细长旋成体亚声速超大攻角非定常流动特性研究

空空导弹作为现代空战的主要攻击手段,要求比目标飞机更高的机动性和敏捷性.新型空空导弹在面对新一代飞机时必须具备全方位攻击能力,尤其对来自后方目标的威胁,则需要更高转弯率和更大机动包络线的航向反转机动等先进高效机动方法.为了保证高效机动的顺利完成,要求导弹在超大攻角(α=0°~180°)范围内具有飞行和机动控制能力.以往对超大攻角流动的观测和研究大多集中在α=40°~60°范围内,最大角度不超过90°.本文采用数值模拟(delayed detached eddy simulation,DDES)与风洞试验(油流显示试验)结合的方法,研究了细长体亚声速下(Ma=0.6)攻角α=0°~180°范围内的瞬时流动特性以及非定常特性.研究表明,数值模拟与油流显示试验获得的物面流线吻合较好,在攻角α=0°~90°范围内,细长体背风侧流动主要为圆柱段引起的集中涡主导,体现为非对称、非定常和涡脱落等流动现象;在攻角α=90°~180°范围内,这时细长体底部朝前,由此带来较大的回流区,回流区内存在较多小尺度旋涡相互作用干扰,随着流动逐渐沿轴向向后发展,背风侧流动逐渐以非对称涡流动为主导.非对称旋涡诱导的物面压力脉动频率St范围St=0.19~0.33,底部回流区诱导的物面压力脉动St范围为St=1.55~1.64.

基于流迹显示技术的前弯跨声速压气机叶栅通道三维流动测量

为了研究前弯跨声速压气机叶栅通道的三维流动状况,利用流迹显示技术,对不同攻角下的流动图谱进行了测量,并针对负攻角以及零攻角、正攻角工况提出了两种流动模型。研究表明,叶片表面层流的转捩形式与攻角无关,压力面均在前缘以旁路转捩形式完成转换,吸力面以层流分离泡形式完成分离转捩。在三维流动结构上,负攻角时流动较为简单,为前缘马蹄涡对、通道涡、吸力面尾缘处壁角涡构成的涡系结构;零攻角与正攻角时,还存在压力面前缘诱导角涡、压力面侧的通道诱导涡的涡系结构。此外,受吸力面尾缘集中脱落涡的影响,压力面尾缘出现了向前缘的回流,导致出现了鞍点三维分离特征线;且在压力面前缘诱导涡轴向流动的黏性与轴向逆压梯度作用下,压力面还出现了附着螺旋点与分离螺旋点的三维分离流动特征。

Test studies of gas flow in rock and coal surrounding a mined coal seam

An analysis of the variation rule of abutment pressure at the mining working face in a single coal seam and the mechanical behavior of surrounding rock during stoping is presented. Consideration of the elastic and plastic deformation zones that develop during the mining process allowed the determination of a relationship between horizontal stress and vertical stress. Based on this, a confined pressure unloading test was conducted by the use of the ＂gas-containing coal tbermo-fluid-solid coupling 3-axis servo seep- age＂ experimental apparatus. Thus, gas flow patterns in the elastic and plastic zones were derived from an experimental point of view. Darcy＇s law and the Klinkenberg effect were used to derive a gas flow equation for the elastic and plastic stress fields. The study of gas flow phenomena at the working face during coal mining is of great importance for the study of gas migration and enrichment patterns.