Impact of Retro Rocket Plumes on Upper Stage Aerodynamics during Stage Separation

In this paper we report on an extensive investigation of the separation process of the first two stages of a carrier rocket corresponding to VEGA, which employs solid rocket motors. The effect of the plume of first stage retro rockets on upper stage aerodynamics and aerothermal loads is analysed mostly by means of windtunnel testing in the hypersonic windtunnel H2K of DLR Cologne. Aerodynamic coefficients are determined by force measurements. In addition pressure distributions on the upper stage surface and Schlieren images for flow visualization are recorded. Infrared thermography measurements are conducted to determine the effect on aerothermal loads. Different flow conditions are achieved by variation of Reynolds number, retro rocket injection pressure ratio and angle of attack

Experimental and Numerical Performance Analysis of a Self Starting, Three-Dimensional SCRamjet Intake

In the present paper, a three-dimensional intake model is investigated in a blow-down wind tunnel and results are compared and complemented with numerical simulations (Reynolds-averaged Navier-Stokes simulations). The intake model was equipped with a movable cowl and therefore the internal contraction ratio was variable and was adjusted to the self starting condition. Three different conditions were investigated: i) at a free stream Mach number of 7, a v-shaped cowl geometry was investigated, ii) at a free stream Mach number of 7 a straight cowl geometry was investigated, and iii) the v-shaped cowl geometry was investigated at a free stream Mach number of 6. Furthermore a one-dimensional post analysis was performed, to calculate overall engine parameter from stream thrust averaged intake performance parameter. The numerical simulations were validated on the basis of wall pressure and rake pressure measurements and the match was generally well. Performance wise, the v-shaped cowl was slightly superior compared to the straight cowl. For the Mach 7 configurations maximum back pressure ratios of approximately 120 were measured, which is about 4 times the nominal operating pressure ratio. For the Mach 6 case, the maximum static back pressure ratio dropped to about 80, which again is approximately 4 times the nominal operating pressure ratio

Investigations on the Turbulent Wake of a Generic Space Launcher Geometry in the Hypersonic Flow Regime

The turbulent wake flow of generic rocket configurations is investigated experimentally and numerically at a freestream Mach number of 6.0 and a unit Reynolds number of 10 x 10^6. The flow condition is based on the trajectory of Ariane V at an altitude of 50 km, which is used as baseline to address the overarching tasks of wake flows in the hypersonic regime like fluid-structural coupling, reverse hot jets and base heating. Experiments using pressure transducers and high-speed schlieren measurement technique were conducted to gain insight into the local pressure fluctuations on the base and the oscillations of the recompression shock. This experimental configuration features a wedge-profiled strut orthogonally mounted to the main body. Additionally, the influence of cylindrical nozzle extensions 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 nozzle extensions. The sting support allows investigations of a undisturbed wake flow. A time-accurate zonal RANS/LES approach was applied to identify shocks, expansion waves, and the highly unsteady recompression region numerically. Subsequently, experimental and numerical results in the strut-averted region are opposed with regard to the wall pressure and recompression shock frequency spectra. For the compared configurations, experimental pressure spectra exhibit dominant Strouhal numbers at about S rD = 0.03 and 0.27 and the recompression shock oscillates at 0.2. In general, the numerical pressure and recompression shock fluctuations agree satisfactorily to 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, 0.21 − 0.22 and 0.31 − 0.33 at the outskirts of the base

Patients' approach to medicines in COVID-19

Several different guidelines and therapeutic recommendations have been reported for the treatment of COVID-19 since the announcement of the pandemic. In our study, the attitudes and approaches of patients with a medical indication for COVID-19 who were given drugs towards drug usage were evaluated. We aimed to present our data on the drug usage characteristics of patients to contribute to the literature. A total of 399 patients were included in the study. In the study, 51.1% of the patients were female, and 48.9% were male. The highest number of the patients were in the 18-30 age group (27.6%), the lowest number of the patients were 65 years old or older (9.8%). Twenty-five questions prepared by the researchers were asked to the patients to evaluate "their knowledge and attitudes on drug usage and disease prevention in COVID-19." Of the patients, 75.7% were not smokers. No history of chronic disease was present in 65.5% of the patients. It was determined that no drug was recommended for 9.8% of the patients, and hydroxychloroquine and favipiravir were recommended together in 49.9%. The rate of the use of chloroquine alone was 4.8%, and the rate of using only favipiravir was 32.8%. Eighty-two percent of the patients reported that they regularly used the drugs that were recommended. Among the patients, 11.5% either never used the recommended drugs or did not use them at the recommended dose and time. Of the 46 (11.5%) patients who did not use the prescribed drugs regularly, none died. In other words, improvement was observed in the patients who did not use the drugs that were recommended to them. Our aim in this study was to determine the rate and characteristics of the drugs prescribed by physicians in diagnosed patients. In this cross-sectional sample of Turkey, it was determined that the rate of recommended drug usage was sufficient with the data of the city where the study was carried out. © 2022 Ondokuz Mayis Universitesi. All rights reserved

Modified Kantrowitz Starting Criteria for Mixed Compression Supersonic Intakes

A proper understanding of the intake starting process of supersonic airbreathing engines is crucial for a successful operation of the supersonic aircraft, especially for three-dimensional geometries in which no reliable starting prediction for a broad Mach number range exists, and the widespread Kantrowitz criterion only provides a conservative prediction. Experimental investigations from the literature are reviewed and put into the perspective of the Kantrowitz theory. First, an empirical relation is developed that is valid for a wide Mach number range, and that can be calibrated to certain classes of intakes by the user. Second, the Kantrowitz assumptions are modified and a semiempirical relation is derived. The semiempirical relation turned out to be an optimistic limit for self-starting

