Academic literature on the topic 'Moving breakdown model'
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Journal articles on the topic "Moving breakdown model"
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Ahamed Mohideen, P. B., and M. Ramachandran. "Strategic approach to breakdown maintenance on construction plant – UAE perspective." Benchmarking: An International Journal 21, no. 2 (April 1, 2014): 226–52. http://dx.doi.org/10.1108/bij-05-2012-0030.
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Purpose – The purpose of this paper is to develop a systematic strategic approach to handle corrective maintenance onto the failures/breakdowns of construction equipment. For the maintenance crew/team, a breakdown code management is proposed, which will provide focused and unambiguous approach to manage any kind of breakdowns in construction equipments. Design/methodology/approach – The past breakdown records of a construction organization in the UAE are considered for analysis. From the failure data, through cause effect analysis (CEA) tools, the components and the breakdown codes namely breakdown main codes (BMC) and breakdown sub-codes (BSC) are formulated. With Pareto analysis, the critical codes are identified and validated through failure modes and effects analyses (FMEA) tools for the critical effect on the affected components. From this identified BSC's further closer failure identification codes namely breakdown symptom codes (BSyC) and breakdown reason codes (BRC) are identified through fault tree analysis (FTA) tools. The approach to modified breakdown maintenance management (MB2M) with breakdown maintenance protocol (BMP) is envisaged. Findings – The study was conducted on four different types of heavy lifting/earth moving/material handling system of equipment and further focused with two earth moving equipment namely dumpers and wheel loaders. Failure analysis is performed and the failure ratio and the component contribution to the failures are identified. Based on the information, the preliminary codes namely BMC and BSC are identified through CEA tools and the BMC and BSC are identified to find the most contributing codes to the maximum number of failures through Pareto analysis. Further the critical sub-codes are further verified through FMEA tools on the severity levels of the sub components due to these codes. The FTA methods are used to identify the closer reasoning and relations of these codes and the further codes namely BSyC and BRC are identified which are the exact cause of the failures. The management of breakdowns is further proposed through MB2M which includes BMP which provides all resources for the breakdowns. Research limitations/implications – The failure data collected are only pertaining to the Middle East region and applicable to similar regions for similar plant mix in construction companies. The sample equipment is only part representative of the construction equipment. A more robust model can be suggested in the future covering all aspects and for other regions as well. Practical implications – The proposed methodology and model approach is highly adaptable to similar industries operating in the Middle East countries. Originality/value – Many authors have studied the preventive maintenance models and procedures and proposals have been proposed. On the breakdown maintenance management of construction equipment, very few studies have been proposed mostly on the cost analysis. This model attempts to provide a code management solution to manage the unpredictable failures in construction equipment through failure data analysis on a construction organization.
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Hemmati, Mostafa. "Electron shock waves moving into an ionized medium." Laser and Particle Beams 13, no. 3 (September 1995): 377–82. http://dx.doi.org/10.1017/s0263034600009502.
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The propagation of electron driven shock waves has been investigated by employing a one-dimensional, three-component fluid model. In the fluid model, the basic set of equations consists of equations of conservation of mass, momentum, and energy, plus Poisson's equation. The wave is assumed to be a shock front followed by a dynamical transition region. Following Fowler's (1976) categorization of breakdown waves, the waves propagating into a preionized medium will be referred to as Class II Waves. To describe the breakdown waves, Shelton and Fowler (1968) used the terms proforce and antiforce waves, depending on whether the applied electric field force on electrons was with or against the direction of wave propagation. Breakdown waves, i.e., return strokes of lightning flashes, therefore, will be referred to as Antiforce Class II waves. The shock boundary conditions and Poisson's equation for Antiforce Class II waves are different from those for Antiforce Waves. The use of a newly derived set of boundary conditions and Poisson's equation for Antiforce Class II waves allows for a successful integration of the set of fluid equations through the dynamical transition region. The wave structure, i.e., electric field, electron concentration, electron temperature, and electron velocity, are very sensitive to the ion concentration ahead of the wave.
