Showing papers by "Earl H. Dowell published in 1983"
59 citations
TL;DR: In this paper, an NACA 64A006 airfoil oscillating in pitch over a range of amplitudes, frequencies, and Mach numbers was used to assess the range of parameters over which linear behavior occurs.
Abstract: The accurate calculation of the aerodynamic forces in unsteady transonic flow requires the solution of the nonlinear flow equations. The aeroelastician, on the other hand, seeks to treat his problems (flutter, for example) by means of linear equations whenever possible. He may do this, even when the underlying flow is nonlinear, if the perturbation forces are linear over some (perhaps small) range of unsteady amplitude of motion. This paper assesses the range of parameters over which linear behavior occurs. In particular calculations are made for an NACA 64A006 airfoil oscillating in pitch over a range of amplitudes, frequencies, and Mach numbers. The primary aerodynamic method used is the well known LTRAN2 code of Ballhaus and Goorjian that provides a finite-difference solution to the low frequency, small disturbance, two-dimensional potential flow equation. Comparisons are made with linear subsonic theory, local linearization, and, for steady flow, with the full potential equation code of Bauer, Garabedian, and Korn.
43 citations
TL;DR: In this paper, a theoretical and experimental study of the forced vibration response of a cantilevered beam with Coulomb damping nonlinearity is described, and a more general representation of the dry friction damper and its associated mass and stiffness are considered.
35 citations
TL;DR: In this article, a component mode analysis is carried out based upon the use of constraint conditions and Lagrange multipliers for a single-degree-of-freedom dry friction damper.
33 citations
TL;DR: In this article, the postbuckling behavior of rectangular orthotropic plates with two free side edges is studied based on a perturbation method and both exact and approximate solutions of the second-order perturbations are given.
7 citations
TL;DR: In this paper, it was shown that for a very narrow range of Mach numbers, a nonzero mean value of lift can occur for an airfoil of symmetrical profile oscillations about a zero angle of attack.
Abstract: Kerlick and Nixon (1981) point out that if the time-marching solution is stopped before the transient is complete and the steady state is reached, then the incorrect conclusion may be reached that a change in the mean lift has occurred in response to the oscillating motion of the airfoil when in fact no such change has occurred. For a narrow Mach number range, however, the time for the transient to decay and for a steady state to be reached is extraordinarily long. What is more, for a very narrow range of Mach numbers, a nonzero mean value of lift can occur for an airfoil of symmetrical profile oscillations about a zero angle of attack. The reason why this nonzero average lift occurs only over a narrow range of Mach numbers has so far not been obtained.
7 citations