generation facilities such as the High Energy Photon Source (HEPS). The objectives, functionality and architecture of Daisy are described in this article.
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Jelínková, V., M. Císlerová, A. Pohlmeier, and D. Van dusschoten. "Tracer experiments within composite soil column investigated by MRI." Soil and Water Research 5, No. 2 (May 24, 2010): 39–48. http://dx.doi.org/10.17221/4/2009-swr.
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The magnetic resonance imaging (MRI) technique was used for the visualisation and interpretation of flow paths. A set of tracer-infiltration experiments was performed on soil columns filled with packed homogeneous sand and with a composite sand-soil system. The flow paths were visualised using a tracer-solution containing Ni(NO<sub>3</sub>)<sub>2</sub> which is characterised by relaxation times different from that of the infiltrating water. The tracer pulse was added under hydraulic steady state conditions. Small disturbances in the tracer front were observed during the breakthrough in the case of a homogeneous sample. More pronounced effects were seen with the composite sample. The vertical components of the velocity fields were evaluated for the experiments presented. The irregularities in the tracer front and in the velocity fields were in this case attributed to the preferential flow phenomena in combination with air bubble entrapment. Beside that, two consecutive tracer pulses were performed with the aim of testing the potential influence of the different solute concentrations on the adsorption power. Both concentrations had negligible impacts on the acquired image. The presented results are constrained by the limits of the described technology; further investigations are being carried out using more advanced equipment. I
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Prakash, R., L. M. Le Page, L. P. McQuellin, S. L. Gai, and S. O’Byrne. "Direct simulation Monte Carlo computations and experiments on leading-edge separation in rarefied hypersonic flow." Journal of Fluid Mechanics 879 (October 2, 2019): 633–81. http://dx.doi.org/10.1017/jfm.2019.692.
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A comprehensive study of the fundamental characteristics of leading-edge separation in rarefied hypersonic flows is undertaken and its salient features are elucidated. Separation of a boundary layer undergoing strong expansion is typical in many practical hypersonic applications such as base flows of re-entry vehicles and flows over deflected control surfaces. Boundary layer growth under such conditions is influenced by effects of rarefaction and thermal non-equilibrium, thereby differing significantly from the conventional no-slip Blasius type. A leading-edge separation configuration presents a fundamental case for studying the characteristics of such a flow separation but with minimal influence from a pre-existing boundary layer. In this work, direct simulation Monte Carlo computations have been performed to investigate flow separation and reattachment in a low-density hypersonic flow over such a configuration. Distinct features of leading-edge flow, limited boundary layer growth, separation, shear layer, flow structure in the recirculation region and reattachment are all explained in detail. The fully numerical shear layer profile after separation is compared against a semi-theoretical profile, which is obtained using the numerical separation profile as the initial condition on existing theoretical concepts of shear layer analysis based on continuum flow separation. Experimental studies have been carried out to determine the surface heat flux using thin-film gauges and computations showed good agreement with the experimental data. Flow visualisation experiments using the non-intrusive planar laser-induced fluorescence technique have been performed to image the fluorescence of nitric oxide, from which velocity and rotational temperature distributions of the separated flow region are determined.
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Ng, Y. T. "Characterising low-speed, transitional cavity flow." Aeronautical Journal 116, no. 1185 (November 2012): 1185–99. http://dx.doi.org/10.1017/s0001924000007557.
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In various studies involving subsonic transition cavity flows, terms like ‘transitional-open’ and ‘transitional-closed’ cavity flow regimes are used in the literature. However, the exact fluid dynamic criteria to distinguish them have not been firmly established. The present work attempts to clarify this. Experiments to measure static pressure and fluctuating pressure distribution in a rectangular cavity with length-to-depth (L/D) ratio of 3 to 20 were performed. Based on pressure measurements on the front, bottom and rear faces of the cavity, additional criteria are established to clearly distinguish the range of criticalL/D(or (L/D)cri) where these different transitional cavity flow regimes occur. The present work ascertains that the (L/D)crifor open and transitional-open cavity flow is 6·0-6·5, for transitional-open and transitional-closed cavity flow is 9-10 and for transitional-closed and closed cavity flow is 14-15. Flow visualisation qualitatively supports the flow pattern in the different cavity flow regimes.
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Gorham, N., T. Becker, Denis W. Shiers, and Helen R. Watling. "Visualisation of Bacterial Behaviour Using Tapping-Mode Atomic Force Microscopy." Advanced Materials Research 71-73 (May 2009): 341–44. http://dx.doi.org/10.4028/www.scientific.net/amr.71-73.341.
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Ex-situ and in-situ Tapping Mode AFM were used to investigate responses of attached bacteria to stressful conditions. For ex-situ measurements, the AFM was equipped with a customised re-positioning stage and sample mount to permit re-examination of the same surface area. For in-situ measurements, the inoculated pyrite coupon was immersed in solution in a flow through cell. Initial experiments using Sulfobacillus thermosulfidooxidans indicated that increased acidity promoted EPS production but increased salinity resulted in cell detachment.
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Ramamurthi, K., and T. J. Tharakan. "Flow visualisation experiments on free draining of a rotating column of liquid using nets and tufts." Experiments in Fluids 21, no. 2 (June 1996): 139–42. http://dx.doi.org/10.1007/bf00193917.
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Saridou, Betty, Joseph Ryan Rose, Stavros Shiaeles, and Basil Papadopoulos. "SAGMAD—A Signature Agnostic Malware Detection System Based on Binary Visualisation and Fuzzy Sets." Electronics 11, no. 7 (March 26, 2022): 1044. http://dx.doi.org/10.3390/electronics11071044.
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Image conversion of byte-level data, or binary visualisation, is a relevant approach to security applications interested in malicious activity detection. However, in practice, binary visualisation has always been seen to have great limitations when dealing with large volumes of data, and would be a reluctant candidate as the core building block of an intrusion detection system (IDS). This is due to the requirements of computational time when processing the flow of byte data into image format. Machine intelligence solutions based on colour tone variations that are intended for pattern recognition would overtax the process. In this paper, we aim to solve this issue by proposing a fast binary visualisation method that uses Fuzzy Set theory and the H-indexing space filling curve. Our model can assign different colour tones on a byte, allowing it to be influenced by neighbouring byte values while preserving optimal locality indexing. With this work, we wish to establish the first steps in pursuit of a signature-free IDS. For our experiment, we used 5000 malicious and benign files of different sizes. Our methodology was tested on various platforms, including GRNET’s High-Performance Computing services. Further improvements in computation time allowed larger files to convert in roughly 0.5 s on a desktop environment. Its performance was also compared with existing machine learning-based detection applications that used traditional binary visualisation. Despite lack of optimal tuning, SAGMAD was able to achieve 91.94% accuracy, 90.63% precision, 92.7% recall, and an F-score of 91.61% on average when tested within previous binary visualisation applications and following their parameterisation scheme. The results exceeded malware file-based experiments and were similar to network intrusion applications. Overall, the results demonstrated here prove our method to be a promising mechanism for a fast AI-based signature-agnostic IDS.
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Vallée, Christophe, Toshifumi Nariai, Takashi Futatsugi, Akio Tomiyama, Dirk Lucas, and Michio Murase. "Experimental Characterisation of the Interfacial Structure during Counter-Current Flow Limitation in a Model of the Hot Leg of a PWR." Science and Technology of Nuclear Installations 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/298452.
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In order to investigate the two-phase flow behaviour during counter-current flow limitation in the hot leg of a pressurised water reactor, dedicated experiments were performed in a scaled down model ofKobe University. The experiments were performed with air and water at atmospheric pressure and room temperature. At high flow rates, CCFL occurs and the discharge of water to the reactor pressure vessel simulator is limited by the formation of slugs carrying liquid back to the steam generator. The structure of the interface was observed from the side of the channel test section using a high-speed video camera. An algorithm was developed to recognise the stratified interface in the camera frames after background subtraction. This method allows extracting the water level at any position in the image as well as performing further statistical treatments. The evolution of the interfacial structure along the horizontal part of the hot leg is shown by the visualisation of the probability distribution of the water level and analysed in function of the liquid and gas flow rates. The data achieved are useful for the analysis of the flow conditions as well as for the validation of modelling approaches like computational fluid dynamics.
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Sudhakar, S., A. Chandankumar, and L. Venkatakrishnan. "Influence of propeller slipstream on vortex flow field over a typical micro air vehicle." Aeronautical Journal 121, no. 1235 (November 17, 2016): 95–113. http://dx.doi.org/10.1017/aer.2016.114.
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ABSTRACTAn experimental study has been carried out to explore the effect of propeller-induced slipstream on the vortex flow field on a fixed-wing Micro Air Vehicle (MAV). Experiments were conducted at a freestream velocity of 10 m/s, corresponding to a Reynolds number based on a root chord of about 1.6 × 105. Surface flow topology on the surface of the MAV wing at propeller-off and propeller-on conditions was captured using surface oil flow visualisation at four angles of incidence. The mean off-body flow over the MAV was documented in the four spanwise planes at different chord position using Stereoscopic Particle Image Velocimetry (SPIV) technique at angle-of-attack of 24° for both conditions. The oil flow visualisation showed minimal differences in flow patterns for propeller-off and propeller-on conditions at 10° and 15° incidence. The small asymmetry between port and starboard side observed at 20° during the propeller-off condition became significantly pronounced at 24°. The fuselage stub which is necessary for housing the motor of the propeller was seen to have a significant effect on the flow symmetry at large incidences that can occur when the MAV encounters sudden vertical gusts. Switching on the propeller restored the symmetry at both incidences. SPIV measurements were carried out at the incidence of 24° which exhibited the highest asymmetry. The off-body data shows the re-establishment of symmetry during propeller-on condition owing to the increase in the magnitude of spanwise and vertical velocities as a result of the propeller slipstream. The findings emphasise the importance of considering the propeller flow and design of the motor housing while evaluating the aerodynamics of low-aspect-ratio MAVs.
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Liddle, S. C., and N. J. Wood. "Investigation into clustering of synthetic jet actuators for flow separation control applications." Aeronautical Journal 109, no. 1091 (January 2005): 35–44. http://dx.doi.org/10.1017/s0001924000000518.
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Abstract An investigation into the behaviour of clustered synthetic jet Actuators for flow-control applications is described. Experiments have been undertaken with two small-scale synthetic jet actuators in a zero-pressure gradient boundary-layer, in order to investigate the effect of configuration yaw angle and relative input signal phase. Oil-flow visualisation and hotwire anemometry techniques were used, demonstrating that changes in the downstream flow structure could be observed. Compared to a streamwise configuration, in which a symmetrical counter-rotating vortex pair was produced by the synthetic jet-boundary-layer interaction, a broader asymmetric interaction was produced in a 15° yaw configuration. Streamwise velocity contour plots, illustrating the development of the interaction downstream, over four phase angles, were presented. Significant differences in the PSD analyses of downstream streamwise velocity time histories were found, suggesting that input signal phase could influence the stability and hence effectiveness of flow structures used in flow-control applications.
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Prince, S. A., M. Vannahme, and J. L. Stollery. "Experiments on the hypersonic turbulent shock-wave/boundary-layer interaction and the effects of surface roughness." Aeronautical Journal 109, no. 1094 (April 2005): 177–84. http://dx.doi.org/10.1017/s0001924000000683.
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Abstract An experimental investigation was performed to study the effects of surface roughness on the Mach 8·2 hypersonic turbulent shockwave–boundary-layer interaction characteristics of a deflected control flap configuration. In particular, the surface pressure and heat transfer distribution along a quasi-2D ramp compression corner model was measured for flap angles between 0° and 38°, along with a Schlieren flow visualisation study. It was found that surface roughness, of scale 10% of the hinge-line boundary layer thickness, significantly increased the extent of the interaction, while increasing the magnitude of the peak pressure and heat flux just aft of reattachment. The incipient separation angle for a fully turbulent, Mach 8·2 boundary layer with a hinge line Reynolds number of 1·44 × 106, was estimated at 28-29°, reducing to between 19-22° with the introduction of laminar sub-layer scale surface roughness.
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Desikan, S. L. N., and J. Kurian. "Experimental investigation of the role of struts in high speed mixing." Aeronautical Journal 117, no. 1188 (February 2013): 193–211. http://dx.doi.org/10.1017/s0001924000007946.
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AbstractThis paper presents the experimental results of the role of struts in supersonic mixing. Experiments were carried out with novel strut configurations to show their capabilities on mixing with reasonable total pressure losses. The performances were compared with the Baseline Strut configurations (BSPI and BSNI). The analysis presented includes the mixing quantifications using Mie scattering signature, flow field visualisation, measurement of wall static pressure and the total pressure loss calculations. The results clearly demonstrated that the proposed strut configurations achieved increased mixing (7-8%) compared to BSPI with increase in total pressure loss (2%). On the other hand, when compared with BSNI, the mixing performance was found to be decreased by 6% with reduced total pressure loss (12%).
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Willoughby, Cerys, and Jeremy G. Frey. "Documentation and Visualisation of Workflows for Effective Communication, Collaboration and Publication @ Source." International Journal of Digital Curation 12, no. 1 (September 16, 2017): 72–87. http://dx.doi.org/10.2218/ijdc.v12i1.532.
