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discrepancy in fvc::grad(U)

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August 3, 2019, 21:41		#4
anon_q Senior Member Join Date: Mar 2018 Posts: 115 Rep Power: 8	The result is correct because the gradient will be calculated as follows: $\begin{bmatrix} \partial_1 U & \partial_1 V & \partial_1 W \\ {\color{green}\partial_2 U} & \partial_2 V & \partial_2 W \\ \partial_3 U & \partial_3 V & \partial_3 W \end{bmatrix}$ As you can see: ${\color{green}\partial_2 U} \equiv \dfrac{\partial U}{\partial y}$ is the 4th element in the tensor (correctly calculated by OpenFOAM). Remember that the tensor class will represent it like this: gradU =Tensor( $\partial_1 U, \partial_1 V, \partial_1 W, {\color{green}\partial_2 U}, \partial_2 V, \partial_2 W, \partial_3 U, \partial_3 V, \partial_3 W$ ) but to access ${\color{green}\partial_2 U \equiv \dfrac{\partial U}{\partial y}}$ we use gradU.yx() watermelon likes this.

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