方案摘要
方案下载应用领域 | 其他 |
检测样本 | 其他 |
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参考标准 | 暂无 |
采用德国LaVison公司的粒子成像测速PIV系统对喷嘴产生的跨声速流场的速度矢量场进行测量记录。测量系统由2kX2k像素CCD相机。光谱物理公司的PIV-400型双腔双脉冲激光器构成。激光器输出能量为350毫焦/脉冲。同时在远场对喷嘴产生的声场进行测量,分析研究等离子体主动控制喷嘴对湍流结构和声场的影响规律。
Localized arc filament plasma actuators were used to control an axisymmetric Mach 0.9 jet with a Reynolds number based on the nozzle exit diameter of 7:6 105. Eight actuators, distributed azimuthally inside the nozzle, near the nozzle exit, were used to excite various instabilities and azimuthal modes of the jet over a large Strouhal number range (StDF of 0.1 to 5.0). Time-resolved pressure measurements were used to investigate the development of
actuation perturbations in the jet, particle image velocimetry measurements were used to evaluate the control effects on the turbulence field, and far-field sound was measured to evaluate the control effects on the radiated acoustic field.The jet responded to the forcing over a large range of excitation Strouhal numbers with varying degrees. As expected,
the low Strouhal number seeded disturbances grew slowly, saturated farther downstream, and stayed saturated for a longer time before decaying gradually. The saturation and decay of the seeded perturbations moved farther upstream as their Strouhal number was increased. Seeded perturbations with higher azimuthal modes exhibited faster decay. Particle image velocimetry results showed that when exciting the jet’s preferred-mode instability at lower azimuthal modes, the jet potential core was shortened and the turbulent kinetic energy was increased significantly. At higher Strouhal numbers and higher azimuthal modes, forcing had less of an impact on the mean velocity and turbulent kinetic energy. Far-field acoustic results showed a significant noise increase (2 to 4 dB) when the jet is excited around the jet’s preferred-mode instability Strouhal number (StDF 0:2–0:5), in agreement with the results in the literature. Noise reduction of 0.5 to over 1.0 dB is observed over a large excitation Strouhal number range; this reduction seems to peak around StDF 1:5 to 2.0 at a 30-deg angle, but around StDF 3:0 to 3.5 at a 90-deg angle. Although forcing the jet with higher azimuthal modes is advantageous for noise mitigation at a 30-deg angle and lower Strouhal numbers, the effect is not as clear at higher forcing Strouhal numbers and at a 90-deg angle.
在一个双稳湍流涡旋火焰中,对间歇性动态的时间-频率定位
Particle-laden Taylor-Couette流:高阶转变和径向局部波浪涡旋的证据
7根杆束的流体-结构相互作用:用实验数据对比数值模拟
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