Effect of plate length and surface roughness on the flow and aeroacoustic characteristics of wall jets

A high momentum jet tangentially flowing over the surface of a rigid flat plate is a wall jet. Understanding the flow physics of wall jets can be helpful in several practical applications, such as cooling off turbine blades, mixing off reactants in a combustion, air curtains, etc. Moreover, the rich flow physics in wall jets has inspired numerous researchers to work in this field. Wall jets are widely investigated to understand the flow turbulence, entrainment, mixing behavior, and formation of coherent structures. Presently, the study on acoustics emission from wall jets is also gaining significant importance. The schematic of a wall jet. As observed from the figure, the wall jet has two flow layers: the inner and outer layers. The former layer is due to the interaction between the jet and the solid surface of a plate, and the outer layer is due to the interaction between the jet and the ambient fluid. The inner layer initiates from the wall surface and extends up to the location of maximum stream-wise velocity, thus resembling a boundary layer. The outer layer region is between the maximum stream-wise velocity and the ambient flow velocity, thus representing a free shear layer.