Reconciling wind tunnel data with real performance: influence of freestream turbulence intensity and large-scale unsteadiness

风洞数据与实际性能的协调：自由流湍流强度和大规模不定常的影响

• 批准号: 2889141
• 金额: --
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Studentship
• 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=studentship-2889141
• 关键词: Reconciling; wind; tunnel; data; real

Our current inability to reconcile test data with actual performance of land, sea, and air vehicles, especially under the unsteady conditions which they often encounter in the real world represents a major barrier in improving designs for the energy efficiency of large platforms. Many forms of transportation vehicles face unsteady or turbulent scenarios and without the understanding of what effects this has on the vehicle, there is no way of confidently improving the vehicles design and its efficiency. Prior to the development of CFD tools, model test data pertaining to vehicle performance and their flow fields was almost always acquired in wind-tunnels (or water-tunnels) with various technical methods used to acquire physical measurements. Typically, these flow facilities incorporated carefully designed flow conditioning devices to ensure that the vehicle model was subjected to steady uniform flow conditions with a purposely low free-stream turbulence (FST) intensity. These FST levels can then be deliberately increased using passive or active grids or a combination of the two.The role that FST, defined by both intensity and length scales (e.g. integral, Taylor, Kolmogorov), plays on boundary layer flows, particularly transition-to-turbulence, is still not fully understood. For example, even in the simplest case of flow over a smooth flat plate, the role that the FST intensity and integral length scale directly plays on boundary layer transitions has only recently been characterised. Beyond this canonical case, the role of FST and, indeed inflow unsteadiness in general on applied aero- and hydrodynamic applications requires further investigation. With the rapid growth and development of additive manufacturing, the research community now has at its disposal the ability to rapidly create prototypes and therefore rapidly test different flow conditioning devices with various intricate geometries far being simple screens and grids. This can create conditions, whether steady or unsteady, within a wind tunnel at lower cost and more rapidly than with conventional fabrication technologies.This project leverages pre-existing physical infrastructure in addition to new equipment designed for the specifics of the problems researched. The project will facilitate the design, build and test of a wind-tunnel flow conditioning device, specifically to elevate the turbulence intensity in addition to being able to induce a level of shear flow. This will lead to 'extreme' testing of various bluff-body vehicles on test models representative of land, sea and air vehicles. This data will then serve as computational fluid dynamics (CFD) validation cases and will allow insight gains leading to improved empirical models and improved platform designs. The initial premise of this project is to use a simplistic bluff body model such as the Ahmed body to conduct high-fidelity flow and performance measurements on. Once this testing has been conducted the project will move onto more complex geometries.

我们目前无法使试验数据与陆、海、空飞行器的实际性能相一致，特别是在真实的世界中经常遇到的不稳定条件下，这是改进大型平台能源效率设计的主要障碍。许多形式的运输车辆面临不稳定或湍流的情况，如果不了解这对车辆的影响，就无法自信地改进车辆设计及其效率。在CFD工具开发之前，与飞行器性能及其流场相关的模型试验数据几乎总是在风洞（或水洞）中获得，并使用各种技术方法获得物理测量结果。通常，这些流动设施包括精心设计的流动调节装置，以确保飞行器模型经受稳定均匀流动条件，并故意降低自由流湍流（FST）强度。这些FST水平然后可以使用被动或主动网格或两者的组合来有意地增加。FST由强度和长度尺度（例如积分、泰勒、柯尔莫戈洛夫）定义，在边界层流动，特别是转捩到湍流中所起的作用仍然没有完全理解。例如，即使在最简单的情况下，流动在一个光滑的平板，的作用，FST强度和积分长度尺度直接发挥边界层过渡只是最近才被表征。除了这个典型的情况下，FST的作用，实际上流入不稳定性一般应用空气动力和水动力的应用需要进一步的调查。随着增材制造的快速增长和发展，研究界现在有能力快速创建原型，从而快速测试具有各种复杂几何形状的不同流动调节装置，而不是简单的屏幕和网格。与传统制造技术相比，这可以在风洞中以更低的成本和更快的速度创造稳定或不稳定的条件。该项目利用了现有的物理基础设施以及针对研究问题的具体设计的新设备。该项目将促进风洞气流调节装置的设计、建造和测试，特别是除了能够引起一定水平的剪切流之外，还能提高湍流强度。这将导致在陆地、海洋和空中车辆的测试模型上对各种钝体车辆进行“极端”测试。然后，这些数据将作为计算流体动力学（CFD）验证案例，并将允许获得洞察力，从而改进经验模型和改进平台设计。该项目的初始前提是使用简化的海崖体模型（如Ahmed体）进行高保真的流动和性能测量。一旦进行了该测试，该项目将转向更复杂的几何形状。