The OpenPALM Coupler: Model Coupling

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AVBP+THERMIQUE2d, aerothermal fluid/structure coupling

Aerothermal modelling aims at studying the thermal behaviour of a body in a fluid flow. It is a thermal fluid structure coupling involving convective and conductive phenomena.
This kind of study aims to predict the wall temperatures of devices in turbulent and unsteady flows. The required precision implies the solution of the Navier-Stokes equations in the fluid and of the heat equation in the bodies, taking into account the thermal exchanges between the different components.
For the moment, the project is setting up a toy coupled model that will be used to explore coupling approaches in particular with respect to the choice of the data to be exchanged and the coupling frequency.

SEVE, land surface modelling

The human activities, their evolution and the expected climatic change raise the question of their impact on environmental resources, such as water availability, its quality, soil quality and biodiversity, on extreme events occurrence or on agricultural productivity. Decision tools to define indicators or predict the impact of management options are still missing and their development is hampered by the lack of comprehensive representation of combined mass and energy fluxes within the different compartments (atmosphere, surface, soil, aquifers, hydrographical networks) of continental areas at the landscape and regional scales. The development of such tools requires overcoming scientific challenges such as:

the coupling of spatial processes acting on the compartments and lateral flows representation:
the impact of spatial structures (organisation and topology of spatial units) on the evolution of state variables describing mass and energy fluxes in the soil, vegetation, atmosphere and hydrographical network compartments ;
the understanding of the functional role of landscape structures to address up scaling issues;
the representation of anthropic forcing to assess the impact of human activities and management options.

Scientists from different fields dealing with continental surface have created the SEVE (Sol Eau Vegetation Energie) working group. One the objectives of the SEVE group, is to produce a multidisciplinary integrated model of continental surface functioning. As a result a concept of a modelling platform, dedicated to the research community, was proposed. The platform must represent spatio-temporal evolution and feedback of processes involved in water, carbon and nitrogen cycles or the pollutant diffusion at landscape and regional scales.
In a first step, we propose to built a prototype of the modelling platform (SEVE-V0) restricted to the landscape scale. The models coupling will be based on the PALM coupling technology. The challenge will be the coupling achievement of a large number of models (more than 15) working at different time steps and over different meshes. Moreover, some models may be time consuming and so a double parallelism should be considered (parallelism in modules execution, parallelism of model).

FLUBIO, fluid-biology interactions

The FLUBIO project studies different issues concerning the interactions between fluids and biology. In particular 1) the Pleurobrachia Pileus propulsion, using hundreds of active cilia clusters and 2) the interaction between a passive ciliate wall (seal fur, bird feathers) and a fluid in motion. For these sudies, several models of the structures, cfd solvers and fluid/structure interaction schemes, as well as experimental data are needed. The different components are coupled by PALM, allowing a great flexibility in the applications. This project is part of the Marie Curie program and is at the origin of an experimental campaign since april 2008.

COMODO-PALM, model nesting

PALM is used at IMAG (Grenoble, France) for a model nesting application. The two models come from the same ocean GCM (OPA) but with different domains and resolutions: a medium resolution general circulation model (North Atlantic, 1/3° NATL3) and a high resolution coastal model (Gascony Gulf, 1/15° BABY15). This project is aimed at the development of new nesting techniques coming from recent research in domain decomposition and exact artificial boundary conditions. The PALM driven implementation makes the application very flexible and allows for the integration of new numerical methods to be tested.

NITROSCAPE, nitrogen cycle modelling at the landscape scale

PALM will be used as part of Component 4 of the EU research project NitroEurope (http://www.nitroeurope.eu/), which began in 2005 and ends in 2010. Component 4 deals with the flows and transformations of nitrogen at the landscape scale (defined here as approximately 5 x 5km) and it is the intention to construct a model (Nitroscape) for this purpose. The Nitroscape model will be created by linking a number of existing models describing agricultural and natural ecosystems, atmospheric transport of nitrogen, farm management and landscape hydrology. The role of PALM is to link these models. The organisations involved in the model linking are the French National Institute for Agricultural Research (INRA EGC et SAS) , France, the Centre for Ecology and Hydrology (CEH), UK, the University of Madrid , Spain, the Institute for Meteorology and Climate Research, Garmisch-Partenkirchen, Germany and the Faculty of Agricultural Sciences, University of Aarhus (DJF), Denmark.

