A device for inhalation of at least one air stream carrying a dose of medicament powder is provided. The device includes a flow passage passing a powder-containing cavity. A part of said flow passage propagates along a generally flat surface region. The flat surface region includes a cavity opening into said powder-containing cavity. The passing of an air stream along said flat surface region and outside said cavity generates an eddy in the cavity and the generated eddy contributes to deaggregation of the powder in said cavity and emptying of the powder from said cavity. Furthermore, a shear driven cavity principle is used in conjunction with such a device and a method of releasing medicament powder.