面向三维流管可视化的各向异性屏幕空间环境光遮蔽算法

屏幕空间环境光遮蔽(AO)算法是一种流行的全局光照技术,此类技术可用于辅助复杂3D流管场景的可视化,以便于更好地理解场景分布特点。对此提出一种屏幕空间各向异性AO方法来实现复杂三维流管场景可视化。其基本思想是利用三维流管的特性设计两个各向异性滤波器,来指导计算流管场景AO时的屏幕空间采样和空间复用步骤。具体而言,这种策略通过各向异性地生成垂直于流管方向的采样点计算AO。该策略可以减少算法在获取满意渲染结果时所需的样本数量。同时为了进一步提高算法性能,提出对邻近像素的AO计算结果进行沿流管方向各向异性空间复用。实验结果表明,该算法在渲染质量和性能上均优于现有的屏幕空间AO算法方案。

Temperature and Pressure Measurements at Cold Exit of Counter-flow Vortex Tube with Flow Visualization of Reversed Flow

In order to clarify the structure of the cold flow discharged from the counter-flow vortex tube(VT), the temperature and pressure of the cold flow were measured, and the existence and behavior of the reversed flow at the cold exit was studied using a simple flow visualization technique consisting of a 0.75mm-diameter needle, and an oil paint droplet. It is observed through this experiment that the Pitot pressure at the cold exit center can either be lower or higher than atmospheric pressure, depending on the inlet pressure and the cold fraction, and that a reversed flow is observed when the Pitot pressure at the cold exit center is lower than atmospheric pressure. In addition, it is observed that when reducing the cold fraction from unity at any arbitrary inlet pressure, the region of reversed and colder flow in the central part of cold exit extends in the downstream direction.