Investigation of the base flow of a generic space launcher with dual-bell nozzle
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ORIGINAL PAPER
Investigation of the base flow of a generic space launcher with dual‑bell nozzle Sven Scharnowski1 · Christian J. Kähler1 Received: 5 May 2020 / Revised: 6 August 2020 / Accepted: 24 August 2020 © The Author(s) 2020
Abstract The typical afterbody flow of a space launcher is characterized by a strong interaction of the engine’s exhaust jet and the separated shear layer emerging from the main body. This interaction is further complicated by strong changes in the spatial and temporal behavior of the afterbody flow during the atmospheric ascent of a launcher. Theoretically, a dual-bell nozzle not only allows for a gain in payload compared to standard single-bell nozzles, but also it alters the wake flow topology due to the two nozzle modes. To predict the benefits as well as the additional risks, the afterbody flow of a generic space launcher model equipped with a cold-flow dual-bell nozzle is investigated in detail. The flow was analyzed for sub-, trans- and supersonic Mach numbers ranging from 0.3 to 2.9 for a variety of nozzle pressure ratios. Particle image velocimetry measurements and schlieren measurements with high repetition rate were performed to determine the dynamics of the separated shear layer, the nozzle jet and their interaction. It is shown that the reattachment length of the base flow decreases with increasing nozzle pressure ratio. Furthermore, the nozzle pressure ratio at which the dual-bell nozzle switches from sea-level mode to altitude mode is reduced by 15% with high subsonic outer flow and by as much as 65% for an outer flow at a Mach number of 1.6. Even for a constant nozzle pressure ratio, the nozzle flow topology depends on the Mach number of the outer flow. keywords Nozzle flow · Dual bell · Flow separation
1 Introduction Access to space is of great importance for the security and comfort of our lives. Satellites in various orbits around the Earth are used to navigate, to communicate and to forecast the weather, among other things. At present, there are about 5000 satellites orbiting the earth and every year hundreds more are added, with an upward trend1. Currently, space launchers are our only means of reaching outer space. Therefore, they are absolutely essential for transporting the satellites that we need for such a wide variety of purposes. This drives the need to develop launch vehicles that are as safe
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12567-020-00333-5) contains supplementary material, which is available to authorized users. * Sven Scharnowski [email protected] 1
Bundeswehr University Munich, Institute of Fluid Mechnics and Aerodynamics, Neubiberg, Germany
and efficient as possible from an economic and ecological point of view. The interaction between the external flow and the structure in the afterbody of a launch vehicle is considered a critical factor. In recent years, many experiments [4, 5, 11, 15, 18, 31, 42, 43, 49] and computational flow simulations [10, 23, 28, 48, 54–56] have
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