Numerical Study on the Performance of a Micropump with a Wiggling Blade

This study is concerned with the numerical simulation for the performance of a micropump having a wiggling blade. The blade is mounted on a straight conduit, and the wiggling motion is expressed by a progressive wave. The flow in the pump is simulated by the two-dimensional finite element method. The Reynolds number Re, based on the phase velocity of the progressive wave and the blade length, ranges from 10 to 150. The similarity for pump performance appears at Re ≥ 100. However, the pump performance deteriorates with decreasing Re at Re < 100. The time variation of the pump flowrate is found to be very small, demonstrating that the pump can deliver almost steady flow. The simulation also reveals the mechanism of the delivery as follows: The flow heading for the pump outlet occurs near the concave surface of the blade, and it is transported by the progressive wave to the blade trailing edge, and eventually, it is shed from the trailing edge.

Numerical study on the propulsive performance of a submerged wiggling micromachine in straight conduit

The propulsive performance of a submerged micromachine wiggling in a straight conduit is numerically analysed. The micromachine, whose geometry is similar to a hydrofoil, is mounted in a straight conduit of width W, and the wiggling motion is expressed by a progressive wave. The flow around the micromachine is simulated by a two-dimensional finite element method. The Reynolds number Re, based on the flow velocity upstream of the micromachine and the micromachine length L, is varied from 1 to 100, while the blockage ratio L/W is independently changed in the range of 0.36 ≤ L/W ≤ 1.25. The flow around the micromachine varies according to the wiggling motion, and it presents complicated behaviour owing to the large-scale eddies. The increment of L/W reduces the minimum pressure on the micromachine surface, while it increases the velocity near the micromachine. The propulsive performance is more affected by L/W at Re = 10 than at Re = 100. When L/W is increased in the case of Re = 10, the thrust force decreases at 0.36 ≤ L/W ≤ 0.81 and increases at L/W ≥ 0.81. The decrement is due to the increase of the skin friction, and the increment is attributable to the change in the pressure distribution. The lift force and the power become larger with L/W. The efficiency takes its minimum value at L/W = 0.81.

A Circular Magneto-Hydrodynamic (MHD) Micropump With Electrolyte Solution

Linear and circular magneto-hydrodynamic (MHD) micro-pumps that operate with electrolyte solutions were studied experimentally. Each pump consisted of a conduit with a square cross-section. The linear pump consisted of a straight conduit with its inlet and an outlet subjected to different pressures. The circular pump consisted of a conduit bent into a loop. Copper electrodes were aligned along the two opposite walls of the conduits. Experiments were carried out with various electrolyte solutions such as NaCl, FeCl2/FeCl3, and CuSO4 at various concentrations. The device was placed in a uniform magnetic field and a potential difference was applied across the electrodes. The resulting current interacted with the magnetic field to produce a Lorenz force that propelled the liquid. The electric current and the flow rate were measured as functions of the imposed potential difference across the electrodes, the electrolyte composition and concentration, and the adverse pressure head. The feasibility of using the closed-loop MHD pump to transfer heat from a heat source to a heat sink was also explored.

Numerical study on the propulsive performance of a wiggling blade in bubbly flow

In order to search for an efficient propulsion mechanism in an air-water bubbly flow, the propulsive performance of a blade wiggling in the bubbly flow is analysed by a two-dimensional numerical method. The blade, whose geometry is similar to an NACA65–010 hydrofoil, is set in a straight conduit, in which the bubbly mixture flows. The wiggling motion is expressed by a progressive wave with reference to the swimming motions of fish. The bubbly flow is calculated by an incompressible two-fluid model in conjunction with the finite element method proposed by the author in an earlier paper. The calculations reveal the effects of a progressive waveform and volumetric fraction of air upstream of the blade on the propulsive performance of the blade. The time variations of the flow properties around the blade are also discussed in relation to the blade motion and propulsive performance.