Numerical simulation for the propulsive performance of a submerged wiggling micromachine

The effect of the Reynolds number on the propulsive performance of a micromachine wiggling in water is analysed numerically. The micromachine, whose geometry is similar to an NACA65-010 hydrofoil, is set in a straight conduit. The wiggling motion is expressed by a progressive wave with reference to the swimming motions of fish. The flow around the micromachine is analysed by using a two-dimensional finite element method. The Reynolds number, Re, ranges from 1 to 100. The analysis reveals that the decrement in Re deteriorates the propulsive performance, and that marked deterioration occurs at Re < 10. The decrement in the thrust force is caused by the increment in the skin friction, and the increment in the power is attributable to the increase of the work against the pressure around the micromachine. The flow induced by the wiggle motion reduces with decreasing Re.