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Workflows processing data from research activities and driving in silico experiments are becoming an increasingly important method for conducting scientific research. Workflows have the advantage that not only can they be automated and used to process data repeatedly, but they can also be reused – in part or whole – enabling them to be evolved for use in new experiments. A number of studies have investigated strategies for storing and sharing workflows for the benefit of reuse. These have revealed that simply storing workflows in repositories without additional context does not enable workflows to be successfully reused. These studies have investigated what additional resources are needed to facilitate users of workflows and in particular to add provenance traces and to make workflows and their resources machine-readable. These additions also include adding metadata for curation, annotations for comprehension, and including data sets to provide additional context to the workflow. Ultimately though, these mechanisms still rely on researchers having access to the software to view and run the workflows. We argue that there are situations where researchers may want to understand a workflow that goes beyond what provenance traces provide and without having to run the workflow directly; there are many situations in which it can be difficult or impossible to run the original workflow. To that end, we have investigated the creation of an interactive workflow visualization that captures the flow chart element of the workflow with additional context including annotations, descriptions, parameters, metadata and input, intermediate, and results data that can be added to the record of a workflow experiment to enhance both curation and add value to enable reuse. We have created interactive workflow visualisations for the popular workflow creation tool KNIME, which does not provide users with an in-built function to extract provenance information that can otherwise only be viewed through the tool itself. Making use of the strengths of KNIME for adding documentation and user-defined metadata we can extract and create a visualisation and curation package that encourages and enhances curation@source, facilitating effective communication, collaboration, and reuse of workflows.
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van den Berg, Coen, and Charles P. Ellington. "The three–dimensional leading–edge vortex of a ‘hovering’ model hawkmoth." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 352, no. 1351 (March 29, 1997): 329–40. http://dx.doi.org/10.1098/rstb.1997.0024.
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Recent flow visualisation experiments with the hawkmoth, Manduca sexta , revealed small but clear leading–edge vortex and a pronounced three–dimensional flow. Details of this flow pattern were studied with a scaled–up, robotic insect (‘the flapper’) that accurately mimicked the wing movements of a hovering hawkmoth. Smoke released from the leading edge of the flapper wing confirmed the existence of a small, strong and stable leading–edge vortex, increasing in size from wingbase to wingtip. Between 25 and 75 % of the wing length, its diameter increased approximately from 10 to 50 % of the wing chord. The leading–edge vortex had a strong axial flow veolocity, which stabilized it and reduced its diamater. The vortex separated from the wing at approximately 75 % of the wing length and thus fed vorticity into a large, tangled tip vortex. If the circulation of the leading–edge vortex were fully used for lift generation, it could support up to two–thirds of the hawkmoth's weight during the downstroke. The growth of this circulation with time and spanwise position clearly identify dynamic stall as the unsteady aerodynamic mechanism responsible for high lift production by hovering hawkmoths and possibly also by many other insect species.
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Furie, Bruce, Lola Bellido-Martin, Vivien Chen, Reema Jasuja, and Barbara Furie. "Imaging fibrin formation and platelet and endothelial cell activation in vivo." Thrombosis and Haemostasis 105, no. 05 (2011): 776–82. http://dx.doi.org/10.1160/th10-12-0771.
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SummaryOver the past six decades research employing in vitro assays has identified enzymes, cofactors, cell receptors and associated ligands important to the haemostatic process and its regulation. These studies have greatly advanced our understanding of the molecular and cellular bases of haemostasis and thrombosis. However, in vitro assays cannot simultaneously reproduce the interactions of all of the components of the haemostatic process that occur in vivo nor do they reflect the importance of haemodynamic factors resulting from blood flow. To overcome these limitations investigators have increasingly turned to animal models of haemostasis and thrombosis. In this article we describe some advances in the visualisation of platelet and endothelial cell activation and blood coagulation in vivo and review what we have learned from our intravital microscopy experiments using primarily the laser-induced injury model for thrombosis.
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Cohen, G. S., and F. Motallebi. "Influence of the height of the vortex generators in the control of shock-induced separation of the boundary layers." Aeronautical Journal 112, no. 1133 (July 2008): 415–20. http://dx.doi.org/10.1017/s0001924000002372.
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Abstract Experiments have been conducted to assess the effects that sub-boundary-layer vortex generators (SBVGs) have on reducing normal shock-induced turbulent boundary-layer separation. The freestream Mach number and Reynolds number were M = 1·45 and 15·9 × 106/m, respectively. Detailed measurements of a fully developed, flat plate turbulent boundary layer were used in order to assess the performance of ten different SBVG configurations. The SBVG performance was assessed by comparing total pressure profiles measured upstream of separation and downstream of reattachment. Static pressure distributions, near surface total pressure distributions, oil flow visualisation and Schlieren photographs were also used. The effect of SBVG height was investigated. The results show the largest SBVGs with height, h = 55%δ, provided the greatest static pressure recovery and maximum mixing. However, the shock pressure rise (wave drag) was highest for this case.
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Shimizu, Yukimaru, Edmond Ismaili, Yasunari Kamada, and Takao Maeda. "Power Augmentation of a HAWT by Mie-type Tip Vanes, considering Wind Tunnel Flow Visualisation, Blade-Aspect Ratios and Reynolds Number." Wind Engineering 27, no. 3 (May 2003): 183–94. http://dx.doi.org/10.1260/030952403769016663.
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Wind tunnel results are reported concerning the effects of blade aspect ratio and Reynolds number on the performance of a horizontal axis wind turbine (HAWT) with Mie-type1 tip attachments. The flow behaviour around the blade tips and the Mie-type tip vanes is presented. Detailed surface oil film visualization and velocity measurements around the blade tips, with and without Mie vanes, were obtained with the two-dimensional, Laser-Doppler Velocimetry method. Experiments were performed with rotors having blades with different aspect ratio and operating at different Reynolds numbers. The properties of the vortices generated by the Mie vanes and the blade tips were carefully studied. It was found that increased power augmentation by Mie vanes is achieved with blades having smaller aspect ratio and smaller Reynolds number.
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Calabretto, Sophie A. W., Trent W. Mattner, and James P. Denier. "The effect of seam imperfections on the unsteady flow within a fluid-filled torus." Journal of Fluid Mechanics 767 (February 12, 2015): 240–53. http://dx.doi.org/10.1017/jfm.2015.46.
