Particle Image Velocimetry (PIV)

Particle Image Velocimetry" is an imaging measurement method used to determine the velocity field in a flow. A typical measurement setup consists of a pulsed laser with light sheet optics, a camera and a computer, which is used both to synchronize the individual components and to evaluate the measurement results in a computer-intensive manner. Since the light scattered by the flow is absorbed by the camera, it is usually necessary to add particles to the flow. The particles must have as good a flow sequence as possible and must not influence the flow itself so that the measurement results are not distorted. As a result, small particles with an average diameter of approx. 1 µm are used, which requires the use of a powerful laser. By exact synchronization of laser and camera it is achieved that two pictures with a short time interval Δt can be taken one after the other. In the next step, the displacement of the particles from one exposure to the next is determined from these image pairs using a suitable correlation method. Together with the known time interval Δt between the individual exposures, the flow velocity is finally calculated from this.