In connection with pneumatic micrometers, the outward flow characteristics of narrowly spaced radial-flow nozzles are studied with analytical methods. Assuming that fluids are incompressible and the velocity distribution in a boundary layer is parabolic, the momentum equation of a laminar boundary layer is solved approximately. Thus it becomes possible to calculate theoretically the inlet length, the velocity distribution in the clearance, the pressures at various radii or the pressure loss of any nozzle. As a corresponding value to the Reynolds number, in this case, R=Vh²/νr₁ should be used, where h is the breadth of a clearance, r₁ is the inner radius of a nozzle and V is a radial mean velocity at r₁. Then profiles of pressure and velocity distributions are determined by R only.