Question: How did Ludwig Prandtl suggest the condition known as the Prandtl Condition?
Sentence (from "Ludwig-Prandtl-Ring"): The Ludwig-Prandtl-Ring is the highest award of the Deutsche Gesellschaft für Luft- und Raumfahrt (German Society for Aeronautics and Astronautics), awarded "for outstanding contribution in the field of aerospace engineering."
Relevant evidence: No