水下航行体俯仰运动微气泡流形态及减阻特性试验研究

为研究水下航行体俯仰运动过程中，微气泡流形态及减阻特性的变化规律，采用自主设计的驱动装置、高速摄像系统和测力系统，在水洞中开展水下航行体俯仰运动微气泡减阻特性试验研究。基于该驱动装置，实现了航行体模型以正弦变化规律的角速度绕其头部转动；基于高速摄像系统，分析了微气泡流形态变化特性；基于测力系统，分析了俯仰运动过程中水下航行体流体动力特性及不同通气量下微气泡减阻特性变化规律。试验结果表明：较低通气量下，在水下航行体俯仰运动过程中，离散的微气泡始终均匀分布在航行体表面；随着通气量的增加，微气泡流密度逐渐增加，透明度逐渐降低，并最终融合成透明空泡；航行体俯仰运动过程中，其航行体轴向力系数和法向力系数基本呈正弦变化规律，且其周期与攻角变化周期基本同步；不同通气量下航行体轴向力系数的变化规律基本相同，均呈正弦变化规律，且随着通气量的增加，相同姿态下的航行体轴向力系数逐渐减低，并最终趋于恒定。

Experimental Study of Microbubble Flow and Drag Reduction Characteristics of Underwater Vehicle in Pitching Movement

To study the characteristics of the microbubble flow and the drag reduction characteristics of the underwater vehicle in the pitching movement, the water tunnel experiments were conducted with a self-designed driving equipment, a high speed camera and a six-component force balance. The driving equipment can rotate the underwater vehicle around its head at a sinusoidal regular angular velocity.The characteristics of microbubble flow are analyzed based on the high-speed camera system, and the hydrodynamic characteristics of underwater vehicle and the variation of microbubble drag reduction characteristics in maneuvering process are analyzed based on the six-component force balance. The results show that the discrete microbubbles are always evenly distributed on the surface of underwater vehicle when the air injection rate is low. As the air injection rate increases, the density of the microbubble flow gradually increases and the transparency gradually decreases. The discrete microbubbles are eventually coalesced into transparent cavities. During the pitching movement, the axial and lateral force coefficients of the underwater vehicle are basically sinusoidal, and the periods are basically synchronous with the changing period of attack angle. The variation of the axial force coefficients at various air injection rates is basically the same, which are all sinusoidal. With the increase in the air injection rate, the axial force coefficient of vehicle under the same posture decreases gradually and eventually becomes constant.