Validation of SA-γ-Reθtand SA-γ turbulence/transition model

AbstractIt is very important to predict the bypass transition in the simulation of flows through turbomachinery. This paper presents a four-equation eddy-viscosity turbulence transition model for prediction of bypass transition. It is based on the SST turbulence model and the laminar kinetic energy concept. A transport equation for the non-turbulent viscosity is proposed to predict the development of the laminar kinetic energy in the pre-transitional boundary layer flow which has been observed in experiments. The turbulence breakdown process is then captured with an intermittency transport equation in the transitional region. The performance of this new transition model is validated through the experimental cases of T3AM, T3A and T3B. Results in this paper show that the new transition model can reach good agreement in predicting bypass transition, and is compatible with modern CFD software by using local variables.

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Extension of the KDO Turbulence/Transition Model to Account for Roughness

10.21203/rs.3.rs-818524/v1 ◽

2021 ◽

Author(s):

Chunfei FANG ◽

Jinglei Xu

Keyword(s):

Cross Flow ◽

Transition Process ◽

Roughness Height ◽

Transition Model ◽

Wall Roughness ◽

Roughness Effect ◽

Developed Turbulence ◽

Turbulent Transition ◽

Turbulence Transition ◽

Grain Surface

Abstract Wall roughness significantly influences both laminar-turbulent transition process and fully developed turbulence. This work has developed a wall roughness extension for the KDO turbulence/transition model. The roughness effect is introduced via the modification of the k and νt boundary conditions, i.e., the wall is considered to be raised at an extra height. The equivalent roughness height is linked to the actual roughness height, and the ratio between them is determined by reasoning. With such a roughness extension, the predictions of the KDO RANS model agree well with the measurements of turbulent boundary layer with a sand grain surface, while the KDO transition model yields accurate cross-flow transition predictions of flow past a 6:1 spheroid.

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Extension of the KDO turbulence/transition model to account for roughness

Advances in Aerodynamics ◽

10.1186/s42774-021-00092-9 ◽

2022 ◽

Vol 4 (1) ◽

Author(s):

Chunfei Fang ◽

Jinglei Xu

Keyword(s):

Cross Flow ◽

Transition Process ◽

Roughness Height ◽

Original Position ◽

Transition Model ◽

Wall Roughness ◽

Developed Turbulence ◽

Turbulence Transition ◽

The Difference ◽

Grain Surface

AbstractWall roughness significantly influences both laminar-turbulent transition process and fully developed turbulence. A wall roughness extension for the KDO turbulence/transition model is developed. The roughness effect is introduced via the modification of the k and νt boundary conditions. The wall is considered to be lifted to a higher position. The difference between the original position and the higher position, named as equivalent roughness height, is linked to the actual roughness height. The ratio between the two heights is determined by reasoning. With such a roughness extension, the predictions of the KDO RANS model agree well with the measurements of turbulent boundary layer with a sand grain surface, while the KDO transition model yields accurate cross-flow transition predictions of flow past a 6:1 spheroid.

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On numerical simulation of flexibly supported airfoil in interaction with incompressible fluid flow using laminar–turbulence transition model

Computers & Mathematics with Applications ◽

10.1016/j.camwa.2019.12.022 ◽

2020 ◽

Author(s):

Ondřej Winter ◽

Petr Sváček

Keyword(s):

Numerical Simulation ◽

Fluid Flow ◽

Incompressible Fluid ◽

Transition Model ◽

Incompressible Fluid Flow ◽

Turbulence Transition

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Modeling Curvature Effects on Turbulence Transition for Turbomachinery Flows

Volume 2B: Turbomachinery ◽

10.1115/gt2014-26958 ◽

2014 ◽

Cited By ~ 1

Author(s):

Enrico Rinaldi ◽

Roberto Suarez Raspopov ◽

Piero Colonna ◽

Rene Pecnik

Keyword(s):

Experimental Data ◽

Correction Term ◽

Pressure Coefficient ◽

Practical Interest ◽

Transition Model ◽

Estimation Of Parameters ◽

Curvature Effects ◽

Turbulence Transition ◽

Turbulence Production ◽

Prediction Capability

The rotation-curvature correction proposed by Spalart and Shur is implemented in the γ–Re~θt transition model of Langtry and Menter. The correction term modifies the turbulence production such that it is damped in convex curvatures and enhanced otherwise. The curvature corrected transition model is first validated on a U-shaped channel flow for which experimental data and reference numerical results are available. The improved prediction capability is then assessed on a series of well documented two-dimensional turbomachinery problems. A better agreement with experimental data is observed in the simulation of the transition onset, which leads to an improved estimation of parameters of practical interest such as the heat transfer and pressure coefficient.

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