Turbulent flows over rough-walls under the influence of streamwise pressure gradients

在流向压力梯度的影响下，粗糙壁上的湍流

• 批准号: EP/W026090/1
• 负责人: Bharathram Ganapathisubramani
• 金额: $ 109.8万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FW026090%2F1
• 关键词: Turbulent; flows; over; rough; walls

The efficiency and performance of an aerodynamic surface (wind turbine blade or a ship rudder) is a trade-off between the lift generated and the drag incurred by it. The required lift force is attained by changing the shape and orientation of the geometry, which generates a pressure and load distribution along its length. The drag incurred depends on the characteristics of the turbulent boundary layer flow that develops over the surface. Unfortunately, these two design requirements are not independent of each other as the turbulent boundary layer depends on the overlying non-zero pressure gradient due to the pressure distribution. Additionally, the boundary layer flow also depends on the topographical features (or roughness) of the surface where features as small as 10 microns are considered to be hydrodynamically "rough". This situation where the boundary layer flow is under the influence of both non-zero pressure gradient and surface roughness is pervasive in engineering and environmental applications. Examples include flow over airfoils/turbine blades, ducts, flow over/around buildings, hills/valleys etc. Despite its prevalence, the effects of pressure gradient on flow over rough surfaces remains largely unexplored. As we strive towards net zero carbon emissions by 2050, it is timely to develop new understanding and modelling strategies that capture the influence of pressure gradients on the performance of flow over rough surfaces.In this project, we aim to characterise the evolution of non-zero pressure gradient (PG) turbulent boundary layers (TBL) over rough surfaces and thereby identify the parameters that dictate the response of boundary layers to streamwise pressure gradients. A comprehensive series of wind-tunnel experiments and numerical simulations will be performed to generate unprecedented data on flow over rough-walls subject to favourable and adverse pressure gradients (FPG and APG). The data will underpin identification and validation of potential universalities (and differences) in mechanisms of momentum/energy transfer compared to zero-pressure-gradient (ZPG) flows. The data will then be used to develop and validate both integral models and new Large-Eddy Simulation (LES) models that can be used to predict the performance of flow over arbitrary rough surfaces under the influence of varied pressure gradients. The data will be made available in the public domain through our roughness database (www.roughnessdatabase.org). The overall aim is to establish the interrelationship between roughness and pressure gradients over a broad range of parameters (for pressure gradient and roughness properties), understand the limitations of current models and develop new modelling methods that can be used for predictions in a wide range of applications.

气动表面(风力机叶片或船舵)的效率和性能是所产生的升力和由此产生的阻力之间的权衡。所需的升力是通过更改几何图形的形状和方向来获得的，这将生成沿其长度的压力和载荷分布。产生的阻力取决于在表面上发展的湍流边界层流动的特性。不幸的是，这两个设计要求并不是相互独立的，因为湍流边界层取决于由于压力分布而导致的上覆非零压力梯度。此外，边界层流动还取决于表面的地形特征(或粗糙度)，其中小至10微米的特征被认为在流体力学上是“粗糙的”。这种边界层流动同时受到非零压力梯度和表面粗糙度影响的情况在工程和环境应用中是普遍存在的。流动的例子包括翼型/涡轮叶片、管道、建筑物上方/周围的流动、丘陵/山谷等。尽管普遍存在压力梯度对粗糙表面流动的影响，但在很大程度上仍有待研究。随着我们努力在2050年实现净零碳排放，现在是时候开发新的理解和模拟策略来捕捉压力梯度对粗糙表面上流动性能的影响。在这个项目中，我们的目标是描述粗糙表面上非零压力梯度(PG)湍流边界层(TBL)的演变，从而确定决定边界层对流向压力梯度的响应的参数。将进行一系列全面的风洞实验和数值模拟，以产生具有有利和不利压力梯度(FPG和APG)的粗糙壁面上的流动数据。这些数据将为确定和验证动量/能量传递机制与零压力梯度(ZPG)流动相比的潜在共性(和差异)奠定基础。这些数据将被用来开发和验证积分模型和新的大涡模拟(LES)模型，这些模型可以用来预测在不同压力梯度影响下任意粗糙表面上的流动性能。这些数据将通过我们的粗糙度数据库(www.roughnessdatabase ase.org)在公共领域公开。总体目标是在广泛的参数范围内建立粗糙度和压力梯度之间的相互关系(对于压力梯度和粗糙度属性)，了解当前模型的局限性，并开发可用于在广泛应用中进行预测的新的建模方法。

项目成果

Development of a floating element photoelastic force balance

浮动元件光弹力天平的研制

• DOI: 10.1007/s00348-023-03664-1
• 发表时间: 2023
• 期刊: Experiments in Fluids
• 影响因子: 2.4
• 作者: McLaughlin B