Question: What German engineer who pioneered the development of rigorous systematic mathematical analyses which he used for underlying the science of aerodynamics, which have come to form the basis of the applied science of aeronautical engineering, also developed the Mixing length model in the early 20th century?
Sentence (from "Mixing length model"): Prandtl himself had reservations about the model, describing it as, "only a rough approximation,"
Relevant evidence: No