Bluff-body wakes and fluid-structure interactions

钝体尾流和流固相互作用

• 批准号: RGPIN-2018-03760
• 负责人: Sumner, David
• 金额: $ 1.97万
• 依托单位: University of Saskatchewan
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=681779
• 关键词: Bluff; body; wakes; fluid; structure

The non-streamlined shape of a "bluff body" causes it to experience high aerodynamic drag forces or wind loading. The body's complex flow field is characterized by flow separation (where the flow does not follow the shape of the body), vortex formation from the body surface, interactions between shear layers (thin regions of fluid across which there are large changes in flow velocity), and an unsteady low-pressure wake behind the body. The phenomenon of "vortex shedding" occurs as vortices are released periodically from the body into the wake; under certain conditions, this may cause unwanted structural motion or "flow-induced vibration" (FIV).******Examples of bluff bodies include buildings, chimney stacks, bridge pylons, offshore structures, trains, road vehicles, rooftop-mounted equipment, and electronic components on circuit boards. The study of bluff-body flows is motivated by industrial problems related to FIV, flow-induced noise, dispersion of pollutants in the atmosphere, and cooling of electronic components. Flow around a bluff body becomes more complex when it is located near other bodies and structures, such as in groups of buildings, oil storage tanks, or stacks, and when the bluff body is "surface-mounted" and of "finite-height". In the latter case, the local flow fields at the surface and over the "free end" of the body strongly influence the wind loading and the tendency towards FIV. Preventing FIV, designing flow control strategies (to mitigate vortex shedding, for example), and implementing methods for drag reduction (to improve the fuel efficiency of a vehicle, for instance), require a good physical understanding of the "fluid-structure interactions" (FSI) for the flow around bluff bodies. The complex nature of these flows, however, poses significant challenges for field measurements, laboratory experiments, and computer simulations.******The main objective of the research program is to improve the fundamental physical understanding of the flow around surface-mounted finite-height bluff bodies (such as finite cylinders and prisms), primarily through wind tunnel experiments but secondarily with computational fluid dynamics. The program will involve the training of MSc, PhD, and undergraduate students. Specific interests of the research program include (i) answering fundamental questions related to the effects of aspect ratio, body shape and orientation, and the boundary layer on the surface; (ii) identifying "critical" conditions where there are marked changes in the flow patterns and forces; (iii) exploring wake and proximity interference effects for small groups of surface-mounted finite-height bluff bodies; (iv) understanding the effectiveness of passive flow control devices for these bodies; and (v) discovering the effects of structural motion (as related to FSI and FIV) on the wake flow patterns.

“钝体”的非流线型形状使其经历高气动阻力或风载荷。机体复杂流场的特征是流动分离（流动不跟随机体形状）、机体表面形成涡、剪切层（流体的薄区域，其间流速变化很大）之间的相互作用以及机体后方的不稳定低压尾迹。当涡旋周期性地从机体释放到尾流中时，就会发生“旋涡脱落”现象；在某些条件下，这可能会导致不必要的结构运动或“流激振动”（FIV）。******钝体的例子包括建筑物、烟囱、桥塔、海上结构、火车、道路车辆、屋顶安装的设备和电路板上的电子元件。崖体流动研究的动机是与FIV、流动引起的噪音、大气中污染物的扩散和电子元件的冷却有关的工业问题。当钝体靠近其他物体和结构（如建筑群、储油罐或堆）时，以及钝体“表面安装”和“有限高度”时，钝体周围的流动变得更加复杂。在后一种情况下，在物体表面和“自由端”上方的局部流场强烈影响风载荷和向FIV的趋势。预防FIV，设计流动控制策略（例如，减轻涡流脱落），实施减阻方法（例如，提高车辆的燃油效率），都需要对钝体周围流动的“流固相互作用”（FSI）有很好的物理理解。然而，这些流动的复杂性给现场测量、实验室实验和计算机模拟带来了重大挑战。******该研究计划的主要目标是通过风洞实验，其次是计算流体动力学，提高对表面安装的有限高度钝体（如有限圆柱体和棱镜）周围流动的基本物理理解。该项目将包括硕士、博士和本科生的培训。该研究项目的具体兴趣包括(i)回答与纵横比、身体形状和方向以及表面边界层的影响有关的基本问题；（ii）识别水流模式和水流力有明显变化的“危急”情况；（iii）探索小群表面安装的有限高度钝体的尾流和邻近干涉效应；（iv）了解这些机构的被动流量控制装置的有效性；(v)发现结构运动（与FSI和FIV相关）对尾流流型的影响。