A dynamic pressure view cell for acoustic stimulation of fluids—Micro-bubble generation and fluid movement in porous media

Abstract

The development and baseline operation of an acoustic view cell for observing fluids, and fluid-fluid and fluid-solid interfaces in porous media over the frequency range of 10–5000 Hz is described. This range includes the industrially relevant frequency range 500-5000 Hz that is not covered by existing devices. Pressure waveforms of arbitrary shape are generated in a 17.46 mm ID by 200 mm and 690.5 mm long glass tubes at flow rates up to 200 ml/min using a syringe pump. Peak-to-peak amplitudes exceeding 80 kPa are readily realized at frequencies from 10 to 5000 Hz in bubble free fluids when actuated with 20 Vpp as exemplified using castor oil. At resonant frequencies, peak-to-peak pressure amplitudes exceeding 500 kPa were obtained (castor oil at 2100 Hz when actuated with 20 Vpp). Impacts of vibration on macroscopic liquid-liquid and liquid-vapour interfaces and interface movement are illustrated. Pressure wave transmission and attenuation in a fluid saturated porous medium, randomly packed 250-330 μm spherical silica beads, is also demonstrated. Attenuation differences and frequency shifts in resonant peaks are used to detect the presence and generation of dispersed micro-bubbles (<180 μm diameter), and bubbles within porous media that are not readily visualized. Envisioned applications include assessment of the impacts of vibration on reaction, mass transfer, and flow/flow pattern outcomes. This knowledge will inform laboratory and pilot scale process studies, where nuisance vibrations may affect the interpretation of process outcomes, and large scale or in situ processes in aquifers or hydrocarbon reservoirs where imposed vibration may be deployed to improve aspects of process performance. Future work will include miscible interface observation and quantitative measurements in the bulk and in porous media where the roles of micro-bubbles comprise subjects of special interest.

The dynamic response of the water retention curve in unsaturated soils during drainage to acoustic excitations

“…Over the past few decades, theoretical and experimental studies on the connection between elastic wave attributes and physical properties of a fluid‐bearing porous medium have attracted the attention of many scholars in fields of porous medium flow and hydrogeology [ Sabatier et al ., ; Beresnev and Johnson , ; Cowin , ; Vogler and Chrysikopoulos , ; Lo et al ., ; Elkhoury et al ., ; Manga et al ., ; Candela et al ., ; Lo et al ., ; Stewart and Shaw , ; Hamzehpour et al ., ]. High‐frequency acoustic vibrations and ultrasonic imaging were used to evaluate the permeability and porosity of various media [ Sabatier et al ., ; Moore and Attenborough , ; Geller and Myer , ; Sabatier et al ., ; Rossel and McBratney , ; Cowin , ; Xiang and Sabatier , ].…”

Reduction of Dispersion in Ultrasonically-Enhanced Micropacked Beds

“…Transient stress is known to produce an increase of permeability 14,15 and wave induced fluid flow 16 . Vibration-induced particle motion by using audible frequencies (50 and 500 Hz) has also been reported for unconsolidated media with liquid and dispersed gas bubbles 17,18 . In oil-recovery systems, where unfavorable viscous conditions exist, ultrasound irradiation has been successfully used to modify the porous structure showing 10% to 50% enhancement in permeation 19,20 .…”

“…Notably, cavitation was not observed during the visualization experiments-nor is it necessary to promote fluid movement in unconsolidated porous media 17,18 . The strong attenuation of ultrasound in porous media 32,41 suggests that any inertial cavitation will only occur in the vicinity of the radiating surfaces.…”

“…Notably, cavitation was not observed during the visualization experimentsnor is it necessary to promote fluid movement in unconsolidated porous media. , The strong attenuation of ultrasound in porous media , suggests that any inertial cavitation will occur only in the vicinity of the radiating surfaces. However, a high frequency acoustic disruption of the compressible media through the bed might still be hindered by the dynamic modification of gas preferential channels.…”

“…Transient stress is known to produce an increase in permeability , and wave induced fluid flow . Vibration-induced particle motion by using audible frequencies (50 and 500 Hz) has also been reported for unconsolidated media with liquid and dispersed gas bubbles. , In oil-recovery systems, where unfavorable viscous conditions exist, ultrasound irradiation has been successfully used to modify the porous structure, showing 10 to 50% enhancement in permeation. , Within this context, the use of acoustic energy in multiphase porous media can be an interesting approach to counteract gas-channeling mass-transfer limitations in micropacked-bed reactors for catalysis.…”