What is causing my thermal lattice Boltzmann model to neglect the source term when trying to simulate a one-phase Stefan problem involving phase change?

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There could be several reasons why the thermal lattice Boltzmann model is neglecting the source term in simulating a one-phase Stefan problem involving phase change. Here are a few possible causes:

1. Misconfigured boundary conditions: The source term in the Stefan problem arises due to the heat source/sink associated with the phase change. If the boundary conditions are not set correctly, the model may fail to incorporate the source term in the energy equation, leading to inaccurate results.

2. Inappropriate choice of relaxation time: In the thermal lattice Boltzmann model, the relaxation time controls the rate of energy transfer between the fluid particles. If the relaxation time is too large, the simulation may not capture the fast dynamics associated with the phase change, and the source term may be neglected.

3. Insufficient resolution: The thermal lattice Boltzmann model requires a fine spatial and temporal resolution to accurately simulate the phase change phenomenon. If the resolution is not adequate, the model may overlook the source term.

4. Inadequate implementation of energy equation: The energy equation in the thermal lattice Boltzmann model is often more complex than the fluid dynamics equations, and may require special care in its implementation. If the energy equation is not implemented correctly, the source term may be neglected.

5. Model limitations: Finally, it is possible that the thermal lattice Boltzmann model being used may not be suitable or accurate enough to capture the full dynamics of the phase change, leading to neglect of the source term.