Transition

The investigated HQ17 airfoil of Horstmann and Quast [16]is a laminar profile. As laminar flow stretches over large parts of the airfoil, a proper prediction of transition plays an important role for a suitable computational representation of the flow. Therefore, transition is fixed by Krumbein's iterative procedure based on the detection of laminar separation [17].

For the clean airfoil case, transition positions on the suction side have been measured by Meyer [18] using flow visualization with a mixture of oil and titanium dioxide. Comparison of measured and predicted transition locations indicate that the Krumbein procedure can be successfully applied to such flows (fig. ). In the laminar region the source terms in the turbulence model are switched off and the free-flow conditions are convected down to the transition position.

Figure: Measured and predicted transition locations for the clean HQ17 airfoil at $Re=10^6$.