Author(s): Rosaria Ester Musumeci; Vincenzo Marletta; Carla Faraci; Bruno Ando; Salvatore Baglio; Enrico Foti
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Keywords: Magnetofluids; Rosensweig effect; Flow resistances; Bed stresses; Bottom velocities
Abstract: A novel direct measurement strategy of bottom velocities and shear stresses based on the use of ferrofluids is presented. The proposed methodology is aimed at overcoming some of the limits of state-of-the-art instruments, for use in both turbulent conditions and in the presence of sediments. A preliminary experimental campaign has been carried out in steady conditions to test the effects of ferrofluid quantity and controlling permanent magnetic force as a function of the fluid velocities. An alternating current (AC) and a direct current (DC) conditioning circuits have been tested. The results have shown that there is a low sensitivity operating condition, when the ferrofluid is fully within the viscous sublayer. For velocities larger than 10 cm/s, the velocity-output voltage calibration curve has a monotone parabolic shape, which clearly proves a relationship between ferrofluid deformation and the bottom shear stresses. The sensitivity of the instrument is increased by a factor of 30 when the DC circuit is used.
Year: 2013