CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Residence Time of RBC's and Haemolysis(Help for Searching)

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 15, 2016, 01:51
Smile Residence Time of RBC's and Haemolysis(Help for Searching)
  #1
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Hai all,

This cfx forum has given me lot regarding the cfd analysis for a centrifugal blood pumps.

Wonderful to be a part of this forum.

I have a problem with the setting up of "additional variables" (Eularian Approach) in CFX, for modelling the shear induced haemolysis of blood cells(RBC's).

I have finalised the model: dHb/Hb = (3.62*10^-7)*(T^0.785)*(Tau*2.416).
(Ref : Garon and Farinas Hyperbolic Model)

I have also seen some relevant posts regarding this. Can someone help me to search with links of threads or any other relevant documents/tutorials for setting up the "Additional Variables" in CFX ?

Any help is blissful. Thank you all in advance.
kastarkas is offline   Reply With Quote

Old   September 15, 2016, 02:24
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,869
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
If I understand you correctly the equation you quote defines the gain in red blood cell damage as a function of local shear stress and T (is that time, temperature or something else?).

To model this is would appear an additional variable with a transport equation (but no diffusion) would be suitable. The initial condition is presumably Hb=0 everywhere and probably at the boundaries too, and the equation you quote would be a source term which would generate Hb.

Read the section on additional variables to understand the different implementations, and source terms to understand total sources or flux approaches.
ghorrocks is offline   Reply With Quote

Old   September 15, 2016, 02:38
Smile
  #3
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Thank you for the reply Glenn. The "T' is time and 'Tau' is shear stress only as you said.

Great. I l look upon the section of "Additional Variables" and i l update asap.

Thanks a lot.
kastarkas is offline   Reply With Quote

Old   September 17, 2016, 08:12
Smile
  #4
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Hai Glenn,

I went through the documentation for source terms and additional variables. I am a bit confused on arriving at inserting the expressions and source terms here.

This is my case.

Transport Eqn : (∂/ ∂t + ∇.V) D = I

(V - Velocity Vector, D - Linear Blood Damage Index)

D = d^(1/0.785)

d = ΔHb/Hb =(3.62*10^-7)*(t^0.785)*(tau^2.416)

[t = exposure time of RBC, tau = shear stress on blood, ΔHb/Hb = Gain in blood damage. ]

'I' is mentioned as the source term causing damage.

My doubt is :

1. Shear stress on blood = (2*Density*Turbulent KE), is that right ?. I saw in the forum thread in which you helped. Should i create this as an additional variable ?

2. You told me about Hb is presumably zero at boundaries and at initial conditon. So shoud i add a term for this equation at the inlet surface..?

3. While inserting an expression in CFX, how will i select the 'time of exposure' from the in built list of variables. ?

Thank you again.

Last edited by kastarkas; September 27, 2016 at 08:47.
kastarkas is offline   Reply With Quote

Old   September 19, 2016, 01:39
Smile
  #5
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Hai all,

Can someone help me out ?

Last edited by kastarkas; September 27, 2016 at 08:48.
kastarkas is offline   Reply With Quote

Old   September 19, 2016, 01:47
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,869
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
1. I have no idea. I am not an expert in blood damage.
2. No, these are boundary and initial conditions. So it is specified in the boundary and initial conditions.
3. Time of exposure of what? Is this simulation time, or something else?
4. Only if you need to use and area or volume integral. I have not seen anything which appears to require one. But I don't understand what you are doing so there might be something I am not aware of.
5 and 6 - I do not understand these questions.
ghorrocks is offline   Reply With Quote

Old   September 19, 2016, 06:09
Smile
  #7
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Thank you glenn for that.

The time, that I mentioned is actually the total time that a blood cell is exposed to shear, and dHb/Hb is given as a funtion of this time and the shear stresses on this cell. So how am i supposed to include that while creating the Expression ?

And also can u please tell me am i right on these steps :

1. create additional variable (dHb/Hb).
(specific and no units).

2. Activate the addtional variable in domain.

3. create source terms with at inlet, with the value of source term as that of the expression equating dHb/Hb .

Last edited by kastarkas; September 27, 2016 at 08:50.
kastarkas is offline   Reply With Quote

Old   September 19, 2016, 08:07
Default
  #8
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,869
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I don't really understand the model you are trying to implement so cannot comment on the detailed implementation.

So I would recommend you do a simplified model to understand how this works so you can adapt it to your case. Take a simulation such as the static mixer tutorial. Add an additional variable with a transport equation. Then add a source term set to 1 [1/s^1] and set the additional variable to zero at the boundaries. When you get this working it should give you the fluid residence time in seconds. Note you will need to sort out exactly what type of additional variable and other details. I will leave that as an exercise for you

So do a simple model first and make sure you understand that before you tackle your more complex one.
ghorrocks is offline   Reply With Quote

Old   September 19, 2016, 15:44
Default
  #9
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Great. Thank you again.
Very much of a relief on hearing that....I l try to implement the basic ones and get it working....and i l come back right here after that...Thanks a lot..

Last edited by kastarkas; September 27, 2016 at 08:51.
kastarkas is offline   Reply With Quote

Old   September 21, 2016, 08:58
Smile
  #10
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Hello everyone,

I need to create a simple expression for time(t) = {V^(1/3)} / u in CEL CFX.

where V = volume of each computational cell and u = magnitude of velocity of each cell.

'V' can be obtained through a syntax for "volume of finite volumes" ie. (volcvol)
although i am not able to find the short name for it in the documentation.

i got volcvol from forum only.

