Dominik Saile

Investigations on the Near-Wake Region of a Generic Space Launcher Geometry

The near-wake of a separated flow behind a generic space launcher model with different afterbody extensions is studied experimentally in the hypersonic flow regime (Mach number 6.0 and unit Reynolds number 16 × 10 6 m −1 ) with the main objective being to show unsteady flow phenomena. This objective is based on the desire to control the base flow of space launchers to reduce drag and dangerous vibrations. The investigations focus on the unsteadiness of the base-pressure fluctuations and the oscillations of the recompression shock. Base-pressure spectra and spectra of the vertical recompression shock oscillation are discussed for various pressure transducer locations, various nozzle lengths and nozzle diameters. The base-pressure spectra exhibits dominant Strouhal numbers centered at 0.08 at the center positions and 0.08, 0.2, 0.38 at the outskirts of the base, and shows a crucial change with a frequency shift to Strouhal number of 0.27 when a nozzle is applied. Additionally, the pressure spectra indicate an azimuthal mode. The spectra of the recompression shock feature a dominant Strouhal number of 0.2 independent of the geometry of the afterbody. Since the incoming boundary layer is suspected to have an influence on the near-wake flow, the state and the flow conditions are examined in introductory experiments by means of infrared images of the model surface and Pitot pressure at the body corner.

Overview of a Supersonic Probe for Solid Propellant Rocket CCP Collection

The present work aims at giving a comprehensive overview of the current development status of an intrusive probe, capable of collecting the condensed combustion products present in the exhaust of a solid rocket motors. The innovative technique was conceived in the EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) framework, a project aiming at characterizing the alumina in terms of size, temperature and spatial distribution to gain detailed information for climatological impact assessment. A supersonic probe was sized to handle a progressive deceleration and cooling of the exhaust gas, as well as the quenching and collection of the suspended particles in a pressure-controlled chamber. The task was achieved by through a quasi 1D gas dynamics code based on the Shapiro method and the normal shock wave theory, which was verified against a hybrid 2D axial-symmetric mesh whose turbulent flow field was solved using the DLR-TAU CFD code. The robustness of the system has been investigated performing a sensitivity and an uncertainty analysis, exploring uncertainties propagation through the numerical code based on Shapiro equations. The sensitivity analysis enabled to define a ranking of importance for the uncertainties on the probe behavior; the uncertainty analysis allowed to estimate failures of the system and/or of the code. Cold flow tests carried out at the vertical facility of DLR-Cologne enabled to gain a proof of concept for both fluid dynamic behavior and collection methodology.

Development of a Probe for Particle Collection in High-Temperature, Supersonic Flow: Conceptual and Detailed Design

An intrusive technique for the collection of the condensed combustion products in the proximity of the rocket nozzle is proposed. In particular, a supersonic probe able to withstand the harsh environment of a plume was sized to handle a progressive deceleration and cool down of the exhaust gas, preventing from liquid particle breakup. The task was achieved by diluting the swallowed flow with a cold inert gas and quenching the suspended particles using a liquid spray in a specific chamber. Preliminary tests performed in the supersonic wind tunnel at DLR confirmed the quality of the collection device.