Numerically Efficient Rotorcraft Trim and Transient Response
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1685 Plymouth Street, Suite, 250, Mountain View, CA, 94043
Cheng-jian He Ph.d.
AbstractWe propose to develo a numerically efficient rotorcraft trim and transient response algorithm. The algorithm is intended for application in a periodic dynamic system with a large number of degrees of freedom as is commonly the case in current comprehensive rotorcraft analysis codes (such as 2GCHAS). The innovation of this proposal can be summarized as follows: 1) Utilizing Model Order Reduction to establish a sufficiently accurate reduced order model based on model reduction from finite elements to find the rotorcraft trim. The transient of the full finite element dynamic equations are solved using the solution from the reduced order model as an initial estimation to reduce the runtimes to reach steady state. 2) Taking advantage of periodicity of a multi-bladed rotor to reduce the size of rotor system equations by a factor of the number of blades. 3) Applying the Quasi-Newton method for the solution of nonlinear equations to overcome the disadvantage of computing and inverting the Jacobian matrix as required in the Newton-Raphson method. Utilization of Broyden-Fletcher-Shanno Rank Two algorithm, one of the most successful algorithm of the Quasi-Newton method in nonlinear equation solutions, will allow the aerodynamic effects to be included in the solution iteration. Thus, the solution convergence speed will be improved.
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