Flow conditioner

A flow conditioner comprising an apertured circular plate intended to be placed in a conduit in an orientation substantially perpendicular to the axis of the conduit, wherein the apertures are circular and are arranged in an inner array of apertures adjacent a central aperture and an outer array of apertures adjacent the inner array said inner array including n apertures said outer array including m apertures, the plate having a diameter D, the centers of the apertures of the inner and outer arrays being located on circles of diameter D.sub.1 and D.sub.2 respectively, the central aperture having a diameter d.sub.1, the apertures of the inner and outer arrays having diameters d.sub.2 and d.sub.3 respectively, and the array radii and aperture diameters being related in accordance with:

• nd.sub.2 D.sub.2 >md.sub.3 D.sub.1,
• the center of the central aperture and the centers of the circular arrays coincide with the center of the circular plate, the apertures in each circular array are equally spaced apart around the center of the plate, all the apertures in any one circular array are of substantially the same diameter, and the size and number of apertures in the circular arrays are such that the impedance to flow presented by the plate increases with the radius on which a given array of apertures is arranged.