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What does outer radius mean in DPM solid cone injection? |
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March 7, 2023, 05:09 |
What does outer radius mean in DPM solid cone injection?
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#1 |
New Member
Jasir Jawad
Join Date: Jul 2022
Posts: 4
Rep Power: 4 |
I am simulating injection of water droplets into a body of superheated steam. I have noticed in the DPM injections point properties, that the user may specify mass flowrate, velocity and radius as well. If this outer radius is the radius of the injector, then isn't it redundant to specify both the velocity and the radius? Or is the outer radius something completely different?
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March 7, 2023, 06:20 |
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#2 |
Senior Member
Alain Islas
Join Date: Nov 2019
Location: Mexico
Posts: 142
Rep Power: 6 |
According to Ansys Fluent User Manuel, you'll find the following
A nonzero inner radius can be specified to model injectors that do not emanate from a single point. Set the radius (defined as shown in Figure 23.3.4) in the Radius field. The particles will be distributed about the axis with the specified radius. |
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March 7, 2023, 06:26 |
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#3 | |
New Member
Jasir Jawad
Join Date: Jul 2022
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Rep Power: 4 |
Quote:
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March 7, 2023, 06:32 |
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#4 |
Senior Member
Alain Islas
Join Date: Nov 2019
Location: Mexico
Posts: 142
Rep Power: 6 |
Yes, I'd set the radius to zero (or a very very small number). Regarding the other question, I don't see a reason to think that there is a dependency between the radius and the velocity of the injection. Why do you think so?
Just be cautious with velocity and mass flow rate, these are independent parameters. Keep in mind that in DPM, the mass flow rate is NOT a continuous mass flow rate (i.e., m_dot = rho*A*velocity is not valid). In DPM, the mass flow rate is discrete, and has nothing to do with the velocity that you input in the setup panel |
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March 7, 2023, 06:45 |
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#5 | |
New Member
Jasir Jawad
Join Date: Jul 2022
Posts: 4
Rep Power: 4 |
Quote:
I understand that the mass flow is discrete for DPM. The mass is injected at each time step based on the total mass flow rate specified. But in terms of design, it is difficult to understand how to achieve the specified velocity without changing the mass flow rate or the diameter/radius of the injector. Anyway, thank you for your help. |
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March 7, 2023, 07:16 |
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#6 |
Senior Member
Alain Islas
Join Date: Nov 2019
Location: Mexico
Posts: 142
Rep Power: 6 |
For the DPM mass flow rate calculation, you can refer to any of my old posts in the Ansys Fluids Forum
https://forum.ansys.com/forums/topic...ion-speed-m-s/ https://forum.ansys.com/forums/topic...tal-flow-rate/ https://forum.ansys.com/forums/topic...les-injection/ https://forum.ansys.com/forums/topic/regarding-dpm-2/ |
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March 7, 2023, 08:12 |
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#7 | |
New Member
Jasir Jawad
Join Date: Jul 2022
Posts: 4
Rep Power: 4 |
Quote:
I have specified 9 injection points (solid cone injection) each with 60 streams. My timestep is 0.005 s. What will be the #particles/second or number of particles per stream? |
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March 8, 2023, 20:37 |
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#8 |
Senior Member
Alain Islas
Join Date: Nov 2019
Location: Mexico
Posts: 142
Rep Power: 6 |
For better assistance, please provide a snapshot of your DPM injection panel
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Tags |
cone injection, dpm, fluent, injections |
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