Pressure Distribution on the Trailing Edge of an Airfoil Oscillating in a Shear Layer

1976 ◽  
Author(s):  
John E. Yates
Keyword(s):  
Pressure Distribution ◽  
Shear Layer ◽  
Trailing Edge

scholarly journals Influence of Thermodynamic Effect on Blade Load in a Cavitating Inducer

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Kengo Kikuta ◽  
Noriyuki Shimiya ◽  
Tomoyuki Hashimoto ◽  
Mitsuru Shimagaki ◽  
Hideaki Nanri ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Liquid Nitrogen ◽  
Cavity Length ◽  
Cold Water ◽  
Pressure Rise ◽  
Cavitation Number ◽  
Design Parameters ◽  
Trailing Edge ◽  
Thermodynamic Effect ◽  
Blade Tip

Distribution of the blade load is one of the design parameters for a cavitating inducer. For experimental investigation of the thermodynamic effect on the blade load, we conducted experiments in both cold water and liquid nitrogen. The thermodynamic effect on cavitation notably appears in this cryogenic fluid although it can be disregarded in cold water. In these experiments, the pressure rise along the blade tip was measured. In water, the pressure increased almost linearly from the leading edge to the trailing edge at higher cavitation number. After that, with a decrease of cavitation number, pressure rise occurred only near the trailing edge. On the other hand, in liquid nitrogen, the pressure distribution was similar to that in water at a higher cavitation number, even if the cavitation number as a cavitation parameter decreased. Because the cavitation growth is suppressed by the thermodynamic effect, the distribution of the blade load does not change even at lower cavitation number. By contrast, the pressure distribution in liquid nitrogen has the same tendency as that in water if the cavity length at the blade tip is taken as a cavitation indication. From these results, it was found that the shift of the blade load to the trailing edge depended on the increase of cavity length, and that the distribution of blade load was indicated only by the cavity length independent of the thermodynamic effect.

The Effect of Reynolds Number and Velocity Distribution on LP Turbine Cascade Performance

1986 ◽  
Author(s):  
D. J. Patterson ◽  
M. Hoeger
Keyword(s):  
Reynolds Number ◽  
Pressure Distribution ◽  
Guide Vane ◽  
Flow Visualisation ◽  
Suction Surface ◽  
Trailing Edge ◽  
Wide Range ◽  
Oil Flow ◽  
Low Reynolds ◽  
Lp Turbine

Because of the laminar boundary-layer’s inability to withstand moderate adverse pressure gradients without separating, profile losses in LP turbines operating at low Reynolds numbers can be high. The choice of design pressure distribution for the blading is thus of great importance. Three sub-sonic LP turbine nozzle-guide-vane cascade profiles have been tested over a wide range of incidence, Mach number and Reynolds number. The three profiles are of low, medium and high deflection and, as such, display significantly different pressure distributions. The tests include detailed boundary-layer traverses, trailing-edge base-pressure monitoring and oil-flow visualisation. It is shown that the loss variation with Reynolds number is a function of pressure distribution and that the trailing-edge loss component is dominant at low Reynolds number. The importance of achieving late flow transition — rather than separation — in the suction-surface trailing-edge region is stressed. The paper concludes by remarking on the advantages and practical implications of each loading design.

scholarly journals Effects of a Curved Trailing Edge on Growth of a Compressible Shear Layer-Comparison between Single and Double Shear Layers-

2005 ◽  
Vol 53 (620) ◽  
pp. 408-413
Author(s):  
Mikiya Araki ◽  
Jun Osaka ◽  
Osamu Imamura ◽  
Mitsuhiro Tsue ◽  
Michikata Kono
Keyword(s):  
Shear Layer ◽  
Shear Layers ◽  
Trailing Edge ◽  
Double Shear

An Experimental and Computational Study of the Formation of a Streamwise Shed Vortex in a Turbine Stage

2002 ◽  
Author(s):  
Graham Pullan ◽  
John Denton ◽  
Michael Dunkley
Keyword(s):  
Shear Layer ◽  
Computational Study ◽  
Vortex Sheet ◽  
Surface Flow ◽  
Secondary Flows ◽  
Flow Visualisation ◽  
Angle Distribution ◽  
Trailing Edge ◽  
Aircraft Wings ◽  
Yaw Angle

Shear layers shed by aircraft wings roll up into vortices. A similar, though far less common, phenomenon can occur in the wake of a turbomachine blade. This paper presents experimental data from a new single stage turbine that has been commissioned at the Whittle Laboratory. Two low aspect ratio stators have been tested with the same rotor row. Surface flow visualisation illustrates the extremely strong secondary flows present in both NGV designs. These secondary flows lead to conventional passage vortices but also to an intense vortex sheet which is shed from the trailing edge of the blades. Pneumatic probe traverses show how this sheet rolls up into a concentrated vortex in the second stator design, but not in the first. A simple numerical experiment is used to model the shear layer instability and the effects of trailing edge shape and exit yaw angle distribution are investigated. It is found that the latter has a strong influence on shear layer rollup: inhibiting the formation of a vortex downstream of NGV 1 but encouraging it behind NGV 2.

