Developed since 1987 by EDF R&D in collaboration with other French, European and international organisations, the openTELEMAC system is a set of scientific computation solvers, coupled and parallelized, dedicated to the modelling of free surface environmental hydraulics. It can carry out simulations of flows, sediment transports, waves and water quality. The system has gradually evolved to the notion of hydro-informatics with a set of solvers dealing with large heterogeneous data and solving complex dependent problems. The various simulation components use high-end algorithms based on the finite element or finite volume methods. The ability to study global, regional, or local scale problems by using the same system, makes openTELEMAC a useful tool for assessing the environmental state in the sea, estuaries, coastline, lakes and rivers.

The TELEMAC environment

The openTELEMAC system is composed of the following components, each of which relates to a specific physics, and all of which are coupled together to solve complex problems:

Hydraulic solvers

MASCARET

Modelling of free-surface Shallow Water Equations in 1D (Saint-Venant equations), with non-hydrostatic reconstruction, solved on the basis of finite differences and finite volumes. A model with interconnected compartments makes it possible to take into account inundation zones, relatively isolated from the major riverbed.

TELEMAC-2D

Modelling of the free-surface Shallow Water Equations in 2D (Saint-Venant Equations). Several turbulence models are available and various other physical terms can be taken into account like bottom friction, Coriolis and tidal generating forces, interaction with weather (wind, air pressure, rain, evaporation). It can also solve the advection-diffusion of tracers such as temperature, salinity or concentrations of material substances.

TELEMAC-3D

Modelling hydrodynamics in 3D with free surface through the so-called free-surface non-hydrostatic Navier-Stokes equations. Similarly to TELEMAC-2D, TELEMAC-3D offers several turbulence models, is able to take account of various phenomena or forcings, and can simulate the advection-diffusion of active (driving density varying in space and time) or passive tracers.

Cross section meander (telemac-3d and gaia coupling)

Lock-exchange problem

Wave propagation solvers

ARTEMIS

Modelling waves in coastal and port areas based on the so-called “mild slope equation” initially proposed by Berkhoff (1972) in a framework of linear potential flows (assumption of small amplitude waves or low wave steepness). It is a so-called phase-resolving model, initially formulated for regular waves (i.e. with a fixed wave period or frequency). It can also handle irregular wave fields (characterised by a frequency spectrum of energy) and/or multidirectional waves, by linear superposition of elementary calculations carried out for a given wave frequency and direction. In terms of physical processes, ARTEMIS is suitable for modelling processes affecting wave propagation over variable bottoms in coastal areas (refraction, shoaling), interactions with obstacles or coastal/port structures (reflection, diffraction), as well as energy dissipation processes due to bottom friction and/or surf-breaking in shallow water. The effects of an ambient current (due to the tide, for example) can also be taken into account. ARTEMIS is particularly well suited to studies of wave penetration and agitation in ports, harbour basins, seawater intake or discharge channels. It can also be used to study the risks of resonance (seiches) in these basins.

Wave simulation over the Alexandria lighthouse archaeological site

TOMAWAC

TOMAWAC is a third generation spectral wave model for sea states evolution from the oceanic to the coastal scale. It models the spatial and temporal evolution of the directional spectrum of wave energy, providing a high-level description of the sea state. TOMAWAC can be used to model a large number of physical processes, including the generation of waves by the wind, their propagation over very large distances on an oceanic scale, and the effects of water depth variations as waves approach the shore (refraction due to variations in bathymetry and/or an ambient current field), the many processes that dissipate wave energy (white-capping, wave breaking due to bathymetry, bottom friction, attenuation by porous media or vegetation) or redistribute wave energy within the spectrum via non-linear transfers between wave frequencies (among 4 or 3 waves). The wind fields supplied as input forcing data, as well as the characteristics of the marine environment (sea level, ambient currents) can, in the general case, be spatially and temporally variable. TOMAWAC can be used for several types of application, including wave climate simulation based on wind fields (from meteorological reanalyses or atmospheric forecast models), on the scale of a few days (storm) or several decades (wave hindcast database), wave propagation studies in coastal areas, by transferring sets of known wave conditions off a site to the coast.

Rip current : The coupling between TOMAWAC and TELEMAC-3D allows to simulate the rip current induced by the waves breaking

Simulated wave height in Indian Ocean from 01/01/2000 to 07/01/2000

Sediment transport solvers

COURLIS

COURLIS modelling sediment transport in rivers and reservoirs where the flows can be considered as 1D. Evolution of riverbeds due to bedload transport is classically modelled by coupling the Shallow-Water equations for hydrodynamic processes (solved in the MASCARET solver) and the Exner equation for bedload mechanisms. COURLIS manages cohesive and non-cohesive sediment transport by suspension.

Longitudinal profil of silt concentration after a reservoir drawdown

GAIA

GAIA solves sediment transport and morphological evolution problems in rivers, coastal seas, estuaries and reservoirs. By a clear treatment of sedimentary processes that happen in the water column, in the bed structure, and at the water–bed interface. The module GAIA efficiently manages the spatial and temporal variability of sediment size classes, the different properties for cohesive and non-cohesive sediments, and the transport modes (bedload and suspension) for two- and three dimensions.

Water quality solvers

TRACER

TRACER modelling solute transport processes, consisting of advection, dispersion and mass reduction/generation by physical, chemical and biological mechanisms. TRACER is the transport and water quality module of the 1D free surface code MASCARET. TRACER simulates the evolution of several coupled tracers without retroaction on the flow with respect to hydraulic conditions, boundary conditions, external sources and biochemical interactions between tracers.

Simulation of water net heating along the Rhône river due to the operation of nuclear power utilities (from bottom to top: from upstream to downstream; from left to right: from 1st January to 31st December 2017)

KHIONE

KHIONE modelling of suspended frazil ice and ice cover, based on an advanced heat balance, taking into account interactions between water, air and frazil concentration, freezing processes and ice cover formation, as well as the effects of ice cover on hydrodynamics or on submerged structures such as clogging on trash racks.

Simulation of frazil concentration in the Saint Lawrence river (a) from Khione user manual and supercooling validation with Carstens experiments (b) from [F. Souillé et al, 2023]

WAQTEL

WAQTEL modelling of biochemical and thermal processes within water bodies in the natural environment. This component includes a complete model of heat exchange with the atmosphere. It includes processes related to the oxygen, algae, ammonia and phosphate cycles, as well as biomass and micro-pollutants processes in suspension or dissolved. WAQTEL is coupled with the 2 codes TELEMAC-2D and TELEMAC-3D. WAQTEL module was built from the processes implemented in TRACER and extended to 2D and 3D for most of the processes. A coupling to the AED2 library is also available for more advanced water quality simulations.

Oxygen evolution in Lagoon

The environment around openTELEMAC

Surrounding the openTELEMAC system solvers and also distributed as open source codes, an ensemble of scripts entirely written in Python have been developed to allow the environmental modeling system to meet the challenges of complex real-world problems. In this framework, distributed Application Programming Interface (API) of the openTELEMAC system with a Python overlay has been developed. This Python wrapping of openTELEMAC system API constitutes a package called TELAPY distributed in the official version of the hydro-informatic system.

Ecosystem of openTELEMAC API. References