Effect of large distributed leading-edge roughness on boundary layer development and transition

1995 ◽  
Author(s):  
Michael Kerho ◽  
Michael Bragg
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Boundary Layer Development ◽  
Edge Roughness ◽  
Layer Development

Separation and Relaminarization at the Circular Arc Leading Edge of a Controlled Diffusion Compressor Stator

2012 ◽  
Author(s):  
Samuel C. T. Perkins ◽  
Alan D. Henderson
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Leading Edge ◽  
Suction Surface ◽  
Circular Arc ◽  
Controlled Diffusion ◽  
Boundary Layer Development ◽  
Layer Development

This paper investigates the influence of Reynolds Number and incidence on boundary layer development at the leading edge of a controlled diffusion (CD) stator blade with circular arc leading edge profile. Steady flow measurements were made inside a large scale 2D compressor cascade at Reynolds numbers of 260,000 and 400,000 for a range of inlet flow angles corresponding to both positive and negative incidence. Detailed static pressure measurements in the leading edge region show the time-mean boundary layer development through the velocity overspeed and following region of accelerating flow on the suction surface. Separation bubbles at the leading edge of the pressure and suction surfaces trigger the boundary layer to undergo an initial and rapid transition to turbulence. On the pressure surface, the bubble forms at all values of incidence tested, whereas on the suction surface a bubble only forms for incidence greater than design. In all cases the bubble length was seen to reduce significantly as Reynolds number is increased. These trends are supported by surface flow visualization results. Quasi-wall shear stress measurements from hot-film sensors were interpreted using a hybrid threshold peak-valley-counting algorithm to yield time-averaged turbulent intermittency on each blade surface. These results in combination with raw quasi-wall shear stress traces show evidence of boundary layer relaminarization on the suction surface, downstream of the leading edge velocity overspeed in the favorable pressure gradient leading to peak suction. The relaminarization process is observed to become less effective as Reynolds number and inlet flow angle are increased. The boundary layer development is shown to have a large influence on the total blade pressure loss. At negative incidence, loss was seen to increase as Reynolds number is decreased, and in contrast at positive incidence, the opposite trend was displayed.

Cavitation noise and inception as influenced by boundary-layer development on a hydrofoil

1977 ◽  
Vol 80 (4) ◽  
pp. 617-640 ◽  
Author(s):  
William K. Blake ◽  
M. J. Wolpert ◽  
F. E. Geib
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Leading Edge ◽  
Variable Pressure ◽  
Frequency Range ◽  
Cavitation Noise ◽  
Two Phase ◽  
Boundary Layer Development ◽  
Pressure Water ◽  
Layer Development

This paper describes measurements of noise from two-phase flow over hydrofoils. The experiments were performed in a variable-pressure water tunnel which was acoustically calibrated so that sound power levels could be deduced from the sound measurements. It is partially reverberant in the frequency range of interest.Cavitation was generated on a hydrofoil in the presence of either a separated laminar boundary layer or a fully turbulent attached boundary layer. The turbulent boundary layer was formed downstream of a trip which was positioned near the leading edge. High-speed photographs show the patterns of cavitation which were obtained in each case. The noise is shown to depend on the type of cavitation produced; and for each type, the dependence on speed and cavitation index has been determined. Dimensionless spectral densities of the sound are shown for each type of flow.

Asymmetric Boundary Layer on a Nonisothermally Heated Cone

1980 ◽  
Vol 47 (3) ◽  
pp. 467-474
Author(s):  
L.-S. Yao ◽  
I. Catton ◽  
J. M. McDonough
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Leading Edge ◽  
Order Effect ◽  
Boundary Layer Stability ◽  
Boundary Layer Development ◽  
Constant Wall Heat Flux ◽  
Dimensional Boundary ◽  
Finite Difference Solution ◽  
Layer Development

The development of a three-dimensional boundary layer along a heated cone is analyzed. The surface of the cone is heated under the condition of constant wall heat flux. The perturbation solution is obtained for the flow close to the leading edge where the buoyancy force can be treated as a higher-order effect. A finite-difference solution is obtained for the flow far downstream from the leading edge where buoyancy is one of the cominant forces. The numerical results clearly describe the boundary-layer development along heated cones of different cone angles as well as the heat transfer rate. Boundary-layer stability is briefly discussed in terms of the boundary-layer shape factor.

Assessing the Influence of Aerosol on Radiation and Its Roles in Planetary Boundary Layer Development

2021 ◽  
Vol 35 (2) ◽  
pp. 384-392
Author(s):  
Zhigang Cheng ◽  
Yubing Pan ◽  
Ju Li ◽  
Xingcan Jia ◽  
Xinyu Zhang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Boundary Layer Development ◽  
Layer Development

Numerical Simulation of Turbine Blade Boundary Layer and Heat Transfer and Assessment of Turbulence Models

1997 ◽  
Vol 119 (4) ◽  
pp. 794-801 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Bypass Transition ◽  
Boundary Layer Development ◽  
Low Reynolds ◽  
Layer Development

The boundary layer development and convective heat transfer on transonic turbine nozzle vanes are investigated using a compressible Navier–Stokes code with three low-Reynolds-number k–ε models. The mean-flow and turbulence transport equations are integrated by a four-stage Runge–Kutta scheme. Numerical predictions are compared with the experimental data acquired at Allison Engine Company. An assessment of the performance of various turbulence models is carried out. The two modes of transition, bypass transition and separation-induced transition, are studied comparatively. Effects of blade surface pressure gradients, free-stream turbulence level, and Reynolds number on the blade boundary layer development, particularly transition onset, are examined. Predictions from a parabolic boundary layer code are included for comparison with those from the elliptic Navier–Stokes code. The present study indicates that the turbine external heat transfer, under real engine conditions, can be predicted well by the Navier–Stokes procedure with the low-Reynolds-number k–ε models employed.

Some Boundary Layer-Porous Wall Coupling Effects in Laminar Flows With Surface Injection

1970 ◽  
Vol 92 (3) ◽  
pp. 257-266
Author(s):  
D. A. Nealy ◽  
P. W. McFadden
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Balance ◽  
Transfer Problem ◽  
Porous Wall ◽  
Laminar Flows ◽  
Stream Velocity ◽  
Axial Conduction ◽  
Boundary Layer Development ◽  
Layer Development

Using the integral form of the laminar boundary layer thermal energy equation, a method is developed which permits calculation of thermal boundary layer development under more general conditions than heretofore treated in the literature. The local Stanton number is expressed in terms of the thermal convection thickness which reflects the cumulative effects of variable free stream velocity, surface temperature, and injection rate on boundary layer development. The boundary layer calculation is combined with the wall heat transfer problem through a coolant heat balance which includes the effect of axial conduction in the wall. The highly coupled boundary layer and wall heat balance equations are solved simultaneously using relatively straightforward numerical integration techniques. Calculated results exhibit good agreement with existing analytical and experimental results. The present results indicate that nonisothermal wall and axial conduction effects significantly affect local heat transfer rates.

Boundary Layer Development and Spillway Energy Losses

1965 ◽  
Vol 91 (3) ◽  
pp. 149-163
Author(s):  
Frank B. Campbell ◽  
Robert C. Cox ◽  
Marden B. Boyd
Keyword(s):  
Boundary Layer ◽  
Energy Losses ◽  
Boundary Layer Development ◽  
Layer Development
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