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Kao, C. Y., F. Brau, U. Ebert, L. Schäfer, and S. Tanveer. "A moving boundary model motivated by electric breakdown: II. Initial value problem." Physica D: Nonlinear Phenomena 239, no. 16 (August 2010): 1542–59. http://dx.doi.org/10.1016/j.physd.2010.03.011.
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Buck, Wolfgang, and Jürgen Parisi. "Temporal Behavior of the Breakdown of Superconductivity." Zeitschrift für Naturforschung A 44, no. 3 (March 1, 1989): 247–56. http://dx.doi.org/10.1515/zna-1989-0313.
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On a very short time scale, breakdown of superconductivity with increasing transport current turns out to be a highly dynamical process, called “current-induced resistive state”. Magnetic flux domains rapidly move perpendicular to the direction of the transport current applied, with increasing velocity as the current is further increased. At sufficiently high currents, superconductivity is completely destroyed, and the sample ends up in the normal state. In this paper, the first timeresolved measurements of voltage signals induced by the motion of single flux domains are reported. A stability analysis of the superconducting state based on the “Gibbs free energy barrier model” describes the temporal voltage profile generated by a single flux domain, which is solitarily moving across the sample cross-section, as well as the superimposed signals of a series of competing domains, existing simultaneously in the sample. In the latter case, the interaction among the flux domains is taken into account by a monopole ansatz. Studying the onset of the breakdown of superconductivity in type I materials, an oscillatory behavior of the domain size was found. After a few periods, these transients change into a stationary number of flux quanta per domain.
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Hu, Xiaojian, and Mingyang Liu. "Traffic flow in the vicinity of crosswalks on a provincial highway in China." Modern Physics Letters B 32, no. 31 (November 10, 2018): 1850378. http://dx.doi.org/10.1142/s0217984918503785.
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In this paper, motorized traffic flow in the vicinity of an unsignalized crosswalk on a provincial highway in China was studied. Based on the Kerner–Klenov–Schreckenberg–Wolf (KKSW) three-phase cellular automaton (CA) traffic flow model for single-lane roads, the cars’ moving rules when there were pedestrians walking on the crosswalk was redefined. A series of simulations were carried out to reveal the cars’ travel process and the influence of pedestrians crossing behavior on traffic flow. The simulations results show the redefined model can be used to study not only the characteristics of traffic flow in the vicinity of crosswalks on provincial highways but also some complex traffic problems such as traffic breakdown, synchronized flow, and moving jams. Moreover, some suggestions about signal control for the pedestrians crossing in the future were presented. Thus, this work is helpful for managing traffic flow and improving road safety and capacity in the vicinity of crosswalks on provincial highways in China.
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Oda, Ichiro. "Higgs potential from Weyl conformal gravity." Modern Physics Letters A 35, no. 37 (October 5, 2020): 2050304. http://dx.doi.org/10.1142/s0217732320503046.
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We consider Weyl’s conformal gravity coupled to a complex matter field in Weyl geometry. It is shown that a Higgs potential naturally arises from a [Formula: see text] term in moving from the Jordan frame to the Einstein frame. A massless Nambu–Goldstone boson, which stems from spontaneous symmetry breakdown of the Weyl gauge invariance, is absorbed into the Weyl gauge field, thereby the gauge field becoming massive. We present a model where the gravitational interaction generates a Higgs potential whose form is a perfect square. Finally, we show that a theory in the Jordan frame is gauge-equivalent to the corresponding theory in the Einstein frame via the BRST formalism.
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Ghani, Rabia. "Integration of FMECA and statistical snalysis for predictive maintenance." Journal of Applied Research in Technology & Engineering 2, no. 1 (January 26, 2021): 33. http://dx.doi.org/10.4995/jarte.2021.14737.