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AbstractWe consider the behaviour of the flow within a fluid-filled torus when there is a sudden change in the rotation rate of the torus. Experimental work on this problem by Madden & Mullin (J. Fluid Mech., vol. 265, 1994, p. 217) demonstrated a flow with a rich and complex dynamics. In particular, planar (top-down) flow visualisation images show a well-defined laminar band at both the inner and outer bend of the toroidal pipe. Hewitt et al. (J. Fluid Mech., vol. 688, 2011, pp. 88–119) demonstrated the existence of finite-time singularities in the resulting viscous boundary layers, and linked the post-singularity structure to one of the laminar bands identified in experiments (Madden & Mullin J. Fluid Mech., vol. 265, 1994, p. 217; del Pino et al.Phys. Fluids, vol. 20 (12), 2008, 124104). The second band (or laminar front) identified by Madden & Mullin was conjectured by Hewitt et al. to be the result of a centrifugal instability, perhaps generated by small imperfections in the experimental apparatus. Here we explore this conjecture further, demonstrating that a small seam imperfection can generate substantial secondary motion but with considerably different dynamics than the centrifugally driven instability of Hewitt et al.
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Beya, Jose Francisco, William Peirson, and Michael Banner. "WHEN DO WAVES BECOME TURBULENT?" Coastal Engineering Proceedings 1, no. 33 (October 9, 2012): 9. http://dx.doi.org/10.9753/icce.v33.posters.9.
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Babanin and Haus (2009) recently presented evidence of high levels of turbulence induced by steep non-breaking waves. They proposed a Reynolds-like threshold wave parameter (a2ω/ν=3000, a wave amplitude, ω wave angular frequency, ν water viscosity) for the spontaneous occurrence of turbulence beneath surface waves. This contradicts the common assumed basis of existing irrotational wave theories and their classical experimental validation. Many laboratory wave experiments were carried out in the early 1960’s (e.g. Wiegel, 1964). In those experiments no evidence of turbulence was reported and steep waves behaved as predicted by the high order irrotational wave theories within the accuracy of the theories and experimental techniques at the time. The spontaneous generation of turbulence under waves can have serious consequences for wave modelling, where the irrotational flow assumption has secured its place in engineering design. This contribution describes unique flow visualisation experiments for large scale steep non-breaking waves using conventional dye techniques in the wave boundary layer extending above the wave trough level. The measurements showed no evidence of turbulent mixing for waves up to a2ω/ν=7000. There is presently no evidence that water waves become spontaneously turbulent (up a2ω/ν=7000) except within the bed boundary layers, under wind forcing or at breaking. Excellent agreement was found with higher order irrotational theories. Orbital velocities, Stokes drift and Stokes coefficients were measured and compared with theoretical values, suggesting that conventional theories underestimate unforced monochromatic wave non-linearity, although the corrections remain small.
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Castellani, Francesco, Abdelgalil Eltayesh, Francesco Natili, Tommaso Tocci, Matteo Becchetti, Lorenzo Capponi, Davide Astolfi, and Gianluca Rossi. "Wind Flow Characterisation over a PV Module through URANS Simulations and Wind Tunnel Optical Flow Methods." Energies 14, no. 20 (October 12, 2021): 6546. http://dx.doi.org/10.3390/en14206546.
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Despite their simplicity, photovoltaic (PV) modules are often arranged in structures that can be affected by severe and complex wind loads: in this context, the wind flow and the dynamic excitation induced by vortex shedding can introduce unexpected aeroelastic responses. This work introduces a novel wind tunnel application of experimental techniques to address this issue by the use of flow visualisation and video postprocessing, through the optical flow algorithm. Numerical simulations based on unsteady Reynolds-averaged Navier–Stokes (RANS) models are performed and compared against the experimental wind tunnel tests on a PV panel that was also instrumented with pressure taps. A setup with a 65∘ tilt angle was examined because, based on preliminary analyses, it was considered interesting for the free flow–wake transition associated with the dynamic response of the PV panel. The comparison of the experimental and numerical average wind fields supported that the proposed optical flow method was appropriate for characterising the wake of the panel, because there was enough seeding to perform the video postprocessing. Experiments and numerical predictions were compared as regards the average pressure distribution on the panel surfaces, and the average percentage was in the error of 7%; this supports that the URANS method was capable of reproducing the average behaviour of the panel, as well as for the selected configuration, which is particularly challenging. Furthermore, the simulated and measured power spectral densities of the wind speed were compared, and this resulted in the numerical model quite faithfully reproducing the frequency of the peak at 5 m/s, while the error was in the order of 20% for the 10 m/s case; this supports that, despite the URANS approach being affected by well-known critical points regarding the simulation of instantaneous quantities, it can be employed to elaborate information that can be particularly useful for the structural design of the panel. This kind of result can be considered as a first step, obtained with simplified and affordable methods, towards a characterisation of the dynamic behaviour of a PV panel in a real-world setup.
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Kingsley-Rowe, J. R., G. D. Lock, and A. G. Davies. "Aerospace applications of luminescent paint." Aeronautical Journal 107, no. 1077 (November 2003): 637–48. http://dx.doi.org/10.1017/s0001924000013518.
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Abstract Luminescent paints allow non-intrusive measurement of pressure and temperature at high spatial resolution without prior knowledge of the flow-field. Experiments have demonstrated that a ‘standard’ luminescent paint technique, developed by BAE Systems, can simultaneously measure steady pressure and temperature. This is achieved through knowledge of the paint phosphorescence lifetime rather than the absolute intensity, which increases the measurement accuracy. In addition, a new ‘fast’ paint has been calibrated at the University of Bath for the measurement of unsteady pressure using a variable frequency pulsing air jet. Pressure measurements were made with both paints in the wake of various excrescences, sized to produce vortex shedding in the frequency range 500–4,200Hz, in a transonic tunnel. The extent of the wakes was determined from a flow visualisation technique. Time-averaged measurements, using both luminescent paints, and transient measurements of the unsteady pressure field, made with the fast paint, were compared with transducer data. For all cases the luminescent paint data compared well with the conventional measurements and the Strouhal number agreed well with data from the literature. The use of luminescent paint for the simultaneous measurement of pressure and temperature over a NACA 0012 aerofoil, as well as the quantification of convective heat transfer is examined in Part 2.
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Xiao, F., X. Y. Li, and K. M. Lam. "Investigation of the hydrodynamic behaviour of particles and aggregates by particle image velocimetry (PIV)." Water Supply 7, no. 2 (July 1, 2007): 213–20. http://dx.doi.org/10.2166/ws.2007.056.
