Comparison of different ground simulation systems on the flow around a high-speed train

2016 ◽  
Vol 231 (2) ◽  
pp. 135-147 ◽  
Author(s):  
Chao Xia ◽  
Xizhuang Shan ◽  
Zhigang Yang
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
High Speed ◽  
Separation Bubble ◽  
Adverse Pressure Gradient ◽  
Boundary Layer Separation ◽  
Wind Tunnel Testing ◽  
High Speed Train ◽  
Simulation Systems ◽  
Tunnel Testing

The influence of different ground simulation systems on the air flow around a high-speed train with zero yaw angle is investigated. Force values, force development graphs, surface pressures, the underbody flow and the wake are studied in detail with Computational Fluid Dynamics, which is initially validated by wind tunnel testing. It shows that the stationary ground has severe deviations from the full moving ground on the aerodynamic performance due to the inaccurate pressure distribution on the underbody. This is mainly attributed to the high level of interaction between the underbody and the boundary layer development. In addition, a ground boundary layer separation bubble can be observed under the tail end of the train for the stationary ground on account of insufficient energy to overcome the increasing adverse pressure gradient. In order to guarantee a correct underbody flow, a partially moving ground is proposed, including the “3-moving ground” and the “1-moving ground”. Such ground simulation systems are well compatible with the fixed rail tracks and the bottom support struts compared to the full moving ground. As a conceivable method to reduce the influence of the boundary layer, raising the high-speed train model with different ground clearances is also studied. Overall, the 3-moving ground is suggested to be the best choice for the ground simulation systems in high speed train wind tunnel testing.

Aerodynamic Measurements on a Low Pressure Turbine Cascade With Different Levels of Distributed Roughness

2011 ◽  
Author(s):  
Marco Montis ◽  
Reinhard Niehuis ◽  
Andreas Fiala
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Separation Bubble ◽  
Reference Conditions ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Low Pressure ◽  
Average Roughness ◽  
Low Pressure Turbine ◽  
High Reynolds

The effect of surface roughness on the aerodynamics of a highly loaded low-pressure turbine airfoil was investigated in a series of cascade tests conducted in a high speed facility. Profile loss and aerodynamic loading of three different surface roughnesses with a ratio of the centerline average roughness to the profile chord of 1.1 · 10−5, 7.1 · 10−5 and 29 · 10−5 were analysed. Tests were carried out under design outlet Mach number, outlet Reynolds number ranging from 5 · 104 to 7 · 105 and inlet turbulence level of 2.5% and 5%. The mid span flow field downstream of the cascade and the loading distribution on the profile were measured for each investigated operating point using a five hole probe and surface static pressure taps. Additional measurements with a hot wire probe in the profile boundary layer under reference conditions (Re2th = 2 · 105) were also conducted. Experimental results show a loss reduction for the highest roughness under reference conditions, due to the partial suppression of the separation bubble on the suction side of the profile. At high Reynolds numbers a massive boundary layer separation on the suction side is observed for the highest roughness, along with a large increase in total pressure loss. The middle roughness tested has no effect on the loading distribution as well as on the loss behaviour of the airfoil under all investigated flow conditions.

Videogrammetry of the Model’s Attitude in Wind Tunnel Testing

2012 ◽  
Vol 190-191 ◽  
pp. 1273-1277 ◽  
Author(s):  
Zheng Yu Zhang ◽  
Zhong Xiang Sun ◽  
Xu Hui Huang ◽  
Yan Sun
Keyword(s):  
Standard Deviation ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Systematic Error ◽  
Measurement System ◽  
High Speed ◽  
Wind Tunnel Test ◽  
Wind Tunnel Testing ◽  
Supersonic Wind Tunnel ◽  
Tunnel Testing

The advanced precision of drag coefficient is 0.0001 for the high speed wind tunnel test of measuring forces, the model’s angle of attack precision is ≤0.01°following errors distribution. A videogrammetric method of model’s attitude is therefore proposed, its uncertainty is investigated, and a compensation method of its systematic error is also presented by this paper. The three engineering videogrammetric experiments of attack angle in 2 meter supersonic wind tunnel testing have demonstrated that measuring standard deviation of videogrammetric measurement system established by this paper is ≤0.0094°, in addition it neither destroys the model’s shape, nor changes the stiffness or strength, so it is useful and effective.

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