Large Eddy Simulation of Complex Turbulent Flows

University dissertation from Division of Fluid Mechanics, Department of Energy Sciences, Lund Institute of Technology, Lund University

Abstract: This thesis concerns the Large Eddy Simulation methodology and its application to predict complex turbulent flows at high Reynolds numbers, and at times also with high Mach numbers. The meaning of the word ?complex? refers both to the presence of complex flow phenomena and the, often, complex geometry of man-made devices restricting the flow. A fairly thorough evaluation study of the numerical methods and the LES framework have been performed in order to assess numerical properties, such as handling of small scales. This is done by numerically solving a number of time-dependent problems in one, two, and three dimensions with and without the use of flux limiters. For evaluation of the methodology when applied to complex turbulent flows, four different flow problems have been considered: ? Incompressible flow around a prolate spheroid at an angle of attack. ? Development and qualitative evaluation of a model for reacting gas-solid flow inside and around a statically fired solid propellant rocket. ? Inflow turbulence effects in compressible injection-driven flow in a nozzleless rocket motor. ? Compressible non-reacting flow, although including air-fuel mixing, in a scramjet engine model. The aim is to clarify issues pertaining to: ? Understanding of subgrid scales and their modeling. ? Understand and determine limitations of LES for different Mach numbers or other parameters. ? The interaction between numerical effects and subgrid scale modeling. ? Analysis of instability problems in solid propellant rocket motors. Progress has been made in all these issues.