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An advanced fluid visualisation technique, particle image velocimetry, was employed to investigate the hydrodynamic properties of particles and aggregates. The experiments were conducted in a settling column filled with a suspension of fluorescent polymeric beads as flow tracers. A thin vertical section of the settling column was illuminated by a laser sheet, while the motions of particles were recorded by a high speed CCD camera. Large solid spheres, flocs of latex microspheres and aggregates of marine diatoms were characterised for their hydrodynamic properties. The trajectories of the tracer particles were tracked when a large particle or aggregate settled through the suspension of the tracers, which gave the streamlines surrounding the falling object. The streamlines demonstrate directly the curvilinear feature of the interaction between approaching particles. However, the available curvilinear model underestimates the collision frequency function of particles by one order of magnitude or two. The collision potentials of the flocs and aggregates are more than an order of magnitude greater than the similar-sized solid spheres. Algal aggregates appear to be highly porous and fractal with a fluid collection efficiency of 10–40%, which would significantly enhance the flocculation between particles and the mass transfer into the aggregates.
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Jędrzejewski, Mateusz, Marta Poćwierz, and Katarzyna Zielonko-Jung. "The Problem of Airflow Around Building Clusters in Different Configurations." Archive of Mechanical Engineering 64, no. 3 (September 1, 2017): 401–18. http://dx.doi.org/10.1515/meceng-2017-0024.
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Abstract In the paper, the authors discuss the construction of a model of an exemplary urban layout. Numerical simulation has been performed by means of a commercial software Fluent using two different turbulence models: the popular k-ε realizable one, and the Reynolds Stress Model (RSM), which is still being developed. The former is a 2-equations model, while the latter – is a RSM model – that consists of 7 equations. The studies have shown that, in this specific case, a more complex model of turbulence is not necessary. The results obtained with this model are not more accurate than the ones obtained using the RKE model. The model, scale 1:400, was tested in a wind tunnel. The pressure measurement near buildings, oil visualization and scour technique were undertaken and described accordingly. Measurements gave the quantitative and qualitative information describing the nature of the flow. Finally, the data were compared with the results of the experiments performed. The pressure coefficients resulting from the experiment were compared with the coefficients obtained from the numerical simulation. At the same time velocity maps and streamlines obtained from the calculations were combined with the results of the oil visualisation and scour technique.
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Watson, M., A. J. Jaworski, and N. J. Wood. "A study of synthetic jets from rectangular and dual-circular orifices." Aeronautical Journal 107, no. 1073 (July 2003): 427–34. http://dx.doi.org/10.1017/s000192400001335x.
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AbstractThe results of an investigation into the effect of both the number of orifices and the geometry of these orifices on the fluid structures exiting from a synthetic jet actuator are presented. The experiments have used smoke and laser visualisation and single hotwire measurement techniques to establish the flow field exiting the various orifices and the fluid velocities in the exit plane of the orifice. The results indicate that the use of two small orifices can perhaps produce two coherent vortex rings with a total circulation greater than that found in the ring produced by a large, single orifice of equivalent area. However, they have also shown that there are three different types of interaction between two adjacent orifices, related to the spacing between them and the level of excitation applied to the diaphragm. In addition, these interactions may affect the overall level of circulation in different ways. Finally the results have shown that a rectangular orifice of a given exit plane area is more likely to produce a turbulent ring than the equivalent circular orifice due to a ‘smoothing’ process which endeavours to create an axisymmetric ring from a non-axisymmetric slug of fluid. This work has shown that when using synthetic jet actuators in flow control applications, care should be taken in selecting the spacing and geometry of the orifices used, as certain set-ups may be more suited to certain applications than others.
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Debugne, Antoine L. R., and Gary R. Hunt. "The influence of spanwise confinement on round fountains." Journal of Fluid Mechanics 845 (April 26, 2018): 263–92. http://dx.doi.org/10.1017/jfm.2018.194.
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We study experimentally the effects of spanwise confinement on turbulent miscible fountains issuing from a round source of radius $r_{0}$. A dense saline solution is ejected vertically upwards into a fresh-water environment between two parallel plates, separated by a gap of width $W$, which provide restraint in the spanwise direction. The resulting fountain, if sufficiently forced, rapidly attaches to the side plates as it rises and is therefore ‘confined’. We report on experiments for five confinement ratios $W/r_{0}$, spanning from strongly confined ($W/r_{0}\rightarrow 2$) to weakly confined ($W/r_{0}\approx 24$), and for source Froude numbers $Fr_{0}$ ranging between $0.5\leqslant Fr_{0}\leqslant 96$. Four distinct flow regimes are observed across which the relative importance of confinement, as manifested by the formation and growth of quasi-two-dimensional structures, varies. The onset of each regime is established as a function of both $W/r_{0}$ and $Fr_{0}$. From our analysis of the time-averaged rise heights, we introduce a ‘confined’ Froude number $Fr_{c}\equiv Fr_{0}(W/r_{0})^{-5/4}$, which encompasses the effects of confinement and acts as the governing parameter for confined fountains. First-order statistics extracted from the flow visualisation, such as the time-averaged rise height and lateral excursions, lend further insight into the flow and support the proposed classification into regimes. For highly confined fountains, the flow becomes quasi-two-dimensional and, akin to quasi-two-dimensional jets and plumes, flaps (or meanders). The characteristic frequency of this flapping motion, identified through an ‘eddy counting’ approach, is non-dimensionalised to a Strouhal number of $St=0.12{-}0.16$, consistent with frequencies found in quasi-two-dimensional jets and plumes.
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Lee, Sarah, W. Pierre L. Bradley, David J. Brewster, Rani Chahal, Laurence Poon, Reny Segal, Savas Totonidis, David Tsang, and Mark Ng. "Airway management in the adult patient with COVID-19: High flow nasal oxygen or not? A summary of evidence and local expert opinion." Anaesthesia and Intensive Care 49, no. 4 (July 2021): 268–74. http://dx.doi.org/10.1177/0310057x211024691.
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The use of high flow nasal oxygen in the care of COVID-19-positive adult patients remains an area of contention. Early guidelines have discouraged the use of high flow nasal oxygen therapy in this setting due to the risk of viral spread to healthcare workers. However, there is the need to balance the relative risks of increased aerosol generation and virus transmission to healthcare workers against the role high flow nasal oxygen has in reducing hypoxaemia when managing the airway in high-risk patients during intubation or sedation procedures. The authors of this article undertook a narrative review to present results from several recent papers. Surrogate outcome studies suggest that the risk of high flow nasal oxygen in dispersing aerosol-sized particles is probably not as great as first perceived. Smoke laser-visualisation experiments and particle counter studies suggest that the generation and dispersion of bio-aerosols via high flow nasal oxygen with flow rates up to 60 l/min is similar to standard oxygen therapies. The risk appears to be similar to oxygen supplementation via a Hudson mask at 15 l/min and significantly less than low flow nasal prong oxygen 1–5 l/min, nasal continuous positive airway pressure with ill-fitting masks, bilevel positive airway pressure, or from a coughing patient. However, given the limited safety data, we recommend a cautious approach. For intubation in the COVID-positive or suspected COVID-positive patient we support the use of high flow nasal oxygen to extend time to desaturation in the at-risk groups, which include the morbidly obese, those with predicted difficult airways and patients with significant hypoxaemia, ensuring well-fitted high flow nasal oxygen prongs with staff wearing full personal protective equipment. For sedation cases, we support the use of high flow nasal oxygen when there is an elevated risk of hypoxaemia (e.g. bariatric endoscopy or prone-positioned procedures), but recommend securing the airway with a cuffed endotracheal tube for the longer duration procedures when theatre staff remain in close proximity to the upper airway, or considering the use of a surgical mask to reduce the risk of exhaled particle dispersion.
