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

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.

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

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.

Modelling Vortex Generating Jet-Induced Transition in Low-Pressure Turbines

2013 ◽  
Author(s):  
Florian Herbst ◽  
Andreas Fiala ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
Cross Flow ◽  
Transition Process ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Layer Transition ◽  
Wall Flows

The current design of low-pressure turbines (LPTs) with steady-blowing vortex generating jets (VGJ) uses steady computational fluid dynamics (CFD). The present work aims to support this design approach by proposing a new semi-empirical transition model for injection-induced laminar-turbulent boundary layer transition. It is based on the detection of cross-flow vortices in the boundary layer which cause inflectional cross-flow velocity profiles. The model is implemented in the CFD code TRACE within the framework of the γ-Reθ transition model and is a reformulated, re-calibrated, and extended version of a previously presented model. It is extensively validated by means of VGJ as well as non-VGJ test cases capturing the local transition process in a physically reasonable way. Quantitative aerodynamic design parameters of several VGJ configurations including steady and periodic-unsteady inflow conditions are predicted in good accordance with experimental values. Furthermore, the quantitative prediction of end-wall flows of LPTs is improved by detecting typical secondary flow structures. For the first time, the newly derived model allows the quantitative design and optimization of LPTs with VGJs.

Coupled Heat Transfer Simulations of Air-Cooled Turbines with an Algebraic Transition Model

2012 ◽  
Vol 455-456 ◽  
pp. 1153-1159
Author(s):  
Qiang Wang ◽  
Zhao Yuan Guo ◽  
Guo Tai Feng
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Load ◽  
Transition Process ◽  
Test Case ◽  
Transition Model ◽  
High Pressure Turbine ◽  
Coupled Heat Transfer ◽  
Turbulent Transition ◽  
Turbine Vane

The investigation was to study the effect of laminar-turbulent transition on predicting thermal load of vane. The Abu-Ghannam and Shaw (AGS) algebraic transition model was applied in the coupled solver, HIT3D. Then the solver was employed to carry out coupled heat transfer simulations, and the test case was 5411 run of NASA0-MARKⅡ vane, a high-pressure turbine vane. The results shown that AGS model was able to predict the transition process in the boundary layer near the vane, and that the simulation with such model leads to thermal load agreeing well the measured one. Then the developed solver was applied to predict a low-pressure vane, and the results shown that CHT simulation with full turbulence model would predict higher thermal load than that with transition model.

Modeling Vortex Generating Jet-Induced Transition in Low-Pressure Turbines

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Florian Herbst ◽  
Andreas Fiala ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
Cross Flow ◽  
Transition Process ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Layer Transition ◽  
Wall Flows

The current design of low-pressure turbines (LPTs) with steady-blowing vortex generating jets (VGJs) uses steady computational fluid dynamics (CFD). The present work aims to support this design approach by proposing a new semiempirical transition model for injection-induced laminar-turbulent boundary layer transition. It is based on the detection of cross-flow vortices in the boundary layer which cause inflectional cross-flow velocity profiles. The model is implemented in the CFD code TRACE within the framework of the γ-Reθ transition model and is a reformulated, recalibrated, and extended version of a previously presented model. It is extensively validated by means of VGJ as well as non-VGJ test cases capturing the local transition process in a physically reasonable way. Quantitative aerodynamic design parameters of several VGJ configurations including steady and periodic-unsteady inflow conditions are predicted in good accordance with experimental values. Furthermore, the quantitative prediction of end-wall flows of LPTs is improved by detecting typical secondary flow structures. For the first time, the newly derived model allows the quantitative design and optimization of LPTs with VGJs.

scholarly journals Symmetry breaking Paradigm In Typical Laminar-Turbulence Transition System

2021 ◽  
Author(s):  
Huang Chun ◽  
Yuchen Jiang
Keyword(s):  
Symmetry Breaking ◽  
Liquid Surface ◽  
Transition Process ◽  
Transition Theory ◽  
Effective Theory ◽  
Arnold Tongue ◽  
Turbulent Transition ◽  
Turbulence Transition ◽  
Ideal System ◽  
Natural Result

Abstract A stationary cylindrical vessel containing a rotating plate near the bottle surface is partially filled with liquid. With the bottom rotating, the shape of the liquid surface would become polygon-like. This polygon vortex phenomenon is a ideal system to demonstrate the Laminar-Turbulent transition process. Within the framework of equilibrium statistical mechanics, a profound comparison with Landau's phase transition theory was applied in symmetry breaking aspect to derive the evolution equation of this system phenomenologically. Comparison between theoretical prediction and experimental data is carried out. We concluded a considerably highly matched result, while some exceptions are viewed as the natural result that the experiment break through the up-limit of using equilibrium mechanics as a effective theory, namely breaking through the Arnold Tongue. Some extremely complex Non-equilibrium approaches was desired to solve this problem thoroughly in the future. So our method could be viewed as a linear approximation of this theoretical framework.

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