Analysis of Rayleigh-Taylor Instability: Statistics on Rising Bubbles and Falling Spikes

Kamath, C ; Gezahegne, A ; Miller, P

关键词: BUBBLES;    RAYLEIGH-TAYLOR INSTABILITY;    SIMULATION;    STATISTICS;    TURBULENCE;   

DOI  :  10.2172/923126
RP-ID  :  UCRL-TR-236111
PID  :  OSTI ID: 923126
Others  :  TRN: US200806%%372

学科分类：物理（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

The analysis of coherent structures in Rayleigh-Taylor simulations is a challenging task as the lack of a precise definition of these structures is compounded by the massive size of the datasets. In an earlier work, we used techniques from image analysis to count these coherent structures in two high-resolution simulations, one a large-eddy simulation with 30 terabytes of analysis data, and the other a direct numerical simulation with 80 terabytes of analysis data. Our analysis indicated that there were four distinct regimes in the process of the mixing of the two fluids, starting from the initial linear stage, followed by the non-linear stage with weak turbulence, the mixing transition stage, and the final stage of strong turbulence. In this paper, we extend our earlier work to focus on only the rising bubbles and the falling spikes. We first consider different ways in which we can constrain the bubble and spike definitions and then extract various statistics on them. Our results on the rising bubble and falling spike counts again show that there are four regimes in the process of fluid mixing, each characterized by an integer-valued slope. Further, the average bubble heights and spike depths are related to similar results obtained using a threshold-based definition. Finally, the ratio of the rising bubbles to all bubbles is very similar in character to the ratio of the falling spikes to all spikes, with near constant values over part of the simulation.