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Journal articles on the topic 'Hydrodynamics; Aerodynamics'
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1
Ennos, A. R. "The aerodynamics and hydrodynamics of plants." Journal of Experimental Biology 202, no. 23 (December 1, 1999): 3281–84. http://dx.doi.org/10.1242/jeb.202.23.3281.
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Because they grow away from their substratum to compete for light, plants have to withstand hydrodynamic or aerodynamic drag. Both water and land plants reconfigure in response to this drag, and this is presumed to reduce the risk of mechanical failure. However, there is little unequivocal evidence of drag reduction in large trees as a result of reconfiguration. Land plants must also transport water internally to their tissues, and many have developed xylem tracheids and vessels that help speed up this process. Recent evidence that tree height is limited by water supply suggests that water transport efficiency must be a crucial element in tree design. However, the resistance of many parts of the xylem is still unknown. More focused work is urgently required to shed light on the evolution and ecology of plants in relation to the flow of fluids.
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Alam, Firoz, Harun Chowdhury, and Hazim Moria. "A review on aerodynamics and hydrodynamics in sports." Energy Procedia 160 (February 2019): 798–805. http://dx.doi.org/10.1016/j.egypro.2019.02.158.
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Syamsuar, Sayuti. "Simulasi dan Verifikasi Prestasi Terbang Model Remote Control Flying Boat Saat Hidroplaning." WARTA ARDHIA 42, no. 1 (September 23, 2017): 1. http://dx.doi.org/10.25104/wa.v42i1.294.1-6.
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Pesawat Wing In Surface Effect A2B tipe B konfigurasi Lippisch mempunyai hambatan air yang cukup besar dibandingkan tenaga mesin saat hydroplaning. Makalah ini berisikan bagian dari analisis dalam perancangan untuk mengetahui karakteristik aerodinamika dan hidrodinamika dari remote control model jenis Flying Boat pada fase hydroplaning. Pada awalnya, dilakukan pemotretan 3D terhadap pesawat model Flying Boat menggunakan kamera laser untuk menghasilkan solid drawing pada program CATIA. Model 3D dianalisis dengan menggunakan piranti lunak CFx pada program AnSys. Planform sayap, memiliki dihedral dan menggunakan airfoil jenis NACA 23012. Karakteristik aerodinamika dan hidrodinamika untuk model 3 D dipresentasikan pada posisi sudut alpha =00. Sedangkan kecepatan yang digunakan adalah 0 sampai25 knots. Untuk memverifikasi data hasil simulasi, digunakan data uji terbang pesawat udara tanpa awak Alap-alap yang mempunyai T/W rasio yang sama, yaitu sudut pitch, kecepatan arah sumbu Z pada sumbu benda, ketinggian dan kecepatan. Gaya angkat aerodimaka arah sumbu Z pada simulasi RC model Flying Boat sebanding dengan gaya angkat aerodinamika arah sumbu Z pada UAV Alap-alap saat take off.
[The Hydroplaning Flight Performance Simulation and Verfication of a Flying Boat Remote Control Model] The Wing in Surface Effect Aircraft A2B type B with Lippisch configuration has higher hydrodynamics drag compared to engine powered aircraft during hydroplaning. This paper explains parts of analysis in aircraft design to identify the aerodynamics and hydrodynamics characteristics of flying boat remote control model during hydroplaning phase. At first, flying boat model was three dimensional photographed using laser camera in order to produce solid drawing for CATIA program. The three dimensional model, later, analyzed by using CFx software in AnSys program. The wing planform has dihedral angle while the airfoil used is NACA 23012. The aerodynamics and hydrodynamics characteristics of this three-dimensional model is represented for alpha =00. Whilst the speed used in simulation was 0 to 25 knots. In verifying the data of the simulation results, the Unmanned Aerial Vehicle UAV Alap-alap flight test data was used in which it has the same T/W ratio for the pitch angle, acceleration in Z body axis, altitude, and speed. The aerodynamics lift in Z axis of flying boat model during simulation is proportional to the aerodynamics lift in Z axis of UAV Alap-alap during take-off.
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Ferreiro, Larrie D. "The mutual influence of aircraft aerodynamics and ship hydrodynamics in theory and experiment." Archive for History of Exact Sciences 68, no. 2 (August 27, 2013): 241–63. http://dx.doi.org/10.1007/s00407-013-0129-x.
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TUCK, E. O., and Y. M. STOKES. "ON THIN OR SLENDER BODIES." ANZIAM Journal 53, no. 3 (January 2012): 190–212. http://dx.doi.org/10.1017/s1446181112000120.
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AbstractThis is a review of thin-body and slender-body theories, with indications of some new applications. Topics discussed include bodies with near-constant surface pressure, subsonic and supersonic aerodynamics, ship hydrodynamics, slender bodies in Stokes flow, slender footings in elastic media, and slender moonpools. Mathematical features of the thin- and slender-body approximations are also discussed, especially nonlocal convolution terms modelling three-dimensionality in the otherwise two-dimensional near field, end effects, and the role of the logarithm of the slenderness ratio. This review was presented by the first author as the IMA Lighthill Memorial Lecture at the British Applied Mathematics Colloquium (BAMC) 2004.
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Jiang, Hua, Yunsai Chen, Xing Zheng, Shanqin Jin, and Qingwei Ma. "A Study on Stable Regularized Moving Least-Squares Interpolation and Coupled with SPH Method." Mathematical Problems in Engineering 2020 (May 30, 2020): 1–28. http://dx.doi.org/10.1155/2020/9042615.
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The smoothed particle hydrodynamics (SPH) method has been popularly applied in various fields, including astrodynamics, thermodynamics, aerodynamics, and hydrodynamics. Generally, a high-precision interpolation is required to calculate the particle physical attributes and their derivatives for the boundary treatment and postproceeding in the SPH simulation. However, as a result of the truncation of kernel function support domain and irregular particle distribution, the interpolation using conventional SPH interpolation experiences low accuracy for the particles near the boundary and free surface. To overcome this drawback, stable regularized moving least-squares (SRMLS) method was introduced for interpolation in SPH. The surface fitting studies were performed with a variety of polyline bases, spatial resolutions, particle distributions, kernel functions, and support domain sizes. Numerical solutions were compared with the results using moving least-squares (MLS) and three SPH methods, including CSPH, K2SPH, and KGFSPH, and it was found that SRMLS not only has nonsingular moment matrix, but also obtains high-accuracy result. Finally, the capability of the algorithm coupled with SRMLS and SPH was illustrated and assessed through several numerical tests.
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Suzuki, Kenta, and Kuniaki Kawabata. "Development of a Robot Simulator for Decommissioning Tasks Utilizing Remotely Operated Robots." Journal of Robotics and Mechatronics 32, no. 6 (December 20, 2020): 1292–300. http://dx.doi.org/10.20965/jrm.2020.p1292.
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This paper describes the development of a robot simulator for remote decommissioning tasks using remotely operated robots at the Fukushima Daiichi Nuclear Power Station of the Tokyo Electric Power Company Holdings. The robot simulator was developed to provide a remote operation training environment to ensure operator proficiency. The developed simulator allows for the calculation of physical aspects, such as the hydrodynamics of a remotely operated vehicle and the aerodynamics of an unmanned aerial vehicle. A disturbed camera view presented to an operator can be generated by setting parameters such as transparency, color, distortion, and noise. We implemented a communication failure emulator on the simulator in addition to functionalities for calculating the integral dose and generating the gamma camera image. We discuss the functional requirements and introduce the implemented functionalities. The simulator was built using the developed functions and can be executed integrally.