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<p>The estimation of time-to-failure of machines is of utmost importance in the Manufacturing Industry. As the world is moving towards Industry 4.0, it is high time that we progress from the traditional methods, where we wait for a breakdown to occur, to the prognostics based methods. It is the need of the era to be aware of any incident before it occurs. This study provides application of Statistical-based Predictive maintenance. A BOPP Production line has been considered as a case study for this research. Since the inception of the line in 2013, it is evident that 60% of breakdowns are due to lack of maintenance and timely replacement of bearings. Therefore, the research is based on the application of FMECA (Failure Modes, Effects and Criticality Analysis) to determine which bearing in the production line is most prone to failure and determination of which statistical model best fits the failure data of the most critical bearing. The result provides the best distribution fit for the failure data and the fit can be utilized for further study on RUL (Remaining Useful Life) of the bearing through Bayesian Inference.</p>
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Yeung, Pollen, Zhaolin Xu, and Dena Seeto. "Diltiazem Reduces Mortality and Breakdown of ATP in Red Blood Cell Induced by Isoproterenol in a Freely Moving Rat Model in Vivo." Metabolites 4, no. 3 (September 11, 2014): 775–89. http://dx.doi.org/10.3390/metabo4030775.
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White, Laurent, Vincent Legat, and Eric Deleersnijder. "Tracer Conservation for Three-Dimensional, Finite-Element, Free-Surface, Ocean Modeling on Moving Prismatic Meshes." Monthly Weather Review 136, no. 2 (February 1, 2008): 420–42. http://dx.doi.org/10.1175/2007mwr2137.1.
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Abstract Large-scale free-surface ocean models designed to run over climatic time scales are required to globally conserve the volume and any tracer up to machine precision. In addition, local consistency is critical and requires that the discrete tracer equation preserve constants in a closed domain and if there is no tracer source or sink. Local consistency, together with monotonicity, will ensure that no spurious tracer extrema occur. A three-dimensional, finite-element, shallow-water model is presented. The mesh is unstructured in the horizontal, extruded in the third dimension, and made up of multiple layers of prisms. In addition, the mesh is allowed to move in the vertical and adapts itself to the free-surface motions. It is shown that achieving consistency requires a discrete compatibility between the tracer and continuity equations. In addition, to ensure global tracer conservation in a consistent way, a discrete compatibility between the tracer, continuity, and free-surface elevation equations must be fulfilled. It is suggested that this compatibility constraint, together with the use of a numerically stable scheme, severely restricts the choice of usable finite-element spatial discretizations. A consistent and conservative time-stepping algorithm is described for which a unique time step is used. It is suggested that future research is needed in order to design a consistent and conservative split-explicit algorithm. Some illustrative test cases are presented in which the method is shown to satisfy all conservation properties. A few experiments in which consistency breaks down are carried out, and the consequences of this breakdown process are investigated.
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Ruhrmann, Andreas, and Xin Zhang. "Influence of Diffuser Angle on a Bluff Body in Ground Effect." Journal of Fluids Engineering 125, no. 2 (March 1, 2003): 332–38. http://dx.doi.org/10.1115/1.1537252.
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The forces and pressures on a generic bluff body in ground effect were investigated. The bluff-body model was equipped with interchangeable underbody diffuser ramps and side plates. Five different diffuser angles were tested: 5, 10, 15, 17, and 20 deg to the horizontal. The experiments were undertaken in a low-speed wind tunnel equipped with a moving ground. Load cells, pressure taps, and surface flow visualization were the techniques used to evaluate the flow field. The flow field is characterized by vortex flow and three-dimensional flow separation. A region of hysteresis was found for the 15, 17, and 20 deg diffusers. As the ride height is varied, five different flow types can be identified with three subtypes within the region of hysteresis. The force reduction phenomenon was found to be caused by both vortex breakdown and flow separation.
Dissertations / Theses on the topic "Moving breakdown model"
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Skočovská, Katarína. "Detekce těžkých kovů v kapalinách metodou spektrometrie laserem buzeného plazmatu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231994.
