On the Forced Convective Flow between Two Corrugated Cylinders
The forced heat convection in the flow between two corrugated cylinders, whose generators are parallel to the flow direction, is studied through perturbation on the small amplitude of the corrugations. The coupled effects of frictional heating and non-linear interaction of the boundaries on the heat transfer rate are obtained.
Finite-volume solutions for laminar flow and heat transfer in a corrugated duct
A finite volume methodology was developed to predict fully developed heat transfer coefficients, friction factors, and streamlines for flow in a corrugated duct. The basis of the method is an algebraic coordinate transformation which maps the complex fluid domain onto a rectangle. The method can be adopted for other convection-diffusion problems in which two boundaries of the flow domain do not lie along the coordinate lines. Representative results were found for laminar flow uniform wall temperature, and for a range of Reynolds number, Prandtl number, corrugation angle, and dimensionless interwall spacing. As seen from the streamlines, the flow patterns are highly complex including large recirculation zones. The pressure drops and friction factor results are higher than the corresponding values for a straight duct. Finally, the performance of the corrugated duct was compared with the straight duct under three different constraints - fixed pumping power, fixed pressure drop, and fixed mass flow rate. There are small differences in the heat transfer rate ratios under these constraints.
Effect of small amplitude wall waviness upon the stability of the laminar boundary layer
The effect of small amplitude wall roughness on the minimum critical Reynolds number of a laminar boundary layer is studied under the assumptions normally employed in parallel flow stability problems. The presence of a single Fourier component of roughness enhances the instability of the flow by introducing a point of inflection and increasing the profile curvature at the critical layer, and the effect becomes increasingly important as the wavelength of the roughness component decreases. Numerical calculations show a 10% reduction in minimum critical Reynolds numbers in the presence of small wavelength roughness with an amplitude of only 1% of the boundary layer thickness.