Laboratory flow

Laboratory flow

Laboratory flumes present a challenging environment in which to achieve accurate flow measurements. Velocimeters help scientists and engineers overcome these challenges, providing excellent measurements of 3D flow structures in flumes or model tanks.

A demonstration of how the Vectrino Profiler velocimeter can be used to measure the turbulent flow profile in the wake of a cylinder.

Highlights

  • Velocimeters are robust and easy to use
  • Work well in flow with poor visibility
  • Measure at rates up to 100 Hz
  • Need suspended particles in the water to function

What and why

What is laboratory flow study and why is it useful?

Instruments called velocimeters are used in flumes to study water flow in structures and around objects. This research helps define the characteristics of the water flow and its movement, and also defines proven physical models for water flow, rather than theoretical numerical models.

Results of flume studies in the laboratory can be applied to larger-scale, real-life scenarios, so these studies have tangible, practical uses. They may help influence the design of a construction or installation by helping to define the forces from water flow before the structure is built.

Studies typically focus on variations in water flow and the effect of such variations on how fluids of different types mix. A non-academic, easy-to-understand example of such mixing processes is the way in which vinaigrette salad dressing is made – the unification of the vinegar and olive oil into one fluid is dependent on the right level of speed and force in the mixing process.

The end result of studying laboratory flow is a qualitative and quantitative characterization of how the water flow pattern is influenced by the range of parameters applied. This data may have real-life practical uses or may function as a physical verification of theoretical numerical models.

Who it's for

Typically, those who are working with laboratory flow are researchers and students investigating water flow in general terms, as well as hydraulics, which covers the transport of liquids through pipes. This group includes civil engineering academics, who perform studies on hydraulic flows, hydroelectric power generation, sediment transport and related topics.

Nortek offers solutions to users who work with water depths from 2 cm to 1 m.

Technical considerations

All Doppler instruments need suspended particles in the water to function. So, it should be ensured that there are particles in the water where the instrument is used, or that such particles can be added. A preferred level of so-called seeding particles is equal to or more than 5 mg per liter (seeding particles can be supplied by Nortek). This may be difficult to achieve in large water tanks with crystal-clear water.

Another consideration is whether there is a high concentration of air bubbles in the water column. Such air bubbles may block the acoustic signal from the Doppler instrument, or lead to a detection of vertical flow that is based on the rising speed of the bubbles, rather than particle movement.

SUSTAIN-laboratory-Miami.jpg#asset:2823University of Miami's Sustain laboratory is a unique resource for fundamental studies on air-sea interactions, wave dynamics, and boundary layer turbulence while providing an experimental test-bed for model development. Researchers at the facility use a Vectrino Profiler velocimeter.

Data presentation

Nortek’s instrumentation makes sure the data related to water flow is collected and stored, but users have to provide their own analytical tools. Users may design their own data analysis tools, or may choose to access and use existing tools, such as MATLAB, developed by other researchers and scientists.

Choice of instrument

For most users, the single-point Vectrino Doppler velocimeter would be the right instrument to use while working with laboratory flow. It has become a default tool for researchers and scientists around the world. The Vectrino stands out due to its great ease of use. It is quick and easy to get started with deployments, installation is simple, data is easily accessible and it is not hazardous in use.

The Vectrino Profiler velocimeter is a natural and optimal choice for boundary layer studies, especially as it provides a short range profile rather than just one single point.

  • Vectrino

    VELOCIMETER

    Vectrino

    Sample 3D velocity at up to 200 Hz for use in hydraulic models and laboratory flumes
  • Vectrino Profiler

    VELOCIMETER

    Vectrino Profiler

    Boundary velocity profile measurements over 30 mm with 1 mm vertical resolution
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