Numerical investigation of flow through wide angle diffusers

This study is aimed at the development of a computational technique for the prediction of the flow field in wide angle diffusers. The finite element technique is used for the solution of the governing equations. A commercial software package, NISA/3DFlUID, modified for this specific application was used. The parameters affecting the flow field have been identified. For a wide range of variation of these parameters, the effects on the flow field have been examined. This investigation is an exhaustive and comprehensive numerical study of diffuser flows. Such a study will result in substantial improvement in the understanding of the anatomy of the flow field. The creation of the current knowledge base will also enable a judicious selection of diffusers for industrial applications. It was found that for laminar flow through wide angle diffusers the computational technique adequately predicted the qualitative and quantitative behavior of the flow field. Therefore new results, as predicted by the current computational technique have been presented. For example, it was found that the effective recirculation length varies exponentially with the angle of expansion of the diffuser. For turbulent flow the standard k-ε model has been found to be qualitatively adequate in representing the flow field. However, the quantitative predictions are being compared with available experimental results and those obtained using other numerical schemes. A wide range of possibilities exist for the constants and boundary conditions employed in k-ε modeling. Such a numerical experimentation requires deep understanding of the equations governing the flow field. The validity and/or adjustments of these constants and boundary conditions for diffuser flow are investigated