Modeling of Compressibility Effects in Turbulent Boundary Layers

177 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2001.Second, since it has been determined that the acoustic (and pseudosound) component of the flow does not have much influence on the dynamics of the supersonic boundary layer; the fluctuating thermal component was studied as the only source of compressibility effects in the boundary layer. An approach to the study of thermal compressibility effects and a possible way to draw a parallel between incompressible and compressible modeling were developed. It has been proposed that the thermal component of the fluctuations can be treated as a perturbation about a variable-mean-density incompressible flow. In this way, terms linear in thermal variables, which can give rise to compressibility, are easily identified. The numerical decomposition procedure was extended to decompose the nonacoustic component of the flow into the incompressible and thermal parts, so that thermal terms can be evaluated directly and compared with leading-order incompressible terms to verify their importance. For the turbulence model development, it has been assumed that the leading-order incompressible problem is known, and a way of reducing the modeling of important thermal terms to this known problem was provided. By this approach, extended incompressible models for the turbulent kinetic energy equation and the Reynolds stress transport equation were derived. It was found that most of the thermal compressibility effects are due directly to density fluctuations. The only exceptions are the thermal contribution to the production of turbulent kinetic energy and the Reynolds stress due to fluctuating thermal divergence.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD