Adding and resolve a differential equation

Luigi · November 15, 2012, 08:19

I have a transport equation of a scalar C in which it appears another (vectorial) variable i.
Also I have a differential equation of i: div(i)=0.
Can I introduce and resolve this equation in Ansys CFX, or it supports only algebraic equations?

cdegroot · November 15, 2012, 16:50

Yes you can add additional transport equations in CFX.

Luigi · November 16, 2012, 05:52

The problem is that I haven't a transport equation, but an additional differential equation to be solved

brunoc · November 20, 2012, 17:50

Well, $\nabla\bullet\textbf{i} = 0$ is also a transport equation. Do you mean you want to solve only this equation and not the others?

If that is the case, you can add and the following Expert Parameters to your simulation:

Code:

FLOW: Flow Analysis 1
  EXPERT PARAMETERS: 
    solve energy = f
    solve fluids = f
    solve turbulence = f
  END
END

You can also go to 'Insert > Solver > Expert Parameters > Model Over-rides' and disable other equations you see fit.

Cheers

Luigi · November 21, 2012, 06:51

I have a transport equation of the variable C, in which there is a term containing i; also, I have the equation div i = 0. So, I have a system of two equation. I don't know how I can solve the latter equation

brunoc · November 21, 2012, 07:29

You have four variables (C, ix, iy, iz) but only two equations. Aren't you missing two extra equations to close your problem?

Luigi · November 21, 2012, 08:05

I think you're right! Maybe I need others equations. I will study better my problem

November 15, 2012, 08:19	Adding and resolve a differential equation	#1
Luigi New Member Luigi Gurreri Join Date: Jul 2012 Posts: 18 Rep Power: 14	I have a transport equation of a scalar C in which it appears another (vectorial) variable i. Also I have a differential equation of i: div(i)=0. Can I introduce and resolve this equation in Ansys CFX, or it supports only algebraic equations?

November 20, 2012, 17:50		#4
brunoc Senior Member Bruno Join Date: Mar 2009 Location: Brazil Posts: 277 Rep Power: 21	Well, $\nabla\bullet\textbf{i} = 0$ is also a transport equation. Do you mean you want to solve only this equation and not the others? If that is the case, you can add and the following Expert Parameters to your simulation: Code: FLOW: Flow Analysis 1 EXPERT PARAMETERS: solve energy = f solve fluids = f solve turbulence = f END END You can also go to 'Insert > Solver > Expert Parameters > Model Over-rides' and disable other equations you see fit. Cheers

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Adding adaptive mesh refinement to the forwardStep tutorial	AlphaSheep	OpenFOAM Running, Solving & CFD	10	August 3, 2019 15:40
chtMultiRegionFoam, adding a member to an existing class (regionProperties)	romain.h	OpenFOAM Running, Solving & CFD	1	October 10, 2012 16:05

November 15, 2012, 16:50		#2
cdegroot Senior Member Chris DeGroot Join Date: Nov 2011 Location: Canada Posts: 414 Rep Power: 18	Yes you can add additional transport equations in CFX.

November 16, 2012, 05:52		#3
Luigi New Member Luigi Gurreri Join Date: Jul 2012 Posts: 18 Rep Power: 14	The problem is that I haven't a transport equation, but an additional differential equation to be solved

November 21, 2012, 06:51		#5
Luigi New Member Luigi Gurreri Join Date: Jul 2012 Posts: 18 Rep Power: 14	I have a transport equation of the variable C, in which there is a term containing i; also, I have the equation div i = 0. So, I have a system of two equation. I don't know how I can solve the latter equation

November 21, 2012, 07:29		#6
brunoc Senior Member Bruno Join Date: Mar 2009 Location: Brazil Posts: 277 Rep Power: 21	You have four variables (C, ix, iy, iz) but only two equations. Aren't you missing two extra equations to close your problem?

November 21, 2012, 08:05		#7
Luigi New Member Luigi Gurreri Join Date: Jul 2012 Posts: 18 Rep Power: 14	I think you're right! Maybe I need others equations. I will study better my problem