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'V' profile channels - faster flow, less maintenance

HOW THE SHAPE OF A TRENCH DRAIN AFFECTS HYDRAULIC PERFORMANCE

V shaped trench drainsStormwater runoff, particularly from peak flows needs adequate drainage to minimise the hazards associated with excessive surface water.

The internal profile of the flow section has a major influence on the hydraulic performance of trench drains. This is why ACO’s ‘V’ profile Polycrete® Channels have been developed on the back of the same drainage principle used for decades in the design of sewers with “egg-shaped” profiles.

‘V’ profile channels in combination with the smooth surface of polymer concrete produce a hydraulically efficient trench drain.

Trench drains are sized to capture, carry and discharge the flows from a design storm event which can occur on average 1 in 10, 20, 50 or 100 years. For the majority of its service life, however, the trench drain will only need to remove very small amounts of runoff on wet days. It is for this purpose, the ‘V’ profile channels outperforms the traditional ‘U’ shaped or rectangular shaped profiles.

V shaped profileDuring minor rainfall, the lower narrower part of the ‘V’ profile channel ensures high liquid velocities. The high velocities originate from a high depth of water which can only be produced by ‘V’ profile channels. In contrast, ‘U’ shaped or rectangular shaped channels allows only for liquids to travel at lower depths and therefore at lower velocities.

Fluid mechanics can further explain this phenomenon, the greater the cross-sectional area in comparison to the wetted perimeter, the more freely flowing the stream will be, this is because less of the water is in proximity to the frictional bed. So as hydraulic radius increases so will velocity. Furthermore, in combination with the smooth finish of polymer concrete with a ‘Mannings coefficient’ of 0.011, this results in less resistance thereby preserving the high velocities.

Higher velocity liquids will produce a better self-cleaning effect which is extremely important because it clears the drain and ensures the full drainage cross section is available for that major storm event which produces peak flows.

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