Yamamoto Takuya
Department of Chemical Engineering, Graduate School of Engineering, Osaka Metropolitan University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
Ultrason Sonochem. 2024 Dec;111:107064. doi: 10.1016/j.ultsonch.2024.107064. Epub 2024 Sep 13.
In this study, we estimated the equilibrium bubble size of acoustic cavitation in a molten metal, which is basic information in ultrasonic casting. For this, the bubble shape instability of acoustic cavitation in the melt was numerically investigated by solving the Keller-Miksis equation and dynamic equation of the distortion amplitude. The acoustic cavitation bubbles are more stable in aluminum and magnesium melts than in water, and the parametric instability mainly determines the bubble stability at 20-160 kHz in molten metals. However, the afterbounce instability does not significantly affect the bubble stability in molten metals owing to the small number of bubble oscillations after the first rapid compression, and the distortion amplitude cannot grow significantly after the first compression. The bubbles in the melt become more unstable with an increase in the ultrasonic frequency owing to the corresponding increase in the bubble wall velocity. Through this stability analysis, we can estimate that the stable bubble size in the aluminum or magnesium melt is approximately three or four times larger than that in water at the same ultrasonic pressure amplitude.
在本研究中，我们估算了熔融金属中声空化的平衡气泡尺寸，这是超声铸造中的基础信息。为此，通过求解凯勒 - 米克斯方程和畸变振幅动力学方程，对熔体中声空化的气泡形状不稳定性进行了数值研究。声空化气泡在铝熔体和镁熔体中比在水中更稳定，并且在20 - 160kHz频率范围内，参数不稳定性主要决定了熔融金属中气泡的稳定性。然而，由于首次快速压缩后气泡振荡次数较少，反弹后不稳定性对熔融金属中气泡稳定性的影响并不显著，并且在首次压缩后畸变振幅不会显著增大。随着超声频率的增加，熔体中的气泡变得更加不稳定，这是由于气泡壁速度相应增加所致。通过这种稳定性分析，我们可以估计，在相同超声压力振幅下，铝熔体或镁熔体中的稳定气泡尺寸大约是水中稳定气泡尺寸的三到四倍。
