Apparatuses and methods that reduce cavitation in interaction chambers are described herein. In an embodiment, an interaction chamber for a fluid processor or fluid homogenizer includes an inlet chamber having an inlet hole and a bottom end, an outlet chamber having an outlet hole and a top end, a microchannel placing the inlet hole in fluid communication with the outlet hole, wherein an entrance to the microchannel from the inlet chamber is offset a distance from the bottom end, and at least one of: (i) a tapered fillet located on a side wall of the microchannel at the microchannel entrance; (ii) a side wall of the microchannel converging inwardly from the inlet chamber to the outlet chamber; (iii) a top wall and/or bottom wall of the microchannel angled from the inlet chamber to the outlet chamber; and (iv) a top fillet that extends around a diameter of inlet chamber.