超音速シンセティックジェットアクチュエータを用いた乱流生成

抄録

We have developed an experimental appratus that generates turbulent flow in a rectangular chamber by the interaction of a group of supersonic synthetic jets, each of which is generated by a piston/cylinder actuator driven by a motor. The four actuators are placed on two opposite sides of the chamber, and the supersonic jets are repeatedly ejected into the chamber from the jet holes on the top of the cylinder. The jets are ejected through either sharp-edged orifice or convergent-divergent nozzle. Shadowgraph visualization and particle image velocimetry (PIV) are used to investigate the characteristics of the generated turbulent flow field. The temperature increase due to the pistons causes the evaporation of engine oil inside the actuators. The PIV uses oil mist that is generated by condensation in the chamber when the hot jets with oil vapers are mixed with cold air. In the shadowgraph visualization, it was found that strong density fluctuations associated with small-scale vortices exist in the flow. For both orifices and convergent-divergent nozzles, the turbulent Reynolds number at the center of the chamber reaches about 1000. The relation between the turbulent Reynolds number and velocity derivative flatness is consistent with previous studies on incompressible turbulence. Although the supersonic jets are repeatedly ejected from two sides of the chamber, strong inhomogeneity due to the jets is not observed near the center of the chamber.