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Saydam, Ahmet Ziya, Serhan Gokcay, and Mustafa Insel. "Evaluation of Aerodynamic Characteristics of Mega-Yacht Superstructures by CFD Simulations." Journal of Ship Production and Design 36, no. 04 (November 13, 2020): 259–70. http://dx.doi.org/10.5957/jspd.09190051.
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Air wake distribution around the superstructure of a mega-yacht is a key concern for the designer because of various reasons such as comfort expectations in recreational deck areas, self-noise generation, air pollution and temperature gradients due to exhaust interactions, and safety of helicopter operations such as landing/take off and hovering. The Reynolds-averaged Navier-Stokes (RANS) technique in computational fluid dynamics (CFD) is frequently used in studies on mega-yacht hydrodynamics and aerodynamics with satisfactory results. In this article, a case study is presented for the utilization of CFD in a mega-yacht's superstructure design. The flow field in recreational open areas has been analyzed for the increase in velocity due to the existence of the superstructure. A reduction in self-noise of the mast structure has been aimed by reducing flow separation and vorticity. Time-dependent velocity data obtained with scale-resolving simulations are presented for the evaluation of helicopter landings. The capabilities and limitations of the RANS technique are discussed along with recent developments in modeling approaches.
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Chaudhary, Harideo. "Application of the Theory of a Single First Order Equation to Traffic Flow." Journal of the Institute of Engineering 9, no. 1 (June 30, 2014): 175–81. http://dx.doi.org/10.3126/jie.v9i1.10681.
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Few years ago, Lighthill and Whitham (1955) published a lengthy paper dealing with the theory of highway traffic flow .The basic idea in their approach to the problem is that the flow of traffic along a highway is analogous to the flow of a fluid in an open channel or pipe. This point of view replaces a long column of closely spaced discrete moving vehicles with an equivalent continuous moving stream of liquid (e.g. water) or gas (e.g. air). In other words, Lighthill and Whitham analyzed the phenomenon of traffic flow as though it were a problem in fluid mechanics. This approach allows some, though certainly not all, of the physical and mathematical relationships of hydrodynamics and aerodynamics to be utilized in the traffic flow problem. (Bank, p. 272) DOI: http://dx.doi.org/10.3126/jie.v9i1.10681Journal of the Institute of Engineering, Vol. 9, No. 1, pp. 175–181
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Ciappi, Lorenzo, Lapo Cheli, Irene Simonetti, Alessandro Bianchini, Giampaolo Manfrida, and Lorenzo Cappietti. "Wave-to-Wire Model of an Oscillating-Water-Column Wave Energy Converter and Its Application to Mediterranean Energy Hot-Spots." Energies 13, no. 21 (October 26, 2020): 5582. http://dx.doi.org/10.3390/en13215582.
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Oscillating water column (OWC) systems are among the most credited solutions for an effective conversion of the notable energy potential conveyed by sea waves. Despite a renewed interest, however, they are often still at a demonstration phase and additional research is required to reach industrial maturity. Within this framework, this study provides a wave-to-wire model for OWC systems based on an impulse air turbine. The model performs a comprehensive simulation of the system to estimate the attendant electric energy production for a specific sea state, based on analytical models of the primary (fixed chamber) and secondary (air turbine) converters coupled with the tertiary converter (electric generator). A rigid piston model is proposed to solve the hydrodynamics, thermodynamics, and hydrodynamics of the chamber, in a coupled fashion with the impulse turbine aerodynamics. This is solved with a novel method by considering the cascades as sets of blades, each one consisting of a finite number of airfoils stacked in the radial direction. The model was applied for two Mediterranean sites located in Tuscany and Sardinia (Italy), which were selected to define the optimal geometry of the turbine for a specified chamber. For each system, the developed analytical wave-to-wire model was applied to calculate the performance parameters and the annual energy production in environmental conditions typical of the Mediterranean Sea. The selected impulse turbines are able to convert 13.69 and 39.36 MWh/year, with an efficiency of 4.95% and 4.76%, respectively, thus proving the interesting prospects of the technology.
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Du, Lei, Zhuang Lin, Yi Jiang, Ping Li, and Yue Dong. "Numerical Investigation on the Scale Effect of a Stepped Planing Hull." Journal of Marine Science and Engineering 7, no. 11 (November 5, 2019): 392. http://dx.doi.org/10.3390/jmse7110392.
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This article discusses the scale effects on a planing boat, utilizing the computational fluid dynamics method. The simulation is compared with a tank test for verification and validation. The planing boat sails use both aerodynamics and hydrodynamics. Studying the performances and wave patterns of different dimensions of the models is the best way to investigate the scale effect without using experimental data. The resistance is discussed in two parts, namely residuary resistance and friction resistance, and is compared to the calculated data using the international towing tank conference (ITTC) formula. The computational fluid dynamics (CFD) calculations of the model are increased by 4.77% on average, and the boat computations are also increased by 3.57%. The computation shows the scale effect in detail. The residuary resistance coefficients at different scales are approximately equal, and the friction resistance coefficients show the scale effect. The scale effect for longitudinal steadiness is also captured for the period of the porpoising behavior. The rational for the full-scaled boat oscillation period and the model is the root of the scales.
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Abene, A., and V. Dubois. "Fundamental aspects of the vortex flow on cones. Angular characterization of hyperlifting vortex torques; the law of filiation." Canadian Journal of Physics 86, no. 8 (August 1, 2008): 1027–31. http://dx.doi.org/10.1139/p08-018.
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This paper describes in detail the fundamental aspects of the vortex flow developed on the upper surface of a cone having an apex angle of 68.6°. It is one of a large number of studies carried out in the wind tunnel of the Valenciennes University aerodynamics and hydrodynamics laboratory whereby visualizations have enabled the flow of vortex structures to be monitored and consequently their development and positioning, under the influence of apex angles and at increasing angles of incidence, to be determined and defined. The existence and the preferential nature of intervortex angles are here confirmed and it has been found, by analogy with studies carried out on other types of slender bodies, that the law of filiation is applicable to the angular characterization of hyperlifting vortex torques and to the angular correspondence existing between their main and secondary structures. These findings suggest that there is a certain universality in the behaviour of these properties although no current theory would seem to be able as yet to provide a straightforward explanation of the phenomena.PACS Nos.: 44, 47
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Tavakoli Dakhrabadi, Mohammad, and Mohammad Saeed Seif. "Hydro-aerodynamic mathematical model and multi-objective optimization of wing-in-ground effect craft in take-off." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 232, no. 4 (May 18, 2017): 421–33. http://dx.doi.org/10.1177/1475090217708478.
