Air bubble entrapment during drop impact on solid and liquid surfaces

Subhayan Halder ◽  
Rafael Granda ◽  
Jingwei Wu ◽  
Abhilash Sankaran ◽  
Vitaliy Yurkiv ◽  
2020 ◽  
pp. 1-14
John Z. Wu ◽  
Christopher S. Pan ◽  
Mahmood Ronaghi ◽  
Bryan M. Wimer ◽  
Uwe Reischl

BACKGROUND: The use of helmets was considered to be one of the important prevention strategies employed on construction sites. The shock absorption performance of a construction (or industrial) helmet is its most important performance parameter. Industrial helmets will experience cumulative structural damage when being impacted repeatedly with impact magnitudes greater than its endurance limit. OBJECTIVE: The current study is to test if the shock absorption performance of Type I construction helmets subjected to repeated impacts can be improved by applying polyethylene air-bubble cushions to the helmet suspension system. METHODS: Drop impact tests were performed using a commercial drop tower test machine following the ANSI Z89.1 Type I drop impact protocol. Typical off-the-shelf Type I construction helmets were evaluated in the study. A 5 mm thick air-bubble cushioning liner was placed between the headform and the helmet to be tested. Helmets were impacted ten times at different drop heights from 0.61 to 1.73 m. The effects of the air-bubble cushioning liner on the helmets’ shock absorption performance were evaluated by comparing the peak transmitted forces collected from the original off-the-shelf helmet samples to the helmets equipped with air-bubble cushioning liners. RESULTS: Our results showed that a typical Type I construction helmet can be subjected to repeated impacts with a magnitude less than 22 J (corresponding to a drop height 0.61 m) without compromising its shock absorption performance. In comparison, the same construction helmet, when equipped with an air-bubble cushioning liner, can be subjected to repeated impacts of a magnitude of 54 J (corresponding to a drop height 1.52 m) without compromising its shock absorption performance. CONCLUSIONS: The results indicate that the helmet’s shock absorbing endurance limit has been increased by 145% with addition of an air-bubble cushioning liner.

2004 ◽  
Vol 16 (5) ◽  
pp. 1349-1365 ◽  
Alexander I. Fedorchenko ◽  
An-Bang Wang

2015 ◽  
Vol 772 ◽  
pp. 427-444 ◽  
Rianne de Jong ◽  
Oscar R. Enríquez ◽  
Devaraj van der Meer

We investigate drop impact dynamics near closed pits and open-ended pores experimentally. The resulting impact phenomena differ greatly in each case. For a pit, we observe three distinct phenomena, which we denote as a splash, a jet and an air bubble, whose appearance depends on the distance between impact location and pit. Furthermore, we found that splash velocities can reach up to seven times the impact velocity. Drop impact near a pore, however, results solely in splashing. Interestingly, two distinct and disconnected splashing regimes occur, with a region of planar spreading in between. For pores, splashes are less pronounced than in the pit case. We state that, for the pit case, the presence of air inside it plays the crucial role of promoting splashing and allowing for air bubbles to appear.

Yukio Tomita ◽  
Toshiyasu Kasai ◽  
Shinya Miura

An air bubble is entrained by the impact of a drop on a water surface. Consequently sound is emitted. There are two categories of the bubble entrainment depending on the drop diameter dD and impact velocity Vimp. One is the regular entrainment where air bubbles are always pinched off, another is the irregular case where bubbles are trapped irregularly. In this paper we explore the mechanism of the irregular bubble entrainment and induced bubble sound.

2007 ◽  
Vol 588 ◽  
pp. 131-152 ◽  
T. SAITO ◽  

Drop impact on a water surface can be followed by underwater sounds originating not at the drop impact but when the entrained bubbles oscillate. Although the sound mechanism in the regular bubble entrainment region is well-known, there is less knowledge on the impact phenomena in the irregular bubble entrainment region where various situations can exist, such as many types of bubble formation or even no bubble generation under some conditions. In the present study, the aim is to clarify the dynamics of the water surface after the impact of a primary drop, mainly with diameter 5.2, 5.7 and 6.2mm, each of which is accompanied by a single satellite drop. Special attention was paid to the breakup behaviour of the water surface for Froude number Fr < 300. It was found that three underwater sounds were generated for a single drop impact, besides the sound due to impact itself. The first two were audible to the human ear, but the third one was almost inaudible. The first underwater sound resulted from the oscillation of a single air bubble formed as a result of the satellite drop impact on the bottom of the contracting cavity, and the second sound was due to the oscillation of air bubbles generated during the collapse of the water column. The formation of these air bubbles strongly depends on the Froude number, Weber number (or Bond number) and the aspect ratio of the drop at impact, although involving probability characteristics. Furthermore it is suggested that an air bubble entrapped in a water column plays an important role in increasing the probability of contact between the column surface and the curved free surface. A Japanese Suikinkutsu was introduced as an application of drop-impact-induced sounds. Using an open-type Suikinkutsu an additional experiment was carried out with larger drops with average diameters of 6.2, 7.2 and 7.8, mm.

2012 ◽  
Vol 109 (26) ◽  
Wilco Bouwhuis ◽  
Roeland C. A. van der Veen ◽  
Tuan Tran ◽  
Diederik L. Keij ◽  
Koen G. Winkels ◽  

1989 ◽  
Vol 50 (C7) ◽  
pp. C7-21-C7-22

Dr. Vikas Tantuway

Aim: To assess reliability indices of Air Bubble Test (ABT) for anatomical and functional success in external Dacryocystorhinostomy (DCR). Methods: Prospective case series of nasolacrimal duct obstruction underwent DCR. Functional success defined as Munk score 0 & 1 & anatomical success as free irrigation at followup.ABT performed by putting antibiotic drops into eye& asking patient to exhale while keeping nose & mouth closed. Formation of bubbles at punctum considered as positive test. Specificity, sensitivity, positive & negative predictive values calculated. Results: There were 103 DCR in 97 patients(23 male,74 female)with mean age 45.56 yr. Anatomical and functional success was 99.02% & 98.05%, respectively.ABT showed sensitivity 96.07%, specificity 100% for anatomical success after DCR. Sensitivity and specificity were 97.02% & 100% for functional success. Conclusion: As non-invasive procedure ABT is a good tool to assess success of DCR, though lacrimal syringing remains the gold standard. Keywords: Anatomical, Dacryocystorhinostomy & Air Bubble Test.

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