Calculation of Three-dimensional Boundary Layers on Ship Forms


Book Description

An implicit finite difference technique, in curvilin ear-orthogonal surface coordinates, has been developed for the solution of the differential equations of three-dimensional laminar and turbulent boundary layers on ship forms. For turbulent flow, a two-layer eddy-viscosity model has been employed as the closure model. The initial and boundary conditions required to solve the equations and the stability and accuracy of the numerical method are discussed at some length. Two mathematically-defined simple three-dimensional ship forms are studied in some detail. These are a tri-axial ellipsoid and a double elliptic ship.




Calculation of Three-Dimensional Boundary Layers Around Ship Hull Forms


Book Description

Numerical investigations is made into complex three-dimensional boundary layers around ship hull forms. At first, simple model of natural transition for boundary layers on ship fore-body surface is presented. Transitional boundary layer from laminar to turbulent calculated by using this model agreed very well with experimental results. Investigation is carried out about influence of the change of laminar boundary layer region and Reynolds number on the flow field around ship forebody. The results shows that unstable flow pattern at bilge part is varied drastically due to above influence at comparatively low Reynolds number since turbulence intensity is smaller than that at high Reynolds number.







Calculation of Three-dimensional Boundary Layers on Bodies at Incidence


Book Description

Three-dimensional thin boundary-layer equations for laminar and turbulent flows are solved by two different numerical schemes. The methods are applied to the flow over bodies of revolution at incidence and the results are compared with the available experimental data in order to study the range of validity of the classical boundary-layer approximations in regions of increasing circumferential gradients and flow reversal associated with the early stages of a free-vortex type of separation. Comparison with the DFVLR 6:1 spheroid data of Meier et al and the 4:1 combination-body data of Ramaprian, Patel and Choi indicate that the methods perform well in regions where the boundary layer remains thin but the predictions deteriorate as the boundary layer thickens. The results point out the need for the development of methods of handle thick boundary layers and viscous-inviscid interactions. (Author).







Orthogonal Coordinate Systems for Three-dimensional Boundary Layers


Book Description

The problem of choosing orthogonal, curvilinear, coordinate systems for use in boundary-layer calculations on arbitrary three-dimensional bodies is considered in some detail. A general method for the practical evaluation of the various geometrical properties of the coordinates occurring in the three-dimensional boundary-layer equations is described. A particular coordinate system which appears to be the most convenient one for ship hulls is then proposed and analyzed further.










Calculations of Three-dimensional Turbulent Boundary Layers Using the Crank-Nicolson Method


Book Description

This report describes the results of the three-dimensional turbulent boundary-layer calculations performed for the Eurovisc Workshop held in Berlin on 1 April 1982. It is shown that the present method, based on the Crank-Nicolson finite-difference scheme and a simple eddy-viscosity model for turbulence, yields satisfactory results provided regions of viscous-inviscid interaction, which were present in at least three of the four test cases, are avoided. (Author).