Intermittency based RANS bypass transition modelling

2006 ◽  
Vol 6 (1/2/3) ◽  
pp. 68 ◽  
Author(s):  
Koen Lodefier ◽  
Bart Merci ◽  
Chris De Langhe ◽  
Erik Dick
Keyword(s):  
Bypass Transition ◽  
Transition Modelling

Effect of the gas to wall temperature ratio on the bypass transition

2019 ◽  
pp. 1-12 ◽  
Author(s):  
Riccardo Rubini ◽  
Roberto Maffulli ◽  
Tony Arts
Keyword(s):  
Turbulence Models ◽  
Boundary Layer Transition ◽  
Effect Of Temperature ◽  
Bypass Transition ◽  
Temperature Ratio ◽  
Layer Transition ◽  
Turbulent Transition ◽  
Transition Models ◽  
Transition Modelling ◽  
Research And Design

The study of the boundary layer transition plays a fundamental role in the field of turbomachinery. The main reason is the strong influence of the transition on the flow field local parameters, such as skin friction and heat transfer, this variation is reflected on the global ones such as efficiency and heat load of the blade row. Turbulent transition models are nowadays commonly used tools in both CFD research and design practice. It is then of particular interest to understand if they are able to predict the effect of temperature on bypass transition and, in case of positive answer, the reasons of their behaviour. This becomes even more interesting as the effect of the flow aero-thermal coupling becomes prominent in the analysis of such phenomena and is typically not accounted for in the validation of turbulence models. In this work we focus our attention on two state of the art transition model that use two radically different approaches to describe transition. To isolate the effects of the temperature ratio on the transition the simulations have been performed keeping the same values of Reynolds and Mach numbers and changing the value of the wall to freestream Temperature Ratio (TR). The results of the two transition models have been compared between them as well as with experimental results. They show that both models are sensitive to TR, though a locally based (rather than correlation based) approach for transition modelling should be favoured.

Transition Modelling With the SST Turbulence Model and an Intermittency Transport Equation

2003 ◽  
Author(s):  
Koen Lodefier ◽  
Bart Merci ◽  
Chris De Langhe ◽  
Erik Dick
Keyword(s):  
Turbulence Model ◽  
Turbulent Viscosity ◽  
Transition Model ◽  
Bypass Transition ◽  
Model Following ◽  
Sst Model ◽  
Sst Turbulence Model ◽  
Transition Modelling ◽  
Intermittency Factor

A transition model for describing bypass transition is presented. It is based on a two-equations k–ω model and a dynamic equation for intermittency factor. The intermittency factor is a multiplier of the turbulent viscosity computed by the turbulence model. Following a suggestion by Menter et al. [1], the start of transition is computed based on local variables. The choice of the Shear-Stress Transport (SST) model instead of a k–ε model is explained. The quality of the transition model, developed on flat plate test cases, is illustrated for cascades.

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.

Effects of Reynolds Number and Free-Stream Turbulence on Boundary Layer Transition in a Compressor Cascade

2000 ◽  
Author(s):  
Heinz-Adolf Schreiber ◽  
Wolfgang Steinert ◽  
Bernhard Küsters
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Bypass Transition ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
High Reynolds Numbers ◽  
High Turbulence ◽  
High Reynolds

An experimental and analytical study has been performed on the effect of Reynolds number and free-stream turbulence on boundary layer transition location on the suction surface of a controlled diffusion airfoil (CDA). The experiments were conducted in a rectilinear cascade facility at Reynolds numbers between 0.7 and 3.0×106 and turbulence intensities from about 0.7 to 4%. An oil streak technique and liquid crystal coatings were used to visualize the boundary layer state. For small turbulence levels and all Reynolds numbers tested the accelerated front portion of the blade is laminar and transition occurs within a laminar separation bubble shortly after the maximum velocity near 35–40% of chord. For high turbulence levels (Tu > 3%) and high Reynolds numbers transition propagates upstream into the accelerated front portion of the CDA blade. For those conditions, the sensitivity to surface roughness increases considerably and at Tu = 4% bypass transition is observed near 7–10% of chord. Experimental results are compared to theoretical predictions using the transition model which is implemented in the MISES code of Youngren and Drela. Overall the results indicate that early bypass transition at high turbulence levels must alter the profile velocity distribution for compressor blades that are designed and optimized for high Reynolds numbers.

Heat Transfer Committee and Turbomachinery Committee Best Paper of 1996 Award: The Path to Predicting Bypass Transition

1997 ◽  
Vol 119 (3) ◽  
pp. 405-411 ◽  
Author(s):  
R. E. Mayle ◽  
A. Schulz
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Energy Equation ◽  
Free Stream ◽  
Bypass Transition ◽  
Turbulence Level ◽  
Free Stream Turbulence ◽  
Energy Profiles ◽  
Computer Codes ◽  
Good Agreement

A theory is presented for calculating the fluctuations in a laminar boundary layer when the free stream is turbulent. The kinetic energy equation for these fluctuations is derived and a new mechanism is revealed for their production. A methodology is presented for solving the equation using standard boundary layer computer codes. Solutions of the equation show that the fluctuations grow at first almost linearly with distance and then more slowly as viscous dissipation becomes important. Comparisons of calculated growth rates and kinetic energy profiles with data show good agreement. In addition, a hypothesis is advanced for the effective forcing frequency and free-stream turbulence level that produce these fluctuations. Finally, a method to calculate the onset of transition is examined and the results compared to data.

Bypass transition in flow over a vibrating flat plate

2020 ◽  
Vol 909 ◽  
Author(s):  
Wenlin Huang ◽  
Dandan Xiao ◽  
Jie Ren ◽  
Zhiheng Wang ◽  
Guang Xi ◽  
...  
Keyword(s):  
Flat Plate ◽  
Bypass Transition

Abstract

Influence of Gas-to-Wall Temperature Ratio on By-Pass Transition

2017 ◽  
Author(s):  
Tânia S. Cação Ferreira ◽  
Tony Arts
Keyword(s):  
Heat Flux ◽  
Wall Temperature ◽  
Analog Circuits ◽  
Guide Vane ◽  
Operating Conditions ◽  
Wall Heat Flux ◽  
Bypass Transition ◽  
Temperature Ratio ◽  
Isentropic Compression ◽  
Pressure Transducers

An investigation of thermal effects on bypass transition was conducted on the highly-loaded turbine guide vane LS89 in the short-duration isentropic Compression Tube (CT-2) facility at the von Karman Institute for Fluid Dynamics (VKI). Measurements from high response surface-mounted thin films coupled with analog circuits provided the time-resolved wall heat flux history whereas pneumatic probes, differential pressure transducers and thermocouples allowed the accurate definition of the inlet and outlet flow conditions. The gas-to-wall temperature ratio, ranging from 1.11 to 1.55, was varied by changing the inlet total temperature. The isentropic exit Mach number ranged from 0.90 to 1.00 and the global freestream turbulence intensity value was set at 0.8, 3.9 and 5.3%. The isentropic exit Reynolds number was kept at 106. The onset of transition was tracked through the wall heat flux signal fluctuations. Within the present operating conditions, no significant effect of the gas/wall temperature ratio was put in evidence. At the present (design) transonic exit conditions, the local free-stream pressure gradient appears to remain the main driver of the onset of transition. A wider range of operating conditions must be considered to draw final conclusions.

Stabilisation of subcritical bypass transition in the leading-edge boundary layer by suction

2014 ◽  
Vol 15 (11) ◽  
pp. 795-805 ◽  
Author(s):  
Michael O. John ◽  
Dominik Obrist ◽  
Leonhard Kleiser
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Bypass Transition
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