Investigation of Accuracy of Non-Linear k–ε Models for Flow Field around a Model Building

Evaluation of the performance of various non-linear k-ε models for predicting flow field around an isolated model building with the rooftop flush vent within the turbulent boundary layer is investigated. Two cubic models, proposed by Ehrhard et al. and Craft et al., and one quadratic model proposed by Shih et al., are examined by comparing their simulation results with the experimental data and standard k-ε model. All the computations are performed by using a self-developed object-oriented C++ programming in OpenFOAM CFD package, which contains applications and utilities for finite volume solvers. In this study, the three non-linear models can reproduce vortex shedding behind the model building during unsteady calculations. The standard k-ε model provided inadequate results for the flow field, because it could not reproduce the basic flow structures, such as reverse flow on the roof. By contrast, the non-linear models are able to predict anisotropic stresses and correctly show the dominant stress over the roof to be the streamwise Reynolds stress. Among the RANS models, the Craft model shows the best agreement with the experimental data. The good performance of the Craft non-linear model in the wake region can be interpreted from the magnitude of the total kinetic energy after considering the solved wind fluctuations.

Keywords:

Computational Fluid Dynamics (CFD) , OpenFOAM , Non-linear k-ε models , Model building