Approximate Method of Integration of Laminar Boundary Layer in Incompressible Fluid


Book Description

A method is given for the approximate solution of the equations of the two-dimensional laminar boundary layer in an incompressible fluid. The method is based on the use of a system of equations of successive moments that is easily solved for simple supplementary assumptions. The solution obtained is given in closed form by simple formulas and is claimed to be no less accurate than the complicated solutions previously obtained, which were based on the use of special classes of flows.




Integral Methods in the Theory of the Boundary Layer


Book Description

The application of the well-known basic principle of mechanics, the principle of Jourdain, to problems of the theory of the boundary layer leads to an equation from which the equations of Von Karman, Leibenson, and Golubev are derived as special cases. The given equation may be employed in other integral methods. The present paper deals with the method of the variation of the thickness of the boundary layer. A number of new approximate formulas valuable in aerodynamic calculations for the fristion distribution are derived from this procedure. The method has been applied only to laminar boundary layers, but it seems probable that it may be generalized to include turbulent layers as well.







Method of Asymptotic Integration of Laminar Boundary Layer Equations


Book Description

After a brief review of the known methods of solving boundary layer problems (numerical, expansions in series, integral), the author presents a brief description of the asymptotic method as an effective analytical tool which makes it possible to reduce the problem of determining the friction and heat transfer to the solution of an ordinary differential equation which includes friction and its derivatives along the longitudinal coordinate. This method is generalized here to the case of the boundary layer in a compressible gas and is applied to calculations of compressible gas flow with arbitrary distributions of velocity past an elliptic cylinder in a wide range of parametric variation, and to the case of flow with gas injection into a boundary layer. The numerical results obtained for an incompressible liquid are approximated by analytical formulas. An approximate method is presented for the case of arbitrary velocity distribution in the outer flow. A system of nonsimilarity parameters is obtained as the result of the analysis of the asymptotic expansions derived here, which describes the flow along the generatrix of the body. The hypothesis of local similarity is discussed and a qualitative criterion for its application is given.







On the Convergence and Exactness of Solutions of the Laminar Boundary-layer Equations Using the N-parameter Integral Formulation of Galerkin-kantorovich-dorodnitsyn


Book Description

The solution of the incompressible, laminar boundary-layer equations using the N-parameter integral method of Galerkin, Kantorovich and Dorodnitsyn is investigated. This method seeks to obtain an approximate solution of a partial differential equation with given boundary conditions by assuming the solution in functional form so that the boundary conditions for one variable are exactly satisfied. The approximating function is then specialized in such a manner as to obtain approximate satisfaction of the given equation. Solutions are presented for the similar flows and four types of nonsimilar flows: flows with an abrupt change from an initial region of flow to a constant velocity flow, analytically prescribed external flows, experimentally determined external flows, and flows which proceed from a stagnation point to a separation point. These results indicate that the GKD method yields solutions which are uniformly better than classical approximation techniques and are of about the same accuracy as the usual 'exact' numerical solution methods such as the series method, the Hartree-Womersley method and finite difference methods. Furthermore, solutions can be obtained as close to the separation point as computationally feasible. (Author).