Two-Phase approach ... help is needed

Tariq SY · January 17, 2012, 12:41

good day everyone.

I am trying to simulate a nanofluid in a tube using two phase approach, Lagrange equations.

I've done the single phase one, Euler equation, but now i found that i have to do the two-phase approach.
what I need to know is how to solve my model on CFX using Lagrange equations in order to simulate a two phase fluid (fluid + solid particles)

advice will be highly appreciated as this work for my close submitting date dissertation.

regards
Tariq

ghorrocks · January 17, 2012, 16:42

CFX uses the Navier Stokes equations and that assumes a continuum. If you are dealing with nanofluids then you do not have a continuum. CFX cannot solve this type of simulation, you need a molecular dynamics package for this.

Or do you mean the nano bit is small particles in a fluid? Can you explain what you are trying to do more completely?

imnull · January 17, 2012, 19:42

--------------

ghorrocks · January 17, 2012, 20:05

60um particles in a 6mm tube is not nano-scale. This is micro-scale and CFX is suitable for this. Molecular dynamics cannot do things of this scale.

People tend to use the word "nanotechnology" for anything small. But nano scale objects are molecular scale objects, but micro scale objects are continuum scale objects and are completely different. I recommend only using the word "nano" if your objects are actually in the nanometre size range.

Back to your original question - what is the size of the objects and what are you trying to do?

imnull · January 17, 2012, 20:11

------------------------

imnull · January 17, 2012, 20:13

-----------------------

ghorrocks · January 17, 2012, 23:16

CFX does not have plasma models. How are you going to model the plasma?

Are the micro particles the spray, or are there particles in the spray? What are you trying to get out of the simulation?

imnull · January 18, 2012, 08:15

-----------------------------------

ghorrocks · January 18, 2012, 16:47

You are going to have to explain what are you doing. What is the gas? What is the solids? What velocity/pressure? Draw a picture of it. What are the boundary conditions?

imnull · January 18, 2012, 18:03

----------------------------------

ghorrocks · January 18, 2012, 18:51

I do not discuss forum issues on email. Put the details on the forum.

Are the particles hard or deformable? I assume hard if they are ceramic.

Why do you say this is plasma spraying? The Mach number is not high enough for plasma effects. Is there something else to generate the plasma?

What are you trying to achieve with the model? What is the model going to tell you?

imnull · January 18, 2012, 20:15

------------------

ghorrocks · January 18, 2012, 20:29

This sounds like a compressible flow with lagrangian particle tracking model. From what you have described the built in models in CFX should be able to handle this.

So what is not working?

imnull · January 18, 2012, 20:45

--------------------------------

ghorrocks · January 18, 2012, 21:05

There are normal tutorials which come with CFX, and a whole heap more on the ANSYS Community website. Lots of these deal with 2 phase flow.

imnull · January 18, 2012, 21:09

------------------------------

imnull · January 18, 2012, 21:16

Glenn, see the first post..

"...what I need to know is how to solve my model on CFX using Lagrange equations in order to simulate a two phase fluid (fluid + solid particles)..."

your answer to read the tutorials is trivial ...

Far · January 18, 2012, 22:46

Quote:

"...what I need to know is how to solve my model on CFX using Lagrange equations in order to simulate a two phase fluid (fluid + solid particles)..."

your answer to read the tutorials is trivial ...

Then tutorials are good point to start. You should ask the specific question(s) in particular problem, no body is going to explain you every thing on forum and it is even not possible to communicate in just text.

imnull · January 18, 2012, 22:48

Quote:

Originally Posted by Far

Then tutorials are good point to start. You should ask the specific question(s) in particular problem, no body is going to explain you every thing on forum and it is even not possible to communicate in just text.

what's the point to start dialog then ...

Tariq SY · January 20, 2012, 14:32

dear ghorrocks
thanks

simply it is just a normal heat transfer fluid, water for say, with solid particles dispersed in it
the particles are in nano size 50-100 nm and they are suppose to enhance the thermal conductivity of the fluid.

The single phase approach considers the nano-fluid (fluid + nano-particles) as a homogeneous fluid. For a homogeneous approach nanofluid can be considered as a single phase with averaged physical properties of individual phases, as the nano size of the particles allow us to fluidize them and consider the particles behaving like a single phase fluid plus to the consideration of a negligible motion slip between the particles and the thermal equilibrium conditions.

the Two Phase approach considers the nano-fluid as heterogeneous mixture.
In the case of heterogeneous mixture the fluid considered to be a two phase fluid. this approach allows us to study the consequences of the interaction between the nano-particles and the fluid layers.

My PROBLEM is that I dont have solid background about the theory of heterogeneous mixture how its dynamic behavior mathematically represented.

i know that I have to define two mediums in the fluid domain field and the integrated (Solid Particle Transport ) model is the best to express the nano-particles presence while it is continues for the fluid .... BUT I DONT KNOW HOW TO DEAL WITH THE SUBSIDIARY FACTORS .... I need a matching tutorial, reference or just an advice about how to learn this.

thanks and best regards
Tariq

January 17, 2012, 12:41	Two-Phase approach ... help is needed	#1
Tariq SY New Member Tariq Obeid Join Date: Jul 2011 Location: London, UK Posts: 2 Rep Power: 0	good day everyone. I am trying to simulate a nanofluid in a tube using two phase approach, Lagrange equations. I've done the single phase one, Euler equation, but now i found that i have to do the two-phase approach. what I need to know is how to solve my model on CFX using Lagrange equations in order to simulate a two phase fluid (fluid + solid particles) advice will be highly appreciated as this work for my close submitting date dissertation. regards Tariq

January 17, 2012, 19:42		#3
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	-------------- Last edited by imnull; January 18, 2012 at 21:31.

January 17, 2012, 20:11		#5
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	------------------------ Last edited by imnull; January 18, 2012 at 21:31.

January 17, 2012, 20:13		#6
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	----------------------- Last edited by imnull; January 18, 2012 at 21:33.

January 18, 2012, 08:15		#8
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	----------------------------------- Last edited by imnull; January 18, 2012 at 21:32.

January 17, 2012, 16:42		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	CFX uses the Navier Stokes equations and that assumes a continuum. If you are dealing with nanofluids then you do not have a continuum. CFX cannot solve this type of simulation, you need a molecular dynamics package for this. Or do you mean the nano bit is small particles in a fluid? Can you explain what you are trying to do more completely?

January 17, 2012, 20:05		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	60um particles in a 6mm tube is not nano-scale. This is micro-scale and CFX is suitable for this. Molecular dynamics cannot do things of this scale. People tend to use the word "nanotechnology" for anything small. But nano scale objects are molecular scale objects, but micro scale objects are continuum scale objects and are completely different. I recommend only using the word "nano" if your objects are actually in the nanometre size range. Back to your original question - what is the size of the objects and what are you trying to do?

January 17, 2012, 23:16		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	CFX does not have plasma models. How are you going to model the plasma? Are the micro particles the spray, or are there particles in the spray? What are you trying to get out of the simulation?

January 18, 2012, 16:47		#9
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	You are going to have to explain what are you doing. What is the gas? What is the solids? What velocity/pressure? Draw a picture of it. What are the boundary conditions?

January 18, 2012, 18:03		#10
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	---------------------------------- Last edited by imnull; January 18, 2012 at 21:32.

January 18, 2012, 18:51		#11
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	I do not discuss forum issues on email. Put the details on the forum. Are the particles hard or deformable? I assume hard if they are ceramic. Why do you say this is plasma spraying? The Mach number is not high enough for plasma effects. Is there something else to generate the plasma? What are you trying to achieve with the model? What is the model going to tell you?

January 18, 2012, 20:15		#12
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	------------------ Last edited by imnull; January 18, 2012 at 21:32.

January 18, 2012, 20:29		#13
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	This sounds like a compressible flow with lagrangian particle tracking model. From what you have described the built in models in CFX should be able to handle this. So what is not working?

January 18, 2012, 20:45		#14
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	-------------------------------- Last edited by imnull; January 18, 2012 at 21:32.

January 18, 2012, 21:05		#15
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	There are normal tutorials which come with CFX, and a whole heap more on the ANSYS Community website. Lots of these deal with 2 phase flow.

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January 18, 2012, 21:09		#16
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	------------------------------ Last edited by imnull; January 18, 2012 at 21:32.

January 18, 2012, 21:16		#17
imnull Member Dmitry Join Date: Nov 2011 Posts: 45 Rep Power: 14	Glenn, see the first post.. "...what I need to know is how to solve my model on CFX using Lagrange equations in order to simulate a two phase fluid (fluid + solid particles)..." your answer to read the tutorials is trivial ... Last edited by imnull; January 18, 2012 at 21:59.

January 20, 2012, 14:32		#20
Tariq SY New Member Tariq Obeid Join Date: Jul 2011 Location: London, UK Posts: 2 Rep Power: 0	dear ghorrocks thanks simply it is just a normal heat transfer fluid, water for say, with solid particles dispersed in it the particles are in nano size 50-100 nm and they are suppose to enhance the thermal conductivity of the fluid. The single phase approach considers the nano-fluid (fluid + nano-particles) as a homogeneous fluid. For a homogeneous approach nanofluid can be considered as a single phase with averaged physical properties of individual phases, as the nano size of the particles allow us to fluidize them and consider the particles behaving like a single phase fluid plus to the consideration of a negligible motion slip between the particles and the thermal equilibrium conditions. the Two Phase approach considers the nano-fluid as heterogeneous mixture. In the case of heterogeneous mixture the fluid considered to be a two phase fluid. this approach allows us to study the consequences of the interaction between the nano-particles and the fluid layers. My PROBLEM is that I dont have solid background about the theory of heterogeneous mixture how its dynamic behavior mathematically represented. i know that I have to define two mediums in the fluid domain field and the integrated (Solid Particle Transport ) model is the best to express the nano-particles presence while it is continues for the fluid .... BUT I DONT KNOW HOW TO DEAL WITH THE SUBSIDIARY FACTORS .... I need a matching tutorial, reference or just an advice about how to learn this. thanks and best regards Tariq