The pressure-Poisson solver is built once per run and reused every step instead of being rebuilt, including its coarse-level LU factor, which profiling had put at 60-65% of each step on a wall-resolved LES duct. Results are bitwise identical to the previous solver. The continuity log's Sum(RHS) column is now Poisson Source Imbalance. The previous src/poisson.c, with its dormant immersed-boundary routines, is available at 53ba654 and earlier.