Sharif Digital Repository

Efficient mixing, typically characterised by chaotic advection, is hard to achieve in low Reynolds number conditions because of the linear nature of the Stokes equation that governs the motion. Here we show that low Reynolds number swimmers moving in quasi-periodic orbits can result in considerable stretching and folding of fluid elements. We accurately follow packets of tracers within the fluid domain and show that their trajectories become chaotic as the swimmer's trajectory densely fills its invariant torus. The mixing process is demonstrated in two dimensions using the Quadroar swimmer that autonomously propels and tumbles along quasi-periodic orbits with multi-loop turning trajectories.... 

Recent advances in the field of microfabrication have made the application of high-throughput microfluidics feasible. Mixing which is an essential part of any miniaturized standalone system remains the key challenge. This paper proposes a geometrically simple micromixer for efficient mixing for high-throughput microfluidic devices. The proposed micromixer utilizes a curved microchannel (spiral microchannel) to induce chaotic advection and enhance the mixing process. It is shown that the spiral microchannel is more efficient in comparison to a straight microchannel, mixing wise. The pressure drop in the spiral microchannel is only slightly higher than that in the straight microchannel. It is...