How can 'u' be accessed ? what is the variable for that. is this the usual variable "velocity" of cel or is there anything else ?

Thank you all in advance..
kastarkas is offline   Reply With Quote

Old   September 21, 2016, 19:53
Default
  #11
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,869
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
The names for all variables are described in the CFX Reference manual, in the chapter titled "Variables in ANSYS CFX". You will find the velocity magnitude can be accessed as either "vel" or "Velocity".
ghorrocks is offline   Reply With Quote

Old   September 22, 2016, 03:54
Smile
  #12
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
hai,
Thank you Glenn

I needed velocity of each cell, . that is the problem
kastarkas is offline   Reply With Quote

Old   September 22, 2016, 06:26
Default
  #13
Senior Member
 
Lance
Join Date: Mar 2009
Posts: 669
Rep Power: 22
Lance is on a distinguished road
Quoting Glenn:
Quote:
Originally Posted by ghorrocks View Post
The names for all variables are described in the CFX Reference manual, in the chapter titled "Variables in ANSYS CFX". You will find the velocity magnitude can be accessed as either "vel" or "Velocity".
vel or Velocity is the velocity in each finite volume. The volume is, as you already found out, Volume of Finite Volumes or volcvol. They are described in the above mentioned section of the reference manual.
Lance is offline   Reply With Quote

Old   September 22, 2016, 06:41
Smile
  #14
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Wow. Thank you Lance on that.
I l try that in 'Pre', and come back with update.

Thank you.
kastarkas is offline   Reply With Quote

Old   September 26, 2016, 04:13
Smile
  #15
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Hello everyone,

With all the help from the thread, I think I moved a bit ahead. Thanks a lot for that.

Last edited by kastarkas; September 27, 2016 at 08:52.
kastarkas is offline   Reply With Quote

Old   October 3, 2016, 01:44
Unhappy
  #16
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Hello friends, i am doing the transient analysis of the same problem.....I am having a problem here....
setup is MRF, transient rotor stator interface.., additional variables and source terms....Time step : 0.0001 s, Total time : 0.02 s, 10 iterations per time step.

It comes around 180 time steps...and it crashed exactly at 104 previously...there was a "less storage space" message and i cleared out the space in the drive where the files are saved.

then i run again and i get the same message..

I have attached the image of the error as well...

Can somebody please fix this for me...

+--------------------------------------------------------------------+
| Writing transient file 105_full.trn |
| Name : Transient Results 1 |
| Type : Standard |
| Option : Every Timestep |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| write_compressed_dataarray: (fwrite failed) syserr:: No space lef- |
| t on device |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| iocnt: write data failed |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| WRITE_BLKS_SER: write data failed: what=G/MFLOIP_FL1 where=ZN1/ES- |
| 1 |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| Writing crash recovery file |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| write_compressed_dataarray: (fwrite failed) syserr:: No space lef- |
| t on device |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| iocnt: write data failed |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| WRITE_BLKS_SER: write data failed: what=G/COURANT_FL1 where=ZN1/V- |
| X |
| |
| |
| |
| |
+--------------------------------------------------------------------+

+--------------------------------------------------------------------+
| An error has occurred in cfx5solve: |
| |
| The ANSYS CFX solver exited with return code 1. No results file |
| has been created. |
+--------------------------------------------------------------------+

End of solution stage.

+--------------------------------------------------------------------+
| An error has occurred in cfx5solve: |
| |
| Error reported by IO module: write_index: warning: new index not |
| at end of file, file may be bad |
+--------------------------------------------------------------------+
Attached Images
File Type: jpg Capture.jpg (86.7 KB, 5 views)
File Type: jpg Capture1.jpg (101.2 KB, 4 views)
File Type: jpg Capture2.jpg (100.0 KB, 6 views)
File Type: jpg transient 2 error.JPG (37.9 KB, 6 views)
kastarkas is offline   Reply With Quote

Old   October 3, 2016, 03:42
Default
  #17
Senior Member
 
Lance
Join Date: Mar 2009
Posts: 669
Rep Power: 22
Lance is on a distinguished road
Quote:
Originally Posted by kastarkas View Post
there was a "less storage space" message and i cleared out the space in the drive where the files are saved.
[...]
then i run again and i get the same message..
[...]
Can somebody please fix this for me...

| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| write_compressed_dataarray: (fwrite failed) syserr:: No space lef- |
| t on device |
1) Buy a bigger hard drive
or
2) Run the simulation on another hard drive
or
3) dont save data as often.
Lance is offline   Reply With Quote

Old   October 3, 2016, 06:54
Smile
  #18
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
Thank you Lance on that..
So is this regarding the memory issue alone ? Does any other error messages have any other significance...?
kastarkas is offline   Reply With Quote

Old   October 4, 2016, 02:46
Default
  #19
Senior Member
 
Lance
Join Date: Mar 2009
Posts: 669
Rep Power: 22
Lance is on a distinguished road
The errors you presented in the last post all relate to writing data to disc, and that the disc is full.
Lance is offline   Reply With Quote

Old   October 4, 2016, 04:50
Smile
  #20
Member
 
kastarkas
Join Date: Aug 2016
Posts: 45
Rep Power: 10
kastarkas is on a distinguished road
OK lance.
I will do the needful regarding the memory and update right here as it is fixed.
Thanks a lot .
kastarkas is offline   Reply With Quote

Reply

Tags
blood damage, blood pump, haemolysis, particle tracking, residence time

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 18:13.