Simultaneous determination of particle size, velocity, and mass flow in dust‑laden supersonic flows

The particle mass concentration and -mass flow rate are fundamental parameters for describing two-phase flows and are products of particle number, -size, -velocity, and -density. When investigating particle-induced heating augmentation, a detailed knowledge of these parameters is essential. In most of previous experimental studies considering particle-induced heating augmentation, only average particle mass flow rates are given, without any relation to measured particle sizes and -velocities within the flow or any indication of measurement uncertainty. In this work, particle number, individual particle sizes, and velocities were measured in a supersonic flow by means of shadowgraphy and particle tracking velocimetry (PTV). The goals are to determine measurement uncertainties, a particle velocity-size relation, and the spatial distribution of number, size, velocity, and mass flow rate across the nozzle exit. Experiments were conducted in a facility with a nozzle exit diameter of 30 mm, at Ma_inf = 2.1 and Re_inf = 8.2e7 1/m. Particles made of Al2O3 and up to 60 µm in size were used for seeding. Particle mass flow rates up to 50 kg/m2 s were achieved. It is shown that an additional correction procedure reduced common software uncertainties regarding shadowgraphy particle size determination from 14% to less than 6%. Discrepancies between calculated particle velocities and experimental data were found. In terms of spatial distribution, larger particles and a higher mass flow rate concentrate in the flow center. The determined particle mass flow rate uncertainty was up to 50% for PTV; for shadowgraphy, it was less than 17%

Dynamic Experimental Simulation of the Demise during Re-Entry Flight

There are many limitations in ground testing in the laboratory, that prohibit fully realistic simulation of the destructive entry-flight. Some of these limitations could be overcome by technical solutions, others are determined by the physics (e.g. gravitational forces acting on the test hardware). The impact of the limitations varies and have been discussed in the community for years. One of the major limitations that could be solved technically, is the testing of satellite components in a static setup. Static testing does not reproduce the dynamic re-entry environment with its changing heat flux distribution and the inertial forces. The Department of Supersonic and Hypersonic Technologies of the German Aerospace Centre DLR constantly works on improving the test facilities, setups and instrumentation and has now developed a solution that allows dynamic demise simulation in the arc heated facility L2K. This development is complementary to the implementation realised in H2K wind tunnel for measurement of the heat flux distribution on spinning samples. We present the spinning device and wind tunnel setup and show results of the first component tests in L2

On subsonic near-wake flows of a space launcher configuration with various base geometries

Buffet/buffeting as load imposing mechanism on the base structures of space launcher has been of strong interest ever since it was found as partially responsible for the failed flight 157 of Ariane 5. Several studies suggested that the base region is most excited at Mach 0.8. A preceding study of the current series on base flow effects revealed a differing excitation in comparison to the other subsonic Mach number cases. It featured an especially pronounced excitation in the recirculation region. Thus, the current work attempts to answer the question why this case appears to be distinct. This is done by decreasing the relative nozzle length and focusing on the Reynolds stress distribution. The research question is approached by experiments in the Vertical Test Section Cologne (VMK) on a base model with supersonic, over-expanded exhaust jet exposed to an ambient flow at Mach 0.8 and a Reynolds number of 1.4x10^6 . Data are acquired by means of particle image velocimetry (PIV) and high-speed schlieren imaging. The results reveal that a most unfavorable configuration appears to exist, which is if the mean shear layer reattachment takes place just on the tip of the nozzle

Particle mass flow determination in dust laden supersonic flows by means of simultaneous application of optical measurement techniques

Particle mass flow rate and particle mass concentration are key parameters for describing two-phase flows, especially for particle-induced heating augmentation analysis. This work addresses the question of how accurate particle mass flow rate can be determined with three non-intrusive measurement approaches, based on shadowgraphy, particle tracking velocimetry (PTV), and scattered light intensity, in supersonic flows. In terms of shadowgraphy and PTV, the particle mass flow rate was determined by measuring individual particle characteristics, namely particle size, velocity, and density, as well as the measurement volume. The presented shadowgraphy procedure is based on the commercial LaVision DaVis software and additional shadowgraphy corrections. Multiple tests were conducted in the experimental test facility GBK of DLR with varying flow conditions, at a Mach number of 2.1, unit Reynolds number (Re∞) ranging from 5e7 1/m to 1.5e8 1/m, total temperature (T0) ranging from 303 to 544 K, and particle materials, namely Al2O3, MgO, and SiO2, in the size range of 1 to 60 µm. Particle size distributions of Al2O3 and MgO particles could be reproduced with shadowgraphy quite well, while the PTV procedure resulted in non-similar distributions. Pycnometer measurements indicated MgO particle density to be significantly lower than reference values. A DaVis parameter variation analysis resulted in a particle mass flow rate uncertainty of shadowgraphy of up to 30%. The particle mass flow rate uncertainty of PTV is approx. 76%, and the respective uncertainty of scaled PTV and scattered light intensity approach is 28%. The particle mass flow rate, measured with shadowgraphy, is 58% higher than those of the semi-axisymmetric scattered light intensity approach, which can be explained by a higher particle concentration at the injection plane