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New laser system measures flow in 3D

Published: 28 February 2017

The John Field Laboratory has a new system in the form of a tomographic PIV – a bright laser and four cameras to measure various fluid mechanical phenomena in 3D. It will be important for research in areas such as hydropower, mining and steel industries, biocomposites and machine components.

– By using a bright laser and four high quality cameras, we can measure everything that flows as long as it is optically transparent. Flows that are three-dimensional are of special interest because you can get a 3D view of how the flow looks. We can now relatively quickly measure and visualize to gain a deeper understanding of various fluid mechanical phenomena, says Sofia Larsson, post doctoral researcher in Fluid Mechanics at Luleå University of Technology.

– Fluid mechanics are everywhere around us and it is extremely important to understand flows, the forces that occur and how they affect different objects. Space, weather, sea, aircraft, ships, automobiles, wind and hydro power, the list goes on and on.

Measurement of volume provides a better picture

The new measuring system makes it possible to measure all three components of velocity (up-down, left-right, forward-backward) in a volume at the same time without disturbing the flow. As shown in the slide show the measuring equipment is placed outside the flow.

– Previously, we have only been able to measure in one plane, not in a volume, which misses out on important information and it can be difficult to assess what is happening in the outside flow of the measurement plane. This is especially true for flows with large three-dimensional effects compared to more simple flows in one direction, for example the flow in a pipe. The better understanding of the flow we have, the easier it is to control the flow in the way that is optimal for different applications.

Project about porous materials

The pictures above (and video below) show the installation setup of the system. It is a common aquarium pump producing a jet that is ejected into the small tank. In the tank there is a calibration plate which is used to set up the cameras.

– It is extremely important to conduct a careful calibration so that the tomographic reconstruction (creation of the 3D image) is correct.

The tomographic PIV (Particle Image Velocimetry) will among other things be used in a project that, together with researchers in mathematics, will study the flow through a thin porous material. The flow through porous materials is applicable in many areas, such as ground water, composite manufacturing and in the production of iron ore pellets.

The laser system is financed by the Kempe Foundations and LTU's lab fund by half each.

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Photo: Ted Karlsson