Diffuser profile

Heinz Wilkening

I like to have an oscillating static pressure along a small channel. As the channel size is rather small as well as the flow velocity (about 1mmx1mm cross-section and airflow of about 10 m/s), I will have laminar flow. To obtain the oscillating pressure my idea was to have repeated decreasing (nozzle) and decreasing (diffuser) channel width. If I use simple sin-function as channel width profile, I get separating flow where the channel with is increasing, which is not very efficient. Can anybody direct me to better profile for such a diffuser?

Thanks for your help! Heinz