Abstract: Real time measurement of the motion of a rigid mobile structure in a fluid is achieved by a device comprising at least four unaligned bright spots arranged in a predetermined way on the structure under observation and at least two synchronized video cameras which are arranged with respect to a fixed point. The dimensions of each bright spot are such that the image of each bright spot is intercepted at the focal plane of each camera by about five to fifteen scanning lines. The processing and computing device provides the following functions: collection of the image coordinates of points whose brightness exceeds a certain predetermined level; counting and memorization of these coordinates and of the lengths of the segments of the bright spots intercepted by the scanning lines; calculation of the image coordinates of the barycenters of the bright spots and, finally, calculation of the three-dimensional coordinates of these barycenters to the fixed point.

Abstract: A hydrodynamic test apparatus including a model support which comprises a submerged frame equipped with rollers and resting on the bottom of a tank is disclosed. A removable plate is attached to the top of the frame and a linear induction motor is attached to the side of the frame. The linear induction motor is supplied with current by conductor rails affixed to the bottom of the tank.