arXiv subjects
Publications and source records attributed to G. Huelsz.
In this work, a new concept for the conversion of heat into electricity is presented. The conversion is based on the combined effects of a thermoacoustic prime mover coupled with a magnetohydrodynamic generator, using different working fluids in each process. The results of preliminary experiments are also presented.
We present the dynamic velocity profiles of a Newtonian fluid (glycerol) and a viscoelastic Maxwell fluid (CPyCl/NaSal in water) driven by an oscillating pressure gradient in a vertical cylindrical pipe. The frequency range explored has been chosen to include the first three resonance peaks of the dynamic permeability of the viscoelastic fluid / pipe system. Three different optical measurement techniques have been employed. Laser Doppler Anemometry has been used to measure the magnitude of the velocity at the centre of the liquid column. Particle Image Velocimetry and Optical Deflectometry are used to determine the velocity profiles at the bulk of the liquid column and at the liquid--air interface respectively. The velocity measurements in the bulk are in good agreement with the theoretical predictions of a linear theory. The results, however, show dramatic differences in the dynamic behaviour of Newtonian and viscoelastic fluids, and demonstrate the importance of resonance phenomena in viscoelastic fluid flows, biofluids in particular, in confined geometries.
In this paper we present an experimental study of the dynamic responses of a Newtonian fluid and a Maxwellian fluid under an oscillating pressure gradient. We use laser Doppler anemometry in order to determine the velocity of each fluid inside a cylindrical tube. In the case of the Newtonian fluid, the dissipative nature is observed and the response obeys the Zhou and Sheng universality (PRB 39, 12027 (1989)). In the dynamic response of the Maxwellian fluid an enhancement at the frequencies predicted by the corresponding theory (PRE 58, 6323 (1998)) is observed.