A Periodically Reversed Flow Driven by a Modulated Traveling Magnetic Field: Part I. Experiments with GaInSn

This study examines a liquid GaInSn metal flow generated by a magnetic field whose traveling direction is periodically reversed, the reversed traveling magnetic field. The modulation frequency ranges from 0 to 6 Hz. Ultrasonic Doppler velocimetry probes the generated fluid flow. First, we investigate the flow generated by a 50 Hz traveling magnetic field without any modulation. It appears that the mean velocity field consists of a main recirculation loop associated with two small end vortices. The turbulent character of the flow is confirmed by Fourier analysis. Then, depending on the modulation frequency, a number of characteristic flow features are exhibited. A transition frequency (approximately 4 Hz) exists, above which the flow is no longer sensitive to the force modulation. Below this transition point, the amplitude of the velocity oscillation increases, and then below fm = 0.05 Hz, it saturates around a value close to that observed without any modulation.