Investigation of the DBD Plasma Effect on Flat Plate Flow

Particle image velocimetry experiments and simulations were conducted in this study to clarify the influence of the DBD plasma actuator on the flow over a flat plate. The result shows that the actuator not only effectively leads to a local rise in near-wall velocity, but also efficiently causes a decrease in the displacement thickness of the boundary layer. Actuator-induced vorticity is generated to intensify the energy exchange between the main flow and the boundary layer, and dynamic energy is thus added directly to the low-energy fluid by the actuator. Although the increase in fluid velocity also brings a rise in dynamic energy loss, the energy added by the actuator can cover this to provide growth in the energy of the boundary layer. The plasma actuator presents a better performance when the free-stream velocity is lower.     

不同发射深度下喷管燃气射流特性研究

为了探索发射水深对发动机水下点火流场特性的影响机制,该文数值研究了不同水深条件下发动机水下点火时实验喷管气水两相流场的非定常演化过程.研究结果表明:射流初期,高密度水介质对喷管出口高温燃气泡强剪切流具有阻滞作用,导致了流场中的压力以及射流产生的推力波动比较剧烈;随着射流的发展,流场中的压力及射流产生的推力波动趋于平缓,波动幅值与频率也随之降低;喷管推力随工作水深的增加而减小,并且推力随时间的变化规律与喷管进口燃气总压变化趋势一致.     

Numerical Study of Fluid Dynamics and Heat Transfer Induced by Plasma Discharges

A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid dynamics.The effects of the applied voltage on the distribution of velocity and temperature in initially static air are parainetrically studied.Furthermore,the spatial structure of plasma discharge and the resulting force contours in streamwise and normal directions are discussed in detail.The result shows that the plasma actuator produces a net force that should always be directed away from the exposed electrode,which results in an ionic wind pushing particles into a jet downstream of the actuator.When the energy added by the plasma is taken into account,the ambient air temperature is increased slightly around the electrode,but the velocity is almost not affected.Therefore it is unlikely that the induced flow is buoyancy driven.For the operating voltages considered in this paper,the maximum induced velocity is found to follow a power law,i.e.,it is proportional to the applied voltage to the 3.5 power.This promises an efficient application in the flow control with plasma actuators.     

水溶性树脂在集装箱角件芯子上的应用

水溶性树脂在集装箱角件芯子上的应用无锡太平洋集装箱通用件有限公司（２１４２１６）俞建阳副总工程师集装箱角件是集装箱的关键部件，要求铸件内腔尺寸精度高，表面光洁，无气孔、夹砂等铸造缺陷．以往生产中，芯子采用水玻璃砂芯，内脏尺寸精度较低，尤其出砂极为困难...