Hydrogen Bubble Flow Visualisation System

The top of the flow tank is manufactured from glass reinforced plastic (GRP) for durability and incorporates a wide shallow working section with a flat black acrylic bed for flow visualization studies. A smooth flow of water at variable velocity is passed through the working section. This is achieved by using a unique fluid drive unit in combination with flow straightness. The depth in the working section can be changed by a set of weir strips at the discharge end.

A number of acrylic models are provided with the equipment such as an aerofoil section and cylinders of different diameter. These can be positioned in the working section to show the flow effects around these shapes. User-defined models can also be used.

A lighting module placed in the water at the side of the working section, produces a wide beam of light below the surface of the water and illuminates the hydrogen bubbles to aid visualization of the flow patterns. The hydrogen bubbles are produced by a fine platinum/iridium cathode wire located under the surface of the water and normal to the direction of flow.
The wire is kept taut by a forked holder and is held in the required position by tripod with adjustable support. Hydrogen bubbles can be produced using plain tap water, however Glauber’s salt. The electronic control console provides all of the necessary electrical services for the flow tank and incorporates the hydrogen bubble generator.

All operating parameters are displayed on a liquid crystal display. Controls are included for the water pump, light source and hydrogen bubble generator. The size of the hydrogen bubbles can be varied by adjusting the current to the cathode wire. The generator automatically maintains the current at the required value by varying the supply voltage to compensate for changes in the loop resistance.