12 research outputs found
Joint European Effort Towards Advanced Rocket Thrust Chamber Technology
The achievements of the FSCD group during the last three years are described. For the case of nozzle flows in quiet ambience, new observations of the plume behaviour for truncated ideal nozzles are reported
Experimental Investigation of Base Flow Buffeting on the ARIANE 5 Launcher Using High Speed PIV
Experiments have been performed on a 1:60 scale Ariane 5 launcher in the DNW HST wind tunnel by means of two-component particle image velocimetry (2C-PIV). Measurements are performed for Mach 0.5 and Mach 0.8. The investigation focuses on studying the flow-buffeting phenomenon in the base of an Ariane V rocket. In total four configurations are tested: reference configuration, skirt, scoop and reference configuration without struts. It has been found that the presence of the struts has a large effect on the flow field; the secondary flow caused by the struts decreases the separated region and increases the overall turbulence. The skirt has the effect that the shear layer separates later and therefore does not reattach on the nozzle. Also in the separated region a secondary recirculation region is formed. For the scoop configuration it was observed that a second wake was formed by the scoop element causing the overall shear layer to become thicker. Finally using POD analysis two dominant modes are identified that can be associated to the separation bubble and shear layer dynamics
Plug nozzles : assessment of prediction methods for flow features and engine performance
Communication to : 40th AIAA aerospaces sciences meeting and exhibit, Reno (USA), January 14-17, 2002SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2002 n.181 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Launch Vehicle Base Buffeting - Recent Experimental and Numerical Investigations
During atmospheric ascent of launcher configurations, a massively separated flow environment in the base region of the launcher can generate strong low frequency wall pressure fluctuations. The nozzle structure can be subjected to dynamic loads resulting from these pressure fluctuations. The loads are usually most severe during the high dynamic pressure phase of
flight at transonic speeds and the aerodynamic
excitation can induce a response of the structural modes called buffeting. In order to obtain a deeper insight into base buffeting related to the Ariane 5 launch vehicle, a set of experiments was performed in the DNW HST wind tunnel in close cooperation with the utilization of modern CFD tools (hybrid RANS/LES). During the test campaign a 1/60 scale Ariane 5 launcher test article was utilized, and detailed unsteady pressure measurements in the base region of the model were for the first time
performed in conjunction with time resolved velocity
field measurements using PIV. The work was performed in the framework of the ESA TRP “Unsteady Subscale Force Measurements within a Launch Vehicle Base Buffeting Environment”
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Chemosensory Ca2+ dynamics correlate with diverse behavioral phenotypes in human sperm.
In the female reproductive tract, mammalian sperm undergo a regulated sequence of prefusion changes that "prime" sperm for fertilization. Among the least understood of these complex processes are the molecular mechanisms that underlie sperm guidance by environmental chemical cues. A "hard-wired" Ca(2+) signaling strategy that orchestrates specific motility patterns according to given functional requirements is an emerging concept for regulation of sperm swimming behavior. The molecular players involved, the spatiotemporal characteristics of such motility-associated Ca(2+) dynamics, and the relation between a distinct Ca(2+) signaling pattern and a behavioral sperm phenotype, however, remain largely unclear. Here, we report the functional characterization of two human sperm chemoreceptors. Using complementary molecular, physiological, and behavioral approaches, we comparatively describe sperm Ca(2+) responses to specific agonists of these novel receptors and bourgeonal, a known sperm chemoattractant. We further show that individual receptor activation induces specific Ca(2+) signaling patterns with unique spatiotemporal dynamics. These distinct Ca(2+) dynamics are correlated to a set of stimulus-specific stereotyped behavioral responses that could play vital roles during various stages of prefusion sperm-egg chemical communication