A Formulation for the Boundary-Layer Equations in General Coordinates


Book Description

This is a working paper in which a formulation is given for solving the boundary-layer equations in general body-fitted curvilinear coordinates while retaining the original Cartesian dependent variables. The solution procedure does not require that any of the coordinates be orthogonal, and much of the software developed for many Navier-Stokes schemes can be readily used. A limited number of calculations has been undertaken to validate the approach. Steger, Joseph L. and Vandalsem, William R. and Panaras, Argyris G. and Rao, K. V. Ames Research Center ...










A Non-parametric Discontinuous Galerkin Formulation of the Integral Boundary Layer Equations with Strong Viscous-inviscid Coupling


Book Description

A non-parametric discontinuous Galerkin (DG) finite-element formulation is developed for the integral boundary layer (IBL) equations with strong viscous-inviscid coupling. This DG formulation eliminates the need of explicit curvilinear coordinates in traditional boundary layer solvers, and thus enables application to complex geometries even involving non-smooth features. The usual curvilinear coordinates are replaced by a local Cartesian basis, which is conveniently constructed in the DG finite-element formulation. This formulation is also applicable to the general convection-source type of partial differential equations defined on curved manifolds. Other benefits of DG methods are maintained, including support for high-order solutions and applicability to general unstructured meshes. For robust solution of the coupled IBL equations, a strong viscous-inviscid coupling scheme is also proposed, utilizing a global Newton method. This method provides for flexible and convenient coupling of viscous and inviscid solutions, and is readily extensible to coupling with more disciplines, such as structural analysis. As a precursor to the three-dimensional strongly-coupled IBL method, a two-dimensional IBL solver coupled with a panel method is implemented. Numerical examples are presented to demonstrate the viability and utility of the proposed methodology.







Boundary-Layer Equations in Generalized Curvilinear Coordinates


Book Description

A set of higher-order boundary-layer equations is derived valid for three-dimensional compressible flows. The equations are written in a generalized curvilinear coordinate system, in which the surface coordinates are nonorthogonal; the third axis is restricted to be normal to the surface. Also, higher-order viscous terms which are retained depend on the surface curvature of the body. Thus, the equations are suitable for the calculation of the boundary layer about arbitrary vehicles. As a starting point, the Navier-Stokes equations are derived in a tensorian notation. Then by means of an order-of-magnitude analysis, the boundary-layer equations are developed. To provide an interface between the analytical partial differentiation notation and the compact tensor notation, a brief review of the most essential theorems of the tensor analysis related to the equations of the fluid dynamics is given. Many useful quantities, such as the contravariant and the covariant metrics and the physical velocity components, are written in both notations. Panaras, Argyris G. Ames Research Center NASA-TM-100003, A-87272, NAS 1.15:100003 RTOP 505-60...










A General Method for Calculating Three-Dimensional Incompressible Laminar and Turbulent Boundary Layers. II. Three-Dimensional Flows in Cartesian Coordinates


Book Description

The report presents a general method for computing three-dimensional laminar and boundary-layer flows in Cartesian coordinates. In the equations, the Reynolds shear stress terms are modeled by an eddy-viscosity formulation developed by the author. A very efficient two-point finite-difference method was used to solve the governing equations. The accuracy of the method is investigated for laminar and turbulent flows. (Author).




Three-dimensional, Time-dependent, Compressible, Turbulent, Integral Boundary-layer Equations in General Curvilinear Coordinates and Their Numerical Solution


Book Description

A method is presented for computing three-dimensional, time-dependent, compressible, turbulent boundary layers in nonorthogonal curvilinear coordinates. An integral method is employed in the interest of computational speed and because the three-dimensional method is an extension of an existing two-dimensional method. After presenting a detailed derivation of the integral form of the boundary-layer equations, the necessary auxiliary relations are given along with the relationships between integral lengths expressed in streamline and nonorthogonal coordinates. A time dependent approach is used to account for time accuracy (if desired) and to provide a method that is compatible with the surface grid used by an inviscid solver for use in viscous-inviscid interaction calculations. The equations are solved using a Runge-Kutta scheme with local time stepping to accelerate convergence. Stability and convergence of the numerical scheme are examined for various space differences compared with measurements and with computations of previous investigators.