Investigations on the turbulent wake of a generic space launcher geometry in the hypersonic flow regime

Abstract

The turbulent wake §ow of generic rocket con¦gurations is investigated experimentally and numerically at a freestream Mach number of 6.0 and a unit Reynolds number of 10 · 10 6 m −1 . The §ow condition is based on the trajectory of Ariane V-like launcher at an altitude of 50 km, which is used as the baseline to address the overarching tasks of wake §ows in the hypersonic regime like §uid-structural coupling, reverse hot jets and base heating. Experimental results using pressure transducers and the high-speed Schlieren measurement technique are shown to gain insight into the local pressure §uctuations on the base and the oscillations of the recompression shock. This experimental con¦guration features a wedgepro¦led strut orthogonally mounted to the main body. Additionally, the in §uence of cylindrical dummy nozzles attached to the base of the rocket is investigated, which is the link to the numerical investigations. Here, the axisymmetric model possesses a cylindrical sting support of the same diameter as the dummy nozzles. The sting support allows investigations for an undisturbed wake §ow. A time-accurate zonal Reynolds-Averaged NavierStokes / Large Eddy Simulation (RANS/LES) approach is applied to identify shocks, expansion waves, and the highly unsteady recompression region numerically. Subsequently, experimental and numerical results in the strut-averted region are compared with regard to the wall pressure and recompression shock frequency spectra. For the compared con¦gurations, experimental pressure spectra exhibit dominant Strouhal numbers at about Sr D = 0.03 and 0.27, and the recompression shock oscillates at 0.2. In general, the pressure and recompression shock §uctuations numerically calculated agree reasonably with the experimental results. The experiments with a blunt base reveal base-pressure spectra with dominant Strouhal numbers at 0.08 at the center position and 0. 145, 0.210.22, and 0.310.33 at the outskirts of the base.

Experimental and numerical investigation of the turbulent wake flow of a generic space launcher configuration

“…16. Additionally, the numerical and experimental base pressure spectra feature also clearly pronounced peaks in the range of Sr D ≈ 0.05 which are presumably associated with the oscillatory movement of the large-scale toroidal vortex within the separation bubble as known from the former investigations performed by the authors on a similar generic con¦guration [34].…”

Numerical investigation of the near wake of generic space launcher systems at transonic and supersonic flows

“…13 to reveal dynamic e¨ects of the recirculation zone on the rocket structure at supersonic §ow conditions. In the radial direction, the time averaged base pressure coe©cient remains at the constant level of c p ≈ −0.03, whereas its rms value exhibits a distinct peak (c p rms ≈ 0.00045) at the inner base corner at x/D ≈ 0.205 which can be explained by high dynamic motion of a large scale toroidal secondary vortex described in [17]. In the streamwise direction, the mean pressure coe©cient remains nearly constant up to x/D ≈ 0.5 where the recompression shock occurs and subsequently, an increase in c p takes place.…”

“…Each unshaped §ow circulation downstream of the base leads to a small shift in the position of the recompression shock and vice versa. The distinct mode of the recompression shock oscillations was determined experimentally and numerically in the range of Sr D ≈ 0.18 [17]. The observed fourth corresponding mode in the base pressure spectra Sr D = 0.192 at r/D = 0.46 is assumed to be a footprint of this coupled e¨ect.…”

“…The excitation of the wall boundary layer by the recompression shock causes the wall pressure §uctuations to reach a higher constant level of c p rms ≈ 0.001 downstream of the shock position. [17], the ¦rst two modes are determined to be the footprints of the inner dynamics of the recirculation zone represented by two counter rotating and interacting toroidal vortices whose dimensions and core positions change in the time. Unsteady supersonic results show that the expansion remains mostly constant, while a coupled e¨ect of the subsequent recompression shock and the recirculation region occurs, leading to a pulsating motion.…”

Investigations of Unsteady Transonic and Supersonic Wake Flow of Generic Space Launcher Configurations Using Zonal RANS/LES and Dynamic Mode Decomposition

“…As shown by Statnikov et al [18][19][20] for both transonic and supersonic cases, numerical results such as computed flow field topology, time-averages and fluctuations of base pressure signals as well as its spectra satisfactorily agree with the experimental data from literature and experimental investigations conducted within TRR 40 [21][22][23]. Using classical spectral analysis and correlation methods, several distinct frequencies were identified indicating a periodic behavior of the base-flow dynamics, e.g., Sr D D 0:1 (shear layer flapping), Sr D D 0:2 (von Kármán vortex shedding) as well as a number of dominant peaks at lower (Sr D 0:05/ and considerably higher frequencies (Sr D 0:7 and Sr D 1) with not fully understood origins.…”