Adverse Effects of Using Laser Diagnostics in High-Speed Compressible Flows

这项建议侧重于研究激光诊断可能对高速可压缩流动产生的不利影响。目标是两个广泛的诊断领域：基于粒子的方法和光谱方法。利用粒子图像测速仪(PIV)进行的颗粒-气体相互作用可以导致高速流动中动量和能量的快速交换，并改变主要的气体动力学特征，如激波。与平面激光诱导荧光(PLIF)相关的气体播撒和与飞秒激光电子激发和标记(LEFT)相关的离解(LEFT)也可以改变返回舱流动近尾迹中的分离。虽然气体-颗粒和气体-激光相互作用可能会对流动产生不利影响并导致测量不确定，但该计划将利用这些机制来改进航空航天系统，包括进气口、热保护和流量控制技术。 使用激波风洞，将分析两个典型的案例，以评估任何不利的诊断影响：欠膨胀的喷嘴和圆柱体。人工流动响应将在输入如颗粒负载水平、种子气体流量和激光能量水平变化时被监测。假设在欠膨胀射流中，颗粒冷却比颗粒阻力对马赫盘位置的影响更大。并假设唇激波边界层相互作用区附近的气体播撒和激光能量沉积将扰动圆柱尾迹附近的自由剪切层，并移动分离点(影响底压和热负荷)。通过正在进行的为期7年的合作，使用舰队和PLIF的6马赫和10马赫实验将在NASA兰利的圆柱壳体上进行。结果将与卡尔加里大学的脉冲设备测量结果进行比较。计算流动成像(CFI)将被用来预测和修正预计将发生的有害气体-颗粒和气体-激光相互作用。CFI和实验将被用来评估如何使用冷却颗粒来改善超音速进气性能，以及如何使用气体播撒和激光能量沉积来控制再入舱后体的流动。 该程序预计将对将更传统的激光诊断技术扩展到高马赫数流以及量化一些新的诊断方法的一般局限性产生很大影响。所选的典型问题涉及火箭推进、高超声速吸气推进、再入空气动力学、导弹和高速弹道学。在激光诊断、数值模拟、风洞实验和航空航天技术领域培训高素质的人员(HQP)是加拿大知识经济增长的宝贵成果。

This proposal focuses on studying the adverse effects that laser diagnostics can have on high-speed, compressible flows. Two broad diagnostic areas are targeted: particle-based and spectroscopic methods. It is expected that particle-gas interactions, which occur with particle-image velocimetry (PIV), can lead to rapid exchanges of momentum and energy in a high-speed flow and alter major gas-dynamic features, such as shock waves. It is also expected that gas seeding associated with planar laser-induced fluorescence (PLIF) and dissociation associated with femtosecond laser electronic excitation and tagging (FLEET) can also alter the separation in the near wake of a re-entry capsule flow. While gas-particle and gas-laser interactions can adversely alter the flow and lead to measurement uncertainty, these mechanisms will be exploited in this program to improve aerospace systems including intakes, thermal protection, and flow-control technologies. Using a shock tunnel, two canonical cases will be analyzed to assess any adverse diagnostic effects: the under-expanded jet and circular cylinder. Artificial flow responses will be monitored as inputs such as particle loading level, seed gas flow rates, and laser energy levels are varied. It is hypothesized that there are conditions where particle cooling has a larger effect than particle drag on displacing the Mach disk location in an under-expanded jet. It is also hypothesized that gas seeding and laser energy deposition near the lip-shock boundary-layer interaction region will perturb the free shear layer in the near wake of the circular cylinder and move the point of separation region (affecting base pressure and heating loads). Through an on-going 7-yr collaboration, Mach 6 and Mach 10 experiments using FLEET and PLIF will be performed at the NASA Langley on the circular cylinder case. Results will be compared to the impulse facility measurements at the University of Calgary. Computational flow imaging (CFI) will be used to both predict and correct for the unwanted gas-particle and gas-laser interactions that are expected to occur. CFI and experiments will be used to assess how cooled particles can be used to improve supersonic intake performance and how gas seeding and laser energy deposition can be used for flow control on the aft-bodies of re-entry capsules. This program is expected to have a large impact on extending more conventional laser diagnostics to high Mach number flows as well as to quantify the limitations of some newer diagnostics in general. The canonical problems chosen are relevant to rocket propulsion, hypersonic air-breathing propulsion, re-entry aerodynamics, missiles, and high-speed ballistics. Training of highly qualified personnel (HQP) in the area of laser diagnostics, numerical simulation, wind tunnel experiments, and aerospace technologies is a valuable output to grow Canada's knowledge-based economy.