Armfield Engineering Education
FLUID MECHANICS
F14 MkII Hydrogen Bubble Flow Visualisation System - Issue 2
The Armfield Hydrogen Bubble Flow Visualisation System has been designed to allow 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 MKII version of the F14 includes a smaller electronic control console that
incorporates improved digital controls and a low voltage LED lighting module that gives improved illumination of the bubbles for clearer demonstrations. Changes in the design of the bubble generator allow the system to be operated without the need for conditioning of the water using salts.
ORDERING SPECIFICATION
• 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 4 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 allows still camera, video camera or web-cam
(not supplied) to record the
flow patterns.
• The following models, supplied for flow visualization 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 visualisation demonstrations.
Demonstration Capabilities
> visualisation 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 web cam (not supplied)
Description
The Armfield Hydrogen Bubble Flow Visualisation 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 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 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, however Glauber’s salt 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 visualisation 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.
The supplied software allows remote operation of the F14-MKII electronic
control console via a PC (not supplied).
This software allows all the control functions to be implemented by the PC, and provides the facility to save a number of set-up strategies. These can be immediately recalled at a later date to simplify the
use of the equipment.
Technical specification
| Item | Value |
|---|---|
| Pulse generator: |
3 to 2500 mS on and off periods |
| Light source: |
12 high intensity LEDs |
| Cathodes: |
35, 50 and 75mm lengths |
| Flow table capacity: | 20 litres (nominal) |
| Ammeter range: |
0 to 100mA |
| Working section: |
length: 425mm |
| width: 285mm | |
| depth: 36mm |
Optional Accessories
F14-MKII-11: Camera Bracket
The accessory enhances the use of the F14-MkII, by providing a mounting frame for a camera, allowing a still camera, video camera or web-cam to record the flow patterns.
TOPComplementary Products
F1: Hydraulics Bench & Accessories with:
F1-301: Computer Aided Learning Programs
F4: Precision Pressure Gauge Calibrator
F5: Osborne Reynolds Demonstration
F6: Air Flow Studies
F9092: Fluid Properties & Hydrostatics Bench
F1-28: Cavitation Demonstration
F12: Particle Drag Coefficients
C10: Laminar Flow Analysis Table
C15: Computer Controlled Wind Tunnel
S2: Mobile Bed & Flow Visualisation Tank
requirements
Electrical supply:
F14-MKII-A: 230V/1ph/50Hz, 2 Amps
F14-MKII-B: 120V/1ph/60Hz, 5 Amps
F14-MKII-G: 220V/1ph/60Hz, 2 Amps
Water:
Fill with clean water.
No permanent connection required.
Shipping specification
Volume: 0.3m3
Gross Weight: 75kg
Overall dimensions
Electrical console:
Height: 100mm
Width: 260mm
Depth: 310mm
Flow tank:
Height: 225mm (Tank only)
Width: 845mm
Depth: 400mm
|
 |
|---|
DATA SHEET
PRODUCT CATEGORY:
Engineering Education
Complementary Products
F1: Hydraulics Bench and Accessories
F1-301: Computer Aided
Learning Programs (PC: Windows™)
F4: Precision Pressure Gauge Calibrator
F5: Osborne Reynolds' Demonstration
F9092: Fluid Properties & Hydrostatics Bench
F1-28: Cavitation Demonstration
F12: Particle Drag Coefficients
F14MKII: Hydrogen Bubble Flow Visualisation
System