[qyv]

I am no means an expert, but from my understanding you are only partially correct. Betz's law essentially says that because the velocity of the fluid exiting the cross section of the turbine is lower than the velocity or the fluid entering, the exiting fluid must consume more volume, and that their is a calculable limit to that difference. If these devices are in fact using vortices/turbulent airflow to induce resonance then perhaps different rules apply to the amount of energy that can be extracted?