FRUIT VIRTUEL, modelling of biological processes in fruits

The objective of the Fruit Virtuel (virtual fruit) project is to provide a general data-processing system allowing to simulate the fruit life cycle. The fruit is an organ made of cells forming various biological tissues. Its main characteristics, such as its size or its composition, are the result of a complex chain of biological processes. These processes are based on the exchanges (transpiration, breathing, photosynthesis, phloem and xylene fluxes and ethylene emission) between the fruit itself and its environment (atmosphere and plant), on various tissues and cellular operating cycle (division, endoreduplication, expansion, metabolic transformations). To increase our quality profile, it is necessary to analyze the fruit as a specific system in which processes interact. For that, a process modelling approach is particularly suitable: such a modelling is the first step to develop a future "virtual fruit" model. In the "virtual fruit" project, PALM will be used, among other things, to facilitate the parameter exchanges between models, to simplify the modification or the addition of a new model, and to take advantage of parallel computing. The first version of "virtual fruit" will focus on the Peach (a version of the Tomato will follow thereafter...).

AVBP+AVTP, Unsteady Conjugate Heat Transfer

Thermal coupling between structure and fluid in motion is of great importance in many industrial engineering applications. In the context of studies dealing with combustion chambers, these complex effects have a significant impact on: the thermal stress of the combustor walls exposed to a flame front, the temperature of multiperforated walls and more generally on the life cycle of the different components undergoing important thermal loads. With the increase in computing power, numerical simulation is becoming the main tool to study this set of themes. Based on its experience in High Performance Computing, CERFACS develops an efficient aero-thermal application (http://www.cerfacs.fr/~duchaine) using the Large Eddy Simulation code AVBP that solves the reactive Navier Stokes equations (http://www.cerfacs.fr/avbp) and AVTP dedicated to conduction in solids. The PALM coupler is used to easily integrate the codes and to make them communicate. The characteristics of the coupler are very well suited for rapidly setting up new configurations as well as for full size production simulations on massively parallel architectures.

MCCM+MOBILE, Coupling a regional airchemistry model with a 2D biosphere model

Climate change influences the entire coupled Bio-Hydro-Atmosphere (BHA) system. Quantication of the feedbacks between the BHA-System and regional climate therefore requires the consideration of physical, chemical and biological processes. Unfortunately, climate change impact analysis still lacks a BHA-modeling system adequate for the purpose.
In order to investigate these complex feedback mechanisms between regional climate and ecosystems, a new BHA-modeling system is developed by coupling the bio-hydrosphere model-framework (MOdular BIosphere simuLation Environment, MoBiLE) with the regional meteorology-chemistry-climate-model MCCM.
MCCM is based on MM5, extended by a chemistry transport model including gas phase air chemistry and primary/secondary aerosols processes. MOBILE replaces the original land-surface scheme in MCCM with a dynamic one. It consists of modules accounting for dynamic vegetation development, soil water and energy balance, biogenic VOC emissions, bio-geochemical C/N cycles in vegetation and soil.
The bidirectional data exchange between MCCM and MOBILE, which is done by the PALM-Coupler, accounts for the different time scales of the underlying processes resulting in information update frequencies between seconds and days.
The PALM coupler handles data exchange for mixed language programming and the non congruent numerical grids of the two models (mapping gridded data). Further research will include dynamic load balancing to maintain efficiency on MPI parallel computers.
For further information http://www.fzk.de/fzk/idcplg?IdcService=FZK&node=4567&lang=en.

AVBP+DOMASIUM, Interaction Between Radiation and Convection for Industrial Combustion Applications

A study of the interaction between radiation and convection for industrial combustion applications is currently carried on. The radiative heat transfer is calculated using DOMASIUM and the fluid properties are calculated using the LES code AVBP. PALM is used as a coupler to permit the exchange of information between the two parallel codes.