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The diploma thesis deals with the use of laser induced breakdown spectroscopy (LIBS) for detection of heavy metals traces, copper and lead, in aqueous solution of copper(II) sulphate pentahydrate and lead(II) ethanoate trihydrate. Results obtained by using single and double-pulse LIBS are compared. The theoretical section focuses on the issue of heavy metals and detection possibilities, describes the fundamental principle of LIBS technique and its modification for liquid analysis. The experimental section describes analyzed samples, the experimental apparatus, double-pulse technique, and method of spectral analysis. The moving breakdown model, which theoretically predicts optimal values of some experimental parameters, is explained briefly in section Optimalizácia. This model has been tested, however the results of experiments did not prove the theory. Furthermore, the experimental section reports the process and results of the optimization of all key measurement parameters and obtaining limits of detection from calibration curves.
Conference papers on the topic "Moving breakdown model"
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Blackmore, Denis, Arnaud Goullet, and Morten Bro̸ns. "Two-Vortex Models for Vortex Breakdown." In ASME 2008 Dynamic Systems and Control Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/dscc2008-2291.
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A simple Hamiltonian dynamical systems model for vortex breakdown of the bubble-type (B-type) is developed and analyzed. This model is constructed using the flow induced by two point vortices moving in a half-plane immersed in an ideal (= inviscid and incompressible) fluid with an ambient uniform horizontal velocity. It is shown — using a combination of modern dynamical systems theory and numerical analysis — that the flows generated by this model capture most of the dynamical features exhibited in B-type vortex breakdown, including the existence of chaotic regimes. Examples are provided to illustrate the variety and complexity of vortex breakdown type flows that can be produced with these models.
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Shi, Ke, and Song Fu. "Study of Shock/Blade Tip Leakage Vortex/Boundary Layer Interaction in a Transonic Rotor With IDDES Method." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95252.
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In the present study, Improved Delayed Detached Eddy Simulation (IDDES) based on k-ω-SST turbulence model is applied to study the unsteady phenomenon in a transonic compressor rotor. Particular emphasis is on the understanding of the complex underlying mechanisms for the flow unsteadiness caused by the interaction of passage shock, blade tip leakage vortex (BTLV) and the blade boundary layer. The sources of the significant unsteadiness of the flow are shown. At the lower span height, where the BTLV is far away, the shock wave ahead of the blade leading edge impinges on the suction surface boundary layer of the adjacent blade, causing the shock wave/boundary layer interaction (SWBLI). Boundary layer thickness grows, while flow separates after the interaction. Predicted by IDDES calculation, this shock-induced separation exists as a separation bubble. The flow reattaches very soon after separation. At the near tip region, the shock wave surface deforms due to the strong interaction between the shock and the BTLV. Oscillation of the shock wave surface near the vortex core infers an unsteady contend between the shock and the vortex. Iso-surfaces of the Q parameter are applied to identify the vortex and its structure. Normally, the vortex breakdown in the rotor passage will lead to stall. However, in the present transonic case, the vortex breakdown was observed even at the near peak efficiency point. While the mass flow rate decreases, the shock waves formed ahead of the rotor blade leading edge were pushed upstream, causing earlier casing wall boundary layer separation. Upstream moving behavior of the shock is considered a new stall process.
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Babu, Harish, and S. Sarkar. "Large Eddy Simulation on the Interactions of Wake and Film-Cooling Near a Leading Edge." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26117.
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The unsteady flow physics due to interactions between a separated shear layer and film cooling jet apart from excitation of periodic passing wake are studied using Large Eddy Simulation (LES). An aerofoil of constant thickness with rounded leading edge induced flow separation, while film cooling jets were injected normal to the crossflow a short distance downstream of the blend point. Wake data extracted from precursor LES of flow past a cylinder are used to replicate a moving bar that generates wakes in front of a cascade (in this case, an infinite row of the model aerofoils). This setup is a simplified representation of rotor-stator interaction in a film cooled gas turbine. The results of numerical simulation are presented to elucidate the formation, convection and breakdown of flow structures associated with the highly anisotropic flow involved in film cooling perturbed by convective wakes. The various vortical structures namely, horseshoe vortex, roller vortex, upright wake vortex, counter rotating vortex pair and DSSN vortex associated with film cooling are resolved. The effects of wake on the evolution of these structures are then discussed.
