Direct Numerical and Large-eddy Simulation of Supersonic Transverse Jets Using a Novel Numerical Method

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

CBET - 0828162 Mahesh, Krishnan The PI plans use of direct numerical and large-eddy simulation to study transverse jets in high-speed cross flow and compare to existing experimental data. The objectives of the proposed research are to develop a high-fidelity Direct Navier-Stokes (DNS) database at low Reynolds numbers, and Large-Eddy Simulation (LES) capability at experimental Reynolds numbers for transverse jets in supersonic cross flow. Specific studies will concern penetration, entrainment and mixing characteristics of this flow and developing a novel numerical methodology using this challenging problem as a testbed. The simulations use a novel numerical method and subgrid model developed by the PI's group for unstructured grids. The algorithm ensures robustness and accuracy without numerical dissipation. It rescales the governing equations and ensures that the discrete equations analytically reduce to the incompressible equations in the limit of low Mach number. Discrete operators are derived to be accurate on highly skewed unstructured grids and a shock-capturing scheme is applied in a corrector step. The subgrid model solves an evolution equation for the subgrid kinetic energy with no adjustable coefficients. If successful, this numerical methodology will have significant impact on a wide class of problems beyond the scope of this work. High-speed transverse jets are central to enabling sustained combustion inside scramjet engines which represent the next frontier in aviation propulsion. Another important application of high-speed transverse jets is thrust vector control under re-entry conditions. The physical understanding developed from the simulations will help develop practical scaling laws, while the unstructured LES methodology will allow actual prediction and design of these systems. The study also seeks to expand knowledge of turbulent mixing to high speeds. There is a lack of consensus on fundamental issues such as what affects jet trajectories, penetration and mixing. This study will be performed by one PhD student and one undergraduate student. The undergraduate student will be chosen from the Minnesota Supercomputing Institute's summer internship program which draws students from across the country. The PI will also participate in another outreach program of the Super-computing Institute involving high school students from the Twin Cities area. The proposed work will form part of the PI's teaching material, and presentations and articles intended for a broad audience.