Surface Water Channel Research Articles

The design of a multi‐purpose multi‐component strain gauge dynamometer

The design, construction and calibration of a multi‐purpose multi‐component strain gauge dynamometer is described. The dynamometer was constructed for use with a free surface water channel, which can also be used as a water tunnel or a cavitation tunnel. In this experimental facility, the large speed range available (0·03 to 6·1 m/s) and the variety of projects encountered require the measurement of a wide range of loads in several different configurations. The dynamometer system has been based on a unit block concept so that the blocks can be assembled into a suitable configuration and complexity of components to suit each particular problem.The basic design concept is described together with the calibration results and the magnitude of the interactions. It is concluded that the overall accuracy of the dynamometer blocks and the absence of interaction coupled with the versatility of the system confirm the choice of the original design.

Flow over a rough surface

NOTE: text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. An experimental investigation was conducted on the flow over a rough surface. The roughness consisted of sets of square cavities ranging in size from 1/8 to 1 in. The flow over this series of roughness was observed for a range of [...] values from 11 to 260. The quantity [...] may be regarded as a Reynolds number for the roughness and it is the essential parameter governing the flow over the roughness elements. It is defined as [...] where [...] is the cavity depth, [...] is the shear velocity, and [...] the kinematic viscosity of the fluid. The desired approaching flow was obtained in an open surface water channel at free stream velocities of from 0.1 to 0.75 ft/sec. The velocity profile showed the characteristics of a turbulent boundary layer. The velocity measurements necessary to determine the profile were obtained by means of a hot film anemometer. Visualization of the flow in the cavities lead to the classification of five characteristic flow types or modes. The observations could be described consistently in terms of these modes and as a function of [...]. At values of [...] below 100 different mode forms appeared periodically and large disturbances of the fluid within the cavity were noted. This type of flow had not been observed previously. At values of [...] beyond about 200 a rather stable vortex formed in the cavities, as had been reported by previous experimenters. Some possible effects of the flow behavior on heat transfer are discussed. Photographic materials on pp. 106-150 are essential and will not clearly reproduce on Xerox copies. Photographic copies should be ordered.