The overall objective of this concerted research action is to develop a flexible, open source, Large-Eddy Simulations (LES) Computational Fluid Dynamics (CFD) code-base for multiscale modelling of several multidisciplinary applications. The code-base will contain tools that can be fine-tuned for specific applications, but which are all developed from a strong common basis.
An integrated code-base in the existing OpenFoam framework will be developed, such that an ‘UGent OpenFoam Community’ can emerge, taking advantage of code sharing and joint code development. The long-term objective is that much faster and solid progress can be made by all research units in the consortium (and later on at UGent) that actively use CFD, building upon shared knowledge and experience of all community members and particularly strengthening progress by cross-fertilization among the partners.
There are clear ‘overlaps’ in the activities, for each of which an objective can be defined:
— Reduced chemistry: implementation of kinetic models with more than 50 species in CFD is at present not common practice for LES. This is in sharp contrast with the increasing number of species in the presently generated chemical models, which is in the order of thousands of species. Therefore a dynamic kinetic model reduction method will be developed for the OpenFoam platform in order to drastically decrease the required CPU time. This will be combined with the classical tools for obtaining reduced chemistry, i.e.: quasi steady state approximation, rate of production and sensitivity analysis. Best practices and examples will help to disseminate these techniques to the other consortium members.
— Sprays: atomizing a liquid to increase the total liquid surface area, by forcing the liquid through a nozzle, is used in countless engineering applications. The complex two-phase fluid dynamics make it challenging to calculate the spray characteristics needed for designing the nozzles for a particular application. Also disperse sprays are important, e.g., for combustion or fire suppression. The project aims at building the tools for spray calculations and tailoring them to the following cases:
— Turbulent steady spray flames: the development of CFD models that provide accurate and reliable results within a reasonable amount of time for spray combustion (extensively applied in energy conversion devices, such as gas turbines, IC engines and furnaces). This is a challenge due to the multi-scale nature associated with the wide range of the characteristic scales of turbulence, chemistry and particle dynamics.
— Unsteady sprays, in internal combustion engines: the spray model is part of the development of a numerical tool allowing research into “dual fuel” combustion modes. Dual fuel engines are considered an economic way to meet upcoming emission standards, as explained in section 1.
— Fire Dynamics: improved understanding of fire dynamics in enclosures, including reduced ventilation conditions and fire suppression, will allow sufficiently fast and accurate simulations which will, combined with real-time multi-sensor data, enable fire forecasting. These overlaps also indicate that joint PhDs among the consortium promotors and co-promotors will be very feasible.
In addition to this global project objective, the following key objectives are defined per subdomain:
⇢For bio-systems : detailed modelling with CFD and experimental validation will lead to
(1) better understanding of the anaerobic digestion (AD) process, and
(2) improved reactor and mixing design. The AD process is important in bio-engineering (e.g., to stabilize waste sludge and to recover bio-energy as methane), but is difficult to scale up, maintaining the yield.
⇢ For chemical processes : coupling detailed kinetic models with CFD, accounting properly for turbulence. The approach will be validated using a unique set of newly acquired experimental data on the flow field in well-defined reactor geometries using 2D/3D Particle Image Velocimetry (PIV) and liquid crystal thermography.
⇢ For internal combustion engines : the development of a numerical tool allowing research into “dual fuel” combustion modes. Dual fuel engines are considered an economic way to meet upcoming emission standards.
⇢ For turbulent steady spray flames : the development of CFD models that provide accurate and reliable results within a reasonable amount of time for spray combustion (extensively applied in energy conversion devices, such as gas turbines, IC engines and furnaces). This is a challenge due to the multi-scale nature associated with the wide range of the characteristic scales of turbulence, chemistry and particle dynamics.
⇢ For fire dynamics :
(1) the accurate modelling of fire and fire-induced flows in compartments with reduced ventilation and water-based fire suppression systems, and
(2) the assessment of the use of current CFD models for performance-based fire design purposes in compartments. Accurate prediction of the fire dynamics in compartments under different conditions is very challenging and validation of the current CFD models is essential for their use for fire safety design purposes of real life applications.
⇢ For fire forecasting :
(1) the design of computationally low-cost multi-sensor analysis techniques for fast and accurate detection of fire characteristics (e.g., the spatio-temporal flames and smoke spreading),
(2) the development of a methodology to use the measured fire characteristics within a fire forecasting framework (i.e., in order to replace or correct model predictions) and
(3) the assessment and optimization of our multi-sensor analysis framework and its forecasting performance for various fire configurations by means of real-world fire experiments.