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Scalable Fluid Simulation using Anisotropic Turbulence Particles
We present a novel, scalable turbulence method that uses a realistic energy
model and an efficient particle representation that allows for the accurate
and robust simulation of small-scale detail.
We compute transport of turbulent energy using a complete two-equation
k-epsilon model with accurate production terms that allows us to capture anisotropic turbulence
effects, which integrate smoothly into the base flow.
We only require a very low grid resolution to resolve the underlying base flow.
As we offload complexity from the fluid solver to the particle system, we can
control the detail of the simulation easily by adjusting the number of particles,
without changing the large scale behavior. In addition, no computations
are wasted on areas that are not visible. We demonstrate that due to
the design of our algorithm it is highly suitable for massively parallel
architectures, and is able to generate detailed turbulent simulations
with millions of particles at high framerates.
The base solver, shown to the left uses only 32 x 8 x 32 cells. The
remaining pictures show the influence of our turbulence model, with a varying
number of particles from 250k to 1M and 4M from left to right.
While the amount of detail directly depends on the number of particles used,
the overall flow remains consistent.
The full video: [MP4, 91MB].
Synthetic Turbulence using Artificial Boundary Layers
We build upon work from classical fluid
mechanics to design an algorithm that allows us to accurately precompute the
turbulence being generated around an object immersed in a flow. This is made
possible by modeling turbulence formation based on an averaged flow field, and
relying on universal laws describing the flow near a wall. We precompute the
confined vorticity in the boundary layer around an object, and simulate the
boundary layer separation during a fluid simulation.
Then, a turbulence model is
used to identify areas where this separated layer will transition into actual
turbulence. We sample these regions with vortex particles, and simulate the
further dynamics of the vortices based on these particles. We will show how our
method complements previous work on synthetic turbulence, and yields physically
plausible results.
The left image shows a quasi-static flow, driven only by our turbulence model without
a costly pressure projection step. The right image shows a high level of turbulence
introduced by a very thin object, which is made possible by our precomputation step.
The full video: [MOV, 92MB].
Example source code: [TGZ].
Wavelet Turbulence for Fluid Simulations
We present a novel wavelet method for the simulation of fluids at high spatial
resolution. The algorithm enables large- and small-scale detail to be edited
separately, allowing high-resolution detail to be added as a post-processing
step. Instead of solving the Navier-Stokes equations over a highly refined
mesh, we use the wavelet decomposition of a low-resolution simulation to
determine the location and energy characteristics of missing high-frequency
components. We then synthesize these missing components using a novel
incompressible turbulence function, and provide a method to maintain the
temporal coherence of the resulting structures. There is no linear system to
solve, so the method parallelizes trivially and requires only a few auxiliary
arrays. The method guarantees that the new frequencies will not interfere with
existing frequencies, allowing animators to set up a low resolution simulation
quickly and later add details without changing the overall fluid motion.
This sequence show the flow around a spherical obstacle. Each image shows
the underlying fluid simulation with little detail on the left, and
a simulation with wavelet turbulence to the right.
The full video: [MOV, 70MB].
Example source code: [WWW].
All additional data (images, videos, slides) can be found here.
- T. Pfaff, N. Thuerey, J. Cohen, S. Tariq, M. Gross, Scalable Fluid Simulation using Anisotropic Turbulence Particles, Proceedings of ACM SIGGRAPH Asia (Seoul, Korea, December 15-18, 2010), ACM Transactions on Graphics, vol. 29, no. 5, pp. 174:1-174:8
[Abstract]
[BibTeX]
[PDF] [Video]
- T. Pfaff, N. Thuerey, A. Selle, M. Gross, Synthetic Turbulence using Artificial Boundary Layers, Proceedings of ACM SIGGRAPH Asia (Yokohama, Japan, December 16-19, 2009), ACM Transactions on Graphics, vol. 28, no. 5, pp. 121:1-121:10
[Abstract]
[PDF] [Video]
- T. Kim, N. Thuerey, D. James, M. Gross, Wavelet Turbulence for Fluid Simulation, Proceedings of ACM SIGGRAPH (Los Angeles, USA, August 11-15, 2008), ACM Transactions on Graphics, vol. 27, no. 3, pp. 50.1-50.6
[Abstract]
[PDF]
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