Hi guys, quick question. I need to find the diffusivity of a species through a sphere (assume the species is concentrated at the center and diffuses outwards in 3D). Im assuming steady-state, so I'm using Fick's First Law, which for 3D scenarios is: J = -D [Del/Nabla Operator]C. First question is, would the equation then be: J = -D[(dC/dx)+(dC/dy)+(dC/dz)]? And if so, how would I go around solving this for J?

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anonymous · Answer

Well all you've done is replace the gradient with its definition...