Impact of Turbulence Model Irregularity on High-Order Discretizations

2009 ◽  
Author(s):  
Todd Oliver ◽  
David Darmofal
Keyword(s):  
Turbulence Model ◽  
High Order

Simulation of the Transitional Flow in a Low Pressure Gas Turbine Cascade With a High-Order Discontinuous Galerkin Method

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
A. Ghidoni ◽  
A. Colombo ◽  
S. Rebay ◽  
F. Bassi
Keyword(s):  
Discontinuous Galerkin ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Time Integration ◽  
High Order ◽  
Transitional Flow ◽  
Navier Stokes ◽  
Implicit Time ◽  
Turbine Cascade ◽  
High Reynolds

In the last decade, discontinuous Galerkin (DG) methods have been the subject of extensive research efforts because of their excellent performance in the high-order accurate discretization of advection-diffusion problems on general unstructured grids, and are nowadays finding use in several different applications. In this paper, the potential offered by a high-order accurate DG space discretization method with implicit time integration for the solution of the Reynolds-averaged Navier–Stokes equations coupled with the k-ω turbulence model is investigated in the numerical simulation of the turbulent flow through the well-known T106A turbine cascade. The numerical results demonstrate that, by exploiting high order accurate DG schemes, it is possible to compute accurate simulations of this flow on very coarse grids, with both the high-Reynolds and low-Reynolds number versions of the k-ω turbulence model.

A high-order Discontinuous Galerkin solver for the incompressible RANS and k–ω turbulence model equations

2014 ◽  
Vol 98 ◽  
pp. 54-68 ◽  
Author(s):  
F. Bassi ◽  
A. Ghidoni ◽  
A. Perbellini ◽  
S. Rebay ◽  
A. Crivellini ◽  
...  
Keyword(s):  
Discontinuous Galerkin ◽  
Turbulence Model ◽  
High Order ◽  
Model Equations

Studies on Unsteady Flow Characteristics in a High Pressure Turbine Cascade Based on a High-Order Large Eddy Simulation Turbulence Model

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Tomohiko Jimbo ◽  
Debasish Biswas ◽  
Yoshiki Niizeki
Keyword(s):  
Turbulence Model ◽  
Physical Process ◽  
Pressure Loss ◽  
Flow Behavior ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Measured Data ◽  
High Order ◽  
Loss Mechanism

In the present paper, unsteady viscous flow analysis around turbine blade cascade using a high-order LES turbulence model is carried out to investigate the basic physical process involved in the pressure loss mechanism. This numerical analysis is assessed to the wind tunnel cascade test. Basically, all the physical phenomena occurring in nature are the effect of some cause, and the effect can somehow be measured. However, to understand the cause, detail information regarding the visualization of the phenomena, which are difficult to measure, are necessary. Therefore, in the present paper, firstly the computed results are compared with the measured data, which are the final outcome of the cause (of the phenomena under investigation), to verify whether our physics-based model could qualitatively predict the measured facts or not. It was found that the present model could well predict measured data. Therefore, the rest of the computed information, which were difficult to measure, were used to visualize the overall flow behavior for acquiring some knowledge of the physical process associated with the pressure loss mechanism. The present study led to an understanding that the interaction of the vortex generated on the suction and pressure surface of the blade and the secondary vortex generated on the end wall, downstream of the trailing edge, resulted in the formation of a large vortex structure in this region. This unsteady three-dimensional flow characteristic is expected to play an important role in the pressure loss mechanism.

Order of Accuracy and Sensitivity to Freestream Conditions of a Modified k-ω Turbulence Model for High-Order Finite Element Methods

2020 ◽  
Author(s):  
Nojan Bagheri-Sadeghi ◽  
Brian T. Helenbrook ◽  
Kenneth D. Visser
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Flat Plate ◽  
Turbulence Model ◽  
Finite Element Methods ◽  
Incompressible Flows ◽  
Grid Point ◽  
High Order ◽  
Surface Boundary ◽  
Wall Distance

Abstract Using turbulence models with finite element methods (FEM) can be challenging as the turbulence variables can assume negative non-physical values and hinder solution convergence. A modified k–ω model was recently proposed by Stefanski et al. (2018) to be used with finite element solvers of compressible flows. The model overcomes this issue by replacing k and ω with working variables that ensure positivity and smoothness of k and ω. In this work the applicability of this model for high-order FEM simulations of incompressible flows was examined. The model was implemented for incompressible flow in an hp-FEM solver using streamline Petrov-Galerkin discretization and was validated and verified using a fully-developed channel flow and a boundary layer flow over a flat plate. Several aspects of the turbulence model behavior were studied. These included the possibilitty of getting orders of accuracy higher than 2, and the model’s sensitivity to freestream values of k and ω. The results suggested that higher orders of accuracy are possible when quadratic and quartic basis functions are used. However, this depended on the way the boundary condition for ω was defined. The commonly used boundary condition for ω, which depends on the wall-distance of the first grid point resulted in poor orders of accuracy compared to the so-called slightly-rough-surface boundary condition which is independent of the wall distance of the first grid point. Additionally, results indicated that increasing the nondimensional wall distance of the first gridpoint makes it more sensitive to the value of ω on the wall. Adding a cross-diffusion term to the transport equation for ω is known to significantly improve the accuracy of turbulence model prediction for certain flows and reduce the sensitivity of the original k–ω model to freestream values of turbulence variables. Following a more recent version of k–ω model, this term was added to the turbulence model and some other modifications including a different production term with a stress-limiter were applied. The drag coefficient of the flat plate from the new turbulence model showed similar sensitivity to the freestream values of turbulence variables as the model of Stefanski et al. (2018).

G050022 Studies on SF6 Gas Arc Plasma Characteristics Based on a High-Order LES Turbulence Model

2011 ◽  
Vol 2011 (0) ◽  
pp. _G050022-1-_G050022-5
Author(s):  
Tomohiko JIMBO ◽  
Debasish BISWAS ◽  
Keisuke UDAGAWA ◽  
Takeshi SHINKAI ◽  
Katsumi SUZUKI
Keyword(s):  
Turbulence Model ◽  
High Order ◽  
Arc Plasma ◽  
Plasma Characteristics
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