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首页> 外文会议>AHS International Annual Forum vol.2; 20070501-03; Virginia Beach,VA(US) >THE NATURE OF VORTEX RING STATE
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THE NATURE OF VORTEX RING STATE

机译：涡环状态的性质

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摘要

A framework for understanding vortex ring state (VRS) is outlined and a simple flight model for vertical descent is developed. At low forward speed, when descent rate is sufficient to reverse the rotor wake trajectory, the rotor blade tip vortices begin to organize in stable, recirculating patterns beneath the rotor disk. With increased descent rate, the pattern transitions into a ringlike structure that passes through the rotor plane and settles above the rotor disk where stable flight conditions can once again exist. In VRS, the organized wake elements act as an equivalent single vortex ring that dominates the descending rotor's inflow field. The self-induced velocity of the vortex ring is the propulsive mechanism that allows the vortex ring to lead or follow the descending rotor. Simultaneously, the ring's self-induced velocity field increases the rotor's inflow in spite of the descent rate. Inflow always reduces the blade's effective angle of attack, leading to thrust loss with the absence of blade stall. An established vortex ring can only propel itself in a single axial direction. A curved flight trajectory therefore precludes VRS. This principle is the governing mechanism that allows a maneuvering rotorcraft to suppress VRS.
机译：概述了理解涡环状态（VRS）的框架，并开发了用于垂直下降的简单飞行模型。在低的前进速度下，当下降速度足以使转子尾流轨迹反转时，转子叶片尖端的涡流开始以稳定的，再循环的形式组织在转子盘下方。随着下降率的增加，模式转变为环形结构，该结构通过转子平面并停留在转子盘上方，在那里可以再次存在稳定的飞行条件。在VRS中，有组织的尾流元件起着等效的单个涡流环的作用，主导着下降转子的流入场。涡流环的自感应速度是一种推动机制，它使涡流环能够引导或跟随下降的转子。同时，尽管下降率下降，环的自感应速度场仍增加了转子的流入量。流入始终会减小叶片的有效攻角，从而在叶片失速的情况下导致推力损失。建立的涡流环只能在单个轴向方向上推动自身。因此，弯曲的飞行轨迹排除了VRS。该原理是允许机动旋翼飞机抑制VRS的控制机构。

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