LES Study Of Free Jets And Jets Impinging On Cuboidal Cavity

Abstract

Numerical solutions based on explicit filtered LES for computing turbulent flow field, of free round jets and impinging round jet on cuboidal cavities, are presented and discussed in this dissertation work. One-parameter fourth-order explicit filter is implemented to account for sub-grid scale effects. Compact difference schemes proposed by Hixon & Turkel involving only bidiagonal matrices is used to evaluate spatial derivatives. Compact schemes with overall fourth order accuracy and eight order accuracy are used in simulating free and impinging jets respectively. Simulations of free round jets are used for validating LES approach. 6 simulations of free round jet, in three levels of computational grids at three different Reynolds number, are performed to understand the effects of Reynolds number and turbulent length scales. Energy in the smaller length scales are found to be higher for higher Reynolds number. Potential core collapse is found to occur at shorter distance for high Reynolds number jets. Accurate computation of smaller length scales of turbulence is found to be essential for high Reynolds number flows. LES of subsonic impinging jets are performed on cuboidal cavities to understand the physical phenomenon. High intensity, low frequency sounds are captured, in the presence of cavity, as reported by other research works. Lip-thickness is found to have an effect on the intensity of sound produced. Matching of Jet shear layer roll up frequency with cavity’s natural frequency to produce resonance phenomenon is attempted and observations are presented.