Simulation of Transitional Boundary-Layer Development on a Highly-Loaded Turbine Cascade With Advanced RANS Modeling

2003 ◽  
Author(s):  
D. Keith Walters ◽  
James H. Leylek
Keyword(s):  
Boundary Layer ◽  
Single Point ◽  
Turbulence Models ◽  
Boundary Layer Transition ◽  
Mean Velocity ◽  
Layer Transition ◽  
New Model ◽  
Boundary Layer Development ◽  
Layer Development ◽  
Highly Loaded

This paper documents computational simulations of the flow over a modern, highly-loaded turbine vane, including boundary-layer transition. Accurate prediction of transition has traditionally been difficult for commonly available RANS-based turbulence models. The present simulations used an advanced version of a three-equation eddy viscosity model recently developed and documented by the current authors. The new model is an elliptic single-point method, developed based on considerations of the universal character of pre-transitional boundary layers that have recently been published in the open literature. Simulations were performed at an engine-realistic chord Reynolds number (2.3×105) and with varying freestream turbulence intensities of 0.6, 10, and 19.5%. Detailed comparisons are made within the developing boundary layer, on both the suction and pressure surfaces, between the simulations and high-fidelity experimental measurements that have been previously documented in the open literature. Comparison of both mean velocity and Reynolds stress profiles indicates that the new model shows potential for predicting boundary layer development, including development of pre-transitional fluctuations and subsequent breakdown to turbulence.

A New Model for Boundary-Layer Transition Using a Single-Point RANS Approach

2002 ◽  
Author(s):  
D. Keith Walters ◽  
James H. Leylek
Keyword(s):  
Boundary Layer ◽  
Single Point ◽  
Turbulence Models ◽  
Boundary Layer Transition ◽  
Heated Wall ◽  
Test Cases ◽  
Predictive Tool ◽  
Layer Transition ◽  
New Model ◽  
Free Stream Turbulence

This paper presents the development and implementation of a new model for bypass and natural transition prediction using Reynolds-Averaged Navier-Stokes (RANS) CFD, based on modification of two-equation, linear eddy-viscosity turbulence models. The new model is developed herein based on considerations of the universal character of transitional boundary layers that have recently been documented in the open literature, and implemented into a popular commercial CFD code (Fluent) in order to assess its performance. Two transitional test cases are presented: (1) a boundary layer developing on a flat heated wall, with free-stream turbulence intensity (Tu∞) ranging from 0.2 to 6%; and (2) flow over a turbine stator vane, with chord Reynolds number 2.3×105, and Tu∞ from 0.6 to 20%. Results are presented in terms of Stanton number, and compared to experimental data for both cases. Results show good agreement with the test cases and suggest that the new approach has potential as a predictive tool.

A New Model for Boundary Layer Transition Using a Single-Point RANS Approach

2004 ◽  
Vol 126 (1) ◽  
pp. 193-202 ◽  
Author(s):  
D. Keith Walters ◽  
James H. Leylek
Keyword(s):  
Boundary Layer ◽  
Single Point ◽  
Turbulence Models ◽  
Boundary Layer Transition ◽  
Heated Wall ◽  
Test Cases ◽  
Predictive Tool ◽  
Layer Transition ◽  
New Model ◽  
Free Stream Turbulence

This paper presents the development and implementation of a new model for bypass and natural transition prediction using Reynolds-averaged Navier-Stokes computational fluid dynamics (CFD), based on modification of two-equation, linear eddy-viscosity turbulence models. The new model is developed herein based on considerations of the universal character of transitional boundary layers that have recently been documented in the open literature, and implemented into a popular commercial CFD code (FLUENT) in order to assess its performance. Two transitional test cases are presented: (1) a boundary layer developing on a flat heated wall, with free-stream turbulence intensity Tu∞ ranging from 0.2 to 6%; and (2) flow over a turbine stator vane, with chord Reynolds number 2.3×105, and Tu∞ from 0.6 to 20%. Results are presented in terms of Stanton number, and compared to experimental data for both cases. Results show good agreement with the test cases and suggest that the new approach has potential as a predictive tool.

Free-Stream Turbulence and Pressure Gradient Effects on Heat Transfer and Boundary Layer Development on Highly Cooled Surfaces

1985 ◽  
Vol 107 (1) ◽  
pp. 54-59 ◽  
Author(s):  
K. Rued ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Stream ◽  
Boundary Layer Transition ◽  
Pressure Gradients ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Boundary Layer Development ◽  
Gradient Effects ◽  
Layer Development

Heat transfer and boundary layer measurements were derived from flows over a cooled flat plate with various free-stream turbulence intensities (Tu = 1.6–11 percent), favorable pressure gradients (k = νe/ue2•due/dx = 0÷6•10−6) and cooling intensities (Tw/Te = 1.0–0.53). Special interest is directed towards the effects of the dominant parameters, including the influence on laminar to turbulent boundary layer transition. It is shown, that free-stream turbulence and pressure gradients are of primary importance. The increase of heat transfer due to wall cooling can be explained primarily by property variations as transition, and the influence of free-stream parameters are not affected.

Effects of Turbulence and Solidity on the Boundary Layer Development in a Low Pressure Turbine

2000 ◽  
Author(s):  
W. J. Solomon
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Boundary Layer Transition ◽  
Turbulence Level ◽  
Suction Surface ◽  
Layer Transition ◽  
Laminar Separation ◽  
Second Stage ◽  
Boundary Layer Development ◽  
Layer Development

Multiple-element surface hot-film instrumentation has been used to investigate boundary layer development in the 2 stage Low Speed Research Turbine (LSRT). Measurements from instrumentation located along the suction surface of the second stage nozzle at mid-span are presented. These results contrast the unsteady, wake-induced boundary layer transition behaviour for various turbine configurations. The boundary layer development on two new turbine blading configurations with identical design vector diagrams but substantially different loading levels are compared with a previously published result. For the conventional loading (Zweifel coefficient) designs, the boundary layer transition occurred without laminar separation. At reduced solidity, wake-induced transition started upstream of a laminar separation line and an intermittent separation bubble developed between the wake-influenced areas. A turbulence grid was installed upstream of the LSRT turbine inlet to increase the turbulence level from about 1% for clean-inlet to about 5% with the grid. The effect of turbulence on the transition onset location was smaller for the reduced solidity design than the baseline. At the high turbulence level, the amplitude of the streamwise fluctuation of the wake-induced transition onset point was reduced considerably. By clocking the first stage nozzle row relative to the second, the alignment of the wake-street from the first stage nozzle with the suction surface of the second stage nozzle was varied. At particular wake clocking alignments, the periodicity of wake induced transition was almost completely eliminated.

Numerical Investigation on the Second Stator Boundary Layer Under Clocking Effects: Comparison of v2f and LCL-Model

2008 ◽  
Author(s):  
Axel Heidecke ◽  
Bernd Stoffel
Keyword(s):  
Boundary Layer ◽  
Numerical Investigation ◽  
Separation Bubble ◽  
Measurement Data ◽  
Turbulence Models ◽  
Boundary Layer Transition ◽  
Navier Stokes ◽  
Layer Transition ◽  
Numerical Work ◽  
Boundary Layer Development

This paper presents the results of a numerical investigation of a 1.5-stage low pressure turbine. The main focus of the numerical work was the prediction of the stator-2 boundary layer development under the influence of the stator stator clocking. The turbine profile used for the examination is a so called high-lift-profile and was designed for a laminar-turbulent transition over a steady separation bubble. The boundary conditions were defined by the 1.5-stage test turbine located at our laboratory, where also the measurement data was derived from. The calculations were conducted with a two-dimensional Navier-Stokes solver using a finite volume discretisation scheme. The higher level turbulence models v′2-f and the LCL-turbulence model, which are capable to predict boundary layer transition were compared with measurement data at midspan.

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.

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.

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.

Boundary Layer Transition Under High Free-Stream Turbulence and Strong Acceleration Conditions: Part 1—Mean Flow Results

1997 ◽  
Vol 119 (3) ◽  
pp. 420-426 ◽  
Author(s):  
R. J. Volino ◽  
T. W. Simon
Keyword(s):  
Boundary Layer ◽  
Skin Friction ◽  
Free Stream ◽  
Boundary Layer Transition ◽  
Temperature Profiles ◽  
Mean Flow ◽  
Transfer Coefficients ◽  
Mean Velocity ◽  
Layer Transition ◽  
Free Stream Turbulence

Measurements from heated boundary layers along a concave-curved test wall subject to high (initially 8 percent) free-stream turbulence intensity and strong (K = (ν/U∞2) dU∞/dx) as high as 9 × 10−6) acceleration are presented and discussed. Conditions for the experiments were chosen to roughly simulate those present on the downstream half of the pressure side of a gas turbine airfoil. Mean velocity and temperature profiles as well as skin friction and heat transfer coefficients are presented. The transition zone is of extended length in spite of the high free-stream turbulence level. Transitional values of skin friction coefficients and Stanton numbers drop below flat-plate, low-free-stream-turbulence, turbulent flow correlations, but remain well above laminar flow values. The mean velocity and temperature profiles exhibit clear changes in shape as the flow passes through transition. To the authors’ knowledge, this is the first detailed documentation of a high-free-stream-turbulence boundary layer flow in such a strong acceleration field.

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