Advanced Flow Visualization Techniques for the Federal Highway Administration Hydraulics Research Laboratory

The Federal Highway Administration’s Hydraulics Research Laboratory has facilities to physically and numerically model hydraulic and sediment transport phenomena to support State highway administration initiatives. Recent advances in physical modeling instrumentation have facilitated flow visualization to support research. Flow visualization is now performed using the hydrogen bubble technique whereby a platinum wire is mounted vertically upstream of a bridge structure (pier, abutment, etc.) in the test flume. A graphite rod is used as an anode. The hydrogen bubbles produced are small enough (Ø < 0.025 mm) that their buoyancy may be ignored within the visualized area. By employing pulsed time line markers with a specially built hydrogen bubble generator, it is possible to visualize the phase speed of the diving current formed at the face of the structure. This diving current is usually responsible for bridge scour.