UDF to define the vector transport equation

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 August 31, 2012, 05:47 UDF to define the vector transport equation #1 Senior Member   Vaze Join Date: Jun 2009 Posts: 133 Rep Power: 8 Hi Through the UDS, scalar transport equation can be defined. I would like to define the vector transport equation. How can i define it? regards Mvee

 August 31, 2012, 08:14 #2 Senior Member     Amir Join Date: May 2009 Location: Shiraz, Iran Posts: 739 Blog Entries: 1 Rep Power: 14 Hi, You would need 3 UDSs as each component! Bests, __________________ Amir

 September 3, 2012, 00:03 #3 Senior Member   Vaze Join Date: Jun 2009 Posts: 133 Rep Power: 8 Hi Amir Can you describe how and which UDS to use? Mvee

September 3, 2012, 03:38
#4
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Amir
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Quote:
 Originally Posted by mvee Hi Amir Can you describe how and which UDS to use? Mvee
Suppose you wanna model momentum equation via UDS. You have to define 3 UDSs; u, v and w; and provide appropriate transport terms such as convection, diffusion, unsteady and source terms for each of them. A UDS has a general form of transport equation which you can modify for your purpose.

Bests,
__________________
Amir

 September 3, 2012, 04:07 #5 Senior Member   Vaze Join Date: Jun 2009 Posts: 133 Rep Power: 8 Hi Amir Problem: Welding arc simulation Description: 1) No. of zones: 3 2) Solid zone: electrode and workpiece (copper) 3) Fluid: argon (electrically conductive) Current is imposed on the electrode which passes from the fluid and workpiece (which is at zero potential). Due to the current electro-magnetic field is generated which is governed by Maxwell’s equation (consists of current continuity and potential vector equation). These equations are having same form as that of our NS equations. I have defined one UDS for voltage to solve current continuity equation. In the similar form do you mean to define UDS for vector A. Can you describe how shall I follow for the physics mentioned above? Also the output of this UDS will go as source term in momentum equation. Thanks Mvee

September 3, 2012, 05:29
#6
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Amir
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Quote:
 Originally Posted by mvee I have defined one UDS for voltage to solve current continuity equation. In the similar form do you mean to define UDS for vector A. Can you describe how shall I follow for the physics mentioned above? Also the output of this UDS will go as source term in momentum equation.
Hi,

Ok, you'll also need a vector transport equation. You can consider a vector transport equation as 3 scalar transport equation (one for each component) and model each of them via a UDS. Here you have a vector A, so define 3 UDS as Ax, Ay and Az as its components. So consider your vector equation and decompose it into 3 scalar equation. Finally with simple UDFs you can add each component of your added equations into each momentum components without any trouble.

Bests,
__________________
Amir

 September 3, 2012, 06:13 #7 Senior Member   Vaze Join Date: Jun 2009 Posts: 133 Rep Power: 8 Hi Amir Thank you very much for your help, still have some doubt. My algorithm will work in following manner - (1) Current continuit equation: =0 /* = applied voltage and = Laplacian operator*/ (2) current density, j = - (3) Potential vector equation: = First and third point can be applied through UDS. How to interface (required to solve point 2) between point 1 and 3? Is it required UDF?

September 3, 2012, 07:34
#8
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Amir
Join Date: May 2009
Location: Shiraz, Iran
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Quote:
 Originally Posted by mvee (1) Current continuit equation: =0 /* = applied voltage and = Laplacian operator*/ (2) current density, j = - (3) Potential vector equation: = First and third point can be applied through UDS. How to interface (required to solve point 2) between point 1 and 3? Is it required UDF?
Dear friend,

It depends. It doesn't need to evaluate j explicitly if you just want to obtain A! you can substitute j from equation 2 into 3 directly and remove the j variable. But if you want to obtain j as well; yes, you'll need a UDF to store the phi gradient into a UDM. It should be noted that you would also need UDFs for defining source terms of equation 3.

Bests,
__________________
Amir

 September 10, 2012, 01:27 #9 Senior Member   Vaze Join Date: Jun 2009 Posts: 133 Rep Power: 8 Hi Amir Thank you very much for your kind co-operation. I have solved these equations. Thank you Mvee

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