Learning Forum

[chuminhkhue]

I analyze a computational model that represents thrombus formation in a straight channel.
I want to conduct the reaction pathway using the UDF file.
To mathematically implement biochemical species and reactions using the computational fluid dynamics package FLUENT.
picture below of the biochemical network represented in model of blood coagulation. 
Q1:The species of blood are X, TF, Xa‐Va, TH, V, INACT, and AT. How to define species in Fluent know that species include diffusion coefficient and initial concentration.
Q2: After defining "the species source term ????_???? ([????_???? ]" by UDF file, how to apply it to the convection diffusion reaction equation (????[????_???? ]/????????+(???? ⃗.????)[????_???? ]=????_???? ????^2 [????_???? ]+????_???? ([????_???? ]))?

[Rob]

Initial concentration would be patch and/or a boundary condition. The species mixture can handle diffusion, and the flow solver the convection. Reaction rates can be chemistry based (Arrhenius rates), or you can code up a sink/source approach using Expressions or UDFs. 

Have you reviewed and completed the relevent sections of Learning and solver tutorials? Note, you may not find a specific set of material but will instead need to take portions of several pieces of content. 

[chuminhkhue]

my question is how to create The species of blood are X, TF, Xa‐Va, TH, V, INACT, and AT, with species including diffusion coefficient and initial concentration (in this case, the species are paticles in blood). need to be set before setting the boundary condition.

[chuminhkhue]

Thank expert. I am going to continue the analysis.

[Rob]

Yes. Add the species and then alter the mixture. You also need to decide if blood is a single fluid with species or a multiphase slurry: that will alter how you set up the mixture(s). 

[chuminhkhue]

Can I make a UDF that shows a liquid turning into a solid when it reaches the threshold?
After that, Ansys Fluent describes the behavior in two ways (fluid <-> solid formed) step by step. 
Could you tell me the tool suitable for it?

[Rob]

Solid as in particles or solid as in freezing? We can do both, but the approach and outcome may be very different. 

[chuminhkhue]

 

Step 1: To conduct a simulation for a liquid to turn into a solid when it reaches the threshold.
Step 2: Ansys Fluent describes the behavior in two ways (fluid <-> solid formed) over time.
Could you explain more details about this? Because I’m newbie, it’s hard to understand everything you said

 

[Rob]

OK, very simple particles will flow, ie are carried with the fluid. A "solid" in the CFD sense is a big lump of stuff that won't move without a lot of coding. In blood I'd expect a small clot to be a particle; anything bigger may not need modelling as it's likely to be immediately fatal! 

[chuminhkhue]

Could you tell me the setup procedure for thrombosis by the solidification method in Ansys Fluent?
Species moving in blood vessels under blood flow.
Thrombosis (TH) is sticky to blood vessels.

[Rob]

I can advise on solver side but am limited on advising on how to do physics. If you manage to figure out the full thrombosis mechanism I suspect you'll get a PhD as a minimum.

In terms of simulation, going from fluids to dispersed solids would be handled by the Eulerian or Mixture reactions (phase change); population balance may then give you options to grow the agglomerations. 

[chuminhkhue]

 

My problem is that I have different “reaction rates” for each type.(mi)
I want to define ” reaction rate.” 
Could I just apply the “volume reaction rate” by the UDF file for all reactions? without editing reactions in the material. Will macros overwrite the default reaction rate?
I don’t want to define it by reaction finite rate.
Could you tell me how to do that and if it is suitable for ansys fluent?

 

[Rob]

Pass, what does the UDF say/do for the reactions? 

[chuminhkhue]

 

I define the “reaction rate” products of different types of species