Two computational studies of a flatback airfoil using non-zonal and embedded scale-resolving turbulence modelling approaches

The contribution presents results from two computational studies conducted by Upstream CFD and ENERCON, which aim to evaluate their respective CFD methodologies for the aerodynamics and aeroacoustics prediction of a flatback airfoil with 35% relative thickness. The CFD is validated against data from two comprehensive experimental campaigns conducted in the NWB facility operated by the German-Dutch Wind Tunnels Foundation (DNW), which include measurements of mean force coefficients, static and total pressure distributions in the wake region, unsteady surface pressures and farfield sound emission. In both numerical studies, scale-resolving approaches based on detached-eddy simulation are utilised, where a comparison is drawn between a purely non-zonal use of the model in which attached boundary layers are fully modelled via RANS and a zonal use with synthetic turbulence being injected into the boundary layers upstream of the trailing edge. First, the aerodynamic flow fields are analysed, showing good agreement with the reference measurements. Farfield noise is then predicted from solid and permeable Ffowcs-Williams and Hawkings surfaces, where both the dominant shedding tone as well as broadband levels compare well with microphone array data

Stoßinduzierte Wirbel in der Axialverdichterauslegung

In der vorliegenden Arbeit wird der Einfluss stoßinduzierter Wirbel in der Axialverdichterauslegung diskutiert, indem zunächst geometrische Einflussfaktoren an vereinfachten Schnittsimulationen variiert werden. Ein Ergebnis ist, dass in einer transsonischen Verdichterkonfiguration weder ein großer noch ein geringer Axialabstand zu bevorzugen ist. Die stoßinduzierten Wirbel sind der dominierende instationäre Effekt in transsonischen Verdichtern. Die Wirbel reduzieren oder erhöhen lokal die Geschwindigkeit und beeinflussen so die Hauptströmung und den Rotoranströmwinkel. Eine empirische Korrelationsfunktion zur Wirbeltrajektionsprognose wird analysiert und deren Vorhersagegenauigkeit verbessert. Die Parameterstudien können genutzt werden, um den optimalen Axialabstand im Auslegungsprozess besser zu bestimmen. Im letzten Teil wird gezeigt, dass die Ergebnisse aus den vereinfachten Schnittsimulationen auf reale dreidimensionale Geometrien übertragbar sind.The present work discusses shock induced vortices in a transonic compressor design. The inlet guide vane wake is affected by the shock due to the pressure gradient that curves the wake. To quantify the influence of these vortices, simplified parameter studies have been carried out in a quasi three dimensional setting. Neither a wide nor a small axial gapping is the most favorable in these kinds of compressors due to the vortices. They affect the total pressure ratio, the performance and the surge margin. They reduce or increase the local velocities that affect the rotor boundary layer and the incidence angle. An existing function that predicts the vortex trajectory (B3 function) has been adapted to increase the accuracy. The function uses a steady state simulation to predict the unsteady vortex trajectory. The last part of this work shows three dimensional vortices in the full scale front stage