TAGGED: udf
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October 25, 2024 at 4:16 amchuminhkhueSubscriber
I am trying to solve the transport equation for a user-defined scalar (UDS) representing the number of particles in a single-phase flow, with velocity at the inlet and zero pressure at the outlet. The flux function I am using is the mass flow rate.
At the inlet, the particles are released at a rate specified as the number of particles per unit area per unit time (flux). The inlet concentration of RP is 2.5 × 10^14 particles/m³ and the inlet concentration of AP is 1.25 × 10^13 particles/m³.
I am defining the specific flux at the inlet as:
-1 × UDS diffusivity × grad(UDS) ⋅ n
with units of kg/(m⋅s) × particles/m³ × m⁻¹.
i conduct it by ufd profile like this
When I apply this specific flux model, my simulation crashes. However, when I set a specific value of 2.5 × 10^14 for RP and 1.25 × 10^13 for AP at the inlet, it runs but I am unsure if it is working correctly.
Can you help me understand why the specific flux model causes the crash and whether I am correctly setting up the boundary conditions for the UDS?
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October 29, 2024 at 3:04 pmRobForum Moderator
If you're using scalar gradients have you told Fluent to retain all values? Can't remember the exact term off hand, but there's a TUI command to avoid some gradients etc being discarded following their use in the calculations. It'll be covered in the Scalar bit of the manual if it's necessary.
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October 29, 2024 at 4:14 pmthamilmaniSubscriber
/solve/set/expert no no yes no
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October 30, 2024 at 4:48 amchuminhkhueSubscriber
Thanks for your reply
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