## Fluids

#### DDPM Granular injection question

• pws137
Subscriber

Hello,

I have several questions about the Eulerian DDPM model. Unless I am confused on the definition of certain parameters, it seems that controlling the diameter, velocity, injection area, and total mass flow rate of the particles for a surface injection is redundant and leads to my simulation diverging. By controlling the surface of injection region and the velocity, is selecting the total mass flow rate not redundant?

I can answer further questions if need be.

-Thanks.

• Rob
Ansys Employee

Why is a boundary condition (injection) redundant? Please post an image of what you're trying to do, along with where the flow and/or particles enter the domain.

• DrAmine
Ansys Employee
? Not clear.
• pws137
Subscriber

Folks, essentially my question is basically if (mass flow rate  = Density * Area * Velocity), during a surface injection in an eulerian density discrete phase model, how does controlling the injection and phase for density, velocity, and the plane of injection not over-define the injection? I am trying to model a solid + liquid slurry flow. I am open to further questions if needed. Thanks.

• DrAmine
Ansys Employee
No mass flow rate has nothing to do with that is just how much mass per time are you feeding into the system
• pws137
Subscriber
Anime forgive me if it sounds that I’m growing impatient I really do appreciate the quick response time but by definition the equation for mass flow rate is m ?•V just consider the units and the result is kg/s. So if one is to control for how many kilograms is entering the system per second, as well as the density, velocity, and surface of injection (essentially the area), how is that not a overdefined boundary condition that would lead to divergence?

If my question is still confusing I can post pictures of the flow phenomenon I’m modeling. I’m sure I did not find an error in FLUENT and that I’m not smarter than the program, but if I’m trying to create an injection of solid particles into a flow, it seems confusing to me why I could control for mass flow rate and the velocity and area of the injection.

Thanks
• DrAmine
Ansys Employee
You define the settings for the Lagrangian phase in the injection panel. You there provide mass flow rate and velocity of the injected particles. Both inputs are independent of each other.