Theoretical Investigation of Laminar and Turbulent Unsteady Boundary Layers Along a Flat Plate.
Abstract
This thesis investigates theoretically the viscous, incompressible and unsteady boundary layer flows along flat plates. Unsteady flows are divided into two major parts. First laminar and impulsive, constant and other types of accelerated fluid flows, starting from rest, are solved by using similarity variables. A physical model is presented and justified for these type of flows. The solutions are generated by computer. The results provide the first singularity free semisimilar solutions that show the development and growth of the boundary layer along a semiinfinite flat plate. Secondly, selfgenerated unsteadiness, turbulence, is divided into two kinds. The first kind is the turbulent boundary layer fluid flows, with constant mainstream velocity, along a semiinfinite flat plate which we call the Blasius turbulent problem. Reynold's timeaveraging turbulent equations with boundary layer approximations and using Prandtl's mixing length as a crude model are solved in their differential form without relying on similarity variables. The problem is reduced to a boundary value problem where an important parameter, the transition point, is introduced. The numerical results show the development of the boundary layer starting from the laminar through the fully developed turbulent regions, including transition. In the fully turbulent regime, most results are within ten percent agreement with experiments. The second kind is the turbulent boundary layer fluid flows, with constant and impulsively started mainstream velocity, along an infinite flat plate, which we call the Rayleigh turbulent problem. A spanaveraging is described parallel to Reynold's timeaveraging. Prandtl's mixing length is utilized again as a crude model in the spanaveraging turbulent equation without relying on similarity variables. The problem is reduced to an initial value problem where an important parameter, the transition time, is introduced. The computer results show the growth of the boundary layer from laminar through the fully turbulent regions, including transition. This thesis provides the first theoretical solution of this type.
 Publication:

Ph.D. Thesis
 Pub Date:
 1985
 Bibcode:
 1985PhDT........15H
 Keywords:

 Physics: Fluid and Plasma;
 Boundary Layer Transition;
 Flat Plates;
 Laminar Boundary Layer;
 Turbulent Boundary Layer;
 Boundary Value Problems;
 Computerized Simulation;
 Unsteady Flow;
 Plasma Physics