Plume-Induced Effects on the Near-Wake Region of a Generic Space Launcher Geometry

Abstract

The near-wake flow of a generic space launcher geometry with jet is investigated experimentally in the hypersonic flow regime at Mach 6 and an unit Reynolds number of 16 • 10 6 by means of unsteady pressure measurements. This corresponds to an altitude of 50 km for an Ariane V-like launcher with an underexpanded nozzle flow. The investigations with a truncated ideal contoured wind tunnel model nozzle designed for Mach number of 2.65 is used to simulate the nozzle flow. The objective of this study is the characterization of the plume-induced loads on the main structural components in the near wake region during flight. A parametric study with the reservoir pressures of 11, 14, 17 and 20 bar is presented. The transducers capture the pressure signal in the radial and azimuthal direction on the base and on the surface of the nozzle. The signals are spectrally analyzed with the objective to characterize and identify unsteady flow effects in order to reduce base drag and vibrations of future space launchers. The base-pressure spectra exhibits global modes at Strouhal numbers of 0.05 to 0.06, 0.09 to 0.1 and 0.2 to 0.25, which are attributed in literature to flapping and shedding. Local modes seem to occur Locally restricted modes can be detected for the tonal disturbances in the high frequency range for transducers on the base closer to the nozzle. The increase of the reservoir pressure shows a consistent increase of the pressure fluctuation level in the base region.

Propulsive jet influence on generic launcher base flow

“…This peak is found by several authors [6,10,15,19]. For hypersonic base flows Statnikov et al [25] and Saile et al [28] found similar peaks. With jet flow we obtained an additional peak at higher Strouhal numbers.…”

“…With increasing jet temperature the fluctuation level increases. Saile et al [28] did investigations on a similar generic rocket model configuration with jet flow and also found base pressure fluctuation peaks between St = 0.8 and St = 1.1. The dominating peaks above St > 0.8 are influenced by the jet temperature and therefore the jet exit velocity.…”

“…The fluctuation levels p′ RMS increase on the base and decrease on the fairing due to the under-expanded plume, see Figs. 27,28,29,30. This effect increases with to the degree of under-expansion and this is in line with the observations described by Deprés [15].…”

“…The used sensors are listed in Table 3. The sensor locations are chosen following the previous studies by Saile et al [27,28]. The radial position from the centerline r/D = 0.42 is limited by the facility itself.…”

“…Published base flow characteristics at higher speeds are sparse. Saile et al [27,28] investigated afterbody pressure fluctuations at M = 6 and researched different fairing extensions and plume effects. They analyzed base pressure fluctuations and found global modes for flapping and shedding.…”