Hydrogen Bubble Flow Visualization System (MODEL ME-FM-1239E-R)
The ARL’s 1239E Hydrogen Bubble Flow Visualization System has been designed to enable viewing of the complex flow patterns associated with water flowing past solid objects or boundaries. The hydrogen bubble technique is highly visual and is particularly useful for laboratory and lecture theatre work. A stream of small hydrogen bubbles accurately follows the water and clearly shows any changes in the direction of the water as it flows around objects in its path.
The Mod-A version of the 1239E includes a smaller electronic control console that incorporates improved digital controls and a low voltage LED lighting module. This enables improved illumination of the bubbles for clearer demonstrations. The bubble generator is supplied with water conditioning salts, although this is not a requirement of use.
- A compact, bench-mounted, self-contained unit used for flow visualisation studies using water as the working fluid
- The unit comprises a flow tank incorporating the working section and pumped recirculation system, plus a separate electronic control console
- A low-voltage variable-speed pump with a unique fluid drive unit is located under the working section
- The electronic control console incorporates manual controls and a four-line, 20-digit LCD that displays the relevant operating parameters
- Flow patterns in the water are indicated by small hydrogen bubbles that are generated by an interchangeable fine platinum/iridium wire cathode
- A low-voltage light source illuminates the hydrogen bubbles in the working section
- Flow visualisation studies can be carried out using plain tap water without the need for additives
- Optional camera mount enables still camera, video camera or webcam to record the flow patterns
- The following models, supplied for flow visualisation studies, are made of clear polished acrylic and supplied in a protective container:
> One pair 330mm long straight guides
> One pair spacer blocks for straight guides (grey PVC)
> One pair blocks with radiused ends
> Four cylinders 6mm, 12mm, 19mm and 25mm diameter
> One aerofoil section
> One flat plate with radiused end
> One rectangular block 70mm x 40mm x 25mm
> One curved plate
- A toolkit is supplied
- A user instruction manual provides installation, commissioning, maintenance data, experimental information and suggested flow visualization demonstrations
- Visualization of two-dimensional flow using hydrogen bubbles
- Observation of flow around standard shapes (cylinder, aerofoil etc)
- Analogy to aerodynamic flow
- Understanding laminar and turbulent flow
- Demonstration of boundary layer growth
- Demonstration of boundary layer separation and eddy formation
- Quantitative analysis of flow patterns using pulsed bubbles
- Observation of flow around user created models (project work)
- Large-scale presentations/recording of patterns using a video camera or webcam
The 1239E Hydrogen Bubble Flow Visualization System is compact, bench mounted and self-contained requiring only filling with water and connecting to a mains electrical supply.
It comprises a flow tank, a separate electronic control console and a comprehensive set of clear acrylic flow visualisation models.
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 visualisation 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 straighteners. 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 visualisation 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 (supplied in three widths) and is held in the required position by an adjustable support tripod. Hydrogen bubbles can be produced using plain tap water, but Glauber’s salt (sodium sulphate) is also supplied with the unit for more detailed studies.
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.
The generator can produce a continuous stream of bubbles if required. However to aid visualization and enable quantitative measurements to be made the bubbles can be turned ‘on’ and ‘off’ in a series of pulses, the pulses and spaces being independently and continuously variable with both times indicated on the display.
on and off periods
|Light source:||12 high-intensity LEDs|
|Cathodes:||35, 50 and 75mm lengths|
|Flow table capacity:||20l (nominal)|
|Current generator range:||0-100mA|
|Working section:||Length: 0.425m|
Fill with clean water.
No permanent connection required.
|Electrical console:||Flow tank:|
|Height:||0.10m||0.225m (tank only)|