This paper presents the results of an experimental investigation of the parametric stabilization of Rayleigh-Bénard convection through the imposition of sinusoidal vibration. The ability to dynamically stabilize Rayleigh-Bénard convection using acceleration modulation is of interest to groups who design and study thermoacoustic machines as the introduction of parasitic convection can have deleterious effects on the desired operation and thermodynamic efficiency of the device. These performance issues caused by suspected convective instability have been seen both in traveling wave thermoacoustic refrigerators and cryogenic pulse tube chillers. This paper reports the results of an experiment intended to determine the vibratory, fluidic, and geometric conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration with comparison to the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135, 654–668 (2014)]. Measurements are obtained using a large-displacement kinematic shaker of an original design with the convecting gas characterized using both thermal transport measurements and flow visualization employing tracer particles illuminated by a diode laser light sheet phase-locked to the shaker. These experiments are believed to be the first demonstrating the suppression of convection through vibration in rectangular containers.
The ability to dynamically stabilize Rayleigh-Bénard convection by imposition of sinusoidal acceleration is of interest to groups who design and study thermoacoustic machines, as the introduction of unwanted convection can have deleterious effects on the desired operation and efficiency of the machine. These performance issues, tentatively attributed to convective instability, have been observed both in traveling wave thermoacoustic refrigerators and in pulse tube cryocoolers. This presentation discusses an ongoing experiment designed to determine the vibratory conditions under which a small, rectangular container of statically unstable fluid may be stabilized by vertical vibration, to test the computational methods of R. M. Carbo [J. Acoust. Soc. Am. 135(2), 654–668 (2014)]. Measurement methods developed to determine the onset and inhibition of convection will be discussed. These include the measurement of heat transport employing a feedback thermal control loop and direct optical observation using a lightsheet produced by a laser diode source illuminating seeded particles. Preliminary results in both the static and vibratory conditions will be presented. [Work supported by the ARL Walker Graduate Assistantship, the Office of Naval Research, and ARPA-E.]
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