II-New: Enabling Analysis of Time-Dependent 3D Transparent Flows via Light Field Imaging and Displays

该项目支持构建一种新型的计算成像系统，用于多尺度流的高效和鲁棒的采集和重建。由于透明流没有自己的图像，而是借用附近物体的外观，因此这里开发的解决方案直接获取离开/通过流波前/体积的光路，然后推断流的物理特性。该采集系统具有便携性和非侵入性的特点，支持现场采集各种类型的流量。流体波前、气液界面流和湍流等时变三维透明流动在化学、生物和环境工程中普遍存在。在实验装置下精确重建这种流动对这些领域及其应用具有更广泛的影响，例如，研究燃煤燃烧器和预测自然现象，如暖雨和飓风。新的3D流采集系统利用新兴的光场（LF）相机和显示器。LF收集从3D场景发出的所有光线。研究小组探索了LF的两个独特属性，射线采样和多视图成像。首先开发了一种可重构的LF摄像机显示系统，以直接捕获流如何改变光路。然后开发定制的计算机视觉算法来推断流的物理特性（密度、速度、涡度等）。与最先进的解决方案相比，新的采集系统是便携式的，可以重新配置，以获取从完全镜面波前到透明气体体积和充满固体颗粒的湍流的各种流动类型。为了验证，直接（与所有尺度解决）的湍流通道流的模拟进行，没有和固体颗粒，对实验测量使用介观方法称为晶格玻尔兹曼（LB）方法。

This project supports construction of a novel computational imaging system for efficient and robust acquisition and reconstruction of multi-scale flows. Since transparent flows do not have their own images but borrow appearance from nearby objects, the solution developed here directly acquires light paths off/through the flow wavefront/volume and then infers the physical properties of the flow. The acquisition system is portable and non-intrusive, to support on-site acquisition of various types of flows. Time-dependent 3D transparent flows such as fluid wavefronts, gas-liquid interfacial flows, and turbulent flows are ubiquitous in chemical, biological and environmental engineering. Accurate reconstruction of such flows under experimental setups have a broader impact on these areas and their applications, e.g., studying coal combustors and predicting natural phenomena such as warm rain and hurricane.The new 3D flow acquisition system leverages emerging light field (LF) cameras and displays. An LF collects all rays emitting from a 3D scene. The research team explores two unique properties of LFs, ray sampling and multi-view imaging. A reconfigurable LF camera-display system is first developed to directly capture how the flow changes the light paths. Tailored computer vision algorithms are then developed to infer physical properties of the flow (density, velocity, vorticity, etc). Compared with state-of-the-art solutions, the new acquisition system is portable and can be re-configured to acquire various flow types ranging from completely specular wavefronts to transparent gas volumes and to turbulent flows laden with solid particles. For validation, direct (with all scales resolved) simulations of turbulent channel flows are conducted, without and with solid particles, against the experimental measurements using a mesoscopic approach known as the lattice Boltzmann (LB) method.