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Raya, Laura, Sara A. Boga, Marcos Garcia-Lorenzo, and Sofia Bayona. "Improving the Discriminability of Haptic Icons: The Haptic Tuning Fork." Applied Sciences 11, no. 18 (September 21, 2021): 8772. http://dx.doi.org/10.3390/app11188772.
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Technological advances enable the capture and management of complex data sets that need to be correctly understood. Visualisation techniques can help in complex data analysis and exploration, but sometimes the visual channel is not enough, or it is not always available. Some authors propose using the haptic channel to reinforce or substitute the visual sense, but the limited human haptic short-term memory still poses a challenge. We present the haptic tuning fork, a reference signal displayed before the haptic information for increasing the discriminability of haptic icons. With this reference, the user does not depend only on short-term memory. We have decided to evaluate the usefulness of the haptic tuning fork in impedance kinesthetic devices as these are the most common. Furthermore, since the renderable signal ranges are device-dependent, we introduce a methodology to select a discriminable set of signals called the haptic scale. Both the haptic tuning fork and the haptic scale proved their usefulness in the performed experiments regarding haptic stimuli varying in frequency.
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Forquin, Pascal, Mahdi Saadati, Dominique Saletti, Bratislav Lukic, Federico Schiaffini, Kenneth Weddfelt, and Per-Lennart Larsson. "Investigation of the Mechanical Behaviour of Lingulid Sandstone Emphasizing the Influence from Pre-Existing Structural Defects—Part 2: Dynamic Testing and Numerical Modelling." Applied Sciences 12, no. 22 (November 16, 2022): 11621. http://dx.doi.org/10.3390/app122211621.
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In the present study, dynamic experiments are developed to investigate the induced damage modes when Lingulid sandstone is subjected to dynamic and impact loading. To do so, a series of spalling tests were carried out in order to investigate the material response at high strain tension rates. This illustrates how structural defects influence the wave propagation in the tested sample, the loading-rate, and the resulting tensile strength. In addition, edge-on-impact tests were performed using both open and sarcophagus configurations. An ultra-high-speed image recording system is used in an open configuration for time-resolved visualisation of damage. The sarcophagus configuration gives the opportunity to visually compare the state of the cracking pattern prior to and after the test. This experimental work points-out that the pre-existing structural defects play a major role on impact loading. This is because the opening of cracks in mode I and the sliding of cracks in mode II are favoured, and by also restricting the fragmentation of the material caused by less critical defects. Next, a numerical simulation, only involving the so-called KST model, is presented to highlight the loading that would be applied to the target in the absence of structural defects. It demonstrates that in such a situation, a wide network of radial cracks would be expected. Finally, a numerical study involving the KST-DFH model illustrates the influence of a structural defect on the amount of damage generated in the target.
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Cohen, G. S., and F. Motallebi. "Sub boundary-layer vortex generators for the control of shock induced separation." Aeronautical Journal 110, no. 1106 (April 2006): 215–26. http://dx.doi.org/10.1017/s0001924000001196.
Full textAbstract:
Abstract The results of an investigation into the effects that sub-boundary layer vortex generators (SBVGs) have on reducing normal shock-induced turbulent boundary-layer separation are presented. The freestream Mach number and Reynolds number were M = 1·45 and 15·9 × 106/m, respectively. Total pressure profiles, static pressure distributions, surface total pressure distributions, oil flow visualisation and Schlieren photographs were used in the results analysis. The effects of SBVG height, lateral spacing and location upstream of the shock were investigated. A novel curved shape SBVG was also evaluated and comparisons against the conventional flat vane type were made. The results show that in all but two cases, separation was completely eliminated. As expected, the largest SBVGs with height, h = 55%δ, provided the greatest pressure recovery and maximum mixing. However, the shock pressure rise was highest for this case. The experiments showed that the mid height SBVG array with the largest spacing provided similar results to the SBVG array with the largest height. Reducing the distance to shock to 10δ upstream also showed some improvement over the SBVG position of 18δ upstream. It was suggested that total elimination of the separated region may not be required to achieve a balance of improved static pressure recovery whilst minimising the pressure rise through the shock. The effect of curving the SBVGs provided an improved near wall mixing with an improved static and surface total pressure recovery downstream of the separation line. The optimum SBVG for the current flow conditions was found to be the curved vanes of h = 40%δ, with the largest spacing, located at 18δ upstream of the shock. Overall, it was apparent from the results that in comparison to larger vortex generators with a height comparable to δ, for SBVGs the parameters involved become more important in order to obtain the highest degree of mixing from a given SBVG configuration.
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Seshadri, S. N., and K. Y. Narayan. "Shock-induced separated flows on the lee surface of delta wings." Aeronautical Journal 91, no. 903 (March 1987): 128–41. http://dx.doi.org/10.1017/s0001924000091387.
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Experiments were conducted to study shock-induced separated flows on the lee surface of delta wings with sharp leading edge at supersonic speeds. Two sets of delta wings of different thickness (10° and 25° normal angle), each with leading edge sweep angles varying from 45° to 70°, were tested. The measurements, carried out in a Mach number range from 1.4 to 3.0, included oil flow visualisations (on both sets of wings) and static pressure distributions (on the thicker wings only). Using the test results, some features of shock-induced separated flows, including in particular the boundary between this type of flow and fully attached flow, have been determined. The experimental results indicate that this boundary does not seem to show any significant dependence on wing thickness within the limit of thicknesses tested. It is shown that this boundary can be predicted for thin delta wings using a well known criterion for incipient separation in a glancing shock wave boundary layer interaction, namely that a pressure rise of 1.5 is required across the shock. Comparison of the predicted boundary with experimental results (from oil flow visualisations) shows good agreement.
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Lippert, Martin C., and Andrew W. Woods. "Turbulent bubble fountains." Journal of Fluid Mechanics 836 (December 11, 2017): 277–303. http://dx.doi.org/10.1017/jfm.2017.818.