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Hydro-aerodynamic mathematical model and multi-objective optimization of a popular wing-in-ground effect craft are presented in this research using a hydro-aerodynamic practical method and the genetic algorithm. The primary components of the wing-in-ground effect craft configuration include a compound wing, catamaran hull form and a power-augmented ram platform. The hydro-aerodynamic practical method with low computational time and high accuracy is performed by coupling hydrodynamic and aerodynamic considerations using the potential flow theory in ground effect and the semi-empirical equations proposed for high-speed marine vehicles. The trade-off between hydrodynamic and aerodynamic characteristics makes it difficult to simultaneously satisfy the design requirements of high hydro-aerodynamic performance. In this article, three goals—reduced hump resistance, increased compound wing lift-to-drag ratio and reduced take-off speed—are selected as the objective functions. The longitudinal position of center of gravity, position of outer wing with respect to main wing, power augmented ram platform angle to horizontal and flap angle are also adopted as design variables. Static height stability and the location of the center of gravity with respect to the aerodynamics centers are considered as constraints for the stable flight in ground effect. The optimal solutions of the multi-objective optimization were not unique, rather a set of non-dominated optima, called the Pareto sets, are obtained. As a result of the multi-objective optimization, 25 Pareto individuals are obtained that the naval architects can use in designing wing-in-ground crafts.
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Афтанюк, В. В., Д. В. ,. Даниленко, and А. В. Афтанюк. "МОДЕЛЮВАННЯ ТА АНАЛІЗ ГІДРОДИНАМІКИ ПАРОГАЗОВИХ ПОТОКІВ У СКРУБЕРІ ВЕНТУРІ." Ship power plants 39, no. 1 (June 12, 2019): 5–13. http://dx.doi.org/10.31653/smf39.2019.5-13.
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The article presents the results of numerical simulation of a Venturi scrubber for purifying contaminated gases from SOx emitted into the atmosphere by marine engines. To model aerodynamics, a solid-state model of a Venturi scrubber was developed. Geometrical parameters and standard models are designed to ensure that they are stowed in clean ship systems. At the first stage, they reached the bottom of the gas stream into the scrubber while feeding the obsolete gas in an amount of 32 m3 /s. On the basis of the obtained model of air flow graphs of velocity and pressure distribution along the axis of the Venturi scrubber were constructed. To determine the rational volume of steam to be fed to the scrubber to ensure a uniform distribution of it on the apparatus, studies of the distribution at different amounts of steam.The study was conducted for three modes of operation of the scrubber, which differ in the amount of saturated steam supplied to the apparatus (1, 5, 10 m3 /s). The simulation results allowed us to analyze the distribution of gas velocities and pressures in the scrubber, the efficiency of spraying and mixing of the gas stream and steam. Based on the analysis of hydrodynamics, the rational mode of operation of the scrubber is determined (steam supply – 10 m3 /s). Further increase in the amount of steam can be considered impractical due to the fact that the gas velocity of the apparatus is greatly increased, which in turn leads to increased resistance of the apparatus and the leakage of dust. The result of the early analysis is the transition to early models of purification systems based on the Venturi scrubber. The developed model can be used as a separate unit in large models of cleaning systems, which include several types of scrubbers for various industries.
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Bashetty, Srikanth, and Selahattin Ozcelik. "Review on Dynamics of Offshore Floating Wind Turbine Platforms." Energies 14, no. 19 (September 22, 2021): 6026. http://dx.doi.org/10.3390/en14196026.
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This paper presents a literature review of the dynamics of offshore floating wind turbine platforms. When moving further offshore, there is an increase in the capacity of wind power. Generating power from renewable resources is enhanced through the extraction of wind energy from an offshore deep-water wind resource. Mounting the turbine on a platform that is not stable brings another difficulty to wind turbine modeling. There is a need to introduce platforms that are more effective to capture this energy, because of the complex dynamics and control of these platforms. This paper highlights the historical developments and progresses in the design of different types of offshore floating wind turbine platforms needed for harvesting the energy from offshore winds. The relative advantages and disadvantages of the platform types with the design challenges are discussed. The major types of floating platforms included in this study are tension leg platform (TLP) type, spar type, and semisubmersible type. This study reviews the previous work on the dynamics of the floating platforms for a single turbine and multiple turbines under various operating environmental conditions. The numerical methods to analyze the aerodynamics of the wind turbine and hydrodynamics of floating platforms are discussed in this paper. This paper also investigates the performance of analytical wake loss models of Jensen, Larsen, and Frandsen that can provide guidelines for using these wake models in future applications. There are still a lot of challenges that need to be addressed to study the accurate behavior of floating platforms operating under combined wind–wave environmental conditions. With the current technological advancements, the offshore floating multi-turbine platform can be a potential solution to harness the abundant offshore wind resource. Based on this literature review, recommendations for future work are suggested.
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Makarov, Vladimir, Gennadii Boiarskikh, Nikolai Makarov, German Dyldin, and Aleksandr Ugolnikov. "Turbomachine criteria for similarity of natural size proportionality." Izvestiya vysshikh uchebnykh zavedenii Gornyi zhurnal 1, no. 8 (December 21, 2020): 81–89. http://dx.doi.org/10.21440/0536-1028-2020-8-81-89.
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Introduction. It is possible to give rise to synergy as a result of science-intensive industries combination with innovative eco-technologies for subsoil use only by developing a brand new approach to nature-like auxiliary technologies. Insufficient adaptability of turbomachines that ensure industrial safety increases the production cost of the mining and oil and gas complexes of the Russian Federation by more than 15%, reducing its competitiveness. Research methodology. Based on the hypothesis of the hydrodynamic analogy of the mechanisms of deceleration of the flow around the airfoil and the formation of its profile resistance, Karman's theory of attached and free vortices, the Zhukovsky-Chaplygin-Kutta hypothesis, the method of conformal transformations, the theory of similarity, the method of singular points by Chaplygin S. A., the criteria for the similarity of natural proportionality are obtained, that is, for the hydrodynamic similarity of the mechanism of energy interaction between the blades of the turbomachine impeller and the wing of a bird. Results. It has been proved that the dominant control over the nature-like proportionality of the aerodynamics of turbomachines is the ratio between the speed and flow acceleration circulation around the airfoil. It has been established that the coefficients of the airfoil resistance, lift and aerodynamic quality of the airfoil cascade are hydrodynamic analogs of the coefficients of the circulation of the velocity and acceleration of the flow and their ratio. Conclusions. It has been experimentally confirmed that the use of the proposed criterion of natural proportionality in the design of turbomachines increases their coefficient of aerodynamic adaptability by more than 2 times, increasing the area of economical operation by 83%.
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Manolas, Dimitris I., Vasilis A. Riziotis, George P. Papadakis, and Spyros G. Voutsinas. "Hydro-Servo-Aero-Elastic Analysis of Floating Offshore Wind Turbines." Fluids 5, no. 4 (November 5, 2020): 200. http://dx.doi.org/10.3390/fluids5040200.
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A fully coupled hydro-servo-aero-elastic simulator for the analysis of floating offshore wind turbines (FOWTs) is presented. All physical aspects are addressed, and the corresponding equations are concurrently solved within the same computational framework, taking into account the wind and wave excitations, the aerodynamic response of the rotor, the hydrodynamic response of the floater, the structural dynamics of the turbine-floater-mooring lines assembly and finally the control system of the wind turbine. The components of the complex multi-physics system of a FOWT interact with each other in an implicitly coupled manner leading to a holistic type of modeling. Different modeling options, of varying fidelity and computational cost, are made available with respect to rotor aerodynamics, hydrodynamic loading of the floater and mooring system dynamics that allow for timely routine certification simulations, but also for computationally intense simulations of less conventional operating states. Structural dynamics is based on nonlinear multibody analysis that allows reproducing the large rigid body motions undergone by the FOWT, as well as large deflections and rotations of the highly flexible blades. The paper includes the description of the main physical models, of the interaction and solution strategy and representative results. Verification is carried out by comparing with other state-of-art tools that participated in the Offshore Code Comparison Collaboration Continuation (OC4) IEA Annex, while the advanced simulation capabilities are demonstrated in the case of half-wake interaction of floating wind turbines by employing the free-wake aerodynamic method.
