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A ribbon mixer (sometimes referred to as a ribbon blender) is a mechanical device that is commonly used to mix different types of granular material. Ribbon mixers are widely used across various industries including food processing, pharmaceuticals, chemical industries, agriculture, cosmetics, plastics etc.

A ribbon mixer typically consists of a U-shaped trough with a rotating central shaft along its length. The central shaft has helical ribbons (blades) attached to it that helps in mixing the material. Mixing in a ribbon mixer is complex phenomenon and is affected by several factors including the material and contact properties of the grains and the walls, filling level of the trough, rotational speed etc. The design of the ribbons can also have a significant impact on the types of mixing behavior, and their efficiencies. One common class of ribbon mixers involve the use of two ribbons of different diameters, commonly referred to as a double ribbon mixer. The inner and outer helical ribbons often have opposing handedness. This promotes axial mixing as the ribbons push the grains along different axial directions.

This example uses the Granular Flow interface to model the filling of a U-shaped trough with two types of grains, followed by their mixing induced by the rotational motion of the ribbons. This model also shows the use of a Bounding Box feature to avoid scenarios that may adversely affect the performance of the Granular Flow interface. The extent of the overall mixing is quantified by the evaluation of the Kramer mixing index. An additional indicator of the extent of axial mixing is also demonstrated.