Timothy J. Wray

Low-Reynolds-Number One-Equation Turbulence Model Based on k-ω Closure

Accurate turbulence modeling remains a critical problem in the prediction capability of computational fluid dynamics. In this paper, a new one-equation eddy-viscosity model is derived from k-ω closure. The ω equation used in this derivation includes a cross-diffusion term that allows the new model to switch between the model properties exhibited by the two-equation k-ω or k-e turbulence models. In addition, the damping function used in conjunction with the proposed one-equation model has not been studied before in the literature. The new model is used to simulate several benchmark canonical flows involving both the free shear layer and wall-bounded turbulent flows with small separation regions. The open-source software OpenFOAM is used for the flowfield calculations. It is shown that the new model improves the accuracy of flow simulations compared to the widely used one-equation Spalart–Allmaras model and is competitive with the shear-stress-transport k-ω model.

Computation of Flow in S Ducts with Wray-Agarwal One-Equation Turbulence Model

This paper focuses on the validation and application of a new one-equation eddy viscosity model derived from k-ω closure (the Wray–Agarwal model) for three-dimensional flows in serpentine diffusers (S ducts). The S-duct geometry produces streamline curvature and an adverse pressure gradient, resulting in flow separation. Two S-duct geometries are employed in this investigation: one was used in an experimental study conducted at NASA John H. Glenn Research Center in the early 1990s, and the other used in an experimental study conducted at ONERA–The French Aerospace Lab in 2006 and considered for computational fluid dynamics technology validation during the AIAA Propulsion Aerodynamics Workshops in 2012 and 2014. The computational fluid dynamics flow solver ANSYS Fluent is used for flow calculations. Results from the new “Wray–Agarwal” one-equation turbulence model, the widely used Spalart–Allmaras, and the shear-stress-transport k-ω models are compared to the available experimental data. Results obtained w...

A New Low Reynolds Number One-Equation Turbulence Model Based on a k-k-ω Closure

Accurate turbulence modeling remains a critical problem in the prediction capability of computational fluid dynamics. In this paper a new one equation eddy viscosity model is derived from k-ω closure. The ω-equation used in this derivation includes a cross diffusion term that allows the new model to switch between a k-ω or k-e behavior. The new model is used to simulate the flow of several canonical separated flow cases. The open source software OpenFOAM is used for the flow calculations. It is shown that the new model increases the accuracy of flow simulations compared to the commonly used Spalart-Allmaras (SA) and Shear-Stress-Transport (SST) k-ω models for several of these flows.

Application of a New One-Equation Turbulence Model to Computation of Separated Flows

Accurate turbulence modeling remains a critical problem in the prediction capability of computational fluid dynamics. One particular flow regime lacking accurate simulation is instances of separated flow. In this paper the Rahman-Agarwal-Siikonen (RAS) model is used to simulate the flow of several canonical separated flow cases. The commercially available software ANSYS FLUENT and the open source software OpenFOAM are used for the flow calculations. It is shown that the RAS model significantly increases the accuracy of flow simulations compared to the commonly used Spalart-Allmaras (SA) and Shear-Stress-Transport (SST) k-ω models.

Computation of Turbulent Flow in a Lid-Driven 2D Cavity and a 3D Box Using a Number of Turbulence Models

In this paper, various turbulence models are used for simulating internal turbulent flow with large recirculation by considering the flow in a 2-D lid-driven square cavity and a 3-D lid driven cubic box. The accuracy of the newly developed Wray-Agarwal (WA) one equation turbulence model is compared against the two well-known industry standard turbulence models the Spalart-Allmaras (SA) model and the ShearStress-Transport (SST) k-ω model. The simulations are performed by numerically solving the ReynoldsAveraged Navier-Stokes (RANS) equations in conjunction with WA, SA and SST k-ω models and comparing the results with the available experimental data and Large Eddy Simulation (LES) results. 2-D numerical solutions are obtained at Reynolds numbers of 10,000, 20,000, 50,000, and 100,000. 3-D numerical solutions are obtained at Reynolds numbers of 3200 and 10,000. All numerical calculation are compared with other numerical results available in the literature. The open-source CFD code OpenFOAM is used to compute the flow field. Computational results clearly demonstrate that the Wray-Agarwal model outperforms in accuracy both the Spalart-Allmaras and Shear-Stress-Transport k-ω models at all Reynolds numbers considered.

Application of the Wray-Agarwal Model to Compressible Flows

This paper employs the recently developed one-equation Wray-Agarwal (WA) eddy viscosity turbulence model to simulate several highly compressible flows. The new model is compared to the one-equation Spalart-Allmaras and two-equation Shear-Stress-Transport k-ω models. Computational results for a 2D slot nozzle-ejector, transonic RAE 2822 airfoil, and transonic flow over an axisymmetric bump with mild separation are presented. It is shown that the Wray-Agarwal model is in better agreement with experimental data than the Spalart-Allmaras model and is competitive with the SST k-ω model.