导电突扩管中磁流体管流的数值模拟

Numerical Simulation of Magnetohydrodynamic Duct Flow with Sudden Expansion

采用基于Open FOAM环境自主开发的低磁雷诺数磁流体求解器,对45°和90°突扩矩形管中液态金属流体在受到垂直流向的外加磁场作用时的速度、感应电流、压力的分布及突扩位置处的MHD三维现象进行数值模拟.结果表明：磁场沿突扩方向时,由于无回流涡,45°比90°突扩管在肩部位置速度分布更优.哈特曼数增大,强射流和突扩结构,在突扩肩部位置引发流动的不稳定性.伴随感应电流的不稳定,流动不稳定发展到突扩位置上游.磁场沿垂直突扩方向时感应电流的三维效应显著.哈特曼数增大,MHD压降显著增大.同方向磁场和相同哈特曼数,不同突扩角度的三维无量纲压力梯度无明显差异.

Liquid metal flow subject to a uniform magnetic field vertical to streamwise direction confined in a rectangular duct with45° and 90° sudden expansion,and electrically conducting walls is numerically studied using magnetohydrodynamic（ MHD） flow solver developed in Open FOAM environment. Velocity distribution,induced electric current,pressure gradient and three-dimensional MHD effect are analyzed in detail. It shows that as external magnetic field is parallel to direction of duct expansion,velocity distribution is better in 45° sudden expansion duct than that in 90° expansion duct since there is no vortex at the expansion. With Hartmann number increasing,high velocity jets and intensive induced electric current cause a strong instability at the expansion.Instability grows to upstream of the expansion through induced electric current. As external magnetic field is vertical to expansion direction,induced electric current along streamwise direction is significant. With Hartmann number increasing,MHD pressure drop increases remarkably. Dimensionless pressure drop in fully developed duct is almost the same in different expansion duct as direction of applied magnetic field and Hartmann number are the same.