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Huang, Yang, and Decheng Wan. "Investigation of Interference Effects Between Wind Turbine and Spar-Type Floating Platform Under Combined Wind-Wave Excitation." Sustainability 12, no. 1 (December 27, 2019): 246. http://dx.doi.org/10.3390/su12010246.
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In order to further understand the coupled aero-hydrodynamic performance of the floating offshore wind turbine (FOWT) in realistic ocean environment, it is necessary to investigate the interference effects between the unsteady aerodynamics of the wind turbine and different degree-of-freedom (DOF) platform motions under combined wind-wave excitation. In this paper, a validated CFD analysis tool FOWT-UALM-SJTU with modified actuator line model is applied for the coupled aero-hydrodynamic simulations of a spar-type FOWT system. The aero-hydrodynamic characteristics of the FOWT with various platform motion modes and different wind turbine states are compared and analyzed to explore the influence of the interference effects between the wind turbine and the floating platform on the performance of the FOWT. The dynamic responses of local relative wind speed and local attack angle at the blade section and wind-wave forces acting on the floating platform are discussed in detail to reveal the interaction mechanism between the aerodynamic loads and different DOF platform motions. It is shown that the surge motion and the pitch motion of the floating platform both significantly alter the local attack angle, while only the platform pitch motion have significant impacts on the local relative wind speed experienced by the rotating blades. Besides, the shaft tilt and the pro-cone angle of the wind turbine and the height-dependent wind speed all contribute to the variation of the local attack angle. The coupling between the platform motions along different DOFs is obviously amplified by the aerodynamic forces derived from the wind turbine. In addition, the wake deflection phenomenon is clearly observed in the near wake region when platform pitch motion is considered. The dynamic pitch motion of the floating platform also contributes to the severe wake velocity deficit and the increased wake width.
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Tamada, Chandan Varma, and Sai Ganesh Sabbavarapu. "Flow Visualization of Footballs to Analyze the Factors Affecting their Aerodynamic Performance Using CFD." Volume 5 - 2020, Issue 9 - September 5, no. 9 (September 23, 2020): 460–75. http://dx.doi.org/10.38124/ijisrt20sep296.
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The motion of a football in air is influenced by the combination of various aerodynamic effects caused by the parameters such as velocity, surface roughness, panel orientation and shape. This paper analyzes the individual and combined effects of these parameters on the flight characteristics of various footballs using CFD Analysis. Four balls, a smooth sphere, a 32-panel conventional football, 14-panel Teamgeist and 6-panel Brazuca ball are subjected to different velocities of air flow over them, both in the laminar and turbulent regime, different surface roughness values and the influence of these parameters on the aerodynamics of the balls is evaluated by the drag force, drag coefficient and hydrodynamic boundary layer separation angle. The effect of the seam length, number of panels and panel orientation are also compared. The results of these effects are discussed later in the paper and are used to explain the knuckling effects and unpredictable trajectory of the Jabulani ball.
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Roddier, Dominique, and Joshua Weinstein. "Floating Wind Turbines." Mechanical Engineering 132, no. 04 (April 1, 2010): 28–32. http://dx.doi.org/10.1115/1.2010-apr-2.
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This article discusses the functioning of floating wind turbines. The engineering requirements for the design of floating offshore wind turbines are extensive. Wind turbine design tools usually consist of an aerodynamic model (for flow around the blades) coupled with a structural code. Aero-elastic models used in the design of fixed turbines calculate all the necessary loading parameters, from turbine thrust and power generation, to blade and tower deflections. The design of floating structures usually involves hydrodynamics tools such as WAMIT Inc.’s software for studying wave interactions with vessels and platforms, or Principia’s DIODORE, to predict the hydrodynamic quantities, such as added mass, damping and wave exciting forces, which are used as a kernel in the time domain simulations. In marine projects, design tools typically need to be validated against model tests in a wave tank or basin. Such work is performed frequently, and scaling laws are very well defined.
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Xiao, H., and D. H. Wang. "Rarefied airfoil aerodynamics based on the generalized hydrodynamic model." Aerospace Science and Technology 92 (September 2019): 148–55. http://dx.doi.org/10.1016/j.ast.2019.06.002.
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Guo, Yang, Dongli Ma, Muqing Yang, and Xing’an Liu. "Numerical Analysis of the Take-Off Performance of a Seaplane in Calm Water." Applied Sciences 11, no. 14 (July 13, 2021): 6442. http://dx.doi.org/10.3390/app11146442.
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Nowadays, with the escalating tensions in maritime dispute and the development of marine economy, there has been renewed interest in seaplanes for their special capacity of taking off and landing on water. Prediction of take-off performance, involving aerodynamic analysis and hydrodynamic analysis, is a main challenge in seaplane design, while the prediction methods have been little improved since the 1960s. This paper aims to investigate the attitude and resistance characteristics of a seaplane at different speeds during the take-off by numerically modeling the air-water flow field using RANS equations with VOF method. The trim and heave motion of seaplane in response to aerodynamic forces, hydrodynamic forces, hydrostatic forces, and propeller thrust was realized by solving rigid body dynamics equations and adopting dynamic overset mesh technique. The variations in heave, trim angle, and resistance characteristics during the takeoff were investigated, and their inherent relationships with the aerodynamic, hydrodynamic, and hydrostatic performance were revealed. Particular investigation on the hydrodynamic resistance indicates that the stagnation line located at the convex bow would contribute a considerable increase of pressure resistance at the first hump, and the trim angel of a seaplane should be operated in an optimum trim range, typical between 4–6 deg, to minimize the hydrodynamic resistance at the second hump. Additionally, the dynamic motion convergence study proves that the utilization of damping terms was an effective way to accelerate the convergence of the dynamic motion ending with a quasi-static state.
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Bielek, Boris, Daniel Szabó, Milan Palko, and Monika Rychtáriková. "Optimisation of Design of Air Inlets in Air Distribution Channels of a Double-Skin Transparent Façade." Slovak Journal of Civil Engineering 25, no. 4 (December 20, 2017): 1–11. http://dx.doi.org/10.1515/sjce-2017-0017.
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Abstract This paper reports on an optimization of design of air inlets in naturally ventilated double-skin transparent facades; the design aims at the proper functioning of these facades from the point of view of their aerodynamic and hydrodynamic behaviour. A comparison was made of five different variants of ventilation louvers used in air openings with different shapes, positions and overall geometry. The aerodynamic response of the louvers was determined by 2D simulations using ANSYS software. The hydrodynamic properties were investigated by conducting driven-rain measurements in a large rain chamber at the Slovak University of Technology in Bratislava.
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Collu, Maurizio, Minoo H. Patel, and Florent Trarieux. "The longitudinal static stability of an aerodynamically alleviated marine vehicle, a mathematical model." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 466, no. 2116 (December 2, 2009): 1055–75. http://dx.doi.org/10.1098/rspa.2009.0459.
