
Accession Number : ADA183040
Title : Analytical and Numerical Computation of RingSymmetric Spacecraft Exhaust Plumes.
Descriptive Note : Contractor rept. AugDec 86,
Corporate Author : FALCOVITZ (JOSEPH) HAIFA (ISRAEL)
Personal Author(s) : Falcovitz,Joseph
PDF Url : ADA183040
Report Date : Dec 1986
Pagination or Media Count : 60
Abstract : A doubleheader approach to the computation of a ringsymmetric spacecraft exhaust plume is presented. We plan to use the present analytic approximation in conjunction with a model for backflow from the exhaust plume of an orbiting spacecraft, induced by oncoming ambient molecules. This process takes place in the regions of centered rarefaction waves (CRW) that flank the central plume. A semiinverse marching characteristic scheme (SIMA) is formulated specifically for accurate computation of a CRW in twodimensional axisymmetric coordinates, as a variant of the classical inverse marching method. It replicates a PrandtlMeyer flow exactly, resulting in an accurate marching scheme for axisymmetric CRW. The analytic PrandtlMeyer flow exactly, resulting in an accurate marching scheme for axisymmetric CRW. The analytic approximation to a ringsymmetric CRW is formulated in two phases. An analysis of the flow near the corner using characteristics coordinates, results in fanwise gradients of flow variables (Riemann invariants). These gradients are then used to extrapolate the flow field along fan characteristics from the presumably PrandtlMeyer flow at the corner while matching exactly the cylindrically diverging flow along the unreflected portion of the CRW leading characteristic. The resulting approximation compares favorably with numerical (SIMA) computations, even at about 10 corner radii away from the corner. Closedform expressions are obtained for lateral plume opacity at the CRW fringes. Keywords: Exhaust plume, Ring plume, Analytic approximation, Laser exhaust, Centered rarefaction waves.
Descriptors : *EXHAUST PLUMES, SUPERSONIC FLOW, MOLECULES, COMPUTATIONS, NUMERICAL METHODS AND PROCEDURES, BACKFLOW, PLUMES, FLOW FIELDS, PRANDTL NUMBER, RAREFACTION, WAVES, VARIABLES, JET FLOW, FINITE DIFFERENCE THEORY, OPACITY, EXTRAPOLATION, APPROXIMATION(MATHEMATICS), NUMERICAL ANALYSIS, INVERSION, METHOD OF CHARACTERISTICS, EXHAUST GASES, HYDROGEN FLUORIDE LASERS, PLANNING, RINGS, ORBITS, SPACECRAFT, FLOW, AXISYMMETRIC, COORDINATES, TWO DIMENSIONAL
Subject Categories : Fluid Mechanics
Numerical Mathematics
Astronautics
Distribution Statement : APPROVED FOR PUBLIC RELEASE