
[Sponsors] 
November 19, 2012, 17:48 

#21 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,535
Rep Power: 104 
What is k? What is this equation representing?


November 19, 2012, 19:36 

#22 
Member
liuzexiang
Join Date: Oct 2012
Location: China
Posts: 64
Rep Power: 6 
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 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,535
Rep Power: 104 
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 
Member
liuzexiang
Join Date: Oct 2012
Location: China
Posts: 64
Rep Power: 6 
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 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,535
Rep Power: 104 
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? 

November 21, 2012, 22:08 

#26 
Member
liuzexiang
Join Date: Oct 2012
Location: China
Posts: 64
Rep Power: 6 
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 
Member
liuzexiang
Join Date: Oct 2012
Location: China
Posts: 64
Rep Power: 6 
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 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,535
Rep Power: 104 
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)*(1b(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 
Member
liuzexiang
Join Date: Oct 2012
Location: China
Posts: 64
Rep Power: 6 
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 !


Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Difficulty in calculating angular velocity of Savonius turbine simulation  alfaruk  CFX  14  March 17, 2017 07:08 
Simulation time vs. Simulation Cell Count  chrisoturner  Main CFD Forum  7  September 8, 2012 17:46 
Fan simulation divergence  ayothicfd  CFX  18  July 20, 2012 05:53 
define the immersed solid domain motion in transient simulation  TURBO_SPP  CFX  0  July 12, 2012 22:10 
GUI crash and simulation engine still running  RPJones  FLOW3D  2  November 9, 2010 09:18 