A Computational Fluid Dynamics Comparison of the Underflow of Different Commercial High-Speed Trains

2015 ◽  
Author(s):  
C. Gil ◽  
C. Paz ◽  
E. Suárez ◽  
M. Conde
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
High Speed Trains

scholarly journals Aerodynamic analysis of uphill drafting in cycling

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
T. van Druenen ◽  
B. Blocken
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Scientific Literature ◽  
Sensitivity Analyses ◽  
Air Resistance ◽  
Wind Tunnel Measurements ◽  
Aerodynamic Effect ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

AbstractSome teams aiming for victory in a mountain stage in cycling take control in the uphill sections of the stage. While drafting, the team imposes a high speed at the front of the peloton defending their team leader from opponent’s attacks. Drafting is a well-known strategy on flat or descending sections and has been studied before in this context. However, there are no systematic and extensive studies in the scientific literature on the aerodynamic effect of uphill drafting. Some studies even suggested that for gradients above 7.2% the speeds drop to 17 km/h and the air resistance can be neglected. In this paper, uphill drafting is analyzed and quantified by means of drag reductions and power reductions obtained by computational fluid dynamics simulations validated with wind tunnel measurements. It is shown that even for gradients above 7.2%, drafting can yield substantial benefits. Drafting allows cyclists to save over 7% of power on a slope of 7.5% at a speed of 6 m/s. At a speed of 8 m/s, this reduction can exceed 16%. Sensitivity analyses indicate that significant power savings can be achieved, also with varying bicycle, cyclist, road and environmental characteristics.

Slam load estimation for high-speed catamarans in irregular head seas by full-scale computational fluid dynamics

2021 ◽  
Vol 234 ◽  
pp. 109160
Author(s):  
Islam Almallah ◽  
Jason Ali-Lavroff ◽  
Damien S. Holloway ◽  
Michael R. Davis
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Full Scale ◽  
Load Estimation

Sailing Yacht Rig Improvements Through Viscous Computational Fluid Dynamics

2005 ◽  
Author(s):  
Vincent G. Chapin ◽  
Romaric Neyhousser ◽  
Stephane Jamme ◽  
Guillaume Dulliand ◽  
Patrick Chassaing
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
High Speed ◽  
Stokes Equations ◽  
Wind Tunnel Test ◽  
Physical Modelling ◽  
Optimized Design ◽  
Linear Interaction ◽  
Sailing Yacht

In this paper we propose a rational viscous Computational Fluid Dynamics (CFD) methodology applied to sailing yacht rig aerodynamic design and analysis. After an outlook of present challenges in high speed sailing, we emphasized the necessity of innovation and CFD to conceive, validate and optimize new aero-hydrodynamic concepts. Then, we present our CFD methodology through CAD, mesh generation, numerical and physical modelling choices, and their validation on typical rig configurations through wind-tunnel test comparisons. The methodology defined, we illustrate the relevance and wide potential of advanced numerical tools to investigate sailing yacht rig design questions like the relation between sail camber, propulsive force and aerodynamic finesse, and like the mast-mainsail non linear interaction. Through these examples, it is shown how sailing yacht rig improvements may be drawn by using viscous CFD based on Reynolds Averaged Navier-Stokes equations (RANS). Then the extensive use of viscous CFD, rather than wind-tunnel tests on scale models, for the evaluation or ranking of improved designs with increased time savings. Viscous CFD methodology is used on a preliminary study of the complex and largely unknown Yves Parlier Hydraplaneur double rig. We show how it is possible to increase our understanding of his flow physics with strong sail interactions, and we hope this methodology will open new roads toward optimized design. Throughout the paper, the necessary comparison between CFD and wind-tunnel test will be presented to focus on limitations and drawbacks of viscous CFD tools, and to address future improvements.

Transient Computational Fluid Dynamics/Discrete Element Method Simulation of Gas–Solid Flow in a Spouted Bed and Its Validation by High-Speed Imaging Experiment

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Ling Zhou ◽  
Lingjie Zhang ◽  
Weidong Shi ◽  
Ramesh Agarwal ◽  
Wei Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Discrete Element Method ◽  
Fluidized Bed ◽  
High Speed ◽  
Discrete Element ◽  
Bubble Shape ◽  
High Speed Imaging ◽  
Bed Height ◽  
Simulation Results

