how to calculate mixed derivative

ziemowitzima · February 15, 2013, 13:39

Dear Foamers,
Is there any way to compute second order mixed derivatives ?

But different than using twice grad operator ?

Thanks !
ZMM

ziemowitzima · February 15, 2013, 14:03

e.g.
could mixed derivative as:
$\frac{\partial^2 f}{\partial x \partial y}$
be calculated using fvc::laplacian method, as follows:

HTML Code:

nu = (0 1 0 0 0 0 0 0 0 ); 
fvc::laplacian(nu,f)

??

It does something, but I am not sure what ...

Thanks
ZMM

mitti · June 5, 2018, 14:19

Did you found any solution for this problem?

Or can anyone else give a hint how to implement it for e.g. a scalar and a vector?

ali moeni · June 27, 2023, 04:30

Hey, I've been studying turbulence models for some time and I came across this issue. I know it's a little late, but it's better than never.

for a similar second-order mixed derivative of velocity, turbulence Models use :

fvc::magSqrGradGrad(U))

however Im not 100% sure.

February 15, 2013, 13:39	how to calculate mixed derivative	#1
ziemowitzima Senior Member Mieszko Młody Join Date: Mar 2009 Location: POLAND, USA Posts: 145 Rep Power: 17	Dear Foamers, Is there any way to compute second order mixed derivatives ? But different than using twice grad operator ? Thanks ! ZMM

February 15, 2013, 14:03		#2
ziemowitzima Senior Member Mieszko Młody Join Date: Mar 2009 Location: POLAND, USA Posts: 145 Rep Power: 17	e.g. could mixed derivative as: $\frac{\partial^2 f}{\partial x \partial y}$ be calculated using fvc::laplacian method, as follows: HTML Code: nu = (0 1 0 0 0 0 0 0 0 ); fvc::laplacian(nu,f) ?? It does something, but I am not sure what ... Thanks ZMM

June 5, 2018, 14:19		#3
mitti New Member Join Date: Nov 2016 Posts: 15 Rep Power: 9	Did you found any solution for this problem? Or can anyone else give a hint how to implement it for e.g. a scalar and a vector? ali moeni likes this.

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June 27, 2023, 04:30		#4
ali moeni New Member Join Date: Oct 2021 Posts: 5 Rep Power: 4	Hey, I've been studying turbulence models for some time and I came across this issue. I know it's a little late, but it's better than never. for a similar second-order mixed derivative of velocity, turbulence Models use : fvc::magSqrGradGrad(U)) however Im not 100% sure.