Thermal Imaging for Discharge and Velocity Measurements in Open Channels

Thermal imaging cameras are powerful tools for measuring the temperature distributions on the surfaces of water bodies. The velocity distribution of a water surface can also be determined by recording the motion of the water surface temperature distribution with a thermal imaging camera and then applying particle image velocimetry (PIV) methods to sequential thermal images to obtain the velocity distribution. In this paper we discuss field and laboratory measurements of velocity distributions in open channel flows using a thermal imaging camera. The laboratory measurements are relatively simple comparisons of measured and calculated velocities for flows in a 71-cm wide channel with actively heated water surfaces. The field measurements include measurements of water velocity in a large power canal from an oblique camera angle with variations in image resolution. The oblique images are rectified and analyzed to determine velocities in the canal. The surveying and rectification processes are described in the paper, and resulting velocity