Method and apparatus for ascertaining the magnitude and direction of the flow speed in a flowing medium

摘要

The invention relates to a method for determining the magnitude and direction of the flow speed in a flowing medium comprising the following steps: (a) Irradiating the flowing medium in a first direction with a laser beam of a defined cross-section having a maximum principal dimension; (b) Observing a defined position (measured volume) in the longitudinal extent of the laser beam in a second direction at a defined angle to the first direction; (c) Measuring the pulse duration of diffuse light pulses given off in the second direction by particles of a defined size contained in the flowing medium and passing through the measured volume; and (d) Turning the laser beam cross-section about the rotary axis defined by the first direction until diffuse light pulses of maximum pulse duration can be observed. By means of this method one obtains in a single measuring operation an indication of the magnitude and direction of flow in the plane formed by the laser beam and the flow direction.