微通道流动转捩数值模拟

应用CFD计算软件ANSYS CFX对水力直径为0.4mm的矩形截面微尺度通道中的气体流动进行了数值模拟.采用了3种流动模型，即γ-Re_θt转捩模型、层流模型和剪切应力输运（SST）模型，并将模拟结果与实验结果进行了对比.模拟结果表明:层流模型及SST模型不具有预测转捩的能力；γ-Re_θt转捩模型捕捉到了临界雷诺数且摩擦因数相对误差在20%以下.在未达到临界雷诺数之前，通道后部已经出现局部湍流区，且局部湍流区随着雷诺数的增大而增大.壁面摩擦因数的最低点对应的流向位置与通道中前后湍流区的交结位置几乎一致. 

Numerical simulation of flow transition in microchannel

Numerical simulation was conducted with CFD software ANSYS CFX to investigate the characteristics of gas flow in a rectangular microchannel with a hydraulic diameter of 0.4mm. Three flow models, namely, γ-Re_θt model, laminar model and shear stress transport (SST) model, were taken in the simulation. The simulation results were compared with the experimental data. Results indicate that laminar model and SST model are incapable of predicting transition. γ-Re_θt model forecasts the critical Reynolds number well and the relative errors of friction factor keep under 20%. Before Reynolds number reaches the critical value, local turbulent regions appear at the rear of the microchannel and the regions expand with the growing Reynolds number. The streamwise position where the inlet and the rear turbulent regions meet is almost identical with the position where the skin friction reaches its minimum value.