A coupled computational fluid dynamics (CFD)/discrete element method (DEM) is used to simulate the gas–solid two-phase flow in a laboratory-scale spouted fluidized bed. Transient experimental results in the spouted fluidized bed are obtained in a special test rig using the high-speed imaging technique. The computational domain of the quasi-three-dimensional (3D) spouted fluidized bed is simulated using the commercial CFD flow solver ANSYS-fluent. Hydrodynamic flow field is computed by solving the incompressible continuity and Navier–Stokes equations, while the motion of the solid particles is modeled by the Newtonian equations of motion. Thus, an Eulerian–Lagrangian approach is used to couple the hydrodynamics with the particle dynamics. The bed height, bubble shape, and static pressure are compared between the simulation and the experiment. At the initial stage of fluidization, the simulation results are in a very good agreement with the experimental results; the bed height and the bubble shape are almost identical. However, the bubble diameter and the height of the bed are slightly smaller than in the experimental measurements near the stage of bubble breakup. The simulation results with their experimental validation demonstrate that the CFD/DEM coupled method can be successfully used to simulate the transient gas–solid flow behavior in a fluidized bed which is not possible to simulate accurately using the granular approach of purely Euler simulation. This work should help in gaining deeper insight into the spouted fluidized bed behavior to determine best practices for further modeling and design of the industrial scale fluidized beds.

Resistance Predictions for Asymmetrical Configurations of High-Speed Catamaran Hull Forms

2015 ◽  
Author(s):  
Srikanth Asapana ◽  
Prasanta K. Sahoo ◽  
Vaibhav Aribenchi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Comparative Analysis ◽  
High Speed ◽  
Public Domain ◽  
Literature Survey ◽  
Historical Background ◽  
Resistance Analysis ◽  
Separation Ratio ◽  
Hull Forms

This paper attempts to undertake a comparative analysis of resistance characteristics between newly developed asymmetrical catamaran hull forms which were derived from existing conventional NPL series of round bilge catamaran hull forms by Molland, Wellicome and Couser (1994). A set of asymmetrical catamaran hull forms with waterline length of 1.6 m with a separation ratio (s/L) of 0.4 were generated by using standard modelling software. The resistance analysis had been carried out by using STAR CCM+, a computational fluid dynamics package for Froude numbers of 0.25, 0.30, 0.60, 0.80 and 1.0. Literature survey indicates that there is scant historical background in public domain to perform resistance analysis on asymmetrical catamaran hull forms. As this is not feasible due to lack of data in areas that were considered crucial, separate resistance analysis is carried out for each hull configuration. Finally, the compared resistance results will attempt to conclude whether asymmetrical catamaran hull forms are more efficient than the conventional catamaran hull forms.

scholarly journals A zonal approach for estimating pressure ratio at compressor extreme off-design conditions

2018 ◽  
Vol 20 (4) ◽  
pp. 393-404 ◽  
Author(s):  
José Galindo ◽  
Roberto Navarro ◽  
Luis Miguel García-Cuevas ◽  
Daniel Tarí ◽  
Hadi Tartoussi ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Pressure Ratio ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Combustion Engines ◽  
One Dimensional ◽  
Performance Map

Zero-dimensional/one-dimensional computational fluid dynamics codes are used to simulate the performance of complete internal combustion engines. In such codes, the operation of a turbocharger compressor is usually addressed employing its performance map. However, simulation of engine transients may drive the compressor to work at operating conditions outside the region provided by the manufacturer map. Therefore, a method is required to extrapolate the performance map to extended off-design conditions. This work examines several extrapolating methods at the different off-design regions, namely, low-pressure ratio zone, low-speed zone and high-speed zone. The accuracy of the methods is assessed with the aid of compressor extreme off-design measurements. In this way, the best method is selected for each region and the manufacturer map is used in design conditions, resulting in a zonal extrapolating approach aiming to preserve accuracy. The transitions between extrapolated zones are corrected, avoiding discontinuities and instabilities.

Computational Fluid Dynamics Study of Oil Behavior in a Scoop, and Factors Affecting Scoop Capture Efficiency

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Evgenia Korsukova ◽  
Hervé Morvan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbines ◽  
High Speed ◽  
Velocity Ratio ◽  
Capture Efficiency ◽  
Parameter Analysis ◽  
Parameter Study ◽  
3D Simulations ◽  
Engine Components