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An assessment of the relative speeds and payload capacities of airborne and waterborne vehicles highlights a gap that can be usefully filled by a new vehicle concept, utilizing both hydrodynamic and aerodynamic forces. A high-speed marine vehicle equipped with aerodynamic surfaces is one such concept. In 1904, Bryan & Williams (Bryan & Williams 1904 Proc. R. Soc. Lond. 73 , 100–116 (doi:10.1098/rspl.1904.0017)) published an article on the longitudinal dynamics of aerial gliders, and this approach remains the foundation of all the mathematical models studying the dynamics of airborne vehicles. In 1932, Perring & Glauert (Perring & Glauert 1932 Reports and Memoranda no. 1493) presented a mathematical approach to study the dynamics of seaplanes experiencing the planing effect. From this work, planing theory has developed. The authors propose a unified mathematical model to study the longitudinal stability of a high-speed planing marine vehicle with aerodynamic surfaces. A kinematics framework is developed. Then, taking into account the aerodynamic, hydrostatic and hydrodynamic forces, the full equations of motion, using a small perturbation assumption, are derived and solved specifically for this concept. This technique reveals a new static stability criterion that can be used to characterize the longitudinal stability of high-speed planing vehicles with aerodynamic surfaces.
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Pegalajar-Jurado, Antonio, Michael Borg, and Henrik Bredmose. "An efficient frequency-domain model for quick load analysis of floating offshore wind turbines." Wind Energy Science 3, no. 2 (October 16, 2018): 693–712. http://dx.doi.org/10.5194/wes-3-693-2018.
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Abstract. A model for Quick Load Analysis of Floating wind turbines (QuLAF) is presented and validated here. The model is a linear, frequency-domain, efficient tool with four planar degrees of freedom: floater surge, heave, pitch and first tower modal deflection. The model relies on state-of-the-art tools from which hydrodynamic, aerodynamic and mooring loads are extracted and cascaded into QuLAF. Hydrodynamic and aerodynamic loads are pre-computed in WAMIT and FAST, respectively, while the mooring system is linearized around the equilibrium position for each wind speed using MoorDyn. An approximate approach to viscous hydrodynamic damping is developed, and the aerodynamic damping is extracted from decay tests specific for each degree of freedom. Without any calibration, the model predicts the motions of the system in stochastic wind and waves with good accuracy when compared to FAST. The damage-equivalent bending moment at the tower base is estimated with errors between 0.2 % and 11.3 % for all the load cases considered. The largest errors are associated with the most severe wave climates for wave-only conditions and with turbine operation around rated wind speed for combined wind and waves. The computational speed of the model is between 1300 and 2700 times faster than real time.
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Fu, S. C., R. M. C. So, and W. W. F. Leung. "A Discrete Flux Scheme for Aerodynamic and Hydrodynamic Flows." Communications in Computational Physics 9, no. 5 (May 2011): 1257–83. http://dx.doi.org/10.4208/cicp.311009.241110s.
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AbstractThe objective of this paper is to seek an alternative to the numerical simulation of the Navier-Stokes equations by a method similar to solving the BGK-type modeled lattice Boltzmann equation. The proposed method is valid for both gas and liquid flows. A discrete flux scheme (DFS) is used to derive the governing equations for two distribution functions; one for mass and another for thermal energy. These equations are derived by considering an infinitesimally small control volume with a velocity lattice representation for the distribution functions. The zero-order moment equation of the mass distribution function is used to recover the continuity equation, while the first-order moment equation recovers the linear momentum equation. The recovered equations are correct to the first order of the Knudsen number(Kn);thus, satisfying the continuum assumption. Similarly, the zero-order moment equation of the thermal energy distribution function is used to recover the thermal energy equation. For aerodynamic flows, it is shown that the finite difference solution of the DFS is equivalent to solving the lattice Boltzmann equation (LBE) with a BGK-type model and a specified equation of state. Thus formulated, the DFS can be used to simulate a variety of aerodynamic and hydrodynamic flows. Examples of classical aeroacoustics, compressible flow with shocks, incompressible isothermal and non-isothermal Couette flows, stratified flow in a cavity, and double diffusive flow inside a rectangle are used to demonstrate the validity and extent of the DFS. Very good to excellent agreement with known analytical and/or numerical solutions is obtained; thus lending evidence to the DFS approach as an alternative to solving the Navier-Stokes equations for fluid flow simulations.
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Chemezov, Denis Alexandrovich, and Tatyana Vladimirovna Lukyanova. "AERODYNAMIC AND HYDRODYNAMIC FLOW PARAMETERS OF GASES AND LIQUIDS." Theoretical & Applied Science 57, no. 01 (January 30, 2018): 101–7. http://dx.doi.org/10.15863/tas.2018.01.57.18.
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Knyaz, V. A., D. G. Stepaniants, E. V. Ippolitov, and M. M. Novikov. "OPTICAL 3D MEASUREMENTS IN HYDRODYNAMIC TUNNEL FOR AIRCRAFT ICING STUDY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2020 (August 12, 2020): 963–68. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2020-963-2020.
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Abstract. The study of how aircraft icing influences on aircraft aerodynamic performance is very important for developing measures and recommendation to improve aircraft flight safety. The effective method of aerodynamic processes modeling is experiment in wind (aerodynamic) tunnel or water (hydrodynamic) tunnel. They allow to perform experiments with a scaled model of an aircraft affected by icing and to visualize the wing flow process and changes caused by icing. While visualization of the wing flow yields useful qualitative information about flow, it is more important to retrieve quantitative 3D data of flow, which allows to forecast icing process and to develop anti-icing techniques and recommendations.The presented study addresses to creating an photogrammetric system and 3D measurement techniques for quantitate evaluation of 3D flow parameters in a hydrodynamic tunnel for aircraft icing influence exploration. Being an initial part of a long-term research project, this study is aimed at developing of an accurate calibration technique of the photogrammetric system for 3D measurement in condition of two optical media interfaces. The developed algorithms for imaging process through two optical media interfaces are used in calibration procedure and object 3D coordinates measuring. The results of the photogrammetric system calibration are given in comparison with standard (single media) case. Experimental 3D reconstruction of a typical object demonstrated high accuracy of the developed algorithms.
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Wu, Yao, Lihua Yang, Tengfei Xu, and Wei Wu. "Thermo-Elasto-Hydrodynamic Characteristics Analysis of Journal Microbearing Lubricated with Rarefied Gas." Micromachines 11, no. 11 (October 22, 2020): 955. http://dx.doi.org/10.3390/mi11110955.
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Temperature rise and elastic deformation are unavoidable issues occurring in high-speed gas microbearings due to the dominant small-scale fluid dynamics in rarefied gas flow applications. In this paper, thermo-elasto-aerodynamic analysis requires simultaneously solving the modified Reynolds equation, modified energy equation, temperature–viscosity relationship and the elasticity equations for predicting the lubrication characteristics of microbearings. A thermo-elasto-aerodynamic lubrication is systematically investigated by using the partial derivative method, finite difference formulation and the finite element approach. The results indicate that, compared with rigid microbearing which has a constant viscosity gas lubricant, the temperature effect increases the load capacity, friction coefficient and stiffness coefficients, and it decreases the attitude angle and damping coefficients of the microbearing. The flexibility of the bearing pad also leads to the increase in load capacity and direct stiffness coefficients, while it remains to further decrease the direct damping coefficients on the basis of thermo-aerodynamic performance. The present study is conducive to accurately analyze the microscopic flow properties in a microbearing-rotor system.
