Fine gas bubbles are perfectly suited to visualising flow fields. Due to analogies, many flow processes that occur in air can also be demonstrated by experiments in water.
The trainer consists of a vertical experimental section in which an interchangeable model is inserted. Water flows from bottom to top through the experimental section. Electrolytically generated hydrogen bubbles rise with the flow, flow around the model and visualise the flow.
Different models are available: drag bodies (e.g. aerofoils and cylinders) or changes in cross-sections. The length of the experimental section enables for a long wake, where, for example, vortex streets form completely. The black background and the lateral illumination ensure optimal observation. The model can be inserted in two different positions.
Learning Objectives And Experiments
- Visualisation of two-dimensional flows
- Streamline course in flow around and through models
- Flow separation
- Vortex formation, demonstration of Karman vortices
- Qualitative observation of the velocity distribution in laminar flow
- Analogy to air flow
- In conjunction with a special camera (i.e. PCO Pixelfy) and suitable software (i.e. ImageJ):
- image processing evaluation of the experiments (particle image velocimetry, particle tracking velocimetry)
Specification
- Electrolytically generated hydrogen bubbles visualise flow fields of different models
- Closed water circuit with experimental section, storage tank, pump, valve to adjust the flow velocity
- Vertical experimental section with black background, LED illumination on both sides and 2 insert positions for the model
- Supplied models: 2 aerofoils, triangle, semicircle, hollow hemisphere, 2 cylinders (different sizes), 2 models for changes in cross-section
- Low-turbulence flow using stabilisation tank with flow straightener
- Bubble generator: platinum wire as cathode and frame of experimental section as anode
- Cathode can be inserted in different positions
- Setting cathode current, pulse and pause duration
- Switch cabinet with displays for cathode current and flow velocity
Technical Specification
- Pump, 3 stages
- max. flow rate: 9,7m³/h
- max. head: 12m
- power consumption: 400W
- Storage tank: approx. 75L
- Experimental section
- LxH: 300x860mm, W=49mm
- Bubble generator
- current: 0…2A
- platinum wire as cathode
Measuring ranges
- flow velocity: 0…13,3cm/s
- current: 0…2000mA
- temperature: 0…100°C (water)
- 230V, 50Hz, 1 phase
- 230V, 60Hz, 1 phase; 120V, 60Hz, 1 phase
