Abstract
The Ronchi-ruling is a grating, with lines, spaces and small pitches of spatial frequency. This is used in the Ronchi test for the evaluation of surface flatness. In this study, a new type of velocimeter, using a Ronchi-ruling, was proposed and its performances were investigated. When the stripes of laser light through a grid of the Ronchi-ruling illuminated the tracer particles moving with the flow, the scattered light signal could be obtained as a wavy signal of light intensity. This signal was detected with a photomultiplier. Frequencies of the obtained signal were measured by an FFT analyzer. The flow velocity was calculated from the grid pitch and the frequency. This method was applied to the measurement of velocity profiles of pipe flows. The profiles measured by this velocimeter agreed with theoretical profiles of the laminar and turbulent flows.
