Computerised visualisation from images of blood flow through frog mesenteric microvessels with multiple complexities.

Blood flow through a frog mesenteric microvessel, consisting of one loop and two successive bends, was recorded by a video-microscopic system and analysed by a PC-based image processing system. After preprocessing, these images were analysed by the image velocimetry, axial tomography and image processing procedures. The blood flow in the microvessel had a Reynolds number of 0.033, and the Dean number varied from 0.004 in the loop to 0.007 in the bend, showing an increase in secondary flow in the bend region. These changes led to outward shifts in the peaks of velocity and concentration profiles, with an increase in the thickness of the outer walls (of about three times) compared with that of the inner walls. The mean velocity and mean cellular concentration showed a similar pattern. The variation in the cellular concentration in the microvessel was visualised by concentration contours and grey-scale images of the cellular distribution. At the inner wall of the complex geometry, the velocity reduced to zero, whereas the cellular concentration varied from 2 to 5%. In the high shear stress regions in the complex geometry, the vessel wall thickness was two-three times more than that in low shear stress regions.