Optimized Free Surface Fluids on Adaptive Grids with the Lattice Boltzmann Method

Nils Thürey, Ulrich RüdeUniversity of Erlangen-Nürnberg, Computer Science 10 LSS, funded by DFG GRK-344

SIGGRAPH2005

Free Surface Fluids with the Lattice Boltzmann Method (LBM):

Optimizations with Adaptive Grids:

Unoptimized:(on average 69s / frame)

Optimized:(on average 24s / frame)

Unoptimized:(on average 76s / frame)

Optimized:(on average 37s / frame)

D2Q9 D3Q19

Stream DFsfrom adjacent Cells

Reconstruct DFs from Empty Celldirections

Reconstruct DFs from Direction ofInterface Normal

nn

Calculate Mass exchange with neighboringCells

mm

Perform Collisionas usual

The common LBM Models in 2D/3D:

CoarsenedInterface Regionwith 3 Grids

+ +

Grid G3, Coarse Grid G2 Grid G1FineActual Representation

on LBM Grid

Fluid Cell

Interface Cell

Coarse to Fine Grid Transfer

Fine to Coarse Grid Transfer

=

Time Stepping:

Step G3

t = 0

Step G2Step G1

t + 1

G2 > G1Step G1

G3 > G2

t + 2

Step G2

Step G1

G1 > G2

t + 3

G2 > G1Step G1

G1 > G2

t + 4

Step G3

Step G2

G2 > G3

Step G1

....

Lattice Boltzmann:- Similar to Cellular Automata - Regular Grid & discrete Velocites- Optimized Implementation possible

Free Surfaces:- Distuingish Empty, Fluid and

Interface Cells- Boundary Conditions and Surface

Tracking are handled at the Interface: