Hydrodynamic Testing

The first phase of hydrodynamic testing has been undertaken with the aim of establishing the characteristics of water flow around a solid structure like the prototype Ocean Hydro Electricity Generator plant. A scale model of the plant was used in various depths and velocities of water flow to demonstrate the venturi system in operation and to note the turbulent effects of the structure. The venturi system caused a significant increase in water velocity through the O.H.E.G. channel. It is estimated that the velocity increased by two thirds of the original water velocity.

Turbulence was created at the leading edges of the structure and at the trailing edges, as to be expected. It was clear that there was an area of turbulent water in the venturi entrance extending slightly into the channel before the water flow regained a laminar form. Turbines would need to be positioned out of the area of turbulent water. The O.H.E.G. structure also creates an increase in water velocity on the outer edge of the chamber. This shows that two prototype units positioned adjacent to each other would be more efficient than one individual unit.

The test apparatus also allowed various different channel widths to be simulated. This showed that there was a greater increase in velocity by reducing the channel width but a much larger area of turbulent water was also created. Increasing the channel width reduced the velocity of the water flow and reduced the turbulence. It appears that a channel width of double one chamber width is preferable. This is due to water velocity being the main factor affecting the kinetic energy present in a body of flowing water. The higher the velocity the higher the kinetic energy and hence more power can be extracted from the water flow. This indicates that a smaller channel would be more efficient; however there is sharp increase in turbulence within the channel when smaller widths are simulated. Turbulence is not desirable and should be limited as much as possible.

 

Flow Illustration

The illustration shows observed fluid flow and turbulence, proving the venturi theory.

 

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