Turbomachinery CFD — Compressors, Turbines & Pumps

How do you simulate rotation in turbomachinery CFD?

Two approaches: frozen rotor (mixing plane) keeps the mesh stationary using a rotating frame, swapping frames at rotor-stator interfaces — fast but misses unsteady interaction. Sliding mesh actually rotates the rotor mesh each time step, capturing unsteady effects at much higher computational cost.

What is tip clearance and why does it matter so much in compressors?

Tip clearance is the gap between blade tip and casing. High-pressure gas leaks backward through this gap, forming tip vortices that reduce efficiency. A 0.1mm change in clearance can shift efficiency by 0.5-1% in high-performance compressors. Accurately resolving it requires fine mesh and often adaptive methods.