高超声速绕平板直立舵干扰气动热研究

针对激波/边界层干扰引起的气动热问题,在中国科学院力学研究所JF12复现高超声速飞行条件激波风洞中开展了大尺寸平板/圆柱形直立舵干扰的气动热实验,热流测量采用E型同轴热电偶,同时开展了相应工况的三维数值模拟.研究结果表明,舵体干扰区存在的流动分离再附现象导致热流分布存在双峰结构,热流峰值出现在舵体前缘0.2倍舵体直径处,为无干扰时的19倍;舵体前干扰区以马蹄涡形状向后发展

高超声速流场激光测速技术研究进展

高超声速气流条件下飞行器内/外部流动中存在强湍流及脉动、边界层转捩、激波-边界层干扰和高温真实气体效应等耦合效应,表征该非定常流动现象对飞行器气动力、气动热以及目标光电特性等产生的影响是高超声速流动研究中的前沿课题.速度作为表征流动过程最重要的参数之一,准确的速度测量对于深入理解上述复杂流动-传输机理以及高超声速飞行器设计具有重要指导意义.本文主要针对高超声速流场速度测量中几种常用的非接触式激光测试技术进行了综述,主要包括基于空间法的粒子图像测速,基于激光吸收光谱、激光诱导荧光和瑞利散射的多普勒测速,基于飞行时间法的分子标记测速,以及基于流场折射率的聚焦激光差分干涉测速技术.本文首先简要介绍每种激光测速技术的基本原理,然后进一步介绍该技术在高超声速自由流、层/湍流边界层、激波/边界层干扰、尾流或其他复杂流动区域的速度及其脉动度测量等方面的典型应用,分析各种技术环境适用性及面临的局限性和挑战.最后对基于激光技术的高超声速流场速度测量进行了总结及发展趋势展望

激波风洞7°尖锥边界层转捩实验研究

高超声速边界层转捩对摩阻、传热等有重要影响,飞行器的研制迫切希望能精确预测和控制边界层转捩。在JF8A激波风洞中开展了7°半锥角的高超声速尖锥边界层转捩实验研究,利用响应频率达到1 MHz量级的高频压力传感器对尖锥壁面脉动压力进行了测量,并结合热流测量结果,研究了高超声速尖锥边界层中扰动波的发展过程。实验结果表明:JF8A激波风洞在雷诺数为6.4×106/m状态下核心流的自由流噪声为2.8%;高频脉动压力测量技术能清晰地捕捉转捩过程中的第二模态波及其发展历程,试验状态下模型的第二模态波频率范围为165～206 kHz。当前研究结果能够为高超声速数值方法验证提供数据支撑

激波风洞7°尖锥边界层转捩实验研究

高超声速边界层转捩对摩阻、传热等有重要影响,飞行器的研制迫切希望能精确预测和控制边界层转捩。在JF8A激波风洞中开展了7°半锥角的高超声速尖锥边界层转捩实验研究,利用响应频率达到1 MHz量级的高频压力传感器对尖锥壁面脉动压力进行了测量,并结合热流测量结果,研究了高超声速尖锥边界层中扰动波的发展过程。实验结果表明:JF8A激波风洞在雷诺数为6.4×10~6/m状态下核心流的自由流噪声为2.8%;高频脉动压力测量技术能清晰地捕捉转捩过程中的第二模态波及其发展历程,试验状态下模型的第二模态波频率范围为165~206 kHz。当前研究结果能够为高超声速数值方法验证提供数据支撑

激波风洞7°尖锥边界层转捩实验研究

高超声速边界层转捩对摩阻、传热等有重要影响,飞行器的研制迫切希望能精确预测和控制边界层转捩。在JF8A激波风洞中开展了7°半锥角的高超声速尖锥边界层转捩实验研究,利用响应频率达到1 MHz量级的高频压力传感器对尖锥壁面脉动压力进行了测量,并结合热流测量结果,研究了高超声速尖锥边界层中扰动波的发展过程。实验结果表明:JF8A激波风洞在雷诺数为6.4×10~6/m状态下核心流的自由流噪声为2.8%;高频脉动压力测量技术能清晰地捕捉转捩过程中的第二模态波及其发展历程,试验状态下模型的第二模态波频率范围为165~206 kHz。当前研究结果能够为高超声速数值方法验证提供数据支撑

传感器安装对平板气动热测量精度的影响

对高超声速飞行器来说,气动热的准确预测是其合理选择防热材料及热结构设计的重要依据,但目前在激波风洞试验中气动热的高精度测量仍较为困难,热流的测量精度受到诸多非理想因素的影响,但传感器安装对热流测量精度的影响却鲜见研究。选取平板模型来研究传感器非理想安装对气动热测量精度的影响,针对不同的传感器安装偏差(凸出或凹入模型表面0.1～0.5 mm),分析不同雷诺数下传感器安装对气动热测量精度的影响规律及机理。研究结果表明:传感器安装对气动热测量精度有较大影响,凸出安装会导致热流测量结果偏大,而凹入安装则会导致测量结果偏小,热流偏差会随着安装偏差的增大而增大,且高来流雷诺数下传感器非理想安装所引起的热流误差更大;以边界层当地厚度对凹凸程度无量纲化,非理想安装带来的测量偏差只与该无量纲参数相关。研究结果能够为气动热测量的实验方案设计及测量误差分析提供一定的理论指导

Evolution of heat transfer at the stagnation point during the detached bow shock establishment

The diffraction of a shock wave over a stationary body is a problem of interest associated with the starting of shock tubes and expansion tubes which are well suited to studies of hypersonic flows. However, these facilities are characterized by very short test times. The transient parameters during the establishment of the detached bow shock in such impulsive facilities are important for both data processing and experimental design. In the present study, numerical simulations are conducted to investigate the diffraction of a normal shock wave over a sphere and the subsequent transient phenomena in a viscous perfect-gas flow field. The incident shock Mach number ranges from 3 to 5 with a specific heat ratio of 1.4. Based on the theoretical description of the reflected shock position during bow shock formation, approximate solutions for the time histories of the stagnation-point heat flux are also derived. The analytical and numerical results agree well. The results show that the stagnation-point pressure and heat flux approach their steady-state values much more rapidly than the shock detachment distance does

Investigation of dual ignition for a detonation-driven shock tunnel in forward driving mode

A detonation-driven shock tunnel is useful as a ground test facility for hypersonic flow research. The forward detonation driving mode is usually used to achieve high-enthalpy flows due to its strong driving capability. Unfortunately, the strong detonation wave front results in diaphragm fragments that disturb the test flow and scratch the nozzle or test models. In this study, a dual ignition system was developed to burst a metal diaphragm without fragmentation in the forward driving mode. A series of experiments were conducted to validate the proposed technique. The influences of the delay time setting on the test conditions were investigated in detail. Numerical simulations were also conducted to obtain a better understanding of the wave processes in the shock tube. The results showed that the dual ignition system solved the diaphragm issues in the forward driving mode. The test time was shortened due to the additional ignition close to the primary diaphragm; the smaller the delay time, the shorter the effective test time. However, a small amount of time loss is considered worthwhile because the severe diaphragm problems have been solved. (C) 2020 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd