One-way-coupling simulation of cavitation accompanied by high-speed droplet impact
One-way-coupling simulation of cavitation accompanied by high-speed droplet impact
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DOI：
10.1063/1.4942894
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发表时间：
2016-03
影响因子：
4.6
通讯作者：
T. Kondo;K. Ando
中科院分区：
文献类型：
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作者：
T. Kondo;K. Ando
由于高速液滴撞击而引起的冲蚀是工业应用中的关键问题。腐蚀是由材料表面的水击载荷引起的，也可能是由液滴内出现的空泡破裂引起的再载荷引起的。在这里，我们模拟空化气泡的动力学伴随着高速液滴对可变形的壁的冲击，以查看气泡崩溃是否足够暴力，以引起对壁的空化侵蚀。压力波的演变在一个单一的水（或明胶）液滴与可变形的壁碰撞速度高达110米/秒的推断从模拟的多组分欧拉流的相变是不允许的。然后，我们研究了空化气泡的动力学从微米/亚微米尺寸的气泡核，应该存在于液滴内。为了简单起见，我们进行Rayleigh-Plesset-type计算在一个单向耦合的方式，即，气泡动力学确定根据压力变化从欧拉流模拟。在模拟中，预先存在的气泡核，其尺寸是微米或亚微米显示大的增长到亚毫米，因为液滴内的张力是通过压力波和液滴界面的相互作用获得的，这支持了由于液滴的影响有空化的可能性。它也被发现，特别是，对于从非常小的核，如纳米气泡的空化所产生的情况下，从cavitationbubble崩溃的辐射压力可以压倒的水锤压力直接产生的影响。因此，在讨论液滴冲击问题中的腐蚀时，可能需要考虑空化。
Erosion due to high-speed droplet impact is a crucial issue in industrial applications. The erosion is caused by the water-hammer loading on material surfaces and possibly by the reloading from collapsing cavitationbubbles that appear within the droplet. Here, we simulate the dynamics of cavitationbubbles accompanied by high-speed droplet impact against a deformable wall in order to see whether the bubble collapse is violent enough to give rise to cavitationerosion on the wall. The evolution of pressurewaves in a single water (or gelatin) droplet to collide with a deformable wall at speed up to 110 m/s is inferred from simulations of multicomponent Euler flow where phase changes are not permitted. Then, we examine the dynamics of cavitationbubbles nucleated from micron/submicron-sized gas bubble nuclei that are supposed to exist inside the droplet. For simplicity, we perform Rayleigh–Plesset-type calculations in a one-way-coupling manner, namely, the bubbledynamics are determined according to the pressure variation obtained from the Euler flow simulation. In the simulation, the preexisting bubble nuclei whose size is either micron or submicron show large growth to submillimeters because tension inside the droplet is obtained through interaction of the pressurewaves and the droplet interface; this supports the possibility of having cavitation due to the droplet impact. It is also found, in particular, for the case of cavitation arising from very small nuclei such as nanobubbles, that radiated pressure from the cavitationbubble collapse can overwhelm the water-hammer pressure directly created by the impact. Hence, cavitation may need to be accounted for when it comes to discussing erosion in the droplet impact problem.