Host Institution: Technische Universität Darmstadt (Germany)

Department of Energy and Power Plant Technology,  Darmstadt University of Technology.

Phone: +49 6151 16 28908

mahmoud@ekt.tu-darmstadt.de

Research interests

In order to oppose to the pollution standards evolution and to optimize the combustion chamber efficiency, the development and the improvement of combustion technologies and methodologies are required. My research studies concerns the numerical investigation of turbulent isothermal and oxy-fuel combustion provided by separated jets. The swirl effects have been also studied with different values of Swirl Number in order to improv the mixing. The turbulence is captured by using the Large Eddy Simulation model according to the Smagronisky-approach with dynamic procedure which was applied to compute the subgrid scale stress. A flamelet/progress variable model along with a presumed probability density function (PDF), are used to capture the turbulent reacting flow. The Turbulence chemistry interaction is accounted for by coupling the Flamelet Generated Manifold (FGM) tabulated chemistry within the Computational Fluid Dynamics (CFD) code, and transport equations are solved by the finite volume method. A non uniform grid is applied and particularly tightened close to the exit jets in order to capture the near field mechanisms.

Personal page

https://www.linkedin.com/profile/view?id=AAIAABYAasoBGvys5fO-saVJfZj0LVRA7717PN8&trk=nav_responsive_tab_profile_pic

Education 

• November 2015 -- Present time: PhD in Mechanical Engineering at TU Darmstadt.
• 2013 - September 2015: First two years of research studies, MEER-Gafsa,Tunisia
• September - November  2014: Training Course at CORIA (COmplexe de Recherche Interprofessionnel en Aérothermochimie), Rouen-France.
• October -December 2013: Training Course at Technical University - Darmstadt, Germany
• 2010 - 2013: The National Engineer's Degree in Chemical Engineering- Processes , Gabes, Tunisia
• 2010 : The National Entrance for Admission to Graduate Training of Engineers.
• 2008 - 2010: Preparatory School for Engineering Studies Nabeul-Tunisia; Physics-Chemistry major.
• 2008 : Bachelor degree, Experimental Sciences major. Pioneer high school Gafsa-Tunisia,

Selected publications

• Rihab Mahmoud, Hassan Boualia, AmmarHidouri, MouldiChrigui, Numerical study of a non-reactive turbulent flow in two separated jets , PhD STUDENTS SPRING WORKSHOP, 09-11 Avril, 2015, Zarzis, Tunisie.
• Hassan Boualia, Rihab Mahmoud, AmmarHidouri, Jean-CharleSautet, MouldiChrigui,  Numerical and experimental study of dynamic and scalar fields in a turbulent flow provided by a tri-coaxial burner.Effects of stratification. , 09-11 Avril, 2015, Zarzis, Tunisie.
• Rihab Mahmoud, Hassan Boualia, AmmarHidouri, MouldiChrigui, Numerical study of a non-reactive turbulent flow and the impact of the axial distance variation of two separated jets on gases mixing zone, Congrès International CIMATEN, 14-16 December, 2014, Sousse, Tunisie.
• Hassan Boualia, Rihab Mahmoud, AmmarHidouri, MouldiChrigui, Jean-CharleSautet, Experimental study of turbulent flow provided by a coaxial burner, Congrès International CIMATEN, 14-16 December, 2014, Sousse, Tunisie.

Project title: Development and Application of an Eulerian Filtered Density Function Methodology coupled to a Tabulated Chemistry Strategy according to FPI/FGM

Objectives. In many combustion systems, a single burning regime usually occurs. This can be described accurately using a classical flamelet formulation which is restricted to processes within the so-called flamelet regime. By including the curvature and unsteadiness effects, the applicability of the flamelet assumption could be extended. In order to consider the effect of turbulence on the chemistry, further information about the fluctuations is needed. In the context of pre-tabulated chemistry, this effect is represented by distributions of the scalars on the sub-grid level. Generally, a presumed shape (mostly a Beta-shape for the mixture fraction) of the probability density function (pdf) on the sub-grid level is assumed. With respect to other scalars this form may not be valid.
An alternative is given by the solution of the transport equation of one-point joint filtered fine grained pdf of the thermochemical variables. However, this equation involves a large number of independent variables, so that a solution is only possible using stochastic solution methods. In contrast to conventional Lagrangian stochastic particle methods, the Eulerian approaches have become attractive. From the literature, it turns out that such methods allow for describing both non-premixed, premixed regimes and partially premixed combustion.
In this project the LES-fdf methodology will be treated following an Eulerian moment method that will be coupled to a flamelet generated manifolds (FGM) tabulated chemistry to describe multi-regime combustion. Emphasize will be first put on the heat transfer and its effect on the flame evolution and pollutant formation under subcritical flow conditions. Supercritical conditions will be then especially considered. The LES-fdf tool will be validated using available experimental data.

Expected results. The Eulerian approaches are attractive as they enable a well account of the turbulence-chemistry interaction using economical computational costs while including tabulated detailed chemistry. Within the OpenFOAM the candidate shall provide a validated LES-fdf tool that relies on the Eulerian method and accounts for heat loss effects. Starting with subcritical flows, the candidate will consider supercritical conditions and their impact on the LES-fdf modeling.

Planned secondment. IT-POLIMI (8-10 months). Chemistry tabulation.