Use gradient of another field for linearUpwind schemes

agustinvo · August 3, 2020, 06:01

Hi,
I was wondering what might happen if you use, for example, the gradient of velocity when setting the divergence scheme of k, epsilon...

Code:

div(phi, k)    bounded Gauss linearUpwind grad(U);

The gradient helps to compute the face values, but I was wondering what does it mean using another field when computing the gradient.

Have a nice day,
Agustín

Wenyuan · August 4, 2020, 05:10

Hi Agustin,

grad(U) doesn't mean the velocity gradient field, which is a tensor. Instead, grad(U) is the scheme that you specify how to calculate the gradient of U in gradSchemes. Then this scheme is used to calculate the gradient of k and compute the face value of k as you mentioned.

If you use the same scheme for grad(U) and grad(k) in gradSchemes, you will get the same result no matter grad(U) or grad(k) is used for linearUpwind.

agustinvo · August 4, 2020, 05:14

Ok, so

Code:

grad(X)

only points to the gradient scheme used for the X field.

Thank you!

August 3, 2020, 06:01	Use gradient of another field for linearUpwind schemes	#1
agustinvo Senior Member Agustín Villa Join Date: Apr 2013 Location: Alcorcón Posts: 313 Rep Power: 15	Hi, I was wondering what might happen if you use, for example, the gradient of velocity when setting the divergence scheme of k, epsilon... Code: div(phi, k) bounded Gauss linearUpwind grad(U); The gradient helps to compute the face values, but I was wondering what does it mean using another field when computing the gradient. Have a nice day, Agustín

August 4, 2020, 05:14		#3
agustinvo Senior Member Agustín Villa Join Date: Apr 2013 Location: Alcorcón Posts: 313 Rep Power: 15	Ok, so Code: grad(X) only points to the gradient scheme used for the X field. Thank you!

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August 4, 2020, 05:10		#2
Wenyuan New Member Wenyuan Fan Join Date: Mar 2017 Posts: 27 Rep Power: 9	Hi Agustin, grad(U) doesn't mean the velocity gradient field, which is a tensor. Instead, grad(U) is the scheme that you specify how to calculate the gradient of U in gradSchemes. Then this scheme is used to calculate the gradient of k and compute the face value of k as you mentioned. If you use the same scheme for grad(U) and grad(k) in gradSchemes, you will get the same result no matter grad(U) or grad(k) is used for linearUpwind.