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

Wissen und verstehen, was man tut: Das Potenzial der Klebtechnik und die Notwendigkeit der Qualitätssicherung

Der Trend zu einer zunehmenden Verwendung von Kleb- und Dichtstoffen hält in vielen Branchen aus Industrie, Handwerk und Dienstleistung weiterhin an. Nicht nur die Automobilindustrie, der gesamte Verkehrsmittelbau inkl. Sonder- und Nutzfahrzeugbau, Schienenfahrzeugbau, Schiffbau, Luft- und Raumfahrt und die Zulieferindustrie der genannten Branchen bedient sich mehr denn je der Klebtechnik, z.B. um neben effizienten und signifikanten Gewichtsreduzierungen auch aerodynamische Effekte zu erzielen. In der Elektronik sind Klebstoffe inzwischen unentbehrlich und tragen in hohem Maße zur Funktionssicherheit bei. Auch im Maschinen- und Anlagenbau setzt sich die Klebtechnik immer mehr durch. Der Industrieverband Klebstoffe geht auch mittelfristig von einem mindestens 4%igem Wachstum des Klebstoffsektors aus

Zur Philosophie des Klebens

Der Leichtbau bedeutet im Betrieb gesteigerte Effizienz und damit Ressourcenschonung. Der damit verbundene Einsatz von Funktionsmaterialien, dem optimalen Werkstoff am richtigen Ort, erfordert die Kombination von zum Teil sehr unterschiedlichen Materialien, bei deren Zusammenfügen klassische Fügeverfahren nicht möglich oder Materialschwächung durch Bohrenfür beispielsweise gewichtserhöhende Schraub- oder Nietverbindungen prohibitiv sind. Das Fügeverfahren der Wahl ist das Kleben. Dieser Beitrag gibt einen Überblick über einige aktuelle Aspekte dieser Technologie

Knee-ankle-foot orthosis with powered knee for support in the elderly

A prototype of a powered knee orthotic device was developed to determine whether fractional external torque and power support to the knee relieves the biomechanical loads and reduces the muscular demand for a subject performing sit-to-stand movements. With this demonstrator, consisting of the subsystems actuation, kinematics, sensors, and control, all relevant sensor data can be acquired and full control is maintained over actuator parameters. A series-elastic actuator based on a direct current motor provides up to 30 Nm torque to the knee via a hinge joint with an additional sliding degree of freedom. For reasons of feasibility under everyday conditions, user intention is monitored by employing a noninvasive, nonsticking muscle activity sensor to replace electromyographic sensors, which require skin preparation. Furthermore, foot plates with force sensors have been developed and included to derive ground reaction forces. The actual knee torque needed to provide the desired support is based on an inverse dynamics model using ground reaction forces signals and leg kinematics. A control algorithm including disturbance feed forward has been implemented. A demonstration experiment with two subjects showed that 23 % of moment support in fact leads to a similar reduction in activation of the main knee extensor muscle. </jats:p

Effects of Prolonged Fasting during Inpatient Multimodal Treatment on Pain and Functional Parameters in Knee and Hip Osteoarthritis: A Prospective Exploratory Observational Study

Preliminary clinical data suggest that pain reduction through fasting may be effective for different diagnoses. This uncontrolled observational clinical study examined the effects of prolonged modified fasting on pain and functional parameters in hip and knee osteoarthritis. Patients admitted to the inpatient department of Internal Medicine and Nature-based Therapies of the Immanuel Hospital Berlin between February 2018 and December 2020 answered questionnaires at the beginning and end of inpatient treatment, as well as at 3, 6, and 12 months after discharge. Additionally, selected blood and anthropometric parameters, as well as subjective pain ratings, were routinely assessed during the inpatient stay. Fasting was the only common intervention for all patients, being performed as part of a multimodal integrative treatment program, with a daily caloric intake of p p p p p p p p < 0.001, d = 0.43). The results suggest that patients with osteoarthritis of the lower extremities may benefit from prolonged fasting as part of a multimodal integrative treatment to improve quality of life, pain, and disease-specific functional parameters. Confirmatory randomized controlled trials are warranted to further investigate these hypotheses