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Analysis of rotorcraft dynamics requires solution of the nonlinear potential-flow equations in time.The solution of these equations must be done in real time for purposes of real-time flight simulators,observers for real-time flight controllers,and preliminary design computations,Reference [1] shows that the linearized potential-flow equations can be transformed into a set of ordinary differential equations by a Galerkin method,although the solution is only valid for above the rotor disk.Reference [1] was unable to find the complete set of velocity potentials(necessary for good convergence)or to find the flow below the disk.Reference [2] found the missing singular potentials and added them to the linear model.Reference [3] describes an approximate method whereby the equations could be extended to the nonlinear case; but the method is not generally valid.Reference [4] proves that the flow below the rotor disk can be found by the use of adjoint variables,and Ref.[5] makes a major breakthrough in improving convergence of the method for all skew angles and everywhere in the flow field.What remains is to extend this method to include the nonlinearities,which are absolutely essential in order to treat low-speed flight and hover(for which the nonlinearities dominate the solution).In this paper,we treat the major effects of the nonlinearities in the system: 1)inclusion of the states in the mass-flow parameter,2)the effect of wake contraction on the solution,and 3)the effect of swirl velocity on the local inflow angle.Numerical solutions are given in the time domain.