REG: Advanced Imaging Capability: Vorticity as Seen by a Moving Particle

摘要 CTS-9610340克里斯罗杰斯塔夫茨大学 其主要目标是开发从运动粒子的角度测量瞬时二维流体速度场的仪器。将购买柯达相机、图像采集卡和辅助设备。 为了准确地预测湍流气流中固体颗粒的行为，必须能够预测颗粒所经历的流体湍流：即在颗粒拉格朗日参考系中。大多数传统的模型和模拟给出了静态欧拉参考系或拉格朗日参考系中的信息。由于粒子具有重力漂移和惯性，其路径不同于流体点（拉格朗日）或静止点（欧拉）。粒子所响应的湍流取决于粒子的物理特性和其先前的周围湍流历史。PI正在对从欧拉坐标系到粒子坐标系的转换进行建模，以进行单点测量，例如流体速度自相关。然而，对于某些粒子，它们的路径由局部流体涡量决定。涡流倾向于将颗粒抛到应变区域。为了模拟这种行为，需要能够测量沿颗粒路径沿着的局部瞬时涡量。可以使用数字颗粒图像测速法来近似涡量，测量运动颗粒参考系中的2-D流体速度场。 目前的困难是空间和时间分辨率，这两个都在这里解决。这些设备还将用于其他一些项目，包括工业和政府机构。

Abstract CTS-9610340 Chris Rogers Tufts University The main goal is to develop instrumentation for the measurement of instantaneous, two dimensional fluid velocity fields from the viewpoint of a moving particle. A Kodak camera, imaging frame grabber and accessory equipment will be purchased. In order to accurately predict the behavior of a solid particle in a turbulent air flow, one must be able to predict the fluid turbulence experienced by the particle: that is in the particle Lagrangian reference frame. Most conventional models and simulations give information in the stationary Eulerian reference frame or in the Lagrangian reference frame. Since the particle has a gravitational drift and inertia, its path is different from that of a fluid point (Lagrangian) or a stationary point (Eulerian). The turbulence to which the particle responds is dependent on the physical particle properties and on its previous history of surrounding turbulence. The PI is modeling a transformation from an Eulerian coordinate system to the particleıs coordinate system for single point measurements, such as fluid velocity autocorrelation. For some particles, however, their path is dictated by local fluid vorticity. Vortices tend to throw particles out into straining regions. To model this behavior, one needs to be able to measure the local instantaneous vorticity along the particle path. One can approximate the vorticity using digital particle image velocimetry, measuring the 2-D fluid velocity field in the reference frame of the moving particle. The current difficulty is spatial and temporal resolution, both of which are addressed here. The equipment will also be used by a number of other projects, both with industry and government agencies.