Now, if we try to simulate this effect with traditional techniques on a coarse grid, we'll encounter a weird phenomenon: namely, the longer our simulation runs, the larger the volume of the sand becomes.
现在,如果我们尝试用传统方法在粗糙的网格上模拟这个效果,我们将会遇到一个奇怪现象:模拟的时间越长,沙子的体积就会变得越大。