Obstacles in flumes reduce the flow cross-section. This may lead to to backwaters upstream of the obstacles.
HM 161.46 contains several piers with different profiles typical for bridge piers. The discharge behaviour with little reduction of cross-section is studied with a single pier. Up to three piers mounted at the same time cause a considerable reduction of cross-section.
The effect of the angle of attack can be studied by turning the mounted pier.
A clamping device fixes the pier(s) in the experimental flume. An angle scale indicates the angle between pier nose and flow.