A general analysis has been developed to study fluid flow and heat transfer characteristics for steady laminar mixed convection on vertical slender cylinders covering the entire range from pure forced to pure natural convection. Two uniquely transformed sets of axisymmetric boundary-layer equations for the constant wall heat flux case and the isothermal surface case are solved using a two-point finite difference method with Newton linearization. Of interest are the effects of the new mixed convection parameter, the cylinder heating/cooling mode, the transverse curvature parameter, and the Prandtl number on the velocity/temperature profiles and on the local skin friction parameter and the heat transfer parameter. The results of the validated computer simulation model are as follows. Depending upon the magnitude and direction of the buoyancy force, i.e., the value of the mixed convection parameter and the heating or cooling mode applied, natural convection can have a significant effect on the thermal flow field around vertical cylinders. Specifically, strong variations of the local skin friction parameter and reversing trends in the heat transfer parameter are produced as the buoyancy force becomes stronger in aiding flow. The skin friction parameter increases with higher curvature parameters and Prandtl numbers. Similarly, the modified Nusselt number is larger for higher transverse curvature parameters; however, this parameter may reverse the impact of the Prandtl number on the Nusselt number for predominantly forced convection.
A powerful similarity solution of the highly nonlinear, coupled boundary-layer equations has been developed for steady laminar mixed convection heat transfer between a rotating cone/disk and power-law fluids. Of special interest are the effects of the power-law viscosity index, a generalized local Prandtl number, the buoyancy parameter, and the type of thermal wall condition on the velocity and temperature fields and hence the skin friction coefficient and the local Nusselt number. While the momentum boundary-layer thickness increases measurably with decreasing viscosity index n, the thermal boundary-layer thickness is less affected by changes in n. The magnitude and direction of the buoyancy force influence the upward velocity profile near the wall and the temperature profiles significantly. Both Prandtl number and buoyancy parameter have a more pronounced effect on the skin friction group, SFG ~ cf, than on the heat transfer group, HTG ~ Nu.
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