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Andersen, Fredrik Herland, and Stefan Mayer. "Parametric Study of the Scavenging Process in Marine Two-Stroke Diesel Engines." In ASME 2015 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/icef2015-1075.
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Large commercial ships such as container vessels and bulk carriers are propelled by low-speed, uniflow scavenged two-stroke diesel engines. The integral in-cylinder process in this type of engine is the scavenging process, where the burned gas from the combustion process is evacuated through the exhaust valve and replaced with fresh air for the subsequent compression stroke. The scavenging air enters the cylinder via inlet ports which are uncovered by the piston at bottom dead center (BDC). The exhaust gas is then displaced by the fresh air. The scavenging ports are angled to introduce a swirling component to the flow. The in-cylinder swirl is beneficial for air-fuel mixture, cooling of the cylinder liner and minimizing dead zones where pockets of exhaust gas are trapped. However, a known characteristic of swirling flows is an adverse pressure gradient in the center of the flow, which might lead to a local deficit in axial velocity and the formation of central recirculation zones, known as vortex breakdown. This paper will present a CFD analysis of the scavenging process in a MAN B&W two-stroke diesel engine. The study include a parameter sweep where the operating conditions such as air amount, port timing and scavenging pressure are varied. The CFD model comprise the full geometry from scavenge receiver to exhaust receiver. Asymmetric inlet and outlet conditions is included as well as the dynamics of a moving piston and valve. Time resolved boundary conditions corresponding to measurements from an operating, full scale production, engine as well as realistic initial conditions are used in the simulations. The CFD model provides a detailed description of the in-cylinder flow from exhaust valve opening (EVO) to exhaust valve closing (EVC). The study reveals a close coupling between the volume flow (delivery ratio) and the in-cylinder bulk purity of air which appears to be independent of operating conditions, rpm, scavenge air pressure, BMEP etc. The bulk purity of air in the cylinder shows good agreement with a simple theoretical perfect displacement model.
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Reihani, Amin, John Hoard, Stefan Klinkert, Chih-Kuang Kuan, and Daniel Styles. "Numerical Evaluation of the Effects of Low Pressure EGR Mixer Configuration on Turbocharger Compressor Performance." In ASME 2018 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icef2018-9686.
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Low-pressure exhaust gas recirculation (LP-EGR) is an EGR configuration in which clean exhaust gas is taken downstream of the turbine and aftertreatment, and then reintroduced upstream of the compressor (1). Employing LP-EGR on Diesel engines can improve fuel economy by reducing pumping losses, lowering intake manifold temperature and facilitating advanced combustion phasing (2, 3). The LP-EGR can also improve compressor and turbine performance by moving their operating points towards higher flow rate and higher efficiency points, which is reflected as a net reduction in pumping losses of the engine. In this study, we focus on effects of introducing LP-EGR on the compressor pressure ratio, and isentropic total-to-total efficiency. The flow field of LP-EGR and air mixing upstream of the compressor as well as the entire compressor stage were studied using a CFD RANS model. The model was validated against turbocharger gas stand measurements. A T-junction mixer was chosen as the design baseline, and various configurations of this mixer were evaluated. The impact of the geometric configuration of the mixer was studied by varying mixing length, EGR jet introduction angle, and EGR-to-air cross section area ratio over a wide range of relevant engine operating conditions. The flow field upstream of the compressor is strongly affected by the dimensionless quantity EGR-to-air momentum ratio. At intermediate momentum ratios, stream-wise counter-rotating vortex pairs (4) are induced in the flow. These vortices can reach the impeller inlet, and depending on vorticity and length scale, perturb the local velocity triangle. At low and high momentum ratios, creeping or impinging jets respectively are formed. In addition prewhirl can be induced by eccentric introduction of EGR. The EGR-induced prewhirl acts similar to an inlet guide vane and can alter the incidence angle at the impeller inlet. The performance of the compressor is altered by the EGR-induced flow