Venke Sankaran

Isolating Flow-field Discontinuities while Preserving Monotonicity and High-order Accuracy on Cartesian Meshes

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Comparison of a Structured-LES and an Unstructured-DES Code for Predicting Combustion Instabilities in a Longitudinal Mode Rocket

Abstract : Summary: Both LES and DES area capable of simulating self-excited combustion instability. Agreement between the simulations and experiments for the unstable case was good. The marginally stable case proved more difficult Cyclic Heat release was captured. LES had a delayed reignition, likely responsible for the higher amplitudes. Cyclic Heat release was captured along with reignition event. Some differences in predictions are due to differences in the grids. No apparent winner, both approaches have strengths and weaknesses.

An Unsteady Preconditioning Scheme Based on Convective-Upwind Split-Pressure (CUSP) Artificial Dissipation

An Unsteady Preconditioning Scheme Based on Convective-Upwind Split-Pressure (CUSP) Artificial Dissipation Report Title Obtaining accurate computational results for unsteady low-Mach number flows presents significant challenges for numerical schemes. In this work, we present a novel preconditioning scheme designed to provide good conditioning for these flows for all Strouhal numbers. The scheme is based on the convective-upwind split-pressure (CUSP) scheme which naturally facilitates the proper scaling of velocity and pressure dissipation terms for unsteady lowMach number flows. Unlike traditional matrix dissipation schemes, the preconditioned CUSP formulation provides scalar-like efficiency and simplicity. Several test cases are presented for steady, unsteady, convection-dominated, and acousticdominated flows that demonstrate significant improvements in accuracy and convergence rate over traditional preconditioning schemes for a wide range of flow conditions. Conference Name: AIAA SciTech 2014 Conference Date: January 07, 2014 2

Computational Modeling of Supercritical and Transcritical Flows

We examine the use of a single-fluid model with the Peng Robinson equation of state to model supercritical and transcritical flows with combustion. Both non-reacting and reacting flows are considered to understand the modeling challenges. Several modifications of the equations of state and mixture rules are tested and shown to have varying strengths and weaknesses. No method works uniformly well for both non reacting and reacting flows, although the use of the Peng-Robinson model with Amagat’s mixture rule and modified compressibility factors appears to be robust and reasonably accurate for supercritical and transcritical combustion.