An accurate prediction of transition onset behind an isolated roughness element has not yet been established. This is particularly important in hypersonic flow, where transition is accompanied by increased surface heating. In the present contribution, a number of direct numerical simulations have been performed of a Mach 6 boundary layer over a flat plate with isolated roughness elements. The effects of roughness shape, planform, ramps, and freestream disturbance levels on instability growth and transition onset are investigated. It is found that the frontal shape has a large effect on the transition onset, which is in agreement with previous studies, whereas the roughness element planform has a marginal influence. A new result is that the roughness shape in the streamwise direction (in particular, the aft section) is also an important characteristic, since an element with a ramped-down aft section allows the detached shear layer to spread out and weaken, leading to a lower instability growth rate. Above a critical value, the instability growth rate is found to be correlated with the amplitude of the low-speed streak formed by the roughness element, suggesting that a more physically based transition criterion should take account of the local liftup effect of the particular roughness shape.

The current paper provides an outline and first results of the ESA-EMAP project. This project pursues activities regarding the experimental modeling of alumina particulates in solid boosters (EMAP). The issue regards the particles residing in the atmosphere after the passage of a launch vehicle with solid rocket propulsion, which might contribute to local and overall ozone depletion. The question is to what extent since the particle size distribution left behind is essentially unclear. For this reason, the ESA-EMAP investigations focus on the characterization of the solid exhaust plume properties for well-defined combustion chamber conditions. Thus, details of the rocket motor assembly, of the developed solid propellant grains, and of first measurement results are provided. The paper presents technical findings concerning the rocket motors and reveals aspects to the feasibility of the applied measurement techniques.

Hypersonic airliners are exposed to temperatures that are beyond the limits of classical aircraft materials. In order to handle this problem the latest development of oxidation resistant materials and composite structures needs to be taken into account. The European research programs ATLLAS and ATLLAS II (2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) were therefore focussing on advanced light-weight, high-temperature capable material development strongly linked to a high-speed passenger aircraft design.For propulsion components, combustor structures were investigated at academic level, both at basic and relevant environments. Within the frame of current work, injectors for ram-based propulsion concepts such as dual-mode ramjet or combined cycle concepts were analysed. Generic strut injector geometries were defined to investigate different materials (ceramic matrix composites and ultra high temperature ceramics) and cooling concepts (passive radiation-cooled vs. active transpiration-cooled). Ceramic strut injectors were designed, manufactured and tested within a high speed combustor at the industrial hypersonic METHYLE test facility. Tests were conducted at operational relevant conditions corresponding to a Mach 6 free flight. All injector variants successfully passed testing. It turned out that active transpiration-cooled CMC-and passive UHTC-solutions show the potential to ensure long range cruises of a high speed airliner.

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Today’s CFD simulations tools and the related computational resources provide engineers an enormously high-fidelity design tool to generate an enormous aerodynamic and aerothermal database, for both the laminar and turbulent state, in a short time span. However, transitional flow simulation is still in its infancy that one still needs to rely on practical engineering correlations composed of typical boundary-layer parameters. This work describes the methodology to extract necessary parameters and profile information of the local boundary layer from any vast simulation dataset in an automatic fashion, allowing to apply a huge variety of best-practise correlations for transition prediction relying on local quantities on any type of 3D geometric body. The validation on a simple test case of a flat plate and application to a representative and complex use cases with the geometry of the HEXAFLY-INT hypersonic glider demonstrate the potential of this engineering methodology.