Quasi-Steady Analysis of Impulse Turbine Under Reciprocating Flow

The impulse turbine, which is a part of an oscillating wave column, plays an indispensable role in wave energy conversion. In this paper, a self-rectifying impulse turbine has been investigated numerically under reciprocating flow and the quasi-steady analysis method of the turbine has been studied. Firstly, the numerical model was validated by corresponding experiment results. Then, the reciprocating flow condition was accurately simulated with the method of setting double velocity inlets. The results showed that there existed hysteretic loops in turbine performance curves. And different pressure drops in acceleration and deceleration led to this hysteretic characteristic. Finally, in order to investigate quasi-steady analysis method, the frequency and amplitude of the reciprocating flow were changed respectively and the results were compared with those of steady flow. It has been found that hysteretic loops are distributed around the curves of steady flow. When the frequency is lower or amplitude is smaller, the results of reciprocating flow are closer to those of steady flow. In conclusion, the performance of steady flow can be used to predict the performance of reciprocating flow with little velocity change in a short time, which reveals the feasibility of quasi-steady analysis method.

Reciprocating flow-assisted nucleic acid purification using a finger-actuated microfluidic device

A finger-actuated microfluidic reciprocator was developed and exploited to improve the recovery rate of nucleic acid purification in a finger-actuated microfluidic device.

Flume Test Simulation and Study of Salt and Fresh Water Mixing Influenced by Tidal Reciprocating Flow

The salt-fresh water mixing is one of the basic topics of estuarine dynamics research. In partially mixed and highly stratified mixed estuaries, the structure of stratified flow is complicated by density gradient and tidal reciprocating flow. The velocity and salinity structures have been experimentally studied in a flume which is 167.8m long, 0.5m wide, and 0.5m deep. The processes of the tidal levels, the flood and ebb current, and the salt-fresh water mixing have been simulated. Furthermore, the partially mixed and highly stratified mixed types have been repeatability showed in the flume, by solving the problems of experiment control and saltwater recycling. The control variable method has been used to dialectically analyze the influence of tidal range and runoff volume on the velocity and salinity distribution. The tide and runoff are respectively considered to affect the mixing type in two contradictory ways. In the condition of tidal reciprocating flow, the periodical change of interface stability has been investigated. It is considered that the interface stability is closely related to the vertical gradient of density and velocity. As a result, the critical value of interface stabilization has been presented. The experimental data and research results can be used for the basic study of estuarine dynamics and applied to practical problems such as estuarine saltwater intrusion.