Pressure on the conical surface of needle valves

Author investigated needle valves in their basic geometry, with conical needle body inserted into the entrance of a sharp-edged cylindrical exit channel. Investigations of two alternative geometries having 90 and 60° included angles were made with scaled-up laboratory model provided with large number of pressure tap holes on the surfaces - together with numerical flowfield computations. Effect of Reynolds number was found generally weak, but variations of the needle lift caused significant changes in the character of the flowfield, with typical three local pressure extremes. A newly observed phenomenon is flow separation from the surface of the cone near its tip.