New explicit algebraic stress and flux model for active scalar and simulation of shear stratified cylinder wake flow

On the numerical simulation of active scalar,a new explicit algebraic expression on active scalar flux was derived based on Wikstrm,Wallin and Johansson model (aWWJ model). Reynolds stress algebraic expressions were added by a term to account for the buoyancy effect. The new explicit Reynolds stress and active scalar flux model was then established. Governing equations of this model were solved by finite volume method with unstructured grids. The thermal shear stratified cylinder wake flow was computed by this new model. The computational results are in good agreement with laboratorial measurements. This work is the development on modeling of explicit algebraic Reynolds stress and scalar flux,and is also a further modification of the aWWJ model for complex situations such as a shear stratified flow.

基于快速溶血预估模型的离心血泵叶轮特性数值分析

离心血泵叶轮形态是决定其内部流场剪切应力致血液细胞损伤的重要因素之一。对具有不同叶轮形态的离心血泵进行流体动力分析及数值溶血预估有助于提高血泵的综合性能。本文采用低雷诺数修正SSTκ-ω湍流模型,对四种不同叶轮形态的离心血泵内部流场进行计算,包括压力场、速度场以及剪切应力场分布等;并运用快速溶血预估模型计算各血泵的标准溶血参数值(NIH)。分析结果表明,虽然四种血泵的压力场分布均符合要求,但对数螺旋线叶轮血泵流道中的涡流和回流得到了明显改善,高剪切应力区域体积只占总体积的0.004%,NIH为0.0089,对血液细胞破坏最小。