NON-STATIONARY AERODYNAMICS OF A TWO-DIMENSIONAL BUMP IN A UNIFORM STREAM AND ITS EFFECT ON THE VIBRATION CHARACTERISTICS OF AN ELASTIC PANEL
Abstract
The linearized theory for small disturbances is applied to a simply supported uniform panel. The velocity potential of arbitrary transient motions of a 2-dimensional bump, on an otherwise flat surface, in a uniform incompressible stream is derived in terms of the sine and cosine integrals of the Fourier functions representing the bump. The effect on vibration characteristics depends on the reduced frequency Omega sub1 of the first natural mode, and the mass ratio of panel to air, K. Coefficients representing the apparent mass, and the damping and quasi-steady forces are obtained in a form for use with normal coordinates; the coordinates are strictly true for a simply supported panel in vacuo. Only the quasi-steady aerodynamic forces have contributions for higher modes, and a lower natural frequency results. The percentage reduction decreases rapidly for higher modes and is inversely proportional to K and Omega sub1 squared >>1. The natural frequencies tend to diminish in the presence of the surrounding fluid. A criterion for dynamic stability is derived which is based on the 2-mode representation. A Duralumin panel of 4 ft span and 0.064 in. thick is estimated to have a 230-ft/sec critical speed at sea level.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1952
- Accession Number
- AD0008268
Entities
People
- S. F. Shen
Organizations
- Massachusetts Institute of Technology