Bøger af Arackal Rahul S

Wall jets generate a high-intensity broadband noise compared to free jets. As discussed in the previous section, a wall jet flow can be related to a number of practical applications, from a simple household appliance to aerospace applications. The current scenario demands quieter flow appliances with lower noise emissions. For instance, the cabin noise of aircraft, high-speed locomotives, and automobiles is influenced by the outer flow and demands a detailed study to understand noise mitigation. Moreover, the prolonged exposure to flow noise is annoying that may cause serious psychological and health issues. Thus, according to the norms laid by the noise regulatory bodies, priority is given to the mitigation of acoustic emissions from flow-related appliances. Over the past few decades, significant noise reduction strategies have been accomplished by varying the surface conditions. The major noise emissions from wall jets are due to the interaction of a turbulent jet with a rigid wall and the trailing edge of the plate.

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.