The Outlet Is Open, Yet the Wave Comes Back — NSCBC and the Price of σ
·9 min read
At σ = 0 a duct reflects 0% and keeps a +0.30 pressure offset; at σ = 0.25 the reflection is 1.9% and the offset drops to 0.0007.
How to Make an Outflow Stop Reflecting Sound — Navier–Stokes Characteristic Boundary Conditions
·6 min read
A six-hour LES drifted 0.3 bar because the outlet reflected sound. NSCBC sets the incoming wave with σ near 0.25 so acoustics leave and the mean holds.