The fincngs of this report we not to be onstrued as an offiial Department of the Army position, unless so designated by other authorized documents.The use of trade names or manutacturers' names In this report does not constitute Indorsement of any commrcial product.Pubki I@SOrting b~re forth8is col~lw~if of in$fonntion is estimate to &vifg hour Per resortse. Includng Ih@ time for rovuW'Vn oinstructtorts1 Woawling e.Isting "to souat. pt#WflA w4 montawf"n It' data faded.
ABSTRACT (Maximum 200 words)A zomal, implici, time-marvhig Navier-Stakes computational tecinique hm been used to compute the turbulent suesoi base flow over cylindrical aftesbodies. A critical element of calculating such flows is the turbulence model.aroseddy viscosity turbulence models have been used In die base region flow computations. These models include two algebraic turbulence models uad a two-equation k-e model. The k-e equations ar developed In a general coordinate system and solved using an implicit, algorithm. C~alculation with the k-c model ame extended up to the walL Flow field comptatonshave been performedl for a cylindrical aftebody at M -2.46 and at angle of attack a = 0. Thw results are copred to the experimental datm for fth sane conditions and the same configuration. Details of the mean flow field as well Be the turbulence quantities have been presented. In addition. fth computed base pressure distribution bas been cmudwidh the experiment. In general,, the k-e turbulence model performs bette In the near wake than the Algebraic models and predicts the base pressure much better.
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A computational capability has been developed for predicting the flowfield about projectiles, including the recirculatory base flow at transonic speeds. In addition, the developed code allows mass injection at the projectile base and hence is used to show the effects of base bleed on base drag. Computations have been made for a secant-ogive-cylinder projectile for a series of Mach numbers in the transonic flow regime. Computed results show the qualitative and quantitative nature of base flow with and without base bleed. Base drag is computed and compared with the experimental data and semiempirical predictions. The reduction in base drag with base bleed is clearly predicted for various mass injection rates. Results are also presented that show the variation of total aerodynamic drag both with and without mass injection for Mach numbers of 0.9 < M< 1.2. The results obtained indicate that, with further development, this computational technique may provide useful design guidance for projectiles.
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