摘要
The influence of buoyancy on vortex shedding from a heated square cylinderand its effects on the heat transfer of mixed convection were simulated. The flow equations, basedon the velocity and the pressure, were solved along with the energy equation by a modified SIMPLERalgorithm - the Quick Scheme and small Control Volume (QSCV) algorithm developed by the authors ofthe present paper. A set of optimized computational domain and artificial lateral boundaryconditions were used along with the QSCV algorithm. Several cases were simulated for the Grashofnumbers up to 1. 8 X 10~5, the Reynolds numbers up to 500, and a range of angles between free streamvelocity and gravity from 0 to 1.5π. In opposing flow, the results distinguish two different flowpatterns: periodic flow for Gr < Gr_c and steady flow with attached twin vortices for Gr > Gr_c, anda precise correlation between Gr_c and Re expressed as Gr_c = 0. 00166(Re)^(2.97795) for Re up to500 was firstly obtained. In cross flow, it could be seen that the Ri = Gr/Re^2 plays a great rolein the wake vortex patterns and the temperature fields. In aiding flow, it is found that the mainflow currents cause a large expansion of the streamlines and isotherms in the direction normal tothe free stream velocity. These changes in the wake vortex patterns and the temperature fieldsgreatly modify the heat flux along the surface of the square cylinder and consequently, the heattransfer rate is strongly dependent upon the Reynolds numbers, the Grashof numbers, and the gravitydirection.
The influence of buoyancy on vortex shedding from a heated square cylinderand its effects on the heat transfer of mixed convection were simulated. The flow equations, basedon the velocity and the pressure, were solved along with the energy equation by a modified SIMPLERalgorithm - the Quick Scheme and small Control Volume (QSCV) algorithm developed by the authors ofthe present paper. A set of optimized computational domain and artificial lateral boundaryconditions were used along with the QSCV algorithm. Several cases were simulated for the Grashofnumbers up to 1. 8 X 10~5, the Reynolds numbers up to 500, and a range of angles between free streamvelocity and gravity from 0 to 1.5π. In opposing flow, the results distinguish two different flowpatterns: periodic flow for Gr < Gr_c and steady flow with attached twin vortices for Gr > Gr_c, anda precise correlation between Gr_c and Re expressed as Gr_c = 0. 00166(Re)^(2.97795) for Re up to500 was firstly obtained. In cross flow, it could be seen that the Ri = Gr/Re^2 plays a great rolein the wake vortex patterns and the temperature fields. In aiding flow, it is found that the mainflow currents cause a large expansion of the streamlines and isotherms in the direction normal tothe free stream velocity. These changes in the wake vortex patterns and the temperature fieldsgreatly modify the heat flux along the surface of the square cylinder and consequently, the heattransfer rate is strongly dependent upon the Reynolds numbers, the Grashof numbers, and the gravitydirection.
