Engineering topics
Publications and source records attributed to Charwat, A. F..
Detailed measurements of the time-dependent velocities induced inside and outside the opening of an acoustically excited, two-dimensional Helmholtz resonator imbedded in a grazing flow are presented. The remarkably clear structure of the perturbation field which evokes a pulsating source and a coherently pulsating vortex-image pair is described.
Measurements of the acoustic impedance of a two-dimensional Helmholtz resonator, i.e., a cavity coupled to the environment through a high-aspect ratio slot are presented as a function of the velocity of a steady flow above the orifice of the resonator. The structure of the unsteady flow above the orifice is outlined from hot-wire measurements. A simplified model of it is proposed and analyzed, leading to a successful correlation of both the resistance and the reactance of the resonator.
Measurement of the time-dependent velocities induced inside and outside the opening of acoustically excited, two-dimensional Helmholtz resonator imbedded in a grazing flow are presented. The remarkably clear structure of the perturbation field which evokes a pulsating source and a coherently pulsating vortex-image pair is described. The simple phenomenological "lid-model" which correlates the variation in the components of the acoustic impedance with the velocity of the grazing flow is discussed and extended.
An analysis of the motion of particles of arbitrary density and size in solid body and potential vortex flows is presented. The study provides a basis for precise, quantitative reduction of tracer-particle visualization of such flows in water tunnels.
Design of a tracer-particle generator for use in holographic flow visualization of complex flow fields is discussed. Desired characteristics of the tracer particles, including a size range of 20 to 200 microns, a spherical shape to facilitate focusing of holograms, and a fluid density near that of ambient particles, are reviewed; a particle injection rate of 100 to 1000 per sec in water tunnels with flow velocities between one and 10 meters per sec is also desirable. The operation of the particle generator, which produces uniform droplets with the specified optical properties, is described.
Holographic visualization techniques are presented of the vortex wake of a lifting wing. The motions of tracer particles in vortical flows are described along with the development of a liquid-drop tracer generator. An analysis is presented of the motion of particles of arbitrary density and size in solid body and potential vortex flows.
Two dimensional unsteady heat conduction in solid with subliming surface, replacing original boundary value problem by ordinary integrodifferential equation