cg50in wrote:You know when I trout fish I look for a rock in the middle of a stream and fish the eddy behind it.
That's a very nice image. I think the difference between problems in arteries and vein problems is the velocity and pressure are so different. Basically in the head you have only gravity to move the blood plus whatever is left that got it up there after passing through the capillary beds (heart, lung muscles...).
So the velocity range should be easy to ballpark, given the distances. If turbulence happens I'd be surprised. Do eddies happen in slow moving stuff? I know not much about this stuff, except for real basics. Don't know anything about blood shear so you are a very welcome contributor,. far's I'm concerned. All I can guess is that where veins and venules split must disturb the flow as much as anything, especially if it's ay a sharpish angle. But where there is a straight stretch it can become smoother, and it it's too slow maybe there is not enough momentum and cells pop through the BBB.