Flow separation in sharp meander bends

It is well known that abrupt changes in flow direction may lead to flow separation from boundaries. While many smaller or confined meandering rivers have bends sharp enough for flow separation, the problem has surprisingly been ignored in the meandering literature. It is nevertheless essential for understanding and predicting meandering dynamics is small streams in renaturalisation projects. We measured flow structure in experimental sharp bends in the Total Environment Simulator at Hull University over fixed and mobile beds. We found some flow structures similar to those in less sharp bends, but significant differences as well such as lack of relation between flow separation and Froude number. The mobile bed responded dramatically to the sharp bend flow with deep outer-bend pools and high bars up to the water surface.