Granular mixing is of great concern in different technological processes and different types of blending mechanisms might be used. For example, in the case of shear blenders, the material mixes while passing through a hopper, i.e. a constriction.

Considering that in many industrial applications, grains are horizontally transported at a constant rate (as on conveyor belts or floating on the surface of a flowing liquid, not much work has been reported in horizontal systems, in this work we study the mixing of grains (disks of diameter d = 8 mm) while driven periodically back and forth through a constriction in a horizontal oscillating frame. The system is composed of two square boxes of size 22 x 22 cm² connected by a slot of size D = 5cm. The ratio D/d >5 ensures a continuous flow without blockages.

We describe the different behaviors of granulates according to their locations in the boxes and quantify the blend of grains of equal size. Initially we start with an equal amount of black and white particles segregated at each side of the slot. Then, in each cycle, we measure a mixing index in both boxes and analyze its evolution during the mixing process, i.e. as a function of the number of oscillations. Finally, we analyze if a stationary blend and well mixed system might be achieved after successive oscillations for different oscillation amplitudes.