High-speed and high-resolution 4 D optical flow-diagnostics system

卡尔斯鲁厄理工学院（KIT）的流体力学研究所（ISTM）在近壁湍流及其通过特定几何图案、壁面粗糙度或通过主动和被动流动控制方法进行控制或修改的研究方面享有国际声誉。目前的建议旨在使高保真光学测量在两个最近升级的设施在ISTM：低雷诺数（Re）通道流风洞和大型高Re开放式射流风洞。互补的实验和数值研究设想这两种流动配置。这使得以下壁湍流机制和控制的整体研究方法：对于典型的通道流，高保真直接数值模拟（DNS）驱动的基本物理的理解。这些经典的模拟的统计2 D和空间充分发展的流动状态的时空分辨实验的补充。这些实验允许评估流动发展和三维效果中没有DNS，最重要的是，提供访问由致动器或表面粗糙度，其中即使在DNS中包括基于模型假设，因此需要验证数据触发的流动现象。这些研究所需的最先进设备被称为（时间和体积分辨）高速4 D光流诊断系统。除了在通道流配置的基本调查，流动控制和修改策略被转移到更复杂的配置，特别是，外部流沿着复杂的几何形状在较高的Re。对于这种流动类型，高保真度模拟是极其苛刻的或不可能的。因此，部署了基于约束模型的求解器。为了改进模型，允许纳入由于非光滑表面或致动器的存在而修改的边界条件，用于输入和验证的可靠实验数据是强制性的。这就需要对大的流域进行高分辨率的体积测量。为此，需要第二流动诊断系统，其被称为高分辨率4D光学流动诊断系统。该系统可与ISTM已有的激光源结合使用，以提供四个时间相关的体积测量序列。采集的数据集将使用基于拉格朗日粒子跟踪（LPT）方法的最先进算法进行处理，包括最先进的体积拉格朗日测速软件，通过计算效率高的数据评估检索高质量的测量结果。因此，所要求的设备可以充分利用ISTM新翻新的风洞基础设施，以实现独特的整体流动诊断和控制研究。

The institute of fluid mechanics (ISTM) at Karlsruhe Institute of Technology (KIT) has developed a reputation as international reference for the studies on near wall turbulence and its control or modification through specific geometric patterns, wall roughness or by means of both active and passive flow control approaches. The present proposal aims at enabling high fidelity optical measurements in the two recently upgraded facilities at ISTM: a low Reynolds number (Re) channel-flow tunnel and a large high-Re open jet wind tunnel. Complementary experimental and numerical investigations are envisioned for both flow configurations. This enables the following holistic research approach on wall-turbulence mechanisms and control: For the canonical channel flow, high-fidelity direct numerical simulations (DNS) drive the fundamental understanding of the underlying physics. These classical simulations of a statistically 2 D and spatially fully developed flow state are complemented by spatio-temporally resolved experiments. These experiments allow to assess flow development and three-dimensionality effects absent in DNS and, most importantly, provide access to flow phenomena triggered by actuators or surface roughness, which even in DNS are included based on model assumptions and thus require validation data. The state-of-the-art equipment requested for these studies is referred to as (temporally and volumetrically resolved) high-speed 4 D optical flow-diagnostics system. In addition to their fundamental investigation in the channel flow configuration, the flow control and modification strategies are transferred to more complex configurations; specifically, to external flows along complex geometries at higher Re. For this flow type high-fidelity simulations are extremely demanding or impossible. Therefore, turbulence-model based solvers are deployed. In order to advance models that allow the incorporation of modified boundary conditions due to non-smooth surfaces or the presence of actuators, reliable experimental data for input and validation are mandatory. This requires high resolution volumetric measurements of large flow domains. For this sake, a second flow diagnostics system is requested, which is referred to as high-resolution 4 D optical flow-diagnostics system. This system can be used in combination with an already available laser source at ISTM, to deliver four temporally-correlated sequences of volumetric measurements. The acquired datasets will be processed with the most advanced algorithms based on the Lagrangian particle tracking (LPT) approach, including state-of-the-art volumetric Lagrangian velocimetry software retrieving high-quality measurements with computationally-efficient data evaluation. The requested equipment thus allows to fully exploit the newly refurbished wind tunnel infrastructure at ISTM in order to enable a unique holistic flow diagnostics and control research.