水平加熱正方形角柱まわりの強制－自然直交流共存対流の流動および伝熱

抄録

Experimental investigations were carried out on the flow and heat transfer of crossing flows induced around a heated horizontal square cylinder placed in a uniform horizontal flow of air. Cylinders of side lengths d = 20 and 30 mm heated with uniform heat flux were utilized in the experiments. The Reynolds and modified Rayleigh numbers based on the side length were ranged as; 45<Re_d<1.3×10³ and 10⁴<Ra_d^*<7.5×10⁵, respectively. Flow fields around the cylinder were visualized using fine particles. When the cylinder is unheated or slightly heated, the incoming flow impinges on the front surface and separates at the upper and lower edges, forming separation bubbles on the top, bottom, and rear surfaces. In addition, Kármán vortex is observed in the wake. With increasing buoyancy, vortex shedding is suppressed and the wake deflected upward, resulting in asymmetry about the horizontal mid-plane. Local Nusselt numbers were also measured, and they showed variations with the buoyancy. When the buoyancy is small, the local Nusselt number distribution is symmetric about the horizontal mid-plane. As buoyancy increases, the local Nusselt number rises and the distribution becomes asymmetric. Overall Nusselt numbers correlate well with the non-dimensional parameter (Gr_d^*/Re_d^2.5). Moreover, the regions of forced, natural and combined convection can be classified with the parameter.