Accession Number:

ADA243915

Title:

Computation of Planar Store Trajectories Using an Adaptive Grid Procedure.

Descriptive Note:

Master's thesis,

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s):

• Hack, William D.

Report Date:

1991-12-01

Pagination or Media Count:

102.0

Abstract:

The objective of this research was to compare a quasi-analytical, potential flowthree-degree-of-freedom model to an implicit-Euler algorithm for the calculation of store trajectories. The implicity algorithm uses a cell- centered, finite-volume, spatial discretization applied to the Euler equations, written in time-dependent, curvilinear-coordinates. A flux-differencing Roe scheme is employed to find the split-fluxes and the StegerWarming flux-vector method is used to calculate the flux-Jacobians. The potential flow and implicit- Euler algorithm are combined with a three-degree-of-freedom algorithm to evaluate the planar, freefall trajectories of a simple store shape. The research uses two different grid-modification techniques in the implicit algorithm evaluation. Data collected for both grids used the minimum time-step in the three-degree-of-freedom algorithm for a Courant number of 10. Two test cases involved updating the flux-Jacobians after every time-step and only once during every 1000 iterations. The effect of multiplying the minimum time-step by factors of 2, 4, 6, 8, 10, and 100 were also examined. The potential flow and implicit algorithm trajectories didnt compare very closely. The various Delta t and Jacobian-update results matched rather closely.

Descriptors:

• *ADAPTIVE SYSTEMS
• ALGORITHMS
• GRIDS
• FREE FALL WEAPONS
• DIFFERENTIAL EQUATIONS
• TRAJECTORIES
• POTENTIAL FLOW
• TEST AND EVALUATION

Subject Categories:

• Ballistics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE