“Back in the day water tunnels were used just as much as wind tunnels in aircraft design. Wright Patterson had quite a few.”
Never knew that. I would think using a non compressible fluid would give very different results than air.
Fluid mechanics is the basis of aeronautical engineering.
Instrumentation in a wind tunnel had it’s associated cost. A water tunnel model with red dye injection upstream of the model gave a great visual, was photographed, and analyzed. It was used in the early stages of development. I sat next to a mothballed Amraam missile water tunnel for several years. Fascinating.