Hi all,

In my CFD study of a fluidized bed reactor (using ANSYS Fluent), I observed that the system reaches a pseudo-steady state around t = 350s. For a parametric study, I want to evaluate the effect of changing certain operating conditions (e.g., coke content, inlet O₂ %, or temperature).

I’m considering two options:

1. Run a full transient simulation for each case (e.g., 350s + 35s with new parameters)

2. Run a single base case simulation to 350s, then modify operating conditions and simulate just the next 35s for each new case.

The second option would significantly reduce computational cost. However, I’m wondering if this is physically valid, especially when the parameter change is moderate.

Question:

Is it acceptable in CFD practice to change operating conditions mid-run (e.g., after 350s) to study system sensitivity? Are there any potential pitfalls (e.g., residual effects or nonphysical transients) I should watch for when using this approach?

Any insights or experiences would be greatly appreciated.

Thanks!