Engineering topics

Williams, M. H.

Publications and source records attributed to Williams, M. H..

23 records · Page 2

NASA NTRS1979

Unsteady airloads in supercritical transonic flows

Results obtained from a simplified theory of unsteady perturbations of supercritical two-dimensional transonic flows, introduced in an earlier paper, are presented. Unsteady loads generated by an oscillating flap and by airfoils oscillating as a whole are given with comparisons to experimental results and finite difference solutions. The theory, which was originally formulated for symmetric airfoils at zero mean angle of attack, is extended to treat asymmetric mean flows.

Williams, M. H.↗

NASA NTRS1977

Generalized Theodorsen solution for singular integral equations of the airfoil class

A class of singular integral equations is considered which arise in various two-dimensional mixed boundary-value problems with simple harmonic time variation. A problem typical of this class is that of determining the lifting pressure distribution on an oscillating airfoil in an unbounded incompressible potential flow. It is shown that Theodorsen's (1935) solution to this problem, with some modification, is valid for a general class of unsteady kernel functions. The technique employed is to consider an equivalent steady problem and then show that the unsteady resolvent and unsteady homogeneous solution can be written directly in terms of the steady solutions and a single frequency-dependent function which reduces to the Theodorsen function for the steady kernel.

Williams, M. H.↗

NASA NTRS1977

Exact solutions in oscillating airfoil theory

A result obtained by Williams (1977) for two-dimensional airfoils oscillating in an arbitrary subsonic parallel flowfield is reformulated to show that the pressure distribution induced by any deformation can be construed from the particular solutions for heaving and pitching motions. Specific formulas are presented for an oscillating control surface with a sealed gap.

Williams, M. H.↗

NASA NTRS1977

The resolvent of singular integral equations

The investigation reported is concerned with the construction of the resolvent for any given kernel function. In problems with ill-behaved inhomogeneous terms as, for instance, in the aerodynamic problem of flow over a flapped airfoil, direct numerical methods become very difficult. A description is presented of a solution method by resolvent which can be employed in such problems.

Williams, M. H.↗

NASA NTRS1977

Effects of inviscid parallel shear flows on steady and unsteady aerodynamics and flutter

A general theory of planar disturbances in inviscid parallel shear flows, analogous to thin-wing theory in potential flows, has been developed. Integral relations between surface pressure and deformation are obtained which are similar to, and can be solved by the same numerical methods as, those of potential flow. Computed results are shown which illustrate the effects of a model turbulent boundary layer on various lifting and nonlifting surfaces, including an elastic panel in low supersonic flow and an airfoil control surface in subsonic flow.

Williams, M. H.↗