FINITE-STATE INDUCED FLOW MODELS .1. 2-DIMENSIONAL THIN AIRFOIL

A new finite state aerodynamic theory is presented for incompressible, two-dimensional flow around thin airfoils. The theory is derived dire ctly from potential flow theory with no assumptions on the time histor y of airfoil motions. The aerodynamic states are the coefficients of a set of induced-flow expansions. As a result, the finite state equatio ns are hierarchical in nature and have closed-form coefficients. There fore, the model can be taken to as many states as are dictated by the spatial texture and frequency range of interest with no intermediate n umerical analysis. The set of first-order state equations is easily co upled with structure and control equations and can be exercised in the frequency or Laplace domain as well as in the time domain. Comparison s are given with Theodorsen theory, Wagner theory, and other methods. Excellent results are found with only a few states.