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We explore the dynamics of turbulent bubble fountains produced when a descending stream of fresh water and air bubbles issues from a nozzle submerged in a tank of water. The bubbles have diameters of 2 to 5 mm and the fountains have source Froude numbers ranging from 10 to 240. The Reynolds numbers of the bubbly fountains range from 4000 to 24 000. The bubbles, carried into the tank by the downward jet of water, lead to a buoyancy force which reduces the downward momentum of the jet, thus producing a fountain. We find that $H_{F}$, the downward penetration distance of the bubbles into the water reservoir, may be characterised by two parameters: $\unicode[STIX]{x1D6EC}$, the ratio of the bubble rise speed to the characteristic fountain velocity, $u_{F}=f_{0}^{1/2}/m_{0}^{1/4}$, and $Fr_{0}$, the source Froude number, given by $m_{0}^{5/4}/(q_{W_{0}}f_{0}^{1/2})$, where $q_{W_{0}}$, $m_{0}$ and $f_{0}$ are the source volume, momentum and buoyancy fluxes. As $\unicode[STIX]{x1D6EC}$ increases, $H_{F}$ decreases, a result which is directly analogous to the height of rise of particles in a particle-laden fountain (Mingotti & Woods, J. Fluid Mech., vol. 793, 2016, R1). Also, we find that $H_{F}$ increases as $Fr_{0}$ increases, a result directly analogous to single-phase fountains (Turner, J. Fluid Mech., vol. 26, 1966, pp. 779–792). We present a model for the conservation of volume, momentum and buoyancy fluxes and use this to predict the penetration distance of the bubbles corresponding to that point at which the fountain liquid velocity equals the bubble rise speed. Using the best-fit value for the entrainment coefficient, $\unicode[STIX]{x1D6FC}=0.04\pm 0.004$, we find that our experimental measurements of the bubble penetration distance are in good accord with the model predictions for $10<Fr_{0}<240$ and $2<\unicode[STIX]{x1D6EC}<15$. In our experiments the bubble rise speed, $u_{slip}$, is large compared to the entrainment velocity of the descending fountain. Thus, only a small fraction of the rising bubbles are re-entrained, and so the buoyancy flux of the fountain is approximately independent of depth. Flow-visualisation experiments also show that the liquid momentum flux is not exhausted at the point of bubble separation and so the liquid in the fountain continues to travel downward, separated from the bubbles. We use the new theoretical model to estimate the flux of air entrained into plunging water jets.
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Lee, Joshua Chun Kwang, Javier Amezcua, and Ross Noel Bannister. "Hybrid ensemble-variational data assimilation in ABC-DA within a tropical framework." Geoscientific Model Development 15, no. 15 (August 11, 2022): 6197–219. http://dx.doi.org/10.5194/gmd-15-6197-2022.
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Abstract. Hybrid ensemble-variational data assimilation (DA) methods have gained significant traction in recent years. These methods aim to alleviate the limitations and maximise the advantages offered by ensemble or variational methods. Most existing hybrid applications focus on the mid-latitudinal context; almost none have explored its benefits in the tropical context. In this article, hybrid ensemble-variational DA is introduced to a tropical configuration of a simplified non-hydrostatic convective-scale fluid dynamics model (the ABC model, named after its three key parameters: the pure gravity wave frequency A, the controller of the acoustic wave speed B, and the constant of proportionality between pressure and density perturbations C), and its existing variational framework, the ABC-DA system. The hybrid ensemble-variational DA algorithm is developed based on the alpha control variable approach, often used in numerical weather prediction. Aspects of the algorithm such as localisation (used to mitigate sampling error caused by finite ensemble sizes) and weighting parameters (used to weight the ensemble and climatological contributions to the background error covariance matrix) are implemented. To produce the flow-dependent error modes (ensemble perturbations) for the ensemble-variational DA algorithm, an ensemble system is also designed for the ABC model which is run alongside the hybrid DA system. A random field perturbations method is used to generate an initial ensemble which is then propagated using the ensemble bred vectors method. This setup allows the ensemble to be centred on the hybrid control analysis. Visualisation software has been developed to focus on the diagnosis of the ensemble system. To demonstrate the hybrid ensemble-variational DA in the ABC-DA system, sensitivity tests using observing system simulation experiments are conducted within a tropical framework. A 30-member ensemble was used to generate the error modes for the experiments. In general, the best performing configuration (with respect to the “truth”) for the hybrid ensemble-variational DA system used an 80%/20% weighting on the ensemble-derived/climatological background error covariance matrix contributions. For the horizontal wind variables though, full weight on the ensemble-derived background error covariance matrix (100%/0%) resulted in the smallest cycle-averaged analysis root mean square errors, mainly due to large errors in the meridional wind field when contributions from the climatological background error covariance matrix were involved, possibly related to a sub-optimal background error covariance model. The ensemble bred vectors method propagated a healthy-looking DA-centred ensemble without bimodalities or evidence of filter collapse. The ensemble was under-dispersive for some variables but for others, the ensemble spread approximately matched the corresponding root mean square errors. Reducing the number of ensemble members led to slightly larger errors across all variables due to the introduction of larger sampling errors into the system.
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González-Serrano, A. F., C. R. Ferreira, V. Pirro, L. S. Eberlin, J. Heinzmann, A. Lucas-Hahn, H. Niemann, and R. G. Cooks. "229 RAPID, UNTARGETED LIPID DETERMINATION IN INDIVIDUAL BOVINE OOCYTES AND PRE-IMPLANTATION EMBRYOS BY HIGH-RESOLUTION DESORPTION ELECTROSPRAY IONIZATION MASS SPECTROMETRY." Reproduction, Fertility and Development 25, no. 1 (2013): 262. http://dx.doi.org/10.1071/rdv25n1ab229.
