Mean Flow Properties of a Three-Dimensional Wall Jet Developing on Concave Cylindrical Surfaces

Abstract

The influence of concave curvature on the mean flow characteristics of a three-dimensional jet is presented in this paper. Measurements have been carried out both on the concave surface and plane surface to find the effect of curvature on the mean flow characteristics. The jet is generated from a centrifugal blower and issued tangentially on plane and concave surfaces separately from the circular orifice. The curved surface plate is provided with an initial straight portion of twenty times the orifice diameter, so that the wall jet is fully developed before it experiences the curvature effects. The radius of the curved surface chosen in the present investigation is 1500 mm. The curvature parameter ranges from 0.0086 to 0.0173 on concave cylindrical surface. The mean flow characteristics include the three-dimensional velocities in the longitudinal and spanwise directions, growth of maximum velocity and growth of length scales. From the results, it is found that the decay of the maximum velocity on the concave surfaces is slower when compared to the decay on the plane surface. It is observed that no effect of curvature on the shape of the mean velocity profiles in the spanwise and longitudinal directions, but variation is observed in V both on the longitudinal and spanwise directions. The growth of halfwidth in the longitudinal direction on the concave surface is lower when compared with the plane surface and this is attributed to stabilizing nature of the jet in the outer layer of the concave curved wall jet.