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The Drop Channel
Svensk Form Excellent Swedish Design Award
"The fixed, onion-like forms shape the run-off water and create a pulsating, rippling effect which well brings the water to the attention to our senses. The onion-shaped gutter is an example of innovation which enhances our everday environment, something the jury wants to encourage."
This was the jurys motivation on why they wanted to award IET (among others)
with this prize. With deep interest we now notice that realized vortex ideas
have aestetic values as well!

The design process and function

The idea and use of the Drop Channel
- It has an aesthetic and smooth shape that fits into the city environment
- It has a splashing and interesting flow during rain
- It has an effect on lighter sediment i.e. a "self cleansing flow" in the channel

The Drop Channel is used for transporting surface water in open canals displaying a pulsating flow in a straight channel. This pulsating flow arises spontaneously by the geometry of the channel due to the fact that the water is passing a row of flow bodies.

The channel is best placed on grass with a slope of some few (3-5) per mil.     

A segment of the Drop Channel Drop Channel with flowing water

Background and conditions
The Drop cannel has its origin in a scientific project concerning self-organising water flow and the effect of flow bodies on the flow. Such flow bodies were proposed and developed by the Austrian natural scientist Viktor Schauberger during the twenties and the thirties. The idea is to let the flow bodies indirectly influence the flow axis in smaller watercourses, i.e. create conditions for self-organisation in a new main stream. The institute (IET) has run a project in order to study these ideas and to look for opportunities for further development.

At this stage we came in contact with the "Ekostadsprojektet" in Malmö, a project aiming to give the Augustenborg area a strong environmental profile. A part of this project is the care taking of rain or surface water that is gathered in the area shall be lead in open canals, and that is shall be absorbed or temporarily stored within the quarter in order to relive the stress on the cloak system of the city. One other important aim is to make the role of the water more vivid in modern humans mind.

The idea was generated to equip some of the canals that naturally lead the water from the drains to the bigger ponds with flow bodies. In this way we came to co-operate with the local water authorities (VA-verket) in Malmö and the landscape architects "Mellanrum" who are responsible for the water part in the "Eco City project".

The design process
The design process could be characterised as an iterative process.  A channel with a smooth profile made of sheet metal covered with a thin layer of concrete was constructed in full scale. In this channel the water flow could be observed. Different types of flow bodies were moulded in modelling clay and their influence on the water flow was closely studied.

Particularly the transport of lighter sediment was studied and with a special emphase if this had a tendency to gather or to be swept away.

Some very important criteria of design were that it should be possible to cast the channel in concrete and that it must be robust in order to stand the effects from playing children. One example of this is that it must not have any brittle parts, something that gave the framework for possible shapes and angles. Of course it was important that it should have an aesthetic and interesting flow.

These criteria, together with the experiences from the flow modelling, resulted in a study with more rounded flow bodies - from the beginning egg shaped and rounded stones.

By placing the "stones" in a certain geometry a vortex flow could be observed just down stream. This vortex flow caused the water to swing from one side to the other just like the tail of a fish. In this way we managed to generate a pulsating flow that reminded us about the flow in "water stairs" or the "Virbela Flowforms". The geometry between the "stones" was critical for the appearance of a robust pulsation. When the system was well tuned, the flow bodies, the water and the channel resulting in a dynamic system that spontaneously generated a pulsation in the flow.

The final shape of the flow bodies became drop shaped or like an onion cut a long the "axis". This shape had the same effect on the flow as the egg shaped stones and met the criteria on the ability for casting, mechanical robustness in combination with aesthetic and smooth design.

Description of the material
The channel is constructed of sulphate resistant concrete, Btg I Stg Degerhamn (construction concrete), K40, air contents minimum 6.0%, vct < 0,40. It is casted in 1,2 m long forms. The weight of one "stone" is about 170 kg.

Retailer, etc
The Drop Channel is manufactured and sold by:
Skanska Prefab AB, Industrivägen 4, 245 34 Staffanstorp, Sweden.

The channels are laid in the Augustenborg quarter in Malmö, Sweden, and they have been displayed in the Bo01 exhibition in Malmö during 2001, as well.
Early experiments with "egg shaped stones" made of modelling clay
Experimental channel with pulsation