# Water ripples and nonzero divergence

In 2-d, one ripple would mean the velocity of water particles move out radially forming a circular wavefront. The Navier Stokes equations say the divergence of velocity has to be zero, but this circular radiation pattern has nonzero divergence. What am I missing here, since water ripples clearly exist?

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Ripples are not in 2-D , they must be in 3-D... –  Mr.ØØ7 May 10 '13 at 11:49
navier-stokes admits divergence-full flows. Sometimes you can try solving divergence-free NS, but it's not always necessary to do it. –  user23873 May 10 '13 at 12:06