AIR LOADINGS ON A ROTOR BLADE AS CAUSED BY TRANSIENT INPUTS OF COLLECTIVE PITCH
Abstract
A method is developed for predicting the nonperiodic air loads caused by control inputs applied to a rotary wing in forward flight. Use is made of a numerical description of the geometry and circulation strength of the vorticity in the wake to compute the time-varying, nonuniform-flow field in the plane of the rotor disc. The method of approach is similar to that developed previously for the steady-state flight condition, the major difference being that the solution procedure lends itself to the treatment of transient phenomena, such as the nonperiodic loadings caused by time-varying collective pitch. Several approximations are made to simplify the analysis. The major assumptions are: (1) the rotor blades are structurally rigid and have only a flapping degree of freedom; (2) the hub of the rotor continues to translate in level, constant-speed flight during the short time interval of interest; (3) the geometry of the wake can be specified a priori; and (4) no account need be taken of the shed vorticity in the wake. Computed flapping and air load distributions are compared with transient data obtained in wind-tunnel tests on a full-scale H-34 rotor. In general, agreement is found leading to the conclusion that calculation and prediction of nonperiodic loadings on rotary wings is a feasible task.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1965
- Accession Number
- AD0624860
Entities
People
- Leonard Segel
Organizations
- Calspan