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Lipid structural analysis in individual pre-implantation mammalian embryos is hampered by the small amount of biological material, such that most studies use staining methods or gas chromatography analysis generate information only on the fatty acyl residues. Recent developments in high-resolution desorption electrospray ionization mass spectrometry (DESI-MS) allow the analysis of free fatty acids (FA) and glycerophospholipids (PL) in individual bovine embryos. Here, we report on the use of DESI-MS for the sensitive analysis of triacylglycerol (TAG) species, profiles of FA and PL in individual bovine oocytes and embryos. Bovine oocytes (n = 40) and blastocysts (n = 42) were frozen in a minimal volume of PBS (2 to 5 µL). Samples were directly deposited on glass slides after thawing. After drying, a volume of 500 µL of methanol : water (1 : 1, vol/vol) was carefully deposited on the surface of the glass slide and removed by orienting the glass slide vertically to eliminate PBS salts. An Orbitrap mass spectrometer was used for the experiments. Parameters for the positive ion mode were as follows: acetonitrile (ACN) supplemented with 3 µL mL–1 of AgNO3 at a 5 µL min–1 flow rate, injection time of 1000 ms, and a mass-to-charge range of m/z 400 to 1500. For the negative ion mode, the solvent combination used was acetonitrile + dimethylformamide (1 : 1, vol/vol) at a 1.0 µL min–1 flow rate, a maximum injection time of 1000 ms, and a mass-to-charge range of m/z 150 to 1000. Positive ion mode data for the detection of TAG species were acquired first, followed by acquisition of FA and PL in the negative ion mode. Detection of TAG by DESI, which is extremely useful for bovine embryo cryopreservation and metabolism research, has been performed by adding AgNO3 in the DESI spray to obtain silver adducts, which are easily recognised by the characteristic 1 : 1 abundance ratio of the 107 : 109 Ag isotopes. The most abundant fatty acyl residues present in TAG species were palmitic (P), linoleic (L), oleic (O), and stearic (S) acids, such as TAG of m/z 937, PPL (50 : 2); m/z 965, POO (52 : 1); m/z 967, POS (52 : 2); m/z 989, OOL/LLS (54 : 4); and m/z 991, OOO, SOL (54 : 3). Free FA and PL profiles collected from the same samples in the negative ion mode were similar to those in our recent report (2012 J. Mass Spectrom. 47, 29–33). Lipid attribution has been performed based on high-resolution mass analysis. Multivariate statistics from this data set will allow visualisation of differences observed in the lipid profiles among samples. In conclusion, we report the use of DESI-MS for the sensitive analysis of TAG in individual bovine oocytes and embryos and the creation of profiles of FA, PL, and TAG species in the same sample by DESI-MS.
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Uenishi, Ryosuke, Syohei Tsugawa, Morihiko Uesaka, Takashi Watanabe, Hirochika Tanigawa, and Katsuya Hirata. "Flow visualisation of Diverse Flows between Co-Rotating Disks in Casing by Numerical Analysis and Experiment." Proceedings of The Computational Mechanics Conference 2016.29 (2016): 4_222. http://dx.doi.org/10.1299/jsmecmd.2016.29.4_222.
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Weston-Davies, Wynne H., Miles A. Nunn, Fernando O. Pinto, Ian J. Mackie, Stephen John Richards, Samuel J. Machin, Raymond Prudo, and Peter Hillmen. "Clinical and Immunological Characterisation of Coversin, a Novel Small Protein Inhibitor of Complement C5 with Potential As a Therapeutic Agent in PNH and Other Complement Mediated Disorders." Blood 124, no. 21 (December 6, 2014): 4280. http://dx.doi.org/10.1182/blood.v124.21.4280.4280.
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Abstract Coversin is a clinical stage recombinant protein molecule (16.7kDa) derived from a salivary molecule from the Ornithodros moubata tick where it assists the parasite to feed without provoking a host immunological response. It prevents activation of complement C5 and binds leukotriene B4 (LTB4) with high affinity. It is not an antibody and can therefore be manufactured in prokaryotic cells such as E. coli leading to potential savings in manufacturing costs. As its mode of action on C5 is similar to that of the monoclonal antibody eculizumab (Soliris®), it is considered to be a promising alternative therapeutic approach to thrombotic and hemolytic diseases mediated by complement activation including atypical hemolytic uremic syndrome (aHUS), catastrophic anti-phospholipid syndrome (APS) and paroxysmal nocturnal hemoglobinuria (PNH). In order to test this hypothesis, experiments were undertaken to determine whether Coversin could inhibit the hemolysis of PNH red cells in vitro using a modified Ham test combined with visualisation of the results by flow cytometric measurement of CD59 expression. Initial experiments showed maximum inhibition of hemolysis compared to control occurred at a concentration of approximately 10mcg/mL. Further experiments using PNH red blood cells also demonstrated the effectiveness of Coversin in blocking in vitro hemolysis of PNH red cells that had both type III (complete GPI-deficiency) and type II (partial GPI deficiency) red cells and also the deposition and accumulation of C3d on both types of PNH red cells. In a comparative experiment Coversin 10mcg/mL was found to be as effective as eculizumab 50mcg/mL, a molar equivalent dose. As Coversin is a non-humanised xenologous protein a mouse study was performed in order to assess immunogenicity and its potential to induce the formation of neutralising antibodies. Daily repeat subcutaneous doses of Coversin (0.57mg/kg) or vehicle were administered to 5 groups of 6 BALB/c mice and blood samples taken after 7, 14, and 28 days administration with an additional group where samples were taken 14 days following cessation of 28 days dosing. Immunoblots showed that by Day 14 33% of mice had developed low titre IgG antibodies to Coversin. By 28 days this had risen to 75% of mice receiving the active compound. Using CH50 lytic assays the antibodies were shown to be non-neutralising and no animals exhibited clinical signs of allergy or injection site reactions. The group of 6 mice that received vehicle showed no evidence of antibodies at 28 days. A heterozygous C5 mutation leading to a p.Arg885His polymorphism and interfering with the binding of eculizumab was recently reported in Japanese PNH patients and this was associated with a poor response to therapy. This was subsequently found to affect 3.5% of the general Japanese and Han Chinese population. A similar polymorphism has now been shown in a 4 year old Caucasian child with persistent thrombocytopenia following a stem cell transplant for chronic granulomatous disease. Prolonged eculizumab treatment was ineffective leading to discovery of the mutation. Serum from the patient was spiked with ascending concentrations of Coversin and CH50 activity was measured by ELISA. This produced a dose response curve corresponding to that found in serum from normal subjects. Coversin, which binds to a slightly different site on the C5 molecule, seems therefore to be unaffected by the polymorphism and to achieve superior inhibition of C5 activation compared to eculizumab. A Phase I, single ascending dose clinical trial was performed in 24 healthy volunteers. In the top dose cohort total blockade of complement C5 was achieved following subcutaneous injection at the predicted therapeutic loading dose of 0.57mg/kg. Activity remained below 50% for 48 hours suggesting that dosing once a day is feasible at steady state (see figure). The drug was well tolerated and no drug-related side effects were seen. Phase II clinical trials in PNH and other thrombotic micro-angiopathies (TMAs) are planned. Coversin appears to be a promising alternative to eculizumab for patients with PNH and other TMAs including those with polymorphisms which interfere with optimal binding of eculizumab to complement C5. Figure 1 Figure 1. Disclosures Weston-Davies: Volution Immuno Pharmaceuticals (VIP) SA: Consultancy. Nunn:Volution Immuno Pharm: Consultancy. Prudo:Volution Immuno Pharmaceuticals (VIP) SA: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.