Chaotic stirring in a new type of mixer with rotating rigid blades

The present study suggests a new conceptual apparatus that can be used to stir fluids at low velocities. This consists of a circular container equipped with one or two blades arranged along the perimeter which drive the fluid motion. It modifies a previous apparatus in which fluid was driven by two flexible belts, which is more difficult to implement in experiments. Using the new device, fluid can be stirred completed with very high fluid stretch-rates in a short time. This could not be obtained in the previous studies by the belts. Based on extensive computations, the greatest averaged fluid stretch-rate is created by rotating two blades of lengths 3π/4 and π/2, with the second blade actuated at a frequency ten times higher than the first blade. When only one blade is employed, shorter periods are beneficial to stirring of fluid and produce higher fluid stretch-rates.