Abstract Due to the continuous reduction of engine sizes, efficient under-race lubrication becomes ever more crucial in order to provide sufficient amount of oil to various engine components. An oil scoop is a rotating component that captures oil from a jet, and axially redirects it to the bearing, providing under-race lubrication. Given the importance of lubrication in high-speed engine components, the efficiency study of under-race lubrication appliances receives rapidly growing demands from manufacturers and therefore is of great interest. This work provides description of computational fluid dynamics (CFD) methods that were found to be most accurate and efficient for a large parameter analysis of the scoop capture efficiencies. One of the main purposes of this paper is to demonstrate an optimal and validated computational approach to modeling under-race lubrication with a focus on oil capture efficiency. Second, to show which factors most influence the scoop capture efficiency. Additionally, simulations allow for the fluid behavior inside the scoop to be observed that cannot be visualized experimentally due to high speeds. An improved method of efficiency calculation is also presented and compared to existing methods (Cageao, P. P., Simmons, K., Prabhakar, A., and Chandra, B., 2019, “Assessment of the Oil Scoop Capture Efficiency in High Speed Rotors,” ASME J. Eng. Gas Turbines Power, 141(1), p. 012401; Korsukova, E., Kruisbrink, A., Morvan, H., Paleo Cageao, P., and Simmons, K., 2016, “Oil Scoop Simulation and Analysis Using CFD and SPH,” ASME Paper No. GT2016-57554.). Results of both two-dimensional (2D) and semi-three-dimensional (3D) simulations are provided. Both qualitative comparison of 2D with semi-3D simulations and quantitative comparison of 2D simulations with experiments (Cageao, P. P., Simmons, K., Prabhakar, A., and Chandra, B., 2019, “Assessment of the Oil Scoop Capture Efficiency in High Speed Rotors,” ASME J. Eng. Gas Turbines Power, 141(1), p. 012401) show consistency. Parameter study using 2D simulations is shown with variation of rotational scoop speed, jet angles, velocity ratio. Key results show that changes of the jet angle and velocity ratio can improve the scoop efficiency.

Study of High Speed Turbulent Flow Over Rotating Two Stage Three Dimensional Double Wedge

2006 ◽  
Author(s):  
Khaled Alhussan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mach Number ◽  
Shock Waves ◽  
High Speed ◽  
Three Dimensional ◽  
Oblique Shock ◽  
Wave Interactions ◽  
Double Wedge ◽  
Slip Surfaces

In this paper some characteristics of non-steady, compressible, flow are explored, including compression and expansion wave interactions and creation. The work to be presented herein is a Computational Fluid Dynamics investigation of the complex fluid phenomena that occur inside three-dimensional region, specifically with regard to the structure of the oblique shock waves, the reflected shock waves and the interactions of the shock waves. The flow is so complex that there exist oblique shock waves, expansion fans, slip surfaces, and shock wave interactions and reflections. The flow is non-steady, turbulent, viscous, compressible, and high-speed supersonic. The work to be presented herein is a Computational Fluid Dynamics analysis of flow over a 15-degree angle double wedge for a compressible air, with spin angle of 10-degree and Mach number of 2.5. The problem to be solved involves formation of shock waves, expansion fans and slip surfaces, so that the general characteristics of supersonic flow are explored through this problem. Shock waves and slip surfaces are discontinuities in fluid mechanics problems. It is essential to evaluate the ability of numerical technique that can solve problems in which shocks and contact surfaces occur. In particular it is necessary to understand the details of developing a mesh that will allow resolution of these discontinuities. Results including contour plots of pressure, temperature, and Mach number will show that CFD is capable of predicting accurate results and is also able to capture the discontinuities in the flow, e.g., the oblique shock waves and the slip surfaces. Through this computational analysis, a better interpretation of the physical phenomenon of the three-dimensional shock waves interaction and reflection can be achieved.

Application of computational fluid dynamics for thermohydrodynamic analysis of high-speed squeeze-film dampers

2019 ◽  
Vol 43 (3) ◽  
pp. 306-321 ◽  
Author(s):  
Maxime Perreault ◽  
Sina Hamzehlouia ◽  
Kamran Behdinan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Radial Clearance ◽  
Base Line ◽  
Squeeze Film Dampers ◽  
Shaft Deflection ◽  
Whirl Speed

In high-speed turbomachinery, the presence of rotor vibrations, which produce undesirable noise or shaft deflection and losses in performance, has brought up the need for the application of a proper mechanism to attenuate the vibration amplitudes. Squeeze-film dampers (SFDs) are a widely employed solution to the steady-state vibrations in high-speed turbomachinery. SFDs contain a thin film of lubricant that is susceptible to changes in temperature. For this reason, the analysis of thermohydrodynamic (THD) effects on the SFD damping properties is essential. This paper develops a computational fluid dynamics (CFD) model to analyze the THD effects in SFDs, and enabling the application of CFD analysis to be a base-line for validating the accuracy of analytical THD SFD models. Specifically, the CFD results are compared against numerical simulations at different operating conditions, including eccentricity ratios and journal whirl speeds. The comparisons demonstrate the effective application of CFD for THD analysis of SFDs. Additionally, the effect of the lubricant THDs on the viscosity, maximum and mass-averaged temperature, as well as heat generation rates inside the SFD lubricant are analyzed. The temperature of the lubricant is seen to rise with increasing whirl speed, eccentricity ratios, damper radial clearance, and shaft radii.

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