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Laboratory of applied hydraulics – Physical scale models

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The CACOH, a world reputed hydraulics laboratory with nearly 85 years’ experience

CNR’s applied hydraulics laboratory was founded in 1936 to study and validate the hydraulic design of all the hydroelectricity production plants and navigation structures of the Rhone river using physical scale models.

The scope of action covered by CNR’s hydraulics laboratory quickly expanded to other fields and problems, allowing CNR to provide its unrivalled expertise to all owners and developers wishing to optimise the performance of their hydropower projects, especially regarding:

  • Dimensioning,
  • Hydraulic operations,
  • Long-term hydrodynamic and sedimentation impacts,
  • Construction conditions,
  • Construction and operating costs.

What is a physical scale model?

A physical scale hydraulic model is a tool that permits studying a stretch of river or design a hydraulic structure using a physical model built on a smaller scale. Physical hydraulic modelling relies on scaling laws used to reproduce, at reduced scale, flow and solid transport conditions in a natural system by ensuring the representation of the dominant forces governing the movement of water and sediments as a function of the relevant proportions.

CACOH, a hydraulics laboratory that covers a huge range of studies and services

The expertise of CNR’s applied hydraulics laboratory covers the following fields of study:

  • Hydropower projects: water intakes, headrace canals and dikes, galleries and gate shafts, hydropower plants, measures of performance on site, etc.
  • Dams and reservoirs: flood spillways, bottom outlets, regulating gates, stilling basins, energy dissipators, reservoir silting, etc.
  • River developments: weirs, structures crossing river valleys, trash racks, flood protection dikes, fish passes, etc.
  • Hydromorphology: sediment continuity, river morphodynamics, ecological restoration of rivers, etc.
  • Erosion and sedimentation: sediment traps, bridge piers, rip-rap, groynes, etc.
  • Torrent hydraulics: river bank profiling, channels, torrent risks, natural dams, etc.
  • Navigation structures: canals, locks, navigable waterways, regulation structures, etc.
  • Urban hydraulics: water intakes, drainage shafts, storm overflows, pumping stations, complex drainage systems, etc.

CACOH, a hydraulics laboratory expert in hydraulic and hybrid physical modelling

Hydraulic physical modelling is not only a competitive and reliable tool for optimising the performance and cost of complex structures but also for efficiently modelling sediment transport in rivers and torrents. Hydraulic physical models allow testing a very wide range of technical solutions and investigating extreme scenarios in perfect safety. Hydraulic physical models are also highly efficient communication and consultation tools for assisting decision-makers to make technical-economic choices.

Despite the increasing technical prowess of mathematical modelling, hydraulic physical models remain indispensable when designing a hydraulic development with complex flows or that is liable to have a hydrodynamic or sedimentary impact difficult to predict in the long-term.

Far from contradicting each other, hydraulic physical models and numerical models can now be used in synergy and are well adapted to joint use for simulating the most difficult hydro-sedimentary phenomena. In this case, the term hybrid modelling is used.

What is a hybrid model?

Hybrid modelling consists in coupling a physical model with one or more numerical models to optimise the quality of the results obtained, and the duration and cost of a study by making up for the weaknesses of one model by the strengths of the other. In particular this type of modelling allows expanding the field covered by the sector modelled by nesting models and/or scales, evaluating and correcting effects of scale, and performing cross validations of results.

CACOH, a hydraulics laboratory equipped with test facilities and leading-edge measurement technologies

The physical scale models designed by the team at CNR’s hydraulics laboratory use test and measurement equipment that range from standard devices to the most advanced in the field:

  • A pumping station and water tower ensuring constant supply to models up to a discharge of 700 l/s;
  • Electromagnetic flowmeters,
  • Real time data acquisition system (levels, pressures, velocities, discharges, efforts, etc.);
  • Natural and artificial materials permit the efficient simulation of very varied sedimentary situations in solid transport studies;
  • Ultrasound probes and high frequency pressure sensors for measuring levels;
  • Measures of velocity by PIV (Particle Image Velocimetry), LSPIV (Large Scale Particle Image Velocimetry);
  • Doppler Ultrasound Velocimetry to measure the velocity of water in movement without disturbing its flow;
  • Automated surveying of emerged and submerged beds: ultrasound echosounders, total station theodolites, photogrammetry in and out of water, etc.

Contact the CACOH

Sales contact: 33(0)4 72 00 68 15