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Bubble Equilibrium

A `circular' bubble, of radius 32 grid points, was initialised at the centre of a 128 by 128 grid. The fluid density was set at tex2html_wrap_inline14853 everywhere with tex2html_wrap_inline14869 inside the bubble and tex2html_wrap_inline14871 elsewhere. The fluids were then allowed to evolve for 10,000 time-steps. The density and the order parameter were measured along a line through the centre of the inner fluid parallel to the y-axis (perpendicular to tex2html_wrap_inline13709 ) and are shown in figures 4-3 and 4-4 respectively at selected times.

   figure4319
Figure 4-3: The density tex2html_wrap_inline12075 as a function of r the distance from the edge of the grid. The density is plotted along a line through the centre of the inner fluid parallel to the y-axis (perpendicular to tex2html_wrap_inline14883 .

   figure4328
Figure 4-4: The order parameter tex2html_wrap_inline12083 plotted against r the distance from the edge of the grid. The order parameter is plotted along a line through the centre of the inner fluid parallel to the y-axis (perpendicular to tex2html_wrap_inline14883 .

The relaxation times used were tex2html_wrap_inline14893 and tex2html_wrap_inline14895 . The relaxation time tex2html_wrap_inline14897 is tex2html_wrap_inline14899 which is the value at which the model is Galilean invariant [9, 38]. This initialisation differs from the final state in four ways. The order parameter has changed from its initial value of tex2html_wrap_inline14901 to its expected value of 0.50. The initially interface width of one lattice unit has increased to about ten lattice units. The shape of the inner fluid has changed from an ellipse with semi-major and semi-minor axis of 32 lu and tex2html_wrap_inline14905 lu to a circle with radius tex2html_wrap_inline14907 lu. The final density is slightly larger in the inner fluid than the outer fluid. The small change in the density occurs everywhere within the first 1,000 time-steps with only a small change in the shape of the interface occurring at subsequent times. The larger change in the order parameter takes 10,000 time-steps to reach the areas furthest from the interface. The movement of the inner fluid from an ellipse to a circle is achieved within the 10,000 time steps.


next up previous contents
Next: The Density and Order Up: Implementation of the Free Previous: Fluid Separation

James Buick
Tue Mar 17 17:29:36 GMT 1998