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The 105mm M774 is a high velocity, long 1/d, fin stabilized projectile. Recent test firings by LCWSL at Yuma Proving Ground, Arizona, revealed that the stabilizing fins were being severely reduced in span due to aerodynamic heating. This brief computational study examines the in-depth temperature response of a thin, swept fin to aerodynamic heating for a series of fin geometries in an effort to determine if a minor design modification can be found which will result in improved performance of the swept fin. The computational results indicate that the aerodynamic heating can be significantly reduced by a relatively small increase in the sweep angle of the fin.

The thin-layer Parabolized Navier-Stokes computational technique developed recently by Schiff and Steger has been shown to be a viable computational tool for predicting Magnus effects at small angle of attack for 2 < M < 4 for slender shell as verified by comparison to wind tunnel force measurements. This computational technique is applied here to examine the ability of the code to predict aerodynamic forces at angles of attack up to 10-degrees and to study the Magnus effect at small angle of attack for a parametric variation of boattail configuration. The model geometries in this study include boattail angles of 0°, 5°, 7–1/2°, and 10° for lengths of one and two calibers. This range of boattail angle and length effectively spans the range for practical shell application. Results are shown which quantize the significant effects of boattail length and angle on the Magnus force at supersonic velocity.

Aerodynamic properties of artillery shell such as normal force and pitching moment reach peak values in a narrow transonic Mach number range. In order to compute these quantities, numerical techniques have been developed to obtain solutions to the three-dimensional transonic small disturbance equation about slender bodies at angle of attack. The computation is based on a plane relaxation technique involving Fourier transforms to partially decouple the three-dimensional difference equations. Particular care is taken to assure accurate solutions near corners found in shell designs. Computed surface pressures are compared to experimental measurements for circular arc and cone cylinder bodies which have been selected as test cases. Computed pitching moments are compared to range measurements for a typical projectile shape.

Test firings of an Army projectile carrying a liquid payload have resulted in sightings of a brief vapor trail early in the flight of the projectile. The purpose of this memorandum is to examine the possibility for aero-thermodynamics to generate a visible condensation trail behind a shell. Flow field computations using thin-layer Navier-Stokes computational techniques have been accomplished to define the local flow temperature distribution about a typical shell at M=.9 and M=2. These results indicate that small regions of flow exist that are conducive to produce condensation; however, these flow conditions are quickly modified by the presence of shock-boundary layer interactions and recompression. It is concluded that aerothermodynamics is an unlikely cause of the reported projectile trails.

A flow simulation tool, developed by the authors at the Army HPC Research Center, for compressible flows governed by the Navier-Stokes equations is used to study missile aerodynamics at supersonic speeds, high angles of attack and for large Reynolds numbers. The goal of this study is the evaluation of this Navier-Stokes computational technique for the prediction of separated flow fields around high-length-to-diameter (L/D) bodies. In particular, this paper addresses two issues: (i) turbulence modelling with a finite element computational technique and (ii) efficient performance of the computational technique on two different multiprocessor mainframes, the Thinking Machines CM-5 and CRAY T3D. The paper first provides a discussion of the Navier-Stokes computational technique and the algorithm issues for achieving efficient performance on the CM-5 and T3D. Next, comparisons are shown between the computation and experiment for supersonic ramp flow to evaluate the suitability of the turbulence model.

I this note we report preliminary work on a modification of the expansion tube. This modification is suggested by our experiences with secondary diaphragm breakage and its effect on flow quality. It appears that diaphragm fragment size significantly affects flow uniformity. Our experiences imply that large diaphragm "petals" of order of the tube diameter introduce disturbances in the same order of magnitude, and the subsequent expansion process does not sufficiently smooth the flow before the gas reaches the test station. On the other hand, small fragments such as result from shattering by the incident shock introduce disturbances of a correspondingly small order. These disturbances are smoothed out further by the expansion, so that a rather smooth flow results. Accordingly, flow quality is improved by forcing the diaphragm to break into small pieces. If at the same time the diaphragm could be retained, additional improvement in flow contamination could be achieved. Preliminary tests with the modification reported here show that such improvements are indeed achieved. The modification consists of a "nozzle plate" installed at the secondary diaphragm location. The plate is shown in Fig. 1. It contains a large number of individual nozzles that are initially sealed against the driven gas by a common dia