17:15 〜 19:15
[SVC33-P12] Single Force Measurements Using Water and Air Jets from a PET Bottle
キーワード：シングルフォース、噴火地震、超音速流
When we analyze seismic waves generated during an explosive volcanic eruption, we sometimes find that the source of the seismic waves is a vertical single force. This single force (FS) is thought to be the reaction force to the ejection of materials during an eruption, and analyzing the single force may allow for the estimation of the mass discharge rate (Q) and the style of the eruption. However, the eruption style could influence the relationship between the seismically observed FS and the ejection reaction force, F, as well as between Q and F. This study investigates the reaction forces of water and air jets from a PET bottle, aiming at improving the seismological single force model.
Tada et al. (2023, VSJ fall meeting) reported experimental and theoretical results for incompressible water jets. They constructed a device to fix a PET bottle and a force sensor, injected air from an air compressor into the bottle to expel water from a nozzle, and measured the resulting vertical force with the force sensor. Comparing the force data from the sensor and images recorded during the series of experiments, they experimentally obtained the relationship between F and Q. The experimental result confirmed their theoretical prediction that F=1.5Qv, where v is the exit speed at the nozzle. The force was 1.5 times larger than the widely used relationship F=Qv.
Here, we update the experimental results. The previous experiment used a single nozzle that was commercially available, the structure of which was unclear. This study added experiments with original simple nozzles with three diameters of 1.6, 2.0, and 2.4 mm. We improved the water level measurement from images. Also, we incorporated a gas flow meter to measure the injected airflow, which allowed the quantification of the reaction forces of air jets.
The water-jet experiments confirmed the previous relationship, F=1.5Qv. Using the definition Q=mAv, where m and A are the density at the nozzle and the nozzle area, respectively, the equation is rewritten as mAF=1.5Q2. The data with all the nozzle sizes fell on the single parabolic curve.
The air jet exhibited a similar relationship when Q was small. However, F became significantly larger than 1.5Qv as Q increased. Nevertheless, the relation between mAF and Q with all the nozzle sizes constituted a single curve. We infer that the overpressure of the under-expansion jet applies additional reaction force. We will compare the experimental results with compressible gas dynamics theory.
Acknowledgements
We appreciate Yusei Yahata and Osamu Kuwano for constructive disucssions and supports. A part of the experiments were performed during the Summer School of the Earthquake Resarch Institute.
Tada et al. (2023, VSJ fall meeting) reported experimental and theoretical results for incompressible water jets. They constructed a device to fix a PET bottle and a force sensor, injected air from an air compressor into the bottle to expel water from a nozzle, and measured the resulting vertical force with the force sensor. Comparing the force data from the sensor and images recorded during the series of experiments, they experimentally obtained the relationship between F and Q. The experimental result confirmed their theoretical prediction that F=1.5Qv, where v is the exit speed at the nozzle. The force was 1.5 times larger than the widely used relationship F=Qv.
Here, we update the experimental results. The previous experiment used a single nozzle that was commercially available, the structure of which was unclear. This study added experiments with original simple nozzles with three diameters of 1.6, 2.0, and 2.4 mm. We improved the water level measurement from images. Also, we incorporated a gas flow meter to measure the injected airflow, which allowed the quantification of the reaction forces of air jets.
The water-jet experiments confirmed the previous relationship, F=1.5Qv. Using the definition Q=mAv, where m and A are the density at the nozzle and the nozzle area, respectively, the equation is rewritten as mAF=1.5Q2. The data with all the nozzle sizes fell on the single parabolic curve.
The air jet exhibited a similar relationship when Q was small. However, F became significantly larger than 1.5Qv as Q increased. Nevertheless, the relation between mAF and Q with all the nozzle sizes constituted a single curve. We infer that the overpressure of the under-expansion jet applies additional reaction force. We will compare the experimental results with compressible gas dynamics theory.
Acknowledgements
We appreciate Yusei Yahata and Osamu Kuwano for constructive disucssions and supports. A part of the experiments were performed during the Summer School of the Earthquake Resarch Institute.