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All of the following pictures show a flow simulation using the lattice-gas rules according to FHP III (with rest particles) after approximately 13000 time steps. The size of the system is 1024x512, the particle density is 1.4 particles per site, and the average velocity is .5 per site. The obstacle is a reflecting plate with 120 of length. The boundary conditions consist of periodic boundaries in all directions and momentum is injected only at the x=0 line. All the representations are calculated by averaging over 32x32 size windows.

The LATG program allows visualization of the flow simulations using different representations. The different representations are selected using the (lower left) push-button selections. From left to right, the selections are by Flow, Intensity, Direction, Occupancy, and Density.

Flow Representation

The Flow representation calculates the average velocity and speed of the current coarse-grain window, that in this case is 32x32. The program draws an arrow with length equal to the speed and direction equal to the vectorial sum of all particle directions.
Flow simulation with arrows indicating flow velocity and intensity. Flow after subtracting the average velocity of the system.

Scrollbars allow location of specific places in the canvas that when combined to zooming, closer examination of vortices can be realized, as in the following figures.
Zoomed Flow simulation where a vortex is under examination. Same zoomed Flow after subtracting the average velocity of the system.

Intensity Representation

The Intensity representation calculates the average magnitude of the momentum of the current coarse-grain window. The program draws a square of color representing the magnitude, according to the colormap to the right of the main canvas.
Intensity simulation where colors indicate magnitude of the momentum. Intensity representation after subtracting the average velocity of the system.

Direction Representation

The Direction representation calculates the angular direction of the total velocity of the current coarse-grain window. The program draws a square of color representing the value of the angle, according to the colormap to the right of the main canvas.
Direction simulation where colors indicate value of the angular direction. Direction representation after subtracting the average velocity of the system.

Occupancy Representation

The Occupancy representation simply puts a black square where there is at least one particle, and nothing where there is a vacant site. The immediate purpose of this representation is to find out if there are a lot of empty sites in a given simulation. Because the models follow incompressible rules, this representation will almost always present a completely black canvas.

Density Representation

The Density representation calculates the local density in terms of number of particles per site, of the simulation. The colors in the figure indicate the magnitude of the density and follow the colormap from the rainbow to the right of the main canvas.

Density representation for the current simulation. The average particle density is 1.4, which examining the rainbow colormap, gives the greenish-yellow color.


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