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Turbulent Fluids |
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Ye Zhao Assistant Professor Fan Chen Ph.D. Student Zhi Yuan Ph.D. Student |
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Title: Enhancing Fluid Animation with Adaptive, Controllable and Intermittent Turbulence. Ye Zhao, Zhi Yuan and Fan Chen Appearing in ACM SIGGRAPH/Eurographic Symposium of Computer Animation, Madrid, Spain, Jul, 2010
Abstract: This paper proposes a new scheme for enhancing fluid animation with controllable turbulence. An existing fluid simulation from ordinary fluid solvers is fluctuated by turbulent variation modeled as a random process of forcing. The variation is precomputed as a sequence of solenoidal noise vector fields directly in the spectral domain, which is fast and easy to implement. The spectral generation enables flexible vortex scale and spectrum control following a user prescribed energy spectrum, e.g. Kolmogorov's cascade theory, so that the fields provide fluctuations in subgrid scales and/or in preferred large octaves. The vector fields are employed as turbulence forces to agitate the existing flow, where they act as a stimulus of turbulence inside the framework of the Navier-Stokes equations, leading to natural integration and temporal consistency. The scheme also facilitates adaptive turbulent enhancement steered by various physical or user-defined properties, such as strain rate, vorticity, distance to objects and scalar density, in critical local regions. Furthermore, an important feature of turbulent fluid, intermittency, is created by applying turbulence control during randomly selected temporal periods. Paper Download: PDF (6.3 M)
Video Download: ZIP (32.5 M)
Figures and Examples:
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Support: U.S. National Science Foundation under grant IIS-0916131, PI: Ye Zhao
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Random vector fields generated for a preferred scale with different deviations. |
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Divergence-free vector fields with two octaves showing blended rotational behaviors from the two scales. Turbulent agitation from the small scale is controlled with different kinetic energy spectrum distributions. |
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Data flow of our forced fluid simulation. A sequence of precomputed solenoidal fields (ST) work as random forces (f) in a forced fluid solver (FNS) to introduce turbulence. The results (U) of large-scale simulations (NS) are combined with the feedback of FNS results, in order to direct the simulation to follow large-scale flows. |
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Turbulence enhancement animation 1: (video 7.5 M) |
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Original coarse simulation |
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Wavelet subgrid turbulence |
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Our subgrid turbulence |
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Original coarse simulation with vortex confinement |
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Wavelet turbulence |
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Our turbulence |
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Our turbulence |
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Our strong turbulence |
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Our increased turbulence |
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Turbulence enhancement animation 2&3: (video 17.5 M) |
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Original laminar fluid |
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Enhanced turbulent fluid |
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Enhanced finer turbulent fluid |
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Turbulence enhancement animation 4 with SPH solver: (video 17.4 M) |
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Created 05/25/2010 |
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We thank Theodore Kim and Nils Thuerey for their publicly released source code of wavelet turbulence, and Rama Hoetzlein for his SPH open source code - Fluids v.1. |