| dc.description.abstract | This numerical study analyzed the thermal-flow characteristics of the compressible laminar flow over the microchannel (dh < 4μm). The channel wall is assumed as non-slip flow condition. Two flow regimes were considered: 1) Ma=0.07~0.21, Re=1~10; 2) Ma=(3~12)×10-4, Re=(1.2~8.9)×10-3. Numerical results show that the compressible laminar flow has abrupt velocity jump near the channel entrance, and the fully developed flow can never be achieved no matter how long the channel is. In addition, further increases inlet velocity, more significant increasing of velocity at the outlet is predicted.
The predicted velocity of present non-slip flow has a flat profile, which is similar to the solution of the slip flow simulation, and the velocity distribution is flatter as the flow approaches the outlet. Near the inlet, velocity profiles have a concave shape due to the viscosity heating at wall. For the heating wall case, the Nusselt number is inversely proportional to the wall temperature. When the wall temperature is higher, the flow needs longer channel to reach a constant Nusselt number.
Comparing with the incompressible flow, nonlinear pressure distribution is obtained due to the compressibility effect. Both pressure and velocity gradient reach the maximum value at the outlet. Furthermore, enforcing higher pressure ratio (inlet value to outlet value), more significant nonlinear level of pressure distribution is observed.
Because of the channel size effect, even the inlet velocity is very low (Main~10-3), numerical results reveal that a slight velocity difference makes a huge dissimilar pressure distribution in microchannel. | en_US |