Exploration and Control of Transverse Jet Shear Layer Instabilities

横向射流剪切层失稳的探索与控制

• 批准号: 0457413
• 负责人: Ann Karagozian
• 金额: --
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0457413&HistoricalAwards=false
• 关键词: Exploration; Control; Transverse; Jet; Shear

PROPOSAL NO.: CTS-0457413PRINCIPAL INVESTIGATOR: A. KARAGOZIANINSTITUTION: UNIVERSITY OF CALIFORNIA-LOS ANGELES EXPLORATION AND CONTROL OF TRANSVERSE JET SHEAR LAYER INSTABILITIES The intellectual merits of this study involve an examination of the fundamental evolution of near field shear layer instabilities and the development of approaches in the control of such instabilities for the jet in crossflow, or transverse jet. This flow is related to many practical applications such as cooling in turbomachinery and jet engine combustors within which effective control could lead to significant improvements in efficiency and reductions in pollutant emissions. As the crossflow velocity increases and the jet transitions from the "free jet" to the "transverse jet", remarkable alterations in the spectral character of the instability have been observed under a prior NSF grant. The nature of this change in the stability characteristics suggests that at critical values of blowing ratio, there is a transition in the transverse jet from being convectively unstable to absolutely unstable or self-excited. Such stability characteristics may explain the transverse jet's ability to mix with surrounding gases in a superior manner to that of the free jet. These differences in the stability characteristics of the jet in crossflow suggest a strategic approach for future control studies in optimizing transverse jet penetration, mixing, and spread. This program will characterize the nature of these instabilities more completely, for a wide range of jet and crossflow conditions, through experiments, theory, and numerical simulations. The role of helical modes in the jet stability will also be explored and exploited in this control methodology. Feedback and feed-forward control will feature prominently in the temporal waveform shaping that is critical to this jet control approach, and will involve extensive testing and analysis. The proposed program has significant broader impacts, including involvement of undergraduate researchers. Outreach presentations and demonstrations will continue to be provided for local high school and, in the future, middle school students, with special focus on Girl Scout troops and students at public schools. Opportunities for local high school students to gain laboratory experiences in the summer will be provided. Cutbacks in funding by the state of California to the public schools' MESA (Mathematics Engineering Science Achievement) programs has made it even more important for universities such as UCLA to extend outreach programs to public middle schools and high schools as a means of encouraging the development of future engineers and scientists. The proposed project will afford an appropriate mechanism for this outreach to take place.

提案编号：CTS-0457413 主要研究员：A. 卡拉戈齐安 机构：加利福尼亚大学洛杉矶分校 横向射流剪切层不稳定性的探索和控制 这项研究的智力价值包括对近场剪切层不稳定性的基本演化的检验以及控制此类不稳定的方法的开发横流或横向射流中射流的不稳定性。 这种流动与许多实际应用相关，例如涡轮机械和喷气发动机燃烧室的冷却，其中有效的控制可以显着提高效率并减少污染物排放。 随着横流速度的增加以及射流从“自由射流”转变为“横向射流”，在先前的 NSF 资助下观察到不稳定性的光谱特征发生显着变化。 稳定性特性的这种变化的性质表明，在吹气比的临界值处，横向射流存在从对流不稳定到绝对不稳定或自激的转变。 这种稳定性特征可以解释横向射流以优于自由射流的方式与周围气体混合的能力。 横流射流稳定性特征的这些差异为未来优化横向射流穿透、混合和扩散的控制研究提供了一种战略方法。 该程序将通过实验、理论和数值模拟，针对各种射流和横流条件，更全面地描述这些不稳定性的本质。在这种控制方法中，还将探索和利用螺旋模式在射流稳定性中的作用。 反馈和前馈控制将在时间波形整形中发挥重要作用，这对于这种射流控制方法至关重要，并且将涉及广泛的测试和分析。 拟议的计划具有更广泛的影响，包括本科生研究人员的参与。将继续为当地高中以及未来的中学生提供外展演示和演示，特别关注女童子军和公立学校的学生。将为当地高中生提供在夏季获得实验室经验的机会。加利福尼亚州对公立学校 MESA（数学工程科学成就）项目的资金削减，使得加州大学洛杉矶分校等大学将推广项目扩展到公立初中和高中，作为鼓励未来工程师和科学家发展的一种手段。拟议的项目将为开展这一外展活动提供适当的机制。