Technical Report DYN


Book Description




Scientific and Technical Aerospace Reports


Book Description

Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.




Analytical Investigations of Equilibrium and Nonequilibrium Compressible Turbulent Boundary Layers


Book Description

An integral method is presented for the adiabatic compressible turbulent boundary layer which extends recent concepts of turbulent equilibrium boundary layers to the study of nonequilibrium flows. Coles' law of the wall and wake is extended to the case of compressible adiabatic flows with pressure gradient by employing Van Driest's generalized velocities. An analytical expression for the compressible turbulent equilibrium dissipation integral is then derived from the integral momentum, mean energy and local skin friction equations. For the general case of nonequilibrium flows with arbitrary pressure gradients, the dissipation integral is 'unhooked' from the equilibrium pressure gradient parameter through the use of a single empirical curve of existing incompressible flow data. Numerical solutions are then presented for a variety of compressible flows. As a first step in developing an integral method for nonadiabatic flows, the family of incompressible equilibrium enthalpy profiles are solved for from the thermal energy equation. (Author).













Turbulent Flows


Book Description

obtained are still severely limited to low Reynolds numbers (about only one decade better than direct numerical simulations), and the interpretation of such calculations for complex, curved geometries is still unclear. It is evident that a lot of work (and a very significant increase in available computing power) is required before such methods can be adopted in daily's engineering practice. I hope to l"Cport on all these topics in a near future. The book is divided into six chapters, each· chapter in subchapters, sections and subsections. The first part is introduced by Chapter 1 which summarizes the equations of fluid mechanies, it is developed in C~apters 2 to 4 devoted to the construction of turbulence models. What has been called "engineering methods" is considered in Chapter 2 where the Reynolds averaged equations al"C established and the closure problem studied (§1-3). A first detailed study of homogeneous turbulent flows follows (§4). It includes a review of available experimental data and their modeling. The eddy viscosity concept is analyzed in §5 with the l"Csulting ~alar-transport equation models such as the famous K-e model. Reynolds stl"Css models (Chapter 4) require a preliminary consideration of two-point turbulence concepts which are developed in Chapter 3 devoted to homogeneous turbulence. We review the two-point moments of velocity fields and their spectral transforms (§ 1), their general dynamics (§2) with the particular case of homogeneous, isotropie turbulence (§3) whel"C the so-called Kolmogorov's assumptions are discussed at length.