Characterization of the supersonic wake of a generic space launcher
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- 作者：A.-M. Schreyer ; S. Stephan ; R. Radespiel
- 关键词：Supersonic wake ; Axisymmetric space ; launcher model ; Pressure ; perturbation sources ; Base flow ; Propulsive ; jet simulation
- 刊名：CEAS Space Journal
- 出版年：2017
- 出版时间：March 2017
- 年：2017
- 卷：9
- 期：1
- 页码：97-110
- 全文大小：
- 刊物类别：Engineering
- 刊物主题：Aerospace Technology and Astronautics;
- 出版者：Springer Vienna
- ISSN：1868-2510
- 卷排序：9
文摘
The wake flow of a generic axisymmetric space-launcher model is investigated experimentally for flow cases with and without propulsive jet to gain insight into the wake-flow phenomena at a supersonic stage of the flight trajectory which is especially critical with respect to dynamic loads on the structure. Measurements are performed at Mach 2.9 and a Reynolds number ReD = 1.3 × 106 based on model diameter D. The nozzle exit velocity of the jet is at Mach 2.5, and the flow is moderately underexpanded (pe/p∞ = 5.7). The flow topology is described based on velocity measurements in the wake by means of particle image velocimetry and schlieren visualizations. Mean and fluctuating mass-flux profiles are obtained from hot-wire measurements, and unsteady wall-pressure measurements on the main-body base are performed simultaneously. This way, the evolution of the wake flow and its spectral content can be observed along with the footprint of this highly dynamic flow on the launcher main-body base. For the case without propulsive jet, a large separated zone is forming downstream of the main body shoulder, and the flow is reattaching further downstream on the afterbody. The afterexpanding propulsive jet (air) causes a displacement of the shear layer away from the wall, preventing the reattachment of the flow. In the spectral analysis of the baseline case, a dominant frequency around StD = 0.25 is found in the pressure-fluctuation signal at the main-body base of the launcher. This frequency is related to the shedding of the separation bubble and is less pronounced in the presence of the propulsive jet. In the shear layer itself, the spectra obtained from the hot-wire signal have a more broadband low-frequency content, which also reflects the characteristic frequency of turbulent structures convected in the shear layer, a swinging motion (StD = 0.6), as well as the radial flapping motion of the shear layer (StD = 0.85), respectively. Moving downstream along the shear layer, spectral content at slightly higher frequencies (StD < 4) gets more pronounced and can be related to the shear layer instability process and the signature of smaller turbulent structures that appear in the wake.