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Ocean Systems Engineering
  Volume 8, Number 2, June 2018 , pages 167-182

Simulation of viscous and inviscid rayleigh-taylor instability with surface tension by using MPS
Kyung Sung Kim and Moo Hyun Kim

     RTI (Rayleigh-Taylor instability) is investigated by a multi-liquid MPS (Moving Particle Semi-implicit) method for both viscous and inviscid flows for various density differences, initial-disturbance amplitudes, viscosities, and surface tensions. The MPS simulation can be continued up to the late stage of high nonlinearity with complicated patterns and its initial developments agree well with the linear theoretical results. According to the relevant linear theory, the difference between inviscid and viscous fluids is the rising velocity at which upward-mushroom-like RTI flow with vortex formation is generated. However, with the developed MPS program, significant differences in both growing patters and developing speeds are observed. Also, more dispersion can be observed in the inviscid case. With larger Atwood (AT) number, stronger RTI flows are developed earlier, as expected, with higher potential-energy differences. With larger initial disturbances, quite different patterns of RTI-development are observed compared to the small-initial-disturbance case. If AT number is small, the surface tension tends to delay and suppress the RTI development when it is sufficiently large. Interestingly, at high AT number, the RTI-suppressions by increased surface tension become less effective.
Key Words
    RTI (Rayleigh-Taylor instability); MPS (Moving Particle Semi-implicit) simulation; Atwood number; viscous vs. inviscid; initial disturbance; surface tension; RTI speed/pattern; mushroom-like RTI flows; comparison to linear theory
Kyung Sung Kim: School of Naval Architecture and Ocean Engineering, Tongmyong University,428 Sinseon-Ro, Nam-Gu, Busan, Republic of Korea
Moo Hyun Kim: Department of Ocean Engineering, Texas A&M University,3136 TAMU, College Station, Texas, USA


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