The Bernoulli effect in horizontal granular flows

The Bernoulli effect that commonly occurs in continuous fluids is simultaneously increasing a fluid's velocity and decreasing static pressure or the fluid's gravitational potential energy. Although, the Bernoulli effect has already been extensively explored, there is a lack of research on the relationship between flow velocity and pressure in a discrete medium. In the present study, this relationship in horizontal granular flows excited by vertical vibration is experimentally studied. It was found that the random motion and horizontal directed motion of the granules restrict each other so that the total pressure remains almost constant with respect to time and height. In fact, it implies that the Bernoulli effect occurs in the granular flows. It was also found that the pressure constant of the Bernoulli effect depends on the vibrating intensity and frequency, which reflects the energy transfer in the granular flows. Our results show a dynamic property of the granular flows, which is different from continuous fluids, even though it is similar to some extent.