[Angkon]

Hi, I want to acquire concentration profile(concentration gradient) iodine injected into blood within left coronary artery, here iodine is the passive scaler and I only need to consider advection diffusion through blood i.e. non-reactive process.
Here boundary conditions that are applied for blood flow are:
1) No slip boundary condition at artery wall,
2) Pulsatile velocity and pressure profile at inlet and outlet respectively, using udf.

I am confused how to define the passive scaler or which module should I use : CFX or Fluent, what should I use multiphase or multispecies or user defined scaler or 'the species option in fluent'. how do I define the source of the scaler what mole fraction should I use?

Thank you in advance.

[Siba11]

Hey. You can use both CFX and Fluent.

Although, I have personally used Fluent. You don't need to use any multiphase models. Just define a UDS (User Defined Scalar) and track its concentration inside your domain.

To define the UDS source, you can go into the "cell zone conditions", and activate the UDS Source term.

[Angkon]

Originally Posted by Siba11

Hey. You can use both CFX and Fluent.

Although, I have personally used Fluent. You don't need to use any multiphase models. Just define a UDS (User Defined Scalar) and track its concentration inside your domain.

To define the UDS source, you can go into the "cell zone conditions", and activate the UDS Source term.

Thank you for your response,
can you provide any reference or tutorial for setting up this model. or provide any uds code reference?
I would be grateful.

[Angkon]

should I include flux function for convection?

[Siba11]

To begin with, we first need to switch ON the user-defined scalar transport equations. (UDS transport equations). This UDS will act as a passive tracer that will flow with the fluid. Since it is ‘passive’, it will not affect the velocity or pressure variables.
Flux Function solves for the convection term (and should be chosen ‘mass flow rate’).
Unsteady Function should be set to ‘default’ to incorporate the transient terms in the CDR equation. The source term will be added from the ‘cell zone condition’. The diffusion term is handled in the ‘Materials’ dialog box under uds-per-diffusivity.

The UDS transport equation has been set up, and this scalar can be accessed via the macro C_UDSI(c,t,0).

[Angkon]

Originally Posted by Siba11

To begin with, we first need to switch ON the user-defined scalar transport equations. (UDS transport equations). This UDS will act as a passive tracer that will flow with the fluid. Since it is ‘passive’, it will not affect the velocity or pressure variables.
Flux Function solves for the convection term (and should be chosen ‘mass flow rate’).
Unsteady Function should be set to ‘default’ to incorporate the transient terms in the CDR equation. The source term will be added from the ‘cell zone condition’. The diffusion term is handled in the ‘Materials’ dialog box under uds-per-diffusivity.

The UDS transport equation has been set up, and this scalar can be accessed via the macro C_UDSI(c,t,0).

do i need to add source term in the udf and is injection rate necessary?

[Chhotelal1234]

For the moisture transport, We have to define UDSI inside a User define function depending on which phase we have chosen, such that if we choose the gas phase then Xf = C_UDSI (c, t, 0) should be written like this.
Am I right or wrong?