DNS of Forced Mixing Layer

Abstract

The non-dimensional form of Navier-Stokes equations for two dimensional mixing layer flow are solved using direct numerical simulation. The governing equations are discretized in streamwise and cross stream direction using a sixth order compact finite difference scheme and a mapped compact finite difference method, respectively. A tangent mapping of $y =\beta\tan(\pi \zeta/2)$ is used to relate the physical domain of $y$ to the computational domain of $\zeta$. The third order Runge-Kutta method is used for the time-advancement purpose. The convective outflow boundary condition is employed to create a non-reflective type boundary condition at the outlet. An inviscid (Stuart flow) and a completely viscous solution of the Navier-Stokes equations are used for verification of the numerical simulation. The numerical results show a very good accuracy and agreement with the exact solution of the Navier-Stokes equation. The results of mixing layer simulation also indicate that the time traces of the velocity components are periodic. Results in self-similar coordinate were also investigated which indicate that the time-averaged statistics for velocity, vorticity, turbulence intensities and Reynolds stress distribution tend to collapse on top of each other at the flow downstream locations.