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The numerical simulation of biomass combustion requires a model that must contain, on one hand, sub-models for biomass conversion to primary products, which involves calculations for heat transfer, biomass decomposition rate, product fractions, chemical composition, and material properties, and on the other hand, sub-models for volatile products transport inside and outside of the biomass particle, their combustion, and the char reduction/oxidation. Creating such a complete mathematical model is particularly challenging, therefore, the present study proposes a versatile alternative&mdash, an originally formulated generalized 3D biomass decomposition model designed to be efficiently integrated with existing CFD technology. The biomass decomposition model provides the chemical composition and mixture fractions of volatile products and char at the cell level, while the heat transfer, species transport, and chemical reaction calculations are to be handled by the CFD software. The combustion model has two separate units: the static modeling that produces a macro function returning source/sink terms and local material properties, and the dynamic modeling that tightly couples the first unit output with the CFD environment independently of the initial biomass composition, using main component fractions as initial data. This article introduces the generalized 3D biomass decomposition model formulation and some aspects related to the CFD framework implementation, while the numerical modeling and testing shall be presented in a second article.

Numerical simulation of nanofluid flows is of maximum importance for a large area of applications, especially in the solar energy technology. Even though a lot of numerical studies are available in the open literature, there is still a large debate in regard to the most appropriate approach when dealing with nanofluids. Plus, a precise simulation of the thermal fluid-solid system encompasses a profound understanding of the fundamental physical phenomena that appear in the nanofluid flow. In this idea, a number of simplifications and approaches are considered, and the aim of this benchmark study is to shed some light in the most suitable CFD approach when dealing with nanofluid flow. Finally, different approaches were considered by different research groups with relevant experience in CFD and are discussed accordingly and in connection with an experimental case that was chosen as a comparison. The current benchmark study was projected to be an ample reference for investigators interested in dealing with the numerical study of the nanofluids’ flow.

Institute of Statistics and Applied Mathematics, 13 Septembrie 13, sect.5, 050711 Bucharest, RomaniaThe flow characteristics and stall delay phenomenon of a stall regulated wind turbine rotor due to blade rotation in steadystate non-yawed conditions are investigated. An incompressible Reynolds-averaged Navier-Stokes solver is applied to carryout the separate flow cases at high wind speeds from 11 m/s to 25 m/s with an interval of 2 m/s. The objective of the presentresearch effort is to validate a first-principles based approach for modeling horizontal axis wind turbines (HAWT) understalled flow conditions using NREL/ Phase VI rotor data. The computational results are compared with the predicted valuesderived by a new stall-delay model and blade element momentum (BEM) method.