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，用于高效、稳健地获取和重建多尺度流。由于透明流没有自己的图像，而是从附近的物体借用外观，因此这里开发的解决方案直接从流波前/体积中获取光路，然后推断出流的物理性质。采集系统是便携式和非侵入式的，支持现场采集各种类型的流量。随时间变化的三维透明流动，如流体波前、气液界面流动和湍流流动，在化学、生物和环境工程中无处不在。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暖雨和飓风等自然现象。新的3D流量采集系统利用了新兴的光场（LF）摄像机和显示器。LF收集从3D场景发出的所有光线。研究小组探索了LFs的两个独特特性，即射线采样和多视图成像。首先开发了一种可重构的LF摄像显示系统，以直接捕捉气流如何改变光路。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，以获取各种流动类型，从完全镜面波前到透明气体体积，再到充满固体颗粒的湍流。为了验证，使用被称为晶格玻尔兹曼（LB）方法的介观方法，对没有和有固体颗粒的湍流通道流动进行了直接（所有尺度都已解决）模拟。

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.