固支方板底部水下爆炸气泡射流研究

Research on bubble jet of underwater explosion at the bottom of fixed square plate

近场水下爆炸气泡坍塌后形成的水射流能对舰船局部结构造成严重毁伤,而射流的形成具有非对称性,导致试验中难以测到其数据,目前关于水下爆炸气泡射流压力时程曲线的研究仍比较少见.为研究水射流的载荷特性,本文开展了当量为2.5 g的TNT炸药在不同爆距下的固支方板底部水下爆炸试验.首先通过水下压力传感器验证了试验数据的准确性,其次通过高速摄像得到了从炸药起爆到气泡与钢板作用产生射流全过程的图像,最后通过钢板中心的壁压传感器测得了水射流压力时程曲线,并在距钢板中心15 cm处设置了另外一组壁压传感器作为对照组,用来确定所测得的射流数据并非杂波.水下传感器记录到的试验数据表明,冲击波超压、气泡脉动周期最大气泡半径与经验公式间的误差在10%以内.高速摄像及壁压传感器记录到的结果显示,爆距为28 cm时能观测到3次射流现象,但由于爆距较远并未测到压力时程曲线,爆距为15,17.5及20 cm时测得了3次射流压力时程曲线,但由于爆距较近,且在冲击波作用下钢板与水面间存在大量气泡,导致高速摄像难以观测到试验现象.压力时程曲线显示,在第一次气泡脉动峰值后产生了3次射流,射流压力大小能达到冲击波的1/4.射流在第一次气泡脉动峰值后1–3 ms后出现,每次射流的时间间隔在0.9–2.4 ms之间.射流载荷持续时长在4–27μs,持续时间随着距离的增加而大幅减小.

The water jet formed after the collapse of the bubble in the near-field underwater explosion can cause serious damage to the local structure of the ship, and the formation of the jet is asymmetric, which makes it difficult to measure its data in the experiment. At present, studies on the pressure time history curves of the bubble jet in the underwater explosion are still relatively rare. In order to study the characteristics of the jet, the underwater explosion test of 2.5 g TNT explosive at the bottom of fixed square plate at different detonation distances was carried out. First, the accuracy of the test data was verified by the underwater pressure sensor. Second, the image of the whole process from the explosive initiation to the bubble jet generated by the action of the bubble and the steel plate was obtained by high-speed camera. Finally, the timehistory curve of water jet pressure was measured by the wall pressure sensor in the center of the steel plate, and another group of wall pressure sensors was set 15 cm away from the center of the steel plate as a control group to ensure that the measured jet data were not clutter. The test data recorded by the underwater sensor show that the error between the shock wave overpressure, the maximum bubble radius of the bubble pulse period and the empirical formula is within 10%. The results recorded by the high-speed camera and wall pressure sensor show that three jets can be observed when the burst distance is 28 cm, but the pressure time history curve is not measured due to the long burst distance. When the burst distances are 15, 17.5 and 20 cm, three jet pressure time history curves are measured. However, due to the short burst distance and the presence of a large number of bubbles between the steel plate and the water surface under the action of the shock wave, it is difficult to observe the test phenomenon with high-speed cameras. The pressure time history curve shows that three jets are generated after the first bubble pulse peak, and the jet pressure can reach 1/4 of the shock wave.The jet appears 1–3 ms after the first bubble pulse peak, and the time interval of each jet is between 0.9 and 2.4 ms. The duration of jet load is between 4–27 μs, and it is greatly reduced as the distance increases.