Change of turbulent structure due to the shape of arterial wall

It is reported that there is riblet-type membrane on the inner surface, just above the endothelial cells, of arterial wall. If arteriosclerosis occurs in the artery, this membrane is buried and the shape of inner surface of arterial wall becomes very rough. Scince this shape change may cause a bad effect on the arterial wall, turbulent structure on a riblet-type wall and that on a rough wall are investigated. Turbulent flow between a flat plate and a riblet-type wall or a rough wall with constant pressure gradient is computed by large eddy simulation. Movement of low speed streaks, low pressure regions and friction on the wall are obtained. It is found that the friction of rough wall increases with decreasing their projection length in flow direction, and that friction of a rough wall is larger than that of a riblet-type wall. The rough wall on which projections are arranged in a check pattern has less friction than the rough wall on which projections are arranged in straight order.