Direct Numerical Simulations of Periodic Turbulent Planar Mixing Layers

Victor Zendejas Lopez, California Institute of Technology

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Turbulent mixing layers are one of the most studied turbulent free shear flows. They are useful for understanding key mechanisms that describe the evolution of more complex turbulent flows found in combustion, aerodynamics, oceanic and atmospheric flows. These mixing layers form when two initially separated parallel streams with different velocities begin to mix. Most simulations of turbulent mixing layers are computationally inefficient, requiring long streamwise domains due to the slow mixing layer growth. In this work, we seek to develop a method for direct numerical simulation (DNS) of incompressible turbulent mixing layers, without the use of auxiliary simulations, in a streamwise periodic domain via the Navier-Stokes equations. We use anticipated self-similarity to solve the equations in a normalized coordinate system to allow for streamwise periodicity. This reduces the computational cost by reducing the overall size of the streamwise domain and provides faster converging statistics for the turbulent mixing layer. This approach is an extension of Ruan and Blanquart (2021) where this technique was originally applied to turbulent flat-plate boundary layers and was shown to reduce computational costs by an estimated one to two orders of magnitude.

Abstract Author(s): Victor Zendejas Lopez, Guillaume Blanquart