15 - Guest lectures

CFD VALIDATION EXPERIMENTS AT DLR: OVERVIEW AND LESSONS-LEARNED

C. Grabe, DLR, Germany

Modelling turbulent flows using the Reynolds-Averaged Navier-Stokes (RANS) equations is a key element for highly accurate flow simulations with CFD solvers and a standard tool in the aviation industry. At the design point of today's commercial aircrafts, RANS turbulence models offer a good compromise between efficiency and accuracy. However, the quality of these predictions deteriorates towards the edge of the flight envelope. This is particularly the case if flow separation is involved, e.g., at low speeds (take-off and landing) near maximum lift. In order to increase confidence in CFD, high-quality validation experiments tailored to the flow phenomena occurring at low speeds of an aircraft are necessary. DLR has designed and conducted such experiments for various relevant flow phenomena including turbulent boundary layers under adverse pressure gradient, thin turbulent boundary layer separation bubbles and reattachment as well as turbulent longitudinal vortices. Moreover, complex aircraft testcases like the high-lift CRM are needed to assess the interplay of different flow features and the capability of RANS turbulence models to capture them. The talk provides an overview of these experiments and their results, the conclusions we can draw from them and an outlook on future requirements.

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