Extraction of separation in three-dimensional unsteady and turbulent experimental flows

三维非定常和湍流实验流中分离的提取

• 批准号: 418362-2012
• 负责人: Vétel, Jérôme
• 金额: $ 2.26万
• 依托单位: École Polytechnique de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=573612
• 关键词: Extraction; separation; three; dimensional; unsteady

The separation phenomenon in fluid dynamics is as common as unpredictable. It causes the aerodynamic stall of aircraft wings, reduces the performance of turbomachines and limits the efficiency of hydraulic turbines. Although it has long been known, to date we can neither detect nor predict it. When it occurs, the fluid flowing along a solid wall suddenly separates. To detect it, common sense suggests us that the separation point should coincide with the location where fluid friction on the wall is zero. This led Ludwig Prandtl to define in 1904 a criterion which predicts the separation of two-dimensional steady flows. It turns out that in the presence of three-dimensional or unsteady phenomena, this criterion is not verified in ex. Although many researchers have examined the problem, the determination of a rigorous and practical criterion to predict flow separation is still challenging. We thus had to wait until 2004 to see an exact and complete theory formulated by George Haller. This new theory is beyond the simple detection criterion. Indeed, it predicts that for flows with a well-defined steady mean, the separation line, or surface, while moving inside the flow, must remain fixed on the solid wall. These theoretical foundations make no assumptions about the nature of the flow studied, so that it applies to any conditions. The objective of this research program is to use the most recent measurement techniques to capture separation phenomena and to analyze and understand the physical mechanisms that generate them. In the medium term, we will check, validate or complement the ideas emanating from theories and in the longer term it is essential to develop a practical tool for separation detection to tackle engineering problems.

流体动力学中的分离现象既常见又不可预测。它会引起飞机机翼的气动失速，降低发动机的性能，限制水轮机的效率。虽然人们早就知道，但迄今为止我们既不能探测也不能预测它。当它发生时，沿沿着固体壁流动的流体突然分离。为了检测它，常识告诉我们，分离点应该与壁面上流体摩擦为零的位置重合。这使得路德维希·普朗特在1904年定义了一个准则，该准则预测了二维定常流的分离。结果表明，在三维或非定常现象的存在下，这一准则在实验中没有得到验证。虽然许多研究人员已经研究了这个问题，确定一个严格的和实用的标准来预测流动分离仍然是具有挑战性的。因此，我们不得不等到2004年才看到乔治哈勒提出的一个精确而完整的理论。这种新理论超越了简单的检测标准。实际上，它预言，对于具有明确定常平均值的流动，分离线或分离面在流动内部移动时，必须保持固定在固体壁上。这些理论基础对所研究的流动的性质不作任何假设，因此它适用于任何条件。 该研究计划的目标是使用最新的测量技术来捕获分离现象，并分析和理解产生这些现象的物理机制。从中期来看，我们将检查、验证或补充理论产生的想法，从长期来看，开发一种实用的分离检测工具以解决工程问题至关重要。