What's the applicable scope of G and RG Vector Macros

lbj007 · October 1, 2020, 08:28

In help manual: The gradients stored in variables with the _G suffix are non-limited values and if used to reconstruct values within the cell (at faces, for example), may potentially result in values that are higher (or lower) than values in the surrounding cells. Therefore, if your UDF needs to compute face values from cell gradients, you should use the reconstruction gradient (RG) values instead of non-limited gradient (G) values.
Can I explain it as " RG macros is more suitable than G macros",so what is the reason of defining G macros since RG is better? Or maybe G has some advantage I don't know. Maybe RG is only suitable when you use the second order discretization scheme? I wonder if someone can explain it

AlexanderZ · October 5, 2020, 02:40

RG is used to define gradient value on faces adjusted to cells
Gradient is calculated in the center of finite volume

lbj007 · October 5, 2020, 22:42

Quote:

Originally Posted by AlexanderZ

RG is used to define gradient value on faces adjusted to cells
Gradient is calculated in the center of finite volume

thanks,now I get it

October 1, 2020, 08:28	What's the applicable scope of G and RG Vector Macros	#1
lbj007 Senior Member Join Date: Feb 2020 Posts: 114 Rep Power: 6	In help manual: The gradients stored in variables with the _G suffix are non-limited values and if used to reconstruct values within the cell (at faces, for example), may potentially result in values that are higher (or lower) than values in the surrounding cells. Therefore, if your UDF needs to compute face values from cell gradients, you should use the reconstruction gradient (RG) values instead of non-limited gradient (G) values. Can I explain it as " RG macros is more suitable than G macros",so what is the reason of defining G macros since RG is better? Or maybe G has some advantage I don't know. Maybe RG is only suitable when you use the second order discretization scheme? I wonder if someone can explain it

October 5, 2020, 02:40		#2
AlexanderZ Senior Member Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34	RG is used to define gradient value on faces adjusted to cells Gradient is calculated in the center of finite volume lbj007 and Mary-31 like this. __________________ best regards ****************************** press LIKE if this message was helpful