## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### Problem with viscosity setting

• Han Jirayuthanyawat
Subscriber

Hi everyone

I'm currently trying to simulate a similar case to the paper attached for the scenario 1 "phantom" (figure 2,3) but in a 3D case. Just to summarize the paper and what I currently did, the paper is trying to replicate a disease called arteriovenous mulformation by a method called embolization which injects Onyx to block the "nodes" of the blood artery of the disease to put in simple terms. What the paper does is to simulate that by two fluid model (multiphase) of blood and onyx. The paper also uses scalar transport which is injected together and coexist with the onyx. The scalar transport represents a concentration of DMSO which will evaporate when in contact with blood resulting in increase viscosity of the onyx. So, smaller concentration of DMSO (Scalar) the higher the viscosity of onyx as given by the linear equation

u,onyx is the viscosity of Onyx at injection (0.018 kg/m/s), ysi(t) from [0,1] is the concentration of the scalar at the cell i at t seconds after injection of the embolic material and B is a dimensionless parameter controlling the maximum increase of viscosity during Onyx solidification (500).

What I did was using CFX with a 3D phantom of 25x3x6 cm and I have put in the given parameters of scenario 1. I have altered the inlet speed to 0.5 m/s instead of 0.15 m/s. I know that the results are not going to be similar because they're doing in 2D while I'm doing in 3D which is expected, but I still cannot replicate the the viscosity of the Onyx to have the same trend as theirs where the injected onyx needs to be more viscous than the inside chamber filled with blood (in my case the blood is more viscous than onyx). I was thinking about looking at the blood viscosity because the paper showed a range from 0.004 Pa s which is the blood viscosity, but then I set the dynamic of the blood as 0.004 Pa s which will not change over time. So, I'm not sure what I did wrong. If you need more information or clarification, please do let me know. Thank you.

Attached paper: Paper

my results for viscosity at 0.2, 0.6, 2.4 s respectively

PS. the value and flow doesn't have to be the same but the behaviour has to (meaning the same trend as fig 2). Also, if you need the output file I can provide but I don't know how to attach it in here. Sorry.

• CFD_Friend
Ansys Employee

Hi Han,

Please refer to CFX user guide as an initial resource. Here is the link to Multiphase modeling guidelines from CFX user guide https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/cfx_mod/i1384390.html?q=multiphase

We cannot access links and cas files through the forum as Ansys employees.

Best regards