FLUENT UDFs for Non-Equilibrium Heat Transfer in Porous Media (Two-Energy Model)

FLUENT UDF manual might not explicitly mention using two temperatures together in a single User Defined Function (UDF). However, there are ways to achieve the non-equilibrium heat transfer with a two-energy model using UDFs. Here's how you can approach it:

1. Define UDFs for Source Terms:

Create separate UDFs for the source terms in both the solid and fluid energy equations. In these UDFs, you can access the following information:

• Cell-centered Variables: You can use C_CENTROID(c,t) to get the current time step values for various variables at the cell centroid, including fluid temperature (C_T(c,t)) and other relevant properties.
• Custom User Defined Memory (C_UDM): This allows you to store and access data from previous time steps. You can define separate UDFMs for solid and fluid temperatures from the previous time step (e.g., C_UDM(c,T_SOLID_PREV) and C_UDM(c,T_FLUID_PREV)) and update them within the UDFs.

Ansys Convection Simulation Slowdown: Dropping CPU Usage (Solid-Fluid Interaction)

 "Slowdown During Convection Simulation in Ansys Workbench"

It's a common challenge to experience slowdowns in Ansys simulations, especially for complex problems involving both solid and fluid bodies with convection. Here are some potential reasons why your CPU usage might be dropping and the simulation slowing down:

1. Convergence Issues:

• The most likely culprit is the solver struggling to converge to a solution. As the simulation progresses, the solution might become more complex, requiring smaller timesteps and more iterations to achieve convergence. This can lead to a decrease in CPU utilization as the solver spends more time calculating with smaller steps.

2. Time Stepping Issues:

• The automatic time stepping algorithm might be adjusting to very small steps as the simulation progresses, leading to unnecessary calculations and reduced efficiency.

Ansys Workbench Setup for Heat Distribution Analysis

Here's some guidance for your setup in Ansys Workbench:

Solver:

For this heat transfer problem involving conduction only, you should use the Steady-State Thermal solver within Ansys Workbench. This solver focuses on situations where the temperature doesn't change with time.

Boundary Conditions:

Troubleshooting Patchy Water Film in Discrete Phase Model (DPM) Coupled with Eulerian Wall Film (EWF) CFD

 There are a few possible reasons why  cloud map might be showing a granular distribution for the water film thickness when using a coupled DPM-EWF model:

1. Particle Size Discretization: In the DPM, you likely define a range of particle sizes to represent the water droplets. This discretization can lead to a blocky or granular appearance in the cloud map, especially if the range is large or the number of size classes is small.

2. Limited Resolution: Cloud maps often have a limited number of cells to represent the solution space. If the water film is thin or the cloud map resolution is coarse, you might see a patchy or granular distribution instead of a smooth film.

3. Turbulent Fluctuations: If you're simulating a turbulent flow, the water film thickness may fluctuate due to the turbulent eddies. These fluctuations can be captured by the DPM and reflected as a granular distribution in the cloud map.