field. Compressor pressure ratio is either increased or decreased depending on the direction of EGR-induced prewhirl with eccentric EGR introduction. The compressor efficiency decreases at low flow rates by introduction of concentric EGR due to perturbation of the velocity triangle at the impeller inlet. On the other hand, at low flow rates compressor efficiency can be improved by eccentric EGR introduction, which generates prewhirl in the direction of rotation of the impeller leading to improved incidence angle. The extent to which the compressor is influenced by the EGR-induced flow field is generally reduced by increasing the EGR mixing length, due to viscous damping and breakdown of large-scale EGR-induced vortices. The LP-EGR configuration provides a potential pathway towards improvement of compressor performance, not only by increasing compressor flow rate, but also by manipulation of the flow field. Given that the engine pumping losses are strongly dependent on compressor performance, specifically the compressor efficiency, this study indicates that LP-EGR provides an important path towards reducing pumping loss and improving fuel conversion efficiency.
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Parra, Jorge, David Cadrecha, Ezequiel González, and Benigno Lázaro. "Trailing Edge Thickness Impact on the Profile Losses of Highly Loaded Low Pressure Turbines Blades." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57955.
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The losses breakdown of modern highly loaded low pressure turbines profiles shows that the trailing edge thickness can account for up to 20% of the overall profile loss depending on the thickness to pitch ratio highly affecting to the LPT overall performance. Additionally, this feature is of significant practical interest as the aerofoil mechanical behaviour and manufacturing costs are largely determined by the size of the trailing edge. Current trailing edge loss models are based on correlations derived from measurements on aerofoils very different with respect to the current state-of-the-art, they do not consider any effect of Reynolds number or lift coefficient, so it is questionable whether they are accurate enough for current applications and therefore an experimental validation campaign is required. The aim of the present experimental investigation is to examine the influence of that geometrical parameter on the unsteady Reynolds lapse characterization by means of four different low speed linear cascades varying the thickness from 50% to 200% of a nominal case. Cascades A, B and C (with small, nominal and large thickness) meet the same lift coefficient reducing the back surface diffusion factor due to the different velocity at the trailing edge because of the blockage generated by the trailing edge thickness. Cascade B2, with nominal thickness, is modified to meet the same diffusion factor as Cascade A to decouple the effect of the diffusion factor from the effect of the trailing edge thickness. Total pressure probes, Laser-Doppler and hot wire anemometry are used to characterize the suction side boundary layer just upstream from the trailing edge as well as the near wake developing close to the trailing edge. Additional characterisations are conducted at half chord downstream from the cascade trailing edge to evaluate its loss coefficient. Upstream located moving bars are used to simulate the incoming wakes shed by one upstream blade row. The hot wire measurements performed slightly upstream from the profile trailing edge are post-processed locked to the passage of the moving bars. The resulting data are analysed to characterise the temporal modulation of the suction side boundary layer momentum thickness by the incoming wakes. The measurements indicate that both the time-mean value and the phase-averaged distribution of the boundary layer integral parameters are largely determined by the diffusion rate of the profile. On the other hand, a negligible effect of the trailing edge thickness is observed for the same diffusion rate. The measurements conducted downstream from the profile, both close to its trailing edge and half chord downstream, illustrate the role of the trailing edge thickness on the initial wake development. The data is recorded for 60s with a sampling rate of 25kHz obtaining between 150 and 650 phase-locked datasets depending on the Reynolds No. Finally, the characterisation of the profile mix-out losses at the downstream plane is presented. The experimental results show that a significant reduction of losses can be achieved with thinner trailing edge, but, an increase in the number of aerofoils need to be allowed in order to get the full potential benefit of this strategy.