Accession Number : AD0008268


Title :   NON-STATIONARY AERODYNAMICS OF A TWO-DIMENSIONAL BUMP IN A UNIFORM STREAM AND ITS EFFECT ON THE VIBRATION CHARACTERISTICS OF AN ELASTIC PANEL


Descriptive Note : Technical rept.


Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS


Personal Author(s) : SHEN, S F


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/008268.pdf


Report Date : May 1952


Pagination or Media Count : 54


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.


Descriptors :   *PANELS , *AERODYNAMIC FORCES , *VIBRATION , RATIOS , STABILITY , DYNAMICS , MASS , THEORY , DAMPING , MOTION , RESONANT FREQUENCY , COEFFICIENTS , COORDINATES , LINEARITY , SEA LEVEL , LOW FREQUENCY , INCOMPRESSIBLE FLOW , FOURIER ANALYSIS , TRANSIENTS , SINE WAVES , VELOCITY , FUNCTIONS


Subject Categories : Construction Equipment, Materials & Supplies
      Fluid Mechanics
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE