We have windtunels to measure air flow, Erlenmeier flasks for chemical reactions, and so on. Why not just load the geometry of the aircraft into a computer simulation and get the results from there. It is much more cost efficient and you can manipulate things faster and easier. For chemical experiments, you can just load some subatomic particles into an object oriented environment under the four physical laws, input the exact situation and the computer will render the results from the interaction. You can rewind, slow down, and use other convenient features on the results. Why do we not perform these experiments exclusively on the computer?