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Content archived on 2022-12-27

MODELLING OF DISPERSION SOURCE TERM IN COMPLEX SITUATIONS

Objective

The purpose of this project is to specify the behaviour of real source terms in order to improve the reliability of existing predictive methods for gas cloud extension. A source term is the representation of the nearfield around a gas release. It can be described by the following parameters : a velocity profile and a concentration profile, in terms of shape, size and direction.
The work programme will consist of developing a simple method for characterizing source terms for complex (real) source conditions aligned to the prediction of gas dispersion. Such a method, which will be based on both experimental investigations and theoretical modelling, should make it possible to account for all major classes of source term topology and initial conditions. It is also meant to interface with the existing techniques (and data) for predicting cloud extension.
Two companies will collaborate within the project : TNO and BERTIN.
- An accident analysis from TNO data base FACTS has been carried out.
On the basis of this analysis, a selection of configurations to be studied
has been performed. Underground ruptures and failures are most important
vent stack cases.
- The set up of turbulence model to be used and boundary conditions has been
done. Turbulence model is validated on a compressible shear layer
representative of phenomena occuring in selected scenario. Boundary
conditions are validated on a supersonic vent stack case with high pressure
ratio. This case shown that it is necessary to mesh until forty to
sixty diameters from the hole.
- Numerical simulations of vent stack cases.
- Experimental study of vent stack cases.
- Numerical simulations of craters.
- Measurements and stability analysis of craters.
- Method selected to derive equivalent simple source terms for complex
releases.
The whole project will be divided into 5 tasks.
TASK 1 - SELECTION OF SCENARIO CONFIGURATIONS TO BE STUDIED
Parameters defining the more representative scenario for hazard assessment of gas releases will be selected. They could include different situations and parameters such as:
- accident topology
- generating conditions
- meteorological conditions.
TASK 2 - ASSESSMENT OF INVESTIGATION TOOLS
2.1 Experimental techniques (TNO)
Test campaign will be achieved scanning the major classes of real source terms selected in Task 1, with the idea of testing primarly the importance of simulating local, near field phenomena (Mach effects, Reynolds effects).
Such tests would therefore provide measurements at the source term level. This will be done by varying the scaling laws (for example, with and without reproducing the real pressure ratios), and, if possible, the geometric scale factor.
2.2 Numerical techniques (BERTIN)
An existing numerical simulation program (3 dimensional finite volumescheme) named CALIFE need to be adapted in order to form a basis for source term modelling. The diversity of fluid flow phenomena likely to occur justifies the use of a three dimensional predictive method.
2.3 Selection of investigation tools
It is a task of synthesis.
TASK 3 - INVESTIGATION OF SOURCE TERM CONFIGURATIONS (TNO-BERTIN)
Configurations from simple ones (for example axisymetric) to more complex ones (fully three dimensional) will gradually be considered. This rational way may entail possible improvements in both the experimental method (changing or adding to types of measurements) and the numerical method (changing assumptions, adding to the physical representation).
The objective of these tasks are :
a) study all the selected scenarios using the investigation tools
b) achieve an acceptable agreement between measurements and calculations.
TASK 4 - DEFINITION OF A PREDICTIVE METHOD FOR CHARACTERIZING COMPLEX SOURCES
The objective of this task is to define a practical method for specifying complex source description in view of predicting cloud extension limits according to an accepted format (for example classical inputs of simple plume models for atmospheric dispersion). TASK 5 - COORDINATION
BERTIN will be in charge of the coordination of the whole project:
- technical report for each task
- semestrial technical meetings.

Topic(s)

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Call for proposal

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Coordinator

Bertin & Cie
EU contribution
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Address
59 rue Pierre Curie Zone Industrielle des Gatines
78373 Plaisir
France

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Total cost
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