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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Application of the multigrid method to grid generation

The multigrid method (MGM), used to numerically solve the pair of nonlinear elliptic equations commonly used to generate two dimensional boundary-fitted coordinate systems is discussed. Two different geometries are considered: one involving a coordinate system fitted about a circle and the other selected for an impinging jet flow problem. Two different relaxation schemes are tried: one is successive point overrelaxation and the other is a four-color scheme vectorizeable to take advantage of a parallel processor computer for greater computational speed. Results using MGM are compared with those using SOR (doing successive overrelaxations with the corresponding relaxation scheme on the fine grid only). It is found that MGM becomes significantly more effective than SOR as more accuracy is demanded and as more corrective grids, or more grid points, are used. For the accuracy required, it is found that MGM is two to three times faster than SOR in computing time. With the four-color relaxation scheme as applied to the impinging jet problem, the advantage of MGM over SOR is not as great. This may be due to the effect of a poor initial guess on MGM for this problem.

Ohring, S.↗
DOE OSTI2020

Emerging Soluble Organic Redox Materials for Next-Generation Grid Energy-Storage Applications

Soluble organic redox molecules have emerged as promising candidate active materials for multiple energy storage systems due to their structural versatility, fast redox process, high capacity storage, sustainability, and environmental friendliness. This review examines recent progress in developing such materials in green and sustainable batteries for grid applications and points out directions for future research.

Zhan, Xiaowen↗
NASA NTRS1980

Numerical grid generation techniques

The state of the art in topology and flow geometry is presented. Solution techniques for partial differential equations are reviewed and included developments in coordinate transformations, conformal mapping, and invariant imbeddings. Applications of these techniques in fluid mechanics, flow geometry, boundary value problems, and fluidics are presented.

Source record↗
NASA NTRS1980

Grid generation for two-dimensional finite element flowfield computation

The finite element method for fluid dynamics was used to develop a two dimensional mesh generation scheme. The method consists of shearing and conformal maps with upper and lower surfaces handled independently to allow sharp leading edges. The method also generates meshes of triangular or quadrilateral elements.

Tatum, K. E.↗
NASA NTRS1982

Elliptic grid generation

Various types of generating systems for boundary-conforming coordinate systems based on the numerical solution of systems of elliptic partial differential equations are discussed. Particular emphasis is given to the determination of functions in these equations which control the distribution of the curvilinear coordinate lines in the field.

Thompson, J. F.↗
NASA NTRS1982

Solution of viscous internal flows on curvilinear grids generated by the Schwarz-Christoffel transformation

The combination of an orthogonal, curvilinear coordinate generation procedure with a stable forward marching viscous flow solution technique is presently employed in the solution of flow fields for arbitrary, axisymmetric ducts. Coordinate generation is accomplished by means of both potential lines and plane potential flow streamlines. Since the coordinate streamlines approximate actual ones, the equations of motion for viscous compressible flow can be parabolized in order to solve for both the boundary layer and the core flow in a single streamwise pass. The method's versatility is demonstrated by two examples of viscous compressible swirling flow through complex radial gas turbine passages.

Anderson, O. L.↗
NASA NTRS1983

Algebraic grid generation with corner singularities

A simple noniterative algebraic procedure is presented for generating smooth computational meshes on a quadrilateral topology. Coordinate distribution and normal derivative are provided on all boundaries, one of which may include a slope discontinuity. The boundary conditions are sufficient to guarantee continuity of global meshes formed of joined patches generated by the procedure. The method extends to 3-D. The procedure involves a synthesis of prior techniques stretching functions, cubic blending functions, and transfinite interpolation - to which is added the functional form of the corner solution. The procedure introduces the concept of generalized blending, which is implemented as an automatic scaling of the boundary derivatives for effective interpolation. Some implications of the treatment at boundaries for techniques solving elliptic PDE's are discussed in an Appendix.

Vinokur, M.↗
NASA NTRS1990

Algebraic grid generation with boundary orthogonality control

This paper presents a new approach in applying the blending function method to the generation of structured finite-difference meshes. It is shown that the surface equation developed by Coons (1967) can be easily adapted to generate two-dimensional meshes, and its extension to hyperspace allows the construction of three-dimensional meshes. The robust method in its basic form blends among the boundary curves/surfaces conforming to their intrinsic slopes. When parameter-controlled boundary-slope corrections are introduced, it is possible to establish varying degrees of orthogonality along the boundaries. Additional controls are made possible by moving points in the parameter space, which affects the movement of points in the physical space. The combination of these controls provides a simple and yet powerful means for exploiting the blending-function method to satisfy the needs of practical CFD applications. Results from a validation program for two-dimensions are shown for a variety of geometries.

Luh, Raymond Ching-Chung↗