Laminar combined convection from a horizontal cylinder-Parallel and contra flow regimes

The laminar combined convection heat transfer from an isothermal horizontal circular cylinder is studied for the two cases when the forced flow is directed either vertically upward (parallel flow) or vertically downward (contra flow). The investigation is based on the solution of the full vorticity transport equation together with the stream function and energy equations. The velocity and thermal boundary layers are developed in time until reaching steady conditions. The variations of vorticity and Nusselt number are obtained over all the cylinder surface including the zone beyond the separation point. The predicted values of the average Nusselt number are compared with the available experimental data and the agreement is satisfactory. The streamline and isotherm patterns are plotted for several cases to show some of the flow field characteristics.