An Experimental and Computational Study of the Formation of a Streamwise Shed Vortex in a Turbine Stage

2003 ◽  
Vol 125 (2) ◽  
pp. 291-297 ◽  
Author(s):  
Graham Pullan ◽  
John Denton ◽  
Michael Dunkley
Keyword(s):  
Shear Layer ◽  
Computational Study ◽  
Vortex Sheet ◽  
Surface Flow ◽  
Secondary Flows ◽  
Angle Distribution ◽  
Trailing Edge ◽  
Aircraft Wings ◽  
Yaw Angle ◽  
Stator Design

Shear layers shed by aircraft wings roll up into vortices. A similar, though far less common, phenomenon can occur in the wake of a turbomachine blade. This paper presents experimental data from a new single-stage turbine that has been commissioned at the Whittle Laboratory. Two low-aspect ratio stators have been tested with the same rotor row. Surface flow visualization illustrates the extremely strong secondary flows present in both NGV designs. These secondary flows lead to conventional passage vortices, but also to an intense vortex sheet which is shed from the trailing edge of the blades. Pneumatic probe traverses show how this sheet rolls up into a concentrated vortex in the second stator design, but not in the first. A simple numerical experiment is used to model the shear layer instability and the effects of trailing edge shape and exit yaw angle distribution are investigated. It is found that the latter has a strong influence on shear layer rollup: inhibiting the formation of a vortex downstream of NGV 1 but encouraging it behind NGV 2.

scholarly journals Prediction of Airfoil Stall Based on a Modified k−v2¯−ω Turbulence Model

Mathematics ◽  
2022 ◽  
Vol 10 (2) ◽  
pp. 272
Author(s):  
Chenyu Wu ◽  
Haoran Li ◽  
Yufei Zhang ◽  
Haixin Chen
Keyword(s):  
Experimental Data ◽  
Shear Layer ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Naca0012 Airfoil ◽  
Separated Shear Layer ◽  
Non Equilibrium

The accuracy of an airfoil stall prediction heavily depends on the computation of the separated shear layer. Capturing the strong non-equilibrium turbulence in the shear layer is crucial for the accuracy of a stall prediction. In this paper, different Reynolds-averaged Navier–Stokes turbulence models are adopted and compared for airfoil stall prediction. The results show that the separated shear layer fixed k−v2¯−ω (abbreviated as SPF k−v2¯−ω) turbulence model captures the non-equilibrium turbulence in the separated shear layer well and gives satisfactory predictions of both thin-airfoil stall and trailing-edge stall. At small Reynolds numbers (Re~105), the relative error between the predicted CL,max of NACA64A010 by the SPF k−v2¯−ω model and the experimental data is less than 3.5%. At high Reynolds numbers (Re~106), the CL,max of NACA64A010 and NACA64A006 predicted by the SPF k−v2¯−ω model also has an error of less than 5.5% relative to the experimental data. The stall of the NACA0012 airfoil, which features trailing-edge stall, is also computed by the SPF k−v2¯−ω model. The SPF k−v2¯−ω model is also applied to a NACA0012 airfoil, which features trailing-edge stall and an error of CL relative to the experiment at CL>1.0 is smaller than 3.5%. The SPF k−v2¯−ω model shows higher accuracy than other turbulence models.

Role of Plate Length on Noise from Wall Jets

2019 ◽  
Vol 105 (6) ◽  
pp. 928-942
Author(s):  
Rahul S. Arackal ◽  
T. J. S. Jothi
Keyword(s):  
Shear Layer ◽  
Strouhal Number ◽  
Frequency Noise ◽  
Noise Levels ◽  
Noise Emission ◽  
Wall Jets ◽  
Trailing Edge ◽  
Number Range ◽  
Nozzle Height ◽  
Plate Length

