基于数值计算方法的矢量合成射流激励器推力特性研究

合成射流激励器具有体积小、质量轻、结构简单、对流体外形影响小等优点,非常适合用于水下机器人的驱动及姿态调节。文章设计了一种矢量合成射流激励器,该激励器的出口是柔性的,采用线驱动方式实现出口偏转角度的连续调节,进而实现推力的矢量控制。建立了用于控制激励器出口偏转角度的数学模型,以及激励器作用力的数学模型。采用有限体积法对该矢量合成射流激励器在不同偏转角度下的流场进行了数值计算,流场设定为三维、粘性、非定常和不可压流场,给出了不同偏转角度下激励器在各个方向上的作用力变化曲线。通过对作用力的计算结果进行分析发现,合成射流的推力比相同质量流量下稳态射流的推力提高50%。另外,还发现激励器各方向作用力的合力基本不随偏角发生改变。结合文中建立的激励器作用力数学模型进行分析,可知合成射流的推力增强效应主要是由激励器外部流体的阻滞作用引起的。

Study on the force characteristics of a vectored synthetic jet actuator based on numerical method

Synthetic jet is a new type of underwater propulsion method with the merit of small size, light weight and high efficiency, all of which makes it a good choice for the propulsion and steering of underwa-ter robots.In this paper,a vectored synthetic jet actuator with a flexible jet nozzle is proposed. The deflec-tion angle of the flexible jet nozzle can be adjusted continuously by the differential actuation of 3 ropes. The actuation model of the flexible jet nozzle and the mathematical model of the propulsion force are es-tablished. The 3D, unsteady, viscosity and incompressible flow-field of the vectored jet actuator with dif-ferent deflection angle is analyzed by using finite volume method. It can be seen that the propulsion effi-ciency of synthetic jet is 50% higher than the normal steady jet by the analysis of the force results of the numerical computation. It can also be seen that the resultant force of different directions keeps unchanged despite the variation of the deflection angle of the flexible jet nozzle. Combined with the mathematical model established in this paper the conclusion that the high efficiency of the synthetic jet is mainly caused by the resistance of the outflow of the actuator can be drawn.