机身减速板流动特性研究

摘要

This paper studies the characteristics of the hinge moment of the fuselage airbrake at the opening angle of 60° with the fuselage angles of attack from 0° to 70°,analyzes the flow structures on the windward side and the leeward side of the airbrake.The experimental results show that the characteristics of the hinge moment can be classified into three regions with α.In the constant region (α=0°～16°),the hinge moment of the airbrake changes little with α increasing,because the positive pressure decreases on the windward side of the airbrake and the negative pressure increases on the leeward side of the airbrake with α increasing,two opposite trends counteract with each other.In the nonlinear increasing region (α=16°～32°),the hinge moment of the airbrake increases greatly with α increasing,because the hinge moment is mainly contributed from the leeward side of the airbrake and the negative pressure increases markedly on the leeward side of the airbrake with α increasing due to the enhanced couple vortices on the leeward side of the airbrake.In the nonlinear decreasing region (α=32°～70°),the hinge moment of the airbrake decreases greatly in the range of 32°～36° because the vortices flow on the leeward side of the airbrake turns to a low speed reattachment flow at α=36°; the hinge moment of the airbrake increases in the range of 36°～44° because the positive pressure on the windward side of the airbrake increases greatly due to the enhanced forebody vortices flow; the hinge moment of the airbrake decreases gradually in the range of 44°～70° because the pressure values on the windward side of the airbrake decreases gradually due to the weakened forebody vortices flow.%现役高机动战斗机普遍采用机身减速板来减小飞行速度和转弯半径并提高机动能力.采用物面测压及空间流场测量相结合的实验方法,在机身减速板开度60°,机身迎角O°～70°条件下,研究了机身减速板铰链力矩随迎角的变化规律,分析了减速板迎风侧和背风侧的流动结构.研究结果表明:减速板铰链力矩按迎角可分为3个区域:常值区(α=0°～16°),减速板铰链力矩基本不变,因为减速板迎风侧正压力逐渐减小,而背风侧负压力逐渐增加,两种相反的变化趋势相互抵消.非线性增长区(α＝16°～32°),减速板铰链力矩显著增加,因为减速板铰链力矩主要贡献区为背风侧,该迎角区内减速板背风侧存在一对不断增强的旋涡,背风侧负压力显著增加.在非线性衰减区(α=32°～70°),减速板铰链力矩在迎角32°～36°范围内急剧减小,因为在迎角36°减速板背风侧旋涡流动变为速度较低的再附流动；减速板铰链力矩在迎角36°～44°范围内逐渐增加,因为该迎角区作用于减速板迎风侧的机身涡不断增强,导致减速板迎风侧正压力显著增加；减速板铰链力矩在迎角44°～70°范围内逐渐减小,因为该迎角区作用于减速板迎风侧的机身涡不断减弱直至破裂,导致减速板迎风侧正压力逐渐减小.