Flow Separation and Performance of Decelerating Channels for Centrifugal Turbomachines

1975 ◽  
Vol 97 (3) ◽  
pp. 388-394 ◽  
Author(s):  
Teruo Sakurai
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Pressure Rise ◽  
Logarithmic Spiral ◽  
Performance Pressure ◽  
Boundary Layer Development ◽  
And Performance ◽  
Layer Development

Fundamental studies on diffusers were performed in order to get a better knowledge of flow in centrifugal turbomachines and to improve their performance. First, the flow inside channels with logarithmic spiral walls was investigated. Boundary layer development and its effect on the diffuser performance (pressure-rise and its efficiency) were analyzed. Effects of diffuser configurations in circular cascades were also made clear. Further, separation in impellers with logarithmic spiral blades was computed and discussed.

Shock-boundary layer interaction and transition modelling in turbomachinery flows

1997 ◽  
Vol 211 (3) ◽  
pp. 225-234 ◽  
Author(s):  
V Michelassi
Keyword(s):  
Boundary Layer ◽  
Turbine Blade ◽  
Turbulence Model ◽  
Flow Separation ◽  
Good Description ◽  
Suction Side ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Boundary Layer Development ◽  
Layer Development

The transonic turbulent compressible flow in channels and turbine linear cascades is computed by using a Navier-Stokes solver. Turbulence effects are simulated by means of the k-ω turbulence model. A realiability constraint is introduced to improve the turbulence model performances and stability in the presence of stagnation points. In both the flow over the bump and the turbine blade, the shock induces a flow separation that affects the boundary layer development. In both cases the proposed model succeeds in predicting the flow separation. For the flow over the turbine blade a simple transition model based on integral parameters is introduced to mimic the effect of the boundary layer transition across the shock wave on the suction side. Relaminarization is also properly predicted on the pressure side, thereby allowing a good description of the boundary layer development and shock pattern.

The prediction of turbulent boundary layer development in compressible flow

1968 ◽  
Vol 31 (4) ◽  
pp. 753-778 ◽  
Author(s):  
J. E. Green
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Compressible Flow ◽  
Pressure Rise ◽  
Skin Friction Coefficient ◽  
Empirical Method ◽  
Entrainment Rate ◽  
Flat Plates ◽  
Boundary Layer Development ◽  
Layer Development

Starting from Head's semi-empirical method for incompressible flow, two approaches to the prediction of turbulent boundary-layer development in compressible flow are explored. The first uses Head's incompressible method in conjunction with a compressibility transformation similar to Stewartson's transformation for laminar flow; the second carries over Head's physical arguments to treat the compressible flow directly. Measurements in supersonic flow, both on flat plates and downstream of an abrupt pressure rise, show broad agreement with the predictions of the second method but do not support the compressibility transformation. In particular, measurements on flat plates reveal that as Mach number increases the entrainment rate decreases to a lesser extent than the skin-friction coefficient. Whilst this result is consistent with the second treatment in this paper, it is difficult to reconcile with any of the compressibility transformations discussed, and the validity of these transformations in turbulent flow is therefore questioned.

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

Endwall Boundary Layer Development in a Multistage Low-Speed Compressor With Tandem Stator Vanes

2021 ◽  
Author(s):  
Michael Hopfinger ◽  
Volker Gümmer
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Shear Stresses ◽  
Flow Area ◽  
Stage Design ◽  
Low Speed ◽  
Boundary Layer Development ◽  
Viscous Shear ◽  
Layer Development ◽  
Highly Loaded

Abstract The development of viscous endwall flow is of major importance when considering highly-loaded compressor stages. Essentially, all losses occurring in a subsonic compressor are caused by viscous shear stresses building up boundary layers on individual aerofoils and endwall surfaces. These boundary layers cause significant aerodynamic blockage and cause a reduction in effective flow area, depending on the specifics of the stage design. The presented work describes the numerical investigation of blockage development in a 3.5-stage low-speed compressor with tandem stator vanes. The research is aimed at understanding the mechanism of blockage generation and growth in tandem vane rows and across the entire compressor. Therefore, the blockage generation is investigated as a function of the operating point, the rotational speed and the inlet boundary layer thickness.

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