Akihiko Mitsuishi

Numerical Study on Fluid Flow and Heat Transfer of Mixed Convection to a Stagnation Region From an Upward-Facing Horizontal Plate

Mixed convection heat transfer from an upward-facing horizontal semi-infinite plate to a stagnation region is studied by means of direct numerical simulation. All the cases studied are simulated under constant heat flux condition on the plate. Assuming that the working fluid is air at room temperature and pressure, the Prandtl number is kept at 0.71. The Reynolds and the modified Grashof numbers are in the ranges of 102 −103 and 107 −108 , respectively. Longitudinal vortical structure, which was discovered in the recent experimental study, is successfully simulated. The typical structure appears as a pair of counter-rotating vortices being elongated over the plate. The relationship between this structure and the heat transfer rate is clarified. Characteristics of the vortices are investigated in detail.Copyright

Fluid Flow and Heat Transfer of Combined Convection Adjacent to Vertical Heated Plates Placed in Uniform Horizontal Flow of Air

Experiments have been carried out for combined convective flows of air adjacent to the vertical heated plates in the uniform horizontal forced flows to investigate relationships between the flow and the heat transfer. The experiments cover the ranges of the Reynolds and modified Rayleigh numbers as; ReL=160-2300 and Ra*L=4.3×105-2.0×108. The flow fields over plates are visualized with particles and smoke. The results show that the stagnation point moves downward away from the center of the plates when the surface heat flux is beyond a critical value. The condition where the stagnation point begins to move is expressed with the non-dimensional parameters as; Gr*L/Re2.5L=0.15. Profiles of measured local heat transfer coefficients are smooth even at the stagnation points in all cases examined. When the buoyancy effect is sufficiently weak, the coefficients agree well with those of the wedge flow. With increasing the surface heat flux, the coefficients are augmented to approach asymptotically the boundary layer solution of natural convection along a vertical heated plate. Finally, forced, natural and combined convective flow regimes are classified by the nondimensional parameter (Gr*L/Re2.5L).