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Nangia, R. K. "Aerodynamic and hydrodynamic aspects of high-speed water surface craft." Aeronautical Journal 91, no. 906 (July 1987): 241–68. http://dx.doi.org/10.1017/s0001924000021345.
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Summary High speeds on water are being attained in racing sport and in attempts on world speed records in various classes. Success, safety and stability of these craft depends upon the favourable interaction of their aerodynamic and hydrodynamic characteristics under the influence of two media, one about 800 times denser than the other. Speed on the straight course and in turns is important. As its velocity increases, a craft experiences increasing dynamic pressure in water and to maintain the balance, the ‘wetted’ area of the craft reduces as it rises up (‘planing’). Modern fast craft have ‘tunnel-hulls’ and lifting areas to generate aerodynamic lift and to assist the craft to attain planing attitudes rapidly. The ‘lifting’ areas may not necessarily be in the correct locations however. An example often seen is that of a power boat riding virtually on its propeller and ‘wallowing’ in an unstable manner. In this case the variation in riding height alters the relative positions of centres of aero- and hydro-lift such that the ‘stability-margins’ are near critical in both the longitudinal and the lateral sense.
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Lai, Tianwei, Yu Guo, Wei Wang, Yu Wang, and Yu Hou. "Development and Application of Integrated Aerodynamic Protuberant Foil Journal and Thrust Bearing in Turboexpander." International Journal of Rotating Machinery 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/8430943.
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Foil bearing provides compliant support and moderate Coulomb friction for rotor-bearing system, which is conducive to stability and reliability of high speed rotating machinery. In this paper, both hydrodynamic lubricated foil journal and foil thrust bearings are applied in a 150 m3·h−1 turboexpander for air separation. In the bearings, protuberant foil is chosen as the supporting subfoil due to its merits of easy fabrication and assembly. Static loading and deflection of the bearings are tested, respectively, before integration into the turboexpander. Afterwards, the loading and deflection curves of the journal and thrust bearings are polynomial fitted using least-square method. Then, performance tests are carried out on the rotor-bearing system, including transient speed-up, high speed, and speed-down processes. In the tests, the turboexpander supported by the hydrodynamic foil bearings operates smoothly with repeatability. Maximal rotor speed of the turboexpander reaches 52000 rpm with hydrodynamic lubricated protuberant foil bearings.
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Wu, Ming. "Modeling and Simulation on the Gas/Water Two-Phase Ballistics of Trans-Media Aircraft." Applied Mechanics and Materials 743 (March 2015): 66–70. http://dx.doi.org/10.4028/www.scientific.net/amm.743.66.
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The trans-media aircraft is the new concept amphibious aircraft, which has been affect by aerodynamic force and hydrodynamic force, and kinetics of it are different from the normal aircraft and planning boat. Based on the aerodynamic and the theory of planning, this paper presents a bouncing vehicle shape base on the shape of hydroskimmer, uses the ALE method to study the skipping. Emphatically analyzed the influence factors of vehicle bounce and movement characteristics. It gives theoretical foundation and study tools for the conceptual design of trans-media, ballistics design optimization and flight stability assessment.
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Zeraatgar, Hamid, Ali Bakhshandeh Rostami, Abolfazl Nazari, and Abolfazl Nazari. "A study on performance of planing-wing hybrid craft." Polish Maritime Research 19, no. 4 (December 1, 2012): 16–22. http://dx.doi.org/10.2478/v10012-012-0036-0.
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ABSTRACT A hybrid craft is defined as a combination of different lifting surfaces. The lift force can be of aerodynamic or hydrodynamic character. This research deals with the conditions of using planing mono-hulls equipped with a couple of wings, called planing-wing hybrid craft. A parametric study is conducted by using Vortex Lattice Method to determine feasibility of using an aerodynamic wing mounted to planing craft. It has been determined that the wing area should be more than twice as much as the wetted surface of the craft, to get an effective wing for planing craft. Furthermore, the wing should be so designed as to obtain its high aspect ratio. Maximum lift force contribution resulting from different wing configurations considered in this study is less than 35 percent of the total hydrodynamic lift force at an arbitrary condition. On this basis it may be concluded that the wing may be effectively used only in special conditions, hence this is not recommended for general application.
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le Roux, J. P. "Relationship between aerodynamic entrainment threshold and hydrodynamic settling velocity of particles." Sedimentary Geology 109, no. 1-2 (March 1997): 199–205. http://dx.doi.org/10.1016/s0037-0738(96)00038-3.
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Matveev, Konstantin I., and Nikolai Kornev. "Dynamics and Stability of Boats With Aerodynamic Support." Journal of Ship Production and Design 29, no. 01 (February 1, 2013): 17–24. http://dx.doi.org/10.5957/jspd.2013.29.1.17.
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Aerodynamic support is beneficial for achieving very high speeds of marine transportation. Wing-in-ground vehicles, power-augmented ram platforms, and ultrafast planing multihulls are examples of marine craft with air assistance. The main technical problems in the development and application of these concepts for marine transportation are to ensure motion stability and to provide adequate seaworthiness. In this article, we illustrate applications of several mathematical models for various air supported marine vehicle concepts and discuss their specific stability issues. The aerodynamic submodels are based on nonlinear vortex-lattice methods and on the extreme ground effect theory, whereas unsteady hydrodynamics of planing surfaces are treated with added-mass strip theories. The static and dynamic stability in the vicinity of equilibrium states can be analyzed by linearized approaches. However, motions in transient regimes and unsteady environments require implementation of nonlinear and fully unsteady modeling methods.
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Wang, Xiao Qin. "Noise Influence of High-Speed Train Based on Air Dynamics." Applied Mechanics and Materials 687-691 (November 2014): 265–69. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.265.
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How to control aerodynamic noise of high speed motor train, this paper starts from the basic theory of hydrodynamics and acoustics, it adopts method of numerical simulation and applies Fluent and VirtuaUab Acousticsand software to make study on characteristics of aerodynamic noise for high speed motor train, the test results indicates that in the stable flow distribution, the baric gradient is relatively larger when its surface pressure is in area with large change in curve curvature, when it is in the area with even curve change, the baric gradient is relatively smaller. In different gradient, the train head, the maximum pressure and the maximum negative pressure ratio of air-conditioner air deflector predicate are in proportion to the square of train speed.
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Granier, B., J. M. Badie, M. Announ, and P. Snabre. "Aerodynamic levitation of stainless steel spheres in Argon plasma jet Part I: Hydrodynamics." High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes) 5, no. 4 (2001): 7. http://dx.doi.org/10.1615/hightempmatproc.v5.i4.10.
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Qiu, Liangjun, and Wenbin Song. "Efficient Decoupled Hydrodynamic and Aerodynamic Analysis of Amphibious Aircraft Water Takeoff Process." Journal of Aircraft 50, no. 5 (September 2013): 1369–79. http://dx.doi.org/10.2514/1.c031846.
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Jiaqiang, Zhang, Hu Junhua, Xie Qifeng, Feng Jinfu, and Xu Hu. "Research on Aerodynamic and Hydrodynamic Performance of Conformal Semi-Ring Wing Configuration." Procedia Engineering 29 (2012): 3100–3104. http://dx.doi.org/10.1016/j.proeng.2012.01.448.
