Simulation with motion

ghorrocks · November 19, 2012, 17:48

What is k? What is this equation representing?

liuzexiang · November 19, 2012, 19:36

i am so sorry that i forgot explain the K. the K in the equation is present electrical conductivity of the flow. the whole equation is the relation of the electrical conductivity with gas volume fraction and temperature of the flow.

ghorrocks · November 20, 2012, 18:34

Why shouldn't this just be a function of the local volume fraction and temperature? Why does the vf and t of somewhere else affect the value (this happens through the averaging process)?

liuzexiang · November 21, 2012, 07:28

there is just the experience formula. so i do the simulate to find the effect to the current density.

ghorrocks · November 21, 2012, 19:21

What do you mean by "there is just the experience formula."?

The electrical conductivity of a control volume should be (in my understanding) a function of the conditions in that control volume only, so:

k=a*gas.vf + b*T

Where gas.vf and T are the local volume fraction and temperature. The solver will then do the current density simulation with a varying conducitivity and will work out all the path effects. This approach is simple to implement.

Is this approach valid? If not valid can you explain why not?

liuzexiang · November 21, 2012, 22:08

yes, i think it is a valid approach and i had gain the differert current density without a varying conducitivity in the simulation.but as the relation of the conductivity and the gas. VF and temperature had established, i can not know how to do in my simulation. so i can not gain the result.

liuzexiang · November 21, 2012, 22:15

sorry,ghorrocks, "there is just the experience formula." means that it is j an experience equation. maybe the temperature also effected the gas.VF. so the relation is a multiplication not a addition.

ghorrocks · November 22, 2012, 05:26

I do not know what you mean by the last comment and I still cannot see you a simple local equation is not suitable.

But I will forget that and just try to implement what you want. You say "k(z)=k0*(1+a*(T(z)-T0)*(1-b(z))),where,k0 and T0 is initialization, and the T(Z) and the b(z) is the temperature function and gas volume fraction function along the z axis respectively.". What function controls k(z), T(z) and b(z)? Is the simulation 1D? Can you post an image of the geometry? And describe the flow?

liuzexiang · November 29, 2012, 04:15

hi, ghorrocks, i am sorry for the late reply. i try to upload a picture but unsuccessful. the simulation is not 1D but 3D. the T(Z) and K(Z) is just the assumption, actually they are the functions of position. so gaining the T and K at different position is the key for the question. thank you !

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November 19, 2012, 17:48		#21
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	What is k? What is this equation representing?

November 19, 2012, 19:36		#22
liuzexiang Member liuzexiang Join Date: Oct 2012 Location: China Posts: 69 Rep Power: 14	i am so sorry that i forgot explain the K. the K in the equation is present electrical conductivity of the flow. the whole equation is the relation of the electrical conductivity with gas volume fraction and temperature of the flow.

November 20, 2012, 18:34		#23
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Why shouldn't this just be a function of the local volume fraction and temperature? Why does the vf and t of somewhere else affect the value (this happens through the averaging process)?

November 21, 2012, 07:28		#24
liuzexiang Member liuzexiang Join Date: Oct 2012 Location: China Posts: 69 Rep Power: 14	there is just the experience formula. so i do the simulate to find the effect to the current density.

November 21, 2012, 19:21		#25
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	What do you mean by "there is just the experience formula."? The electrical conductivity of a control volume should be (in my understanding) a function of the conditions in that control volume only, so: k=agas.vf + bT Where gas.vf and T are the local volume fraction and temperature. The solver will then do the current density simulation with a varying conducitivity and will work out all the path effects. This approach is simple to implement. Is this approach valid? If not valid can you explain why not?

November 21, 2012, 22:08		#26
liuzexiang Member liuzexiang Join Date: Oct 2012 Location: China Posts: 69 Rep Power: 14	yes, i think it is a valid approach and i had gain the differert current density without a varying conducitivity in the simulation.but as the relation of the conductivity and the gas. VF and temperature had established, i can not know how to do in my simulation. so i can not gain the result.

November 21, 2012, 22:15		#27
liuzexiang Member liuzexiang Join Date: Oct 2012 Location: China Posts: 69 Rep Power: 14	sorry,ghorrocks, "there is just the experience formula." means that it is j an experience equation. maybe the temperature also effected the gas.VF. so the relation is a multiplication not a addition.

November 22, 2012, 05:26		#28
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	I do not know what you mean by the last comment and I still cannot see you a simple local equation is not suitable. But I will forget that and just try to implement what you want. You say "k(z)=k0(1+a(T(z)-T0)*(1-b(z))),where,k0 and T0 is initialization, and the T(Z) and the b(z) is the temperature function and gas volume fraction function along the z axis respectively.". What function controls k(z), T(z) and b(z)? Is the simulation 1D? Can you post an image of the geometry? And describe the flow?

November 29, 2012, 04:15		#29
liuzexiang Member liuzexiang Join Date: Oct 2012 Location: China Posts: 69 Rep Power: 14	hi, ghorrocks, i am sorry for the late reply. i try to upload a picture but unsuccessful. the simulation is not 1D but 3D. the T(Z) and K(Z) is just the assumption, actually they are the functions of position. so gaining the T and K at different position is the key for the question. thank you !