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تسجيل مستخدم جديدEnergy decay in three-dimensional freely cooling granular gas
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The kinetic energy of a freely cooling granular gas decreases as a power law $t^{-theta}$ at large times $t$. Two theoretical conjectures exist for the exponent $theta$. One based on ballistic aggregation of compact spherical aggregates predicts $theta= 2d/(d+2)$ in $d$ dimensions. The other based on Burgers equation describing anisotropic, extended clusters predicts $theta=d/2$ when $2le d le 4$. We do extensive simulations in three dimensions to find that while $theta$ is as predicted by ballistic aggregation, the cluster statistics and velocity distribution differ from it. Thus, the freely cooling granular gas fits to neither the ballistic aggregation or a Burgers equation description.
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