An Experimental Approach to the Measurement of Wall Pressure Generated by an Underwater Spark‐Generated Bubble by a Hopkinson Bar

Abstract

e wall pressure loading due to the underwater spark-generated bubble, having served as an efficient technique to study the underwater explosion, has drawn much attention. Compared with the numerical study of the pressure characteristics, the direct experimental investigation is much rarer. Recently, an improved pressure-measuring system by using a Hopkinson pressure bar as the sensing element is proposed, set up, and validated by the current authors. In this article, the improved methodology and experimental system is used to detect and analyze the pressure loading on the target plate surface due to the underwater spark-generated bubble beneath the plate. A series of experiments with 3 mm, 5 mm, 10 mm, 15 mm, . . ., 60 mm standoffs are carried out. e experimental results and the related analysis and discussions are presented. Based on the results, the improved methodology can be used to detect the pressure loading due to the spark-generated bubble. ere is multipeak oscillation near the peak of the shock pressure loading profile. e peak pressure versus the standoff is also summarized. According to the characteristics of the induced water jet pressure and the bubble-collapse pressure loading given in this article, enough attention should be paid to not only the jet and the first bubble-collapse pressure loadings but also the secondary bubble-collapse pressure loadings especially when the dimensionless distance c > 1.

Correction of higher mode Pochhammer–Chree dispersion in experimental blast loading measurements

“…The Hopkinson pressure bar [1], or HPB, is commonly used as a dynamic force transducer in investigations of the loading from explosive events, as it combines the durability and sensitivity required to record the high-pressure transient features inherent in blast and shock waves [2][3][4][5][6][7][8][9][10][11]. In a HPB, a stress wave applied to one end of the bar propagates down its length, and is recorded by strain gauges fixed to the bar surface some distance away.…”

A New Measurement Based on HPB to Measure the Wall Pressure of Electric-Spark-Generated Bubble near the Hemispheric Boundary

“…When the bubble shrinks to its minimal volume, it will emit another shock wave in water. To obtain a series of continuous separate loadings, Yao et al [23,24] proposed a new pressure measuring methodology to measure the pressure loading on the rigid plate due to the high-voltage electric-spark-generated bubble. To meet the requirements of the underwater operation conditions, all the key elements of the test system are enclosed in a waterproof enclosure.…”

“…Based on Yao et al's [23,24] work, we change the shape of the target to study the pressure loading on the hemispheric boundary generated by the electric-spark-generated bubble. As an efficient way, the electric-spark-generated bubble [25][26][27][28][29][30] is used to study the underwater bubble dynamics for its low cost.…”

Experimental Research on the Influence of Different Curved Rigid Boundaries on Electric Spark Bubbles

“…Cui Xiongwei [ 25 ] used HPB to study underwater explosions. Subsequent research has proven that the measured values of the measurement system are stable and have clear advantages in the measurement of short-range explosion shockwave loads and high-voltage electric spark bubble loads [ 26 , 27 ].…”

“…Our previous paper [ 19 ] studied the design of a new wall pressure load measurement system based on the work of Yao and Cui [ 26 , 27 ]. By changing the shape of the target plate, the morphology and load characteristics of bubbles produced by near-field underwater explosions were studied and analyzed under curved surface boundary conditions.…”