- Author
- Rehm, R. G. | Baum, H. R. | Lewis, J. | Cordes, M. R.
- Title
- Linearized Finite-Difference Computation of Fluid heating in an Enclosure. Interim Report.
- Coporate
- National Bureau of Standards, Gaithersburg, MD
- Report
- NBSIR 79-1754, May 1979, 76 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- buoyant flow | gases | predictive models | enclosures
- Abstract
- In an earlier paper, approximate equations of motion were derived which are applicable to nondissipative, very nonadiabatic, buoyant flows of a perfect gas. In the present paper, these approximate equations are in a form in which they can be integrated by finite difference techniques. The nonlinear equations are made dimensionless, specialized to two dimensions and linearized. Finite difference approximations, using central differences in space and leapfrog in time, are made to the linearized equations. To start the comutation, a first-order scheme is used for the initial time step. The dependent variables are density, the horizontal and vertical velocity components and pressure, and these variables are defined at various positions within a grid cell. The computer time required for various size computations and the accuracies obtained are reported. At each time step, a large sparse system of linear algebraic euations, the finite difference approximation to the alliptic equation for th pressure, must be solved. A hybrid method, combining the interactive algorithm called conjugate gradients with a fast direct method for solving Poisson's equation, is used to solve the algebraic system efficiently and accurately. Examples of computations of the flow fields induced by heating are presented and discussed.