The present study experimentally investigates the effect of the growth of inner layer on noise emission characteristics of wall jets. The plate length L considered for the current study vary in the range of L/h = 2.5 to 30, where h is the nozzle height. The jet is issued from a nozzle having the exit dimensions of 20 cm in width and 2 cm in height h. The jet Reynolds number, based on the nozzle height and jet exit velocity Uj, is varied up to 7.0 · 104. Acoustic measurements revealed the distinct variations in the noise levels with different plate lengths. The L/h = 2.5 wall jet has an increase in noise levels by around 10 dB compared to that of a free jet (background noise). Wall jets in the range of L/h = 5 to 20 radiate higher noise levels compared to other plates, while the least noise emissions are observed from fully developed wall jets (L/h > 20). The significant sources identified for noise emissions are the trailing edge and the secondary shear layer in the wall jets. The low frequency noise corresponding to the Strouhal number (based on h) below 0.2 is characterized as the trailing edge noise. The spectra of the wall jets collapse in the Strouhal number range (based on the inner layer thickness of wall jets) of ∼0.2 to 1.0 indicating the secondary shear layer noise of wall jets.

Engineering Extrapolation to Flight Reynolds Number for Supercritical Airfoil Pressure Distribution Based on CFD Results

2013 ◽  
Vol 444-445 ◽  
pp. 517-523
Author(s):  
Da Wei Liu ◽  
Xin Xu ◽  
Zhi Wei ◽  
De Hua Chen
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Pressure Distribution ◽  
Low Reynolds Number ◽  
Trailing Edge ◽  
Supercritical Airfoil ◽  
Short Period ◽  
Wind Tunnel Data ◽  
Mach Numbers ◽  
Low Reynolds

Pressure distribution of supercritical airfoil at flight Reynolds number could not be fully simulated except in cryogenic wind tunnel such as NTF (National Transonic Facility) and ETW (European Transonic Wind tunnel), which is costly and time resuming. This paper aimed to explore an engineering extrapolation to flight Reynolds number from low Reynolds number wind tunnel data for supercritical airfoil pressure distribution. However, the extrapolation method requiring plenty of data was investigated based on the CFD results for the reason of low cost and short period. Flows over a typical supercritical airfoil were numerically simulated by solving the two dimensional Navier-Stokes equations, with applications of ROE scheme spatial discretization and LU-SGS time march. Influence of computational grids convergence and turbulent models were investigated during the process of simulation. The supercritical airfoil pressure distribution were obtained with Reynolds numbers varied from 3.0×106to 30×106per airfoil chord, angles of attack from 0 degree to 6 degree and Mach numbers from 0.74 to 0.8. Simulated results indicated that weak shock existed on the upper surface of supercritical airfoil at cruise condition, that the shock location, shock strength and trailing edge pressure were dependent of Reynolds number, attack angles and Mach numbers. A similar parameter describing the Reynolds number effects factors was obtained by analyzing the relationship of shock wave location, shock front pressure and trailing edge pressure. Based on the similar parameter, airfoil pressure distribution at Reynolds number 30×106was obtained by extrapolation. It was shown that extrapolated result compared well with simulated result at Reynolds number 30×106, implying that the engineering method was at least promising applying to the extrapolation of low Reynolds number wind tunnel data.

The plane turbulent shear layer with periodic excitation

1985 ◽  
Vol 150 ◽  
pp. 281-309 ◽  
Author(s):  
H. E. Fiedler ◽  
P. Mensing
Keyword(s):  
Shear Layer ◽  
Vortex Formation ◽  
Turbulent Shear ◽  
Universal Curve ◽  
Periodic Excitation ◽  
Trailing Edge ◽  
Turbulent Shear Layer ◽  
Vortex Pairing ◽  
Turbulent Separation ◽  
Neutral Flow

The influence of periodic excitation on a plane turbulent one-stream shear layer with turbulent separation was investigated. For the qualitative study flow visualization was employed. Quantitative data were obtained with hot-wire anemometry and spectrum analysis. It was found that sinusoidal perturbations with frequencies of order f0 [lsim ] u0/100θ0 (depending on excitation strength), introduced at the trailing edge are always amplified. Maximum amplification factors are observed for the lowest perturbation levels. The frequency and amplitude of excitation determine the downstream location of the amplification maximum in the flow. At sufficient amplitude two-dimensional vortices are formed which subsequently decay without pairing. The development of the periodic r.m.s. values along x follows a universal curve for all frequencies and amplitudes when properly normalized.At high excitation amplitudes the flow development depends strongly on the geometrical conditions of the excitation arrangement at the trailing edge. Thus regular vortex pairing as well as suppression of pairing can be achieved.The excited shear layer has considerably stronger, yet nonlinear, spread than the neutral. The region of vortex formation, irrespective of whether it includes pairing or not, is associated with a step-like increase in width, while after the position of maximum vortex energy, i.e. in the region of decay, the spread is reduced to values below the neutral. There the overall lateral fluctuation energy is increased, while the longitudinal may be decreased as compared with the neutral flow.

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