Abstract

Strong single expansion and collapse of the central bubble in a streamer of an odd number of cavitation bubbles in acetone is numerically studied. The conditions considered are close to those in the well-known experiments on neutron emission during acoustic cavitation of deuterated acetone. Initially, all the bubbles are spherical, with the same radius of 5 \(\mu\)m, equidistant from the neighboring ones, with the centers in a straight line. The vapor in the bubbles is in the saturation state at the ambient liquid temperature of 273 K. The liquid pressure varies harmonically with a frequency of 19.3 kHz and an amplitude of 15 bar. The initial spacing of the bubbles is characterized by the ratio \(d^{*}\) of the initial distance between the centers of the neighboring bubbles to the maximum radius of a single bubble during its expansion under similar conditions. It is shown that in the final stage of collapse, a radially converging shock wave arises in the central bubble in the vicinity of its surface. During the convergence, its non-sphericity and that of the pressure and temperature fields behind it rapidly increase. For \(d^{*}=40\), the shape of the shock wave until the moment at which some part of the shock wave front enters a small central region with a radius of 2.5 \(\mu\)m, keeps close to spherical. As \(d^{*}\) decreases, the shock wave becomes more flattened along the axis of symmetry. With increasing \(d^{*}\), the maximum pressures and temperatures in the central bubble at the mentioned moment monotonically grow to the values corresponding to a single bubble. Under \(d^{*}>20\) the growth is fairly slow.

中文翻译：

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拖缆中部气泡的膨胀和破裂

摘要

数值研究了在丙酮中有奇数个空化气泡的流光中，中心气泡的强烈单个膨胀和破裂。所考虑的条件与氘化丙酮声空化过程中中子发射的众所周知实验的条件相近。最初，所有气泡都是球形的，半径为5 \（\ mu \） m，与相邻的气泡等距，且中心在一条直线上。气泡中的蒸汽在273 K的周围液体温度下处于饱和状态。液体压力以19.3 kHz的频率和15 bar的振幅谐波变化。气泡的初始间距的特征在于比率\（d ^ {*} \）相邻气泡中心之间的初始距离到单个气泡在类似条件下膨胀期间的最大半径的距离。结果表明，在坍塌的最后阶段，在中心气泡表面附近产生了径向收敛的冲击波。在收敛过程中，它的非球形性以及它背后的压力和温度场的非球形性迅速增加。对于\（d ^ {*} = 40 \），冲击波的形状一直保持到冲击波波前的某些部分进入半径为2.5 \（\ mu \） m的小中心区域为止。接近球形。随着\（d ^ {*} \）减小，冲击波沿对称轴变得更加平坦。随着\（d ^ {*} \）的增加，在提到的时刻中央气泡中的最大压力和温度单调增长到对应于单个气泡的值。在\（d ^ {*}> 20 \）下，增长相当缓慢。