On the effects of high-order scattering in 3D cubical and rectangular furnaces

The discrete ordinates method (DOM/Sn) is implemented to investigate the high order scattering effects of absorbing–emitting–scattering grey gas media inside the three-dimensional cubical and rectangular furnaces. To validate the numerical method, the furnaces are considered first to be filled with non-scattering grey gases, and the results of the higher order approximations of the DOM show an excellent agreement compared with those available in the literature. The DOM is then extended to apply in the scattering media inside the furnaces, and the results of various scattering approaches such as out-scattering, iso-scattering, linear aniso-scattering and nonlinear aniso-scattering are obtained and presented in this paper

Radiative heat transfer during turbulent combustion

We investigate the radiative heat transfer in a co-flowing turbulent nonpremixed propane-air flame inside a three-dimensional cylindrical combustion chamber. The radiation from the luminous flame, which is due to the appearance of soot particles in the flame, is studied here, through the balance equation of radiative transfer which is solved by the Discrete Ordinates Method (DOM) coupling with a Large Eddy Simulation (LES) of the flow, temperature, combustion species and soot formation. The effect of scattering is ignored as it is found that the absorption dominates the radiating medium. Assessments of the various orders of DOM are also made and we find that the results of the incident radiation predicted by the higher order approximations of the DOM are in good agreement

Large eddy simulation for turbulent non-premixed fuel-rich combustion in a cylindrical combustor

No abstract available

LES of non-newtonian physiological blood flow

Large Eddy Simulation (LES) is performed to study the physiological pulsatile transition to turbulent non-Newtonian blood flow through a 3D model of arterial stenosis using the different non-Newtonian blood viscosity models. The computational domain has been chosen is a simple channel with a biological type stenosis formed eccentrically on the top wall. The physiological pulsation is generated at the inlet of the model using the fourth harmonic of the Fourier series of the physiological pressure pulse (Womersley [1]). The computational results are presented in terms of the post-stenotic re-circulation zone, shear stress, mean and turbulent kinetic energy

LES of physiological pulsatile flow in a model arterial stenosis

Physiological pulsatile flow in a 3D model of arterial stenosisis investigated by applying Large Eddy Simulation(LES)technique. The computational domain has been chosen is as imple channel with a biological type stenosis formed eccentrically on the top wall. The physiological pulsation is generated at the inlet of the model using the fourth harmonic of the Fourier series of the physiological pressure pulse. The flow Reynolds numbers which are typical of those found in human large artery are chosen in the present work. Transitions to turbulent of the pulsatile flow in the post stenosis are examined through the various numerical results and explained physically along with the relevant medical concerns

LES of physiological blood flow in diseased basilar artery: semi-patient specific model

Large Eddy Simulation (LES) is applied to study physiological pulsatile spiral and non-spiral blood flow through a model of an irregular stenosis with an adjacent post-stenotic fusiform irregular aneurysm in basilar artery. The stenosis and the aneurysm are of 75% area reduction and 126% area enlargement, respectively, at their centres [1]. Numerical results of various important physical quantities are presented to particularly investigate the transition-to-turbulence nature of the pulsatile flow with their relevant clinical implications

An analytical investigation of the physical dimensions of natural convection flow on a vertical heated plate

Analytical results of the boundary layer of natural convection air flow on a vertical heated plate are presented for both isothermal and constant heat flux plates. We investigate the effects of the heat flux and the temperature of the plate on the development of the physical boundary layer along the plate. The ranges of temperature and heat flux examined are 10°C ≤ T ≤ 100°C and 50 ≤ qP ≤ 600 (w/m2) respectively. The results show that the variation in the plate temperature has a significant effect on the transition of air on the isothermal plate, and the difference between the temperature of air and plate has more effect on the transition especially when TP ≤ 60°C. In addition, the temperature of the flow on the constant heat flux plate shows a little effect on the transition, where the transition mostly depends on the heat flux. At qP = 220 (w/m2) and Ta=29°C with declining the temperature of air by 69%, the critical height declines by 3.8%. The analytical results are compared with different previous experimental studies for different operation conditions, where a satisfactory agreement is achieved

Pulsatile spiral blood flow through arterial stenosis

Pulsatile spiral blood flow in a modelled three-dimensional arterial stenosis, with a 75% cross-sectional area reduction, is investigated by using numerical fluid dynamics. Two-equation k-ω model is used for the simulation of the transitional flow with Reynolds numbers 500 and 1000. It is found that the spiral component increases the static pressure in the vessel during the deceleration phase of the flow pulse. In addition, the spiral component reduces the turbulence intensity and wall shear stress found in the post-stenosis region of the vessel in the early stages of the flow pulse. Hence, the findings agree with the results of Stonebridge et al. (2004). In addition, the results of the effects of a spiral component on time-varying flow are presented and discussed along with the relevant pathological issues

Numerical Study of Single Coal Particle Combustion in O2/N2 and O2/CO2 Atmospheres

No abstract available

Kinetic Modelling for Tar Evolution and Formation in a Downdraft Gasifier

Biomass gasification modeling is a powerful tool used to optimize the design of a gasifier. A detailed kinetic model was built by the current authors [1] to predict the behavior of air blown downdraft gasifier for a wide range of materials within the range of (38≤C≤52) %, (5.2≤H≤7) %, and (21.7≤O≤45) %. The model was verified and showed a good stability for a wide range of working parameters like equivalence ratio and moisture content. In the current research, 4 main tar species are added to the model to represent tar formation using detailed kinetic reactions. The yield of tar species is discussed for different zones of a gasifier based on temperature of each zone. Mass and energy balance are calculated. 18 different kinetic reactions are implemented in the kinetic code to predict the optimum working conditions that leads to the production of higher value producer gas. Results conclude that using ER of 0.3 with moisture content levels lower than 10% will lead to the production of higher yields of syngas with lower amounts of tar