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• Semi-resolved CFD–DEM is extended to particulate flows with thermal convection. • Background fluid properties are corrected using kernel-based approximation. • Model A is adopted to address fluid-particle interaction with more force models. • Turbulence model is incorporated into the semi-resolved CFD–DEM. • The semi-resolved CFD–DEM provides better predictions and more details in modeling thermal particulate flows in fluidized bed. • Several phenomena observed in thermal fluidized bed are discussed. Particulate flows with heat transfer widely exist in industry including fluidized bed reactor and powder-based 3D printing, and are frequently modeled with CFD–DEM coupled approaches. Recently, we developed a semi-resolved CFD–DEM approach, which bridges the simulation gap between the resolved and unresolved CFD–DEM (Wang et al., 2019). The semi-resolved CFD–DEM is as efficient as the conventional unresolved CFD–DEM and as accurate as the resolved CFD–DEM, while it is validated for particulate flows with momentum exchange with Model B without heat exchange. In this paper, we further extend the semi-resolved CFD–DEM approach to model particulate flows with momentum exchange and thermal convection. Firstly, similar to background fluid velocity, background fluid temperature is corrected through kernel-based approximations on the neighboring fluid cells rather than simply taking values in the local cell containing the concerned particle. Secondly, Model A is adopted in the semi-resolved CFD–DEM, leading to more powerful capabilities in handling complicated flows. Force models like the Magnus force, virtual mass force are also included. Thirdly, turbulence model is incorporated into the semi-resolved CFD–DEM approach to address possible turbulence effects. Finally, the developed semi-resolved CFD–DEM is applied to modeling the complex particulate flows in fluidized bed. The obtained numerical results are compared with experimental data and results from other sources. It is demonstrated that the present semi-resolved CFD–DEM is effective in modeling particulate flows with thermal convection. Compared to the conventional unresolved CFD–DEM, this semi-resolved CFD–DEM can provide better predictions and more details on particle temperature distribution, mean temperature, solid/fluid fraction, velocity autocorrelation and vorticity field. [ABSTRACT FROM AUTHOR]

• Natural thermal convection induces fluid motion. • Particle shape-effects do play an important role in the particle and overall system dynamics. • Thermal heat exchange significantly affects the motion of the two-phase flow. • Multi-grid FEM-FBM is robust and potentially powerful tool for real particulate flow simulations. In particulate flows, particle-particle collisions play a very important role in determining the flow behavior of the fluid-particle two-phase systems. Thus, it is very important in the numerical simulations of particulate flows to treat the particle-particle interactions with a felicitous method. In this paper, a recently developed direct numerical simulation (DNS) technique, the Finite Element Fictitious Boundary Method (FEM-FBM), for thermal convective particulate flows is used for the simulations of dense particulate suspensions of elliptic shaped particles. The momentum and temperature flow fields are coupled with the aid of Boussinesq approximation. The thermal and momentum interactions between solid and fluid phases are handled by using the Fictitious boundary method (FBM). The continuity, momentum, and energy equations are solved on a fixed Eulerian mesh which is independent of flow features by using a multi-grid finite element scheme. A modified collision model is proposed that can handle not only the interactions between the circular particles but also effectively treat the collisions between the elliptic shaped particles. Firstly, we validate the newly developed collision model for isothermal circular particles together with a comparative study of "drafting, kissing and tumbling" (DKT) motion of both elliptic and circular shaped isothermal particles. Then we investigated the DKT motions of the hot and cold elliptic particles with energy exchange and studied the lateral behavior of the particles in numerous settings. Further, we studied the DKT motion of catalyst particles and investigate the particles behavior at different Grashof numbers. Numerical tests are performed to show that the present method is robust and provides an efficient approach for the simulations of particulate flows with a large number of elliptic particles. [ABSTRACT FROM AUTHOR]

This paper presents a direct numerical simulation (DNS) technique, the Finite Element Fictitious Boundary Method (FEM-FBM) for the simulation of fluid-solid two-phase flows with heat transfer. The heat transfer equation is introduced to study thermal convection in fluid-solid two-phase flows. The Boussinesq approximation is considered for the coupling of momentum and temperature flow fields. Multi-grid finite element solver is used to compute flow equations of mass, momentum, and energy on a fixed Eulerian mesh which is independent of time and the solid particles are allowed to move freely in the whole computational domain. Fictitious boundary method (FBM) is used to treat the particles inside the fluid, FBM takes account of the thermal and momentum interaction between the fluid and the particles. The accuracy and stability of presented method are validated by comparing our test cases results with the results reported in the available literature. Numerical tests are performed to show that this method is potentially powerful and provides an efficient approach to simulate complex thermal convective particulate flows with a large number of particles. [ABSTRACT FROM AUTHOR]