Flow and Heat Transfer Characteristics around A Permeable Porous Obstacle

在钝化不透水物体上的流体流动中会出现各种流型。然而，在多孔体内部流动与周围外部流动的相互作用等基本问题上，可渗透多孔障碍物周围的流动形态和流动特性仍然是模糊的。本文对多孔障碍物周围的强迫对流进行了实验和数值研究，重点研究了多孔表面条件的影响。结果表明，渗透率等孔隙参数的影响可以引起流动形态的显著变化，抑制卡曼涡的形成，渗透率的增加会增强渗流障碍物的流动。文中还指出，最佳流型与阻力的减小有关，阻力的减小取决于通道的雷诺数和堵塞比。此外，还对多孔表面上的停滞流动进行了分析研究，特别是对停滞点的边界层厚度进行了研究。多孔区的渗透率越大，雷诺数越大，可渗透界面上的边界层厚度越小。在渗透率为k→0的极限范围内，渗流行为与不透水表面的情况一致。

Various flow patterns appear in fluid flow over a bluff impermeable body. However, the flow patterns and the flow characteristics around a permeable porous obstacle still remain vague in such fundamental aspects as the interaction between the inner-flow through the porous body and the surrounding outer-flow.An experimental and numerical study has been made on the forced convection around the porous obstacle concentrating on the effect of the porous surface condition. The results show that the effects of porous parameter such as permeability can cause a significant change in flow patterns and suppress the formation of the Karman vortex, and that flow through the porous obstacle is enhanced by an increase in permeability. Here it is also noted that the preferred flow pattern is associated with the reduction of drag force, which depends on the Reynolds number and the blockage ratio of the channel.Moreover, an analytical study has been carried out on the stagnation flow over a porous surface with particular attention to the boundary layer thickness at the stagnation point. The larger permeability of the porous region and the higher Reynolds number yield the reduction of the boundary layer thickness above the permeable interface. In the limit of the permeability k→0, flow behavior coincides with that for the case of the impermeable surface.