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Ma, Dongli, Zhi Li, Muqing Yang, Yang Guo, and Haode Hu. "Sea-unammned aerial vehicle takeoff characteristics analysis method based on approximate equilibrium hypothesis." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 3 (January 3, 2018): 916–27. http://dx.doi.org/10.1177/0954410017751765.
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In this paper, transient multiphase flow computational fluid dynamics simulations based on volume of fluid model are conducted for a sea-unmanned aerial vehicle. The approximate equilibrium hypothesis is implemented after estimating the acceleration in the vertical direction. The complete configuration model and hull model are employed in simulation to predict the aerodynamic and hydrodynamic forces separately for different demands of aerodynamic and hydrodynamic computational fluid dynamics predictions and computing efficiency. In takeoff characteristics analysis, the computational fluid dynamics simulations are conducted as inputs for piecewise interpolation method. The calculated results show that the sea-unmanned aerial vehicle takeoff characteristics are totally different from a conventional aircraft. The drag-peak at hump speed is the obvious feature of the sea-unmanned aerial vehicle/seaplane. In most cases, if a sea-unmanned aerial vehicle will takeoff successfully as long as it can pass the drag peak. The takeoff distance and time calculated by piecewise interpolation method match the experimental data within 7% deviation. The accuracy is acceptable for conceptual design stage of a sea-unmanned aerial vehicle/seaplane. The results are applicable to consultation in choosing takeoff field or choosing powerplant.
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Knyaz, V. A., E. V. Ippolitov, and M. M. Novikov. "3D RECONSTRUCTION OF ICE SHAPE USING VISIBLE AND THERMAL RANGE IMAGING FOR AIRCRAFT ICING STUDY." International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2021 (June 28, 2021): 527–32. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2021-527-2021.
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Abstract. Aircraft icing is one of the main factors decreasing the flight safety. Qualitative and quantitative understanding of the icing process is crucially needed for developing anti-icing measures and safety recommendations. Changes in aerodynamic characteristics of aircraft caused by changes in shape of aircraft surfaces due to the ice accretion can lead to significant aerodynamic performance degradation. So the reliable and accurate information of how the shape of the ice accretion influences on aerodynamic characteristics is a key point for predicting the changes in aerodynamic performance.The study addresses to a problem of accurate shape measuring of ice accretion for further experimental study of iced-aircraft aerodynamic in a hydrodynamic tunnel. For this purpose the evaluation of various techniques of ice 3D measurements is performed that include as visible so thermal imaging of ice accretion. The results of evaluation serves for the decision of preferable technique to be used in experimental study. Also the framework is developed for creating physical models of iced aircraft based on result of real ice accretion shape measurement. It allows to produce stereolithography (SLA) copies of of an aircraft under icing condition for different levels of icing. These SLA-models of an aircraft under icing condition are then used for flow behaviour study in order to identify critical flying condition.
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Hou, Guoqiang, Hua Su, Guoding Chen, and Yuhai Tian. "Performance analysis of compliant cylindrical intershaft seal." Science Progress 103, no. 3 (July 2020): 003685042094195. http://dx.doi.org/10.1177/0036850420941957.
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To improve the intershaft seal performance of the dual-rotor turbofan engine and extend the life of the intershaft seal, a compliant cylindrical aerodynamic intershaft seal structure is proposed, which avoids the problem of leakage increase after tooth wear of intershaft labyrinth seal. According to the proposed seal structure, the force condition of the floating seal ring is analyzed, and an aeroelastic coupling method for the floating seal ring eccentricity is presented. And the leakage characteristics, with different seal structures and operating conditions are calculated and compared when the two rotors are under homodromy/counter-rotating condition. The results show that, for the dual-rotor cylindrical hydrodynamic gas film seal, the hydrodynamic effect under homodromy condition is enhanced greatly while the hydrodynamic effect is significantly weakened under counter-rotating condition; the rotational direction of rotors, seal width, rotor circular precession eccentricity, rotational speed and rotor radius all have pronounced influence on the seal performance. For the application of hydrodynamic form of compliant cylindrical intershaft seal, the seal performance under homodromy condition is better than that under counter-rotating condition.
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Matveev, Konstantin I. "Aero-Hydrodynamic Aspects of Power-augmented Ram Wings." Journal of Ship Research 57, no. 02 (June 1, 2013): 86–97. http://dx.doi.org/10.5957/jsr.2013.57.2.86.
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The subject of this article is the two-dimensional interaction of air and water flows under a power-augmented ram wing. The extreme ground effect theory is applied for the air flow, whereas the water flow is treated with a linearized model based on a method of hydrodynamic singularities. Calculated aerodynamic characteristics of power-augmented ram platforms and water surface deformations at moderate and high Froude numbers are presented for a horizontal plate with a flap, a trimmed plate without a flap, and an S-shaped profile. Additionally, plates in contact with water are modeled. The transition from airborne to waterborne states is accompanied by drastic variations of the lift and center of pressure. It is found that solutions can be nonunique when the plate trailing edge is very close to the water surface.
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Van Wassenbergh, S., K. van Manen, T. A. Marcroft, M. E. Alfaro, and E. J. Stamhuis. "Boxfish swimming paradox resolved: forces by the flow of water around the body promote manoeuvrability." Journal of The Royal Society Interface 12, no. 103 (February 2015): 20141146. http://dx.doi.org/10.1098/rsif.2014.1146.
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The shape of the carapace protecting the body of boxfishes has been attributed an important hydrodynamic role in drag reduction and in providing automatic, flow-direction realignment and is therefore used in bioinspired design of cars. However, tight swimming-course stabilization is paradoxical given the frequent, high-performance manoeuvring that boxfishes display in their spatially complex, coral reef territories. Here, by performing flow-tank measurements of hydrodynamic drag and yaw moments together with computational fluid dynamics simulations, we reverse several assumptions about the hydrodynamic role of the boxfish carapace. Firstly, despite serving as a model system in aerodynamic design, drag-reduction performance was relatively low compared with more generalized fish morphologies. Secondly, the current theory of course stabilization owing to flow over the boxfish carapace was rejected, as destabilizing moments were found consistently. This solves the boxfish swimming paradox: destabilizing moments enhance manoeuvrability, which is in accordance with the ecological demands for efficient turning and tilting.
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Schlegel, Michael, Bernd R. Noack, Peter Jordan, Andreas Dillmann, Elmar Gröschel, Wolfgang Schröder, Mingjun Wei, Jonathan B. Freund, Oliver Lehmann, and Gilead Tadmor. "On least-order flow representations for aerodynamics and aeroacoustics." Journal of Fluid Mechanics 697 (March 16, 2012): 367–98. http://dx.doi.org/10.1017/jfm.2012.70.
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AbstractWe propose a generalization of proper orthogonal decomposition (POD) for optimal flow resolution of linearly related observables. This Galerkin expansion, termed ‘observable inferred decomposition’ (OID), addresses a need in aerodynamic and aeroacoustic applications by identifying the modes contributing most to these observables. Thus, OID constitutes a building block for physical understanding, least-biased conditional sampling, state estimation and control design. From a continuum of OID versions, two variants are tailored for purposes of observer and control design, respectively. Firstly, the most probable flow state consistent with the observable is constructed by a ‘least-residual’ variant. This version constitutes a simple, easily generalizable reconstruction of the most probable hydrodynamic state to preprocess efficient observer design. Secondly, the ‘least-energetic’ variant identifies modes with the largest gain for the observable. This version is a building block for Lyapunov control design. The efficient dimension reduction of OID as compared to POD is demonstrated for several shear flows. In particular, three aerodynamic and aeroacoustic goal functionals are studied: (i) lift and drag fluctuation of a two-dimensional cylinder wake flow; (ii) aeroacoustic density fluctuations measured by a sensor array and emitted from a two-dimensional compressible mixing layer; and (iii) aeroacoustic pressure monitored by a sensor array and emitted from a three-dimensional compressible jet. The most ‘drag-related’, ‘lift-related’ and ‘loud’ structures are distilled and interpreted in terms of known physical processes.
