Question

Which is the diffusion terms of the y-momentum equation?

(a) (frac{partial au_{xy}}{partial x}+frac{partial au_{yy}}{partial y}+frac{partial au_{zy}}{partial z})

(b) (frac{partial au_{yx}}{partial x}+frac{partial au_{yy}}{partial y}+frac{partial au_{yz}}{partial z})

(c) (frac{partial au_{xx}}{partial x}+frac{partial au_{yx}}{partial x}+frac{partial au_{zx}}{partial x})

(d) (frac{partial au_{xy}}{partial y}+frac{partial au_{yy}}{partial y}+frac{partial au_{zy}}{partial y})

Answer 1

Right answer is (a) (frac{partial au_{xy}}{partial x}+frac{partial au_{yy}}{partial y}+frac{partial au_{zy}}{partial z})

Easy explanation: (frac{partial au_{xy}}{partial x}+frac{partial au_{yy}}{partial y}+frac{partial au_{zy}}{partial z}) are the diffusion terms of the y-momentum equation. It involves all the shear stress tensors which are in the y-direction.