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Large Eddy Simulation of Turbulent Channel Flow with 3D Roughness Using a Roughness Element Model 下载免费PDF全文
Large eddy simulation of turbulent channel flow with dense and small 3D roughness elements is carried out using a roughness element model Profiles of mean Reynolds stress, mean velocity and rms velocity as well as turbulent structures near the wall are obtained. The shear stress in the rough wall is larger than that in the smooth wall side and the rough wall has a larger influence on the channel flow. Profiles of mean streamwise velocity near the wall have logarithmic velocity distributions for both smooth and roughness walls, while there is a velocity decrease for the rough wall due to larger fractional drag. All the three components of rms velocities in the rough wall region are larger than that in the smooth wall region, and the roughness elements on the wall increase turbulent intensity in all directions. The s~reak spacing and average diameter of near wall quasi-s~reamwise vortices increase with the presence of roughness elements on the wall and it is shown that the rough wall induces complex and strong streamwise vortices. Results of dense and small 3D roughness elements in both turbulent statistics and structure, obtained with a relatively simple method, are found to be comparable to related experiments. 相似文献
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通过同步辐射小角度x射线散射方法(SAXS),研究了三种Al_Zn_ Mg_Cu合金沉淀析出过程显微结构参数(析出相尺寸和体积分数),随时效温度和时效时间 的演化,同时分析了Zn含量对合金沉淀析出过程的影响.结果表明,三种合金(A,B,C) 在实验条件下析出相均属于纳米尺度,析出相的最大体积分数随Zn含量的增加而增加,最大体积分数分别为0.023—0.028,0.052—0.054和0.04.在一定时效温度下,体积分数随时效时间的变化规律,符合析出相的形核、核长大和粗化动力学过程.
关键词:
小角度x射线散射
Al_Zn_Mg_Cu合金
时效
析出相尺寸
析出相体积分数 相似文献
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应用小角x射线散射技术分析了Al-Zn-Mg-Cu-Li合金在130,150和160℃温度时效24 h析出粒子的微结构参数的变化情况. 粒子的半径随着时效温度的增高而增加,它的比内表面积和体积百分数随着时效温度的增高而减小. 对Porod曲线q3J(q)-q2的分析表明,析出粒子与基体之间有明显的界面.
关键词:
小角x射线散射
Al-Zn-Mg-Cu-Li合金
时效
析出粒子 相似文献
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