Flow Field around Swimming Mosquito Larvae

Unlike most natural swimmers, larvae of mosquitoes swim tail first where the posterior end of the body leads the anterior end. To achieve this mosquito larvae display a high amplitude, side-to-side flexural motion of their body. Their body size and swimming speed also put them in an intermediate Reynolds number regime (1<Re<2000) where both inertial and viscous forces are likely dominant. This study experimentally investigates the hydrodynamics of tail-first swimming in mosquito larvae through Particle Image Velocimetry (PIV) analysis. Analysis of the velocity and vorticity field around the larvae revealed the presence of jets and favourable pressure gradient near the head and tail of the larvae at about mid-stroke which are likely responsible for the generation of thrust

Onset of instability of a flag in uniform flow

AbstractThis paper numerically and analytically studies the onset of instability of a flag in uniform flow. The three-dimensional (3D) simulation is performed by using an immersed-boundary method coupled with a nonlinear finite element method. The global stability, bistability and instability are identified in the 3D simulations. The Squire's theorem is extended to analyze the stability of the fluid-flag system with 3D initial perturbations. It is found that if a parallel flow around the flag admits an unstable 3D disturbance for a certain value of the flutter speed, then a two-dimensional (2D) disturbance at a lower flutter speed is also admitted. In addition, the growth rate of 2D disturbance is larger than that of the 3D disturbance

Red blood cell partitioning and blood flux redistribution in microvascular bifurcation

AbstractThis paper studies red blood cell (RBC) partitioning and blood flux redistribution in microvascular bifurcation by immersed boundary and lattice Boltzmann method. The effects of the initial position of RBC at low Reynolds number regime on the RBC deformation, RBC partitioning, blood flux redistribution and pressure distribution are discussed in detail. It is shown that the blood flux in the daughter branches and the initial position of RBC are important for RBC partitioning. RBC tends to enter the higher-flux-rate branch if the initial position of RBC is near the center of the mother vessel. The RBC may enter the lower-flux-rate branch if it is located near the wall of mother vessel on the lower-flux-rate branch side. Moreover, the blood flux is redistributed when an RBC presents in the daughter branch. Such redistribution is caused by the pressure distribution and reduces the superiority of RBC entering the same branch. The results obtained in the present work may provide a physical insight into the understanding of RBC partitioning and blood flux redistribution in microvascular bifurcation

Numerical study on the power extraction performance of a flapping foil with a flexible tail

10.1063/1.4905537Physics of Fluids27