CFD Techniques and Energy Applications

The use of solar energy to generate electric power is suggested as a promising technology. Specifically, the solar chimney power plant which generates electricity from free solar energy using air natural convection flow has gained interest during the last few decades. In this chapter, a numerical analysis of the performance of a solar chimney power plant using steady-state Navier–Stokes and energy equations in cylindrical coordinate system was presented. The fluid flow inside the chimney was assumed to be turbulent and simulated with the k–ε model, using FLUENT software package. The computed results were in good agreement with the experimental measurements of the Spanish Manzanares power plant. Besides, some theoretical models were proposed taking into account the air kinetic energy difference within the solar collector. The numerical model was then coupled with a mathematical model for a geothermal heat exchanger to investigate the option of coupling solar and geothermal sources for a continuous day and night operation. Several scenarios were proposed and assessed. The results particularly focused on the effects of the main geometrical parameters of the collector, the weather conditions as well as the effectiveness of the heat exchanger on the air mass flow rate, the temperature rise within the collector, and the overall performance of the combined renewable energy plant. The results show the benefits of the hybrid solar–geothermal plant compared to the single solar chimney plant for day and night periods.

A numerical simulation was developed to study the behavior of the airflow characteristics inside the solar chimney power plant (SCPP). A two-dimensional (2D) steady model has been carried out using the commercial computational fluid dynamics (CFD) code ANSYS Fluent 17.0. In this chapter, five turbulence models were tested to present the airflow characteristics distribution such as the magnitude velocity, temperature, pressure, and turbulence characteristics. The above work showed that the turbulence model types have a direct effect on the numerical results. Computational results were compared to the experimental data found by Kasaeian et al. (2014) to choose the adequate model.

The behavior of a negatively buoyant jet in laminar conditions that result from the injection of lighter fluids downwards into a large container of homogeneous fluid of denser density was studied numerically using OpenFoam with the finite volume method. The fluid characteristics effect on the evolution of the pure water injected in the tank full of salt water has been investigated particularly the molecular diffusivity that affects the mixing layer, the relative difference of density between two liquids, and the kinematic viscosity of the salt water that has an important effect in the transient phase as well as the subsequent steady state in terms of stationary penetration depth and jet profile.

The sloshing phenomena occur when a partially filled container is subjected to external excitation. The aim of the present chapter is to perform a numerical simulation of the liquid sloshing using the “Fluent” software. The simulation of the two-phase application was achieved using the volume of fluid (VOF). The container was subjected to sinusoidal excitation. To impose the external excitation, an user-defined function was developed and interpreted in “Fluent”. Four numerical simulations were developed with different turbulence models: standard k–ε, RNG k–ε, Realizable k–ε, and standard k–ε. The fluid flow characteristics were presented and discussed for the different simulation cases. The numerical results are compared with the experimental data. The comparison between the numerical and the experimental results shows a good agreement for the turbulence model standard k–ε.

For automotive applications, a turbocharger which consists essentially of a radial turbine and a centrifugal compressor is used to get more available output torque for internal combustion engines. The volute is also an important component for a turbocharger turbine. It transforms a part of the engine exhaust gas energy into kinetic energy and guides the flow toward the rotor inducer at a suitable flow angle value. This chapter presents our numerical model in order to capture the flow fields within a vanned volute under steady conditions. Numerical simulations were conducted using the CFX 17.0 package to solve Navier–Stokes equations by means of a finite volume discretization method. The good agreement between the experimental and numerical results of the turbine performance confirms the validation of our numerical model. Then, many computed flow discharge parameters such as the averaged volute exit flow angle were plotted to understand the behavior of the volute under different turbine expansion ratios. Furthermore, several loss coefficient distribution and entropy contours were plotted to characterize the occurring losses. In addition, pressure distributions, velocity, and turbulence parameters as well as streamlines were numerically obtained to analyze the flow behavior within the turbine volute.

This chapter presents some CFD simulation results of the hydrodynamic structure around a modified anchor system. Using the CFD code ANSYS Fluent 17.0, the finite volume method was used to solve the Navier–Stokes equations. This study was carried out using the standard k–ε turbulence model. The comparison between our numerical results and the experimental results found in the literature shows a good agreement.

This work focused on the numerical study of forced convection, for a thermodependent Newtonian fluid in an eccentric horizontal annular duct. The inner and outer cylinders were heated with constant heat flux. The governing equations were solved numerically by a finite difference method with implicit scheme. The dynamic profile was assumed to be fully developed while the temperature profile was assumed uniform at the entrance. The aim of this work was to present the effects of eccentricity on the dynamic and thermal fields along the duct. The thermodependency effect of the fluid was also examined, and some interesting results regarding the reduction of the dynamic blocking phenomenon of the flow in the narrow part of the duct for large eccentricities were presented. These results reduce the strictness of precautions for neglecting axial diffusion when making computations in such geometries.

The objective of this study is to predict numerically the flow effects of two coaxial jets with different swirl numbers (swirl number) on the characteristics of the turbulent diffusion flame. The study focused on the rotation influence of the secondary flow; that is to say, two configurations were processed and compared: co-swirl and counter-swirl. Obviously, the latter showed higher shear than the first. The calculation results were validated by actual measurement (laser anemometry) of the same configuration for two cases: co- and counter-swirl for reactant with combustion. The calculation results focused on the characteristics of the average flow (reactive) and its turbulence for the two cases cited above. Different parameters were presented such as velocities, temperature, turbulent kinetic energy, and mass fractions of species. The obtained results confirm the swirl effects to stabilize the flame.