Smoothed Particle Hydrodynamics in OpenFOAM for jet application

In the following of the work of Dabonneville also presented to OFW12, this paper aims at presenting the coupling of two methods for improving the computation of jets issuing for injectors. The present work is part of a project called "Labex EMC3: Energy Materials and Clean Combustion Centre".The purpose is to reduce the pollutants emissions, for this it is necessary to understand all the phenomena involved in the combustion chambers. Understanding the physical phenomena that appear in the combustion chamber is crucial for optimising motors efficiency and minimising the costs of external de-polluting components. The physical principles occurring in the combustion chamber can be summarized as follow : the injection system atomise the fuel, which is evaporated and mixed inside the chamber. Once the mixing is sufficiently homogeneous, combustion can occurs.

The starting point, and therefore the key issue, is the atomization process. If this phenomenon is erroneously predicted, it will influence evaporation and mixing inside the chamber. Today, Computational Fluid Dynamics has become one essential tool for designing and optimising these combustion chambers. But at the present time, computing primary atomisation and mixing area in combustion chamber is not feasible with the present development of LES and DNS. Constraints come from the Eulerian formalism which needs, in the region close to the nozzle, a sufficiently fine enough mesh to accurately describe the injection gradients. This is basically represented by a severe CFL condition.

Following the first implementation of Dabonneville, a Zonal Domain decomposition will be used in order to overcome these constrains. But here, instead of coupling two Finite Volume Methods (FVM), the coupling of a meshless Lagrangian method with a FVM is proposed. The goal would be to use the Lagrangian method in the primary atomisation zone. In the present implementation, a Smoothed Particle Hydrodynamics (SPH) method was chosen as a candidate for the Lagrangian method, based on the implementation of Cherfils. The SPH version is an unsteady Lagrangian Weakly Compressible SPH, commonly referred as WCSPH.

This paper will first present the development of a SPH method in the framework of OpenFOAM-3.0.1. Then, some comparisons with very well documented "dam break" test-case configuration will be presented in order to validate the newly SPH implementation. Finally, fully SPH and FVM computations of a co-flow jet configuration will be presented. The used configuration is the one of Aristodemos. In a near future, coupling between the Lagrangian SPH method with the Eulerian formalism inside the combustion chamber will hopefully be performed.