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The laminar, two-dimensional flow in HM 152 is a good approximation of the flow of ideal fluids: the potential flow. All physical systems described with the Laplace equation can be demonstrated with potential flow. This includes current and thermal flows as well as magnetic flux.
The core element of the HM 152 trainer is a classic Hele-Shaw cell with additional water connections for sources and sinks. The laminar, two-dimensional flow is achieved by water flowing at low velocity in a narrow gap between two parallel glass plates. The parallel flow generated in this way is non-vortical and can be regarded as potential flow. Sources and sinks are generated via eight water connections in the bottom glass plate. The streamlines are displayed on the glass plate by injecting a contrast medium (ink).
In experiments the flow around bodies is demonstrated by inserting models into the parallel flow. Interchangeable models such as a cylinder, guide vane profile or nozzle contour are included.
To model the flow without models, it is possible to overlay parallel flow, sources, sinks and dipoles as required. This allows the demonstration of the formation of Rankine half-bodies.
The water flow rate and the quantity of contrast medium injected can be adjusted by using valves. The water connections are also activated by valves and can be combined as required.
The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.
Learning Objectives / Experiments
- visualisation of streamlines in
* flow around drag bodies: cylinder, guide vane profile, square, rectangle
* flow through models: nozzle contour, sudden contraction or enlargement
* flow separation, flow with 90° deflection
- modelling the flow around bodies by overlaying parallel flow and sources and/or sinks
* formation of Rankine half-bodies
* demonstration of a dipole
- analogy between potential flow and other physical systems which are described by the Laplace equation