Asymptotic solution for combined free and forced convection in vertical and horizontal conduits with uniform suction and blowing



Significant changes in heat and momentum transfer rates can be caused by finite interfacial velocities and external field forces. This study considers the nonlinear problem of combined free and forced convection in vertical and horizontal two-dimensional conduits with finite transverse velocity.

Similarity transformations for the temperature function have been found which reduce the energy, momentum, continuity, and state equations for these configurations to nonlinear systems of two coupled ordianary differential euqations. These equations are solved by approximate methods to give Nusselt numbers and friction factors as well as velocity and temperature profiles.

Stream to wall temperature differences increase with suction and decrease with injection. The effects of interfacial velocity on temperature profiles and heat transfer increase dramatically with Prandtl number. Because blowing and suction strongly affect temperature profiles they substantially modify natural convection effects in vertical flows. Suction creates steeper transverse temperature gradients and accentuates buoyancy effects in vertical flows. Conversely injection flattens temperature profiles and thus decreases the influence of buoyancy on the velocity field.