A method and apparatus for measuring flow parameters of an unknown fluid uses four pressure sensors at fixed, spaced locations within a cylindrical member having a constricted and a full diameter portion. The constricted portion has a smooth surface of transition at its entry, internal corrugations, and a sharp increase to the full diameter at its exit. There are no moving parts. All flow parameters can be calculated from the four pressure measurements taken at the entry and exit of the constricted portion and two aligned but separated locations spaced from the sharp increase to full diameter.