A method to measure time average velocity distribution of fluctuating airflow through the digital image processing of multi-couples of images visualized by oil mist or smoke particles is proposed. Some fast algorithms for pattern tracking to avoid the increase of computation time with the increase of data amount are also proposed, and their performances are compared. It is shown through the comparison that the algorithm, in which the similarity of gray level patterns is defined with the accumulation of gray level differences between corresponding pixels, the accumulations are executed in parts and the candidates which differ significantly from the most promising candidate are abandoned successively through F-inspection, is the most reasonable one. In this algorithm, the reliability of calculated result is also obtained; it can be used as a measure to estimate the quality of visualized images.
This study uses a flow simulation package on a graphics workstation to simulate the blood flow behavior in an abdominal aortic aneurysm and in the left ventricle (LV) of the heart. Both the simulation package and our own user developed graphics routines were used to view the three dimensional flow patterns. Vessel pressures and shear stresses both inside and outside of the vessel and heart LV could be observed, and our graphics routines allowed us to travel through the vessels. The asymmetric aneurysm was 8.0cm length and the Reynolds number was 700. In the aneurysm center, two symmetric vortices were formed, and flow separation started at the aneurysm inlet. Regions of high pressure were observed at the aneurysm exit caused by the symmetric vortices that were formed. The shear stress was low in the aneurysm portion of the vessel, and local maximum values were observed at the distal aneurysm constriction. A realistic model of the LV of the heart was constructed from a dog heart cast in diastole. The LV walls moved towards the center of the aortic outlet, and the left ventricular wall motion was assumed to follow the blood flow. This technique allowed effects such as cardiac infarction to be implemented, and showed complex flow field formation. In both the aneurysm and heart LV cases, having a three-dimensional graphics capability showed effects that would be difficult to observe with two-dimensional graphics and simulations only.