涡流发生器控制喷水推进器进水管流动分离的数值研究

Numerical Study of Flow Separation Control in Waterjet Intake Duct by Vortex Generator

关键词:  喷水推进  涡流发生器  流动控制  流动分离  流向涡

Key words:  Waterjet propulsion  Vortex Generator  Flow control  Flow separation  Streamwise vortex

摘要:

为抑制某型喷水推进平入口进水管低进速比下管内流动分离，提升喷射泵来流的品质，应用涡流发生器（VG）流动控制技术，在进水管内部以及入口前的船底加装涡流发生器。采用雷诺时均模型和SST k-ω湍流模型数值模拟进水管内流场，从流动分离、涡系分布和整体性能等方面分析了不同位置VG对进水管流场特性的影响，揭示了VG抑制进水管流动分离的控制机理。结果表明，VG产生流向涡驱动主流与斜坡侧边界层低能流体进行动量交换，增加边界层内的流向动量，从而抑制进水管斜坡侧的流动分离。流向涡在分离区内会发生方向偏移导致进水管内流场不对称。VG在进水管内产生的流向涡强度以及自身附加损失都会影响其控制效果。通过优选VG安装位置，进水管出口的不均匀度系数从0.406下降至0.318，旋流度从3.23°下降至2.14°，出口总压畸变减小，整体效率得到有效提升。

Abstract:

In order to suppress the flow separation in the submerged intake duct for a waterjet propulsion system at low Inlet Velocity Ratio （IVR） and improve the quality of the flow entering the jet pump， the vortex generator （VG） flow control technology is applied to install vortex generator inside the intake duct and at the bottom of the ship in front of the entrance. Flow’s Reynolds-averaged Navier-Stokes equations （RANS） are solved with the SST k-ω turbulence model to simulate the flow field inside the intake duct. The effects of vortex generator at different positions on the flow field characteristics of the intake duct are analyzed from the aspects of flow separation， vortex distribution and overall performance. The flow control mechanism of vortex generator suppressing the flow separation is revealed. The results show that the streamwise vortex generated by the vortex generator induce the momentum exchange between the mainstream and the low-energy fluid in the boundary layer on the ramp side， which increases the streamwise momentum in the boundary layer to suppress the local flow separation on the ramp side. When the streamwise vortex moves through the separation zone， it deflects leading to the asymmetry of the flow field in the intake duct. However， for the intake duct， the strength of the streamwise vortex and the extra loss of the vortex generator will affect the control effect. Through optimizing the installation position of VG， the uniformity coefficient of the intake duct outflow decreases from 0.406 to 0.318， the swirling angle decreases from 3.23° to 2.14° and the total pressure distortion is reduced， and the overall efficiency is improved.