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Dmitriev, S. M., A. V. Gerasimov, A. A. Dobrov, D. V. Doronkov, A. N. Pronin, A. V. Ryazanov, D. N. Solntsev, and A. E. Khrobostov. "Investigation of Coolant Local Hydrodynamics in the Mixed Core of the VVER Reactor." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 63, no. 2 (March 27, 2020): 151–62. http://dx.doi.org/10.21122/1029-7448-2020-63-2-151-162.
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The article presents the results of experimental studies of the local hydrodynamics of the coolant flow in the mixed core of the VVER reactor, consisting of the TVSA-T and TVSA-T mod.2 fuel assemblies. Modeling of the flow of the coolant flow in the fuel rod bundle was carried out on an aerodynamic test stand. The research was carried out on a model of a fragment of a mixed core of a VVER reactor consisting of one TVSA-T segment and two segments of the TVSA-T.mod2. The flow pressure fields were measured with a five-channel pneumometric probe. The flow pressure field was converted to the direction and value of the coolant velocity vector according to the dependencies obtained during calibration. To obtain a detailed data of the flow, a characteristic cross-section area of the model was selected, including the space cross flow between fuel assemblies and four rows of fuel rods of each of the TVSA fuel assemblies. In the framework of this study the analysis of the spatial distribution of the projections of the velocity of the coolant flow was fulfilled that has made it possible to pinpoint regularities that are intrinsic to the coolant flowing around spacing, mixing and combined spacing grates of the TVSA. Also, the values of the transverse flow of the coolant caused by the flow along hydraulically nonidentical grates were determined and their localization in the longitudinal and cross sections of the experimental model was revealed. Besides, the effect of accumulation of hydrodynamic flow disturbances in the longitudinal and cross sections of the model caused by the staggered arrangement of hydraulically non-identical grates was determined. The results of the study of the coolant cross flow between fuel assemblies interaction, i.e. between the adjacent TVSA-T and TVSA-T mod.2 fuel assemblies were adopted for practical use in the JSC of “Afrikantov OKB Mechanical Engineering” for assessing the heat engineering reliability of VVER reactor cores; also, they were included in the database for verification of computational hydrodynamics programs (CFD codes) and for detailed cell-based calculation of the reactor core.
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Jiang, Yichen, Guanqing Hu, Zhi Zong, Li Zou, and Guoqing Jin. "Influence of an Integral Heave Plate on the Dynamic Response of Floating Offshore Wind Turbine Under Operational and Storm Conditions." Energies 13, no. 22 (November 22, 2020): 6122. http://dx.doi.org/10.3390/en13226122.
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The hydrodynamic performance of the floating foundation for offshore wind turbines is essential to its stability and energy harvesting. A semi-submersible platform with an integral heave plate is proposed in order to reduce the vertical motion responses. In this study, we compare the heave, pitch, and roll free decay motions of the new platform with a WindFloat-type platform based on Reynolds-Averaged Navier-Stokes simulations. The differences of the linear and quadratic damping properties between these platforms are revealed. Then, a FAST (Fatigue, Aerodynamics, Structures, and Turbulence) model with the consideration of fluid viscosity effects is set up to investigate the performance of the new platform under storm and operational conditions. The time-domain responses, motion spectra, and the mooring-tension statistics of these two platforms are evaluated. It is found that the integral heave plate can increase the viscous hydrodynamic damping, significantly decrease the heave and pitch motion responses, and increase the safety of the mooring cables, especially for the storm condition.
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FRANCIS, LISBETH. "Sailing Downwind: Aerodynamic Performance of the Velella Sail." Journal of Experimental Biology 158, no. 1 (July 1, 1991): 117–32. http://dx.doi.org/10.1242/jeb.158.1.117.
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Using a wind tunnel built over a shallow pool and methods devised for measuring the performance of yacht sails, I describe aerodynamic performance in situ for the sailor-by-the-wind, Velella velella. By contrast with designers of the modern yacht mainsail, natural selection has apparently favored stability and seaworthiness over performance to windward. The Velella sail is a low aspect ratio airfoil with an unusually flat polar plot. Primarily a drag-based locomotory structure, this thin, leaf-like sail generates maximum force when oriented at attack angles between 50° and 90°. In the wind tunnel, free-sailing animals spontaneously assumed stable orientations at attack angles ranging from 28° to 87° and sailed with their hulls approximately broadside to the apparent flow of oncoming water. At these angles, aerodynamic force on the sail is asymmetrical, with the center of pressure upwind of the sail midline. Since aerodynamic force on the sail is balanced at equilibrium by hydrodynamic force on the hull, this orientation must be caused by asymmetrical forces acting on surface and underwater parts as the wind drags the animal along the surface of the water.
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Vartak, Richa, Suyash M. Patil, Aishwarya Saraswat, Manali Patki, Nitesh K. Kunda, and Ketan Patel. "Aerosolized nanoliposomal carrier of remdesivir: an effective alternative for COVID-19 treatment in vitro." Nanomedicine 16, no. 14 (June 2021): 1187–202. http://dx.doi.org/10.2217/nnm-2020-0475.
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Aim: To formulate an aerosolized nanoliposomal carrier for remdesivir (AL-Rem) against coronavirus disease 2019. Methods: AL-Rem was prepared using modified hydration technique. Cytotoxicity in lung adenocarcinoma cells, stability and aerodynamic characteristics of developed liposomes were evaluated. Results: AL-Rem showed high encapsulation efficiency of 99.79%, with hydrodynamic diameter of 71.46 ± 1.35 nm and surface charge of -32 mV. AL-Rem demonstrated minimal cytotoxicity in A549 cells and retained monolayer integrity of Calu-3 cells. AL-Rem showed sustained release, with complete drug release obtained within 50 h in simulated lung fluid. Long-term stability indicated >90% drug recovery at 4°C. Desirable aerosol performance, with mass median aerodynamic diameter of 4.56 ± 0.55 and fine particle fraction of 74.40 ± 2.96%, confirmed successful nebulization of AL-Rem. Conclusion: AL-Rem represents an effective alternative for coronavirus disease 2019 treatment.
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Daniel, Mathews, and Jeetu S Babu. "Equilibrium Molecular Dynamics Investigation of Fluid Slip in Nanoscale Channels." International Journal of Engineering & Technology 7, no. 3.27 (August 15, 2018): 8. http://dx.doi.org/10.14419/ijet.v7i3.27.17641.
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Interfacial hydrodynamic slip is an importantfactor while considering fluid flow through nanochannels. Various studies have been done both in NEMD and EMD to study the fluid slippage over solid surface. Molecular Dynamics Study of Fluid Solid Interfacial Slip and its Effect on Aerodynamic Drag[1] is one such example where dependence of slip and the drag properties are studied. In this paper we try to examine different types of surface roughness affects the fluid slip with MD simulation of poiseuille flow.