M. BERKACHE Amar

The influence of solidity variations on the aerodynamic performance of H type vertical axis wind turbine is studied in this paper. The wind turbine model used in this paper is the three blade wind turbine with the symmetrical airfoil, NACA0021. The length of the chord is 0.265m.
Numerical investigations were implemented for the different solidity by changing the radius and blade number. A two-dimensional model of the wind turbine is employed. The approach of Reynolds-Averaged Navier–Stokes equations, completed by the K- ώ SST turbulence model is used. Motion mesh model capability of a computational fluid dynamics (CFD) solver is used. For each value of the solidity, the aerodynamic performances and the flow field characteristics are studied at several values of the tip speed ratio, λ = 0.5 to λ = 3 with an incoming wind speed of 8 m/s.
The results show that increasing the number of blades will reduce the maximum value of the power coefficient of the wind turbine. Also, the VAWT with a lower solidity can obtain the maximum Cp at a high tip speed ratio. The effects of changing the radius and blade number on aerodynamic performance are almost identical.
Finally, for the validation, experimental data from the literature and computational results were compared. In conclusion, to study the influence of solidity in the performance of the wind turbine is to provide the reference for the design of H type vertical axis wind turbines.

This paper presents an experimental and numerical study of viscous boundary layer flow with thermal effects. The research at the Thermal Laboratory of the Prime Institute of Poitiers involved a turbulent boundary layer in a wind tunnel on an epoxy-coated flat plate. The plate was heated to 80°C using a power supply system.
Results revealed notable differences in the thermal boundary layer's behavior at varying wall temperatures.

Unsteady flow simulation around rotor blades of vertical axis wind turbine

This study investigates the impact of cooling nozzle shape on the cooling film of a gas turbine blade using 3D numerical simulations. Efficient cooling is crucial for gas turbine blades, which operate under extreme temperatures. The design of cooling nozzles plays a key role in enhancing heat transfer and reducing thermal stress. Different nozzle shapes were simulated using CFD techniques, considering three-dimensional flow and conjugate heat transfer. The turbulence was modeled with a k-ω (SST) approach. Results showed that nozzle shape significantly affects film effectiveness, with the crescent shape providing the best cooling at a blowing ratio of M=2. Additionally, a 30° inclination angle offered the best film cooling effect.

This study investigates the effects of employing a multi-perforation cooling system on crossflow interactions, utilizing both numerical simulations and experimental methods. A 30° inclined multi-perforation cooling system is applied on a heated flat plate as part of the experimental setup. Large Eddy Simulation (LES) is utilized for Computational Fluid Dynamics (CFD) calculations to analyze the impact of multi-perforation on heat transfer dynamics. Validation is conducted by comparing the results with experimental investigations. The study encompasses both aerodynamic and thermal considerations, employing Particle Image Velocimetry (PIV) and infrared techniques for analysis, while wall heat flux is measured using electrical discharge. Experimental data on film cooling are collected through these methods, focusing on the impact of blowing ratio (M) and the number of open jet rows (R). The LES-based CFD simulations accurately predict the trajectory of the cooling film. Notably, the influence of flow through the multi-perforation on the primary flow is observable across both configurations of open jet rows (4R and 8R near the wall). The outcomes substantiate the formation of a cooling film emanating from the jet’s fourth row (4R configuration), thereby validating the LES simulations. Visualization of wall temperatures illustrates the formation of a cooling film, discernible through the visible heat distribution from row 4R. However, discrepancies arise in predicting the adiabatic cooling efficiency towards the exit of the 4R region and the commencement of the 8R region, potentially attributed to the alterations induced by the additional multi-perforated injection. The novelty and the main objective of this study is to evaluate the impact of the variation of geometric parameters between the jets and the main flow on the dispersion of the jets themselves. A novel function, tailored to the temperature evolution of the cooling gas, is employed for data analysis. Two geometry configurations, featuring varying open hole areas, are evaluated. The film-cooled heat transfer coefficient, depicted by the Nusselt number, and the adiabatic film cooling efficiency results, serve to appraise the film cooling efficacy of the configurations.

This research presents a comprehensive 3D numerical analysis of how the shape of cooling nozzles affects the cooling film on a gas turbine blade. Gas turbine blades function at extremely high temperatures, so effective cooling is crucial for maintaining their performance and lifespan. The design of cooling systems, particularly the configuration of cooling nozzles, is key to improving heat transfer and reducing thermal stresses. In this study, different nozzle shapes were simulated using computational fluid dynamics (CFD) methods. The CFD simulations incorporated three-dimensional fluid flow and conjugate heat transfer between the hot gas inside the turbine blade and the coolant flowing through the nozzles. Turbulence was modeled using the Reynolds-averaged Navier-Stokes equations with a k-ω (SST) shear stress transport turbulence model. The results indicated that the shape of the cooling nozzle significantly affects film effectiveness, which measures the efficiency of coolant protection. Among the three nozzle shapes tested, Cylindrical, Rectangular, and Crescent. The Crescent shape provided the best cooling performance at a blowing ratio of M=2. Additionally, when examining the effect of inclination angles on cooling performance, the film cooling effectiveness for the different nozzle shapes at angles of 30° and 60° revealed that the 30° angle offered the most effective cooling.

This study investigates interactions between discrete coolant jets in a transverse flow, as seen in turbine blade cooling. Numerical solutions and specific turbulence modeling aim to replicate the scenario accurately. Comparing outcomes from two turbulence models reveals differences near the wall due to jet injection at a 45-degree angle with a sub-unity blowing rate. Researchers intend to identify these distinctions via data analysis and simulation review. Insights into coolant behavior and the importance of precise turbulence modeling are highlighted, benefiting turbine blade cooling system design and efficiency. Lessons for diverse engineering applications with transverse flows are emphasized, along-side the need to advance turbulence modeling for accurate simulations. Overall, the study advances understanding of complex turbine blade cooling, emphasizing analysis, simulations, and accurate modeling for engineering insights.

To produce electricity from the wind, horizontal axis turbines exceeding 80 m in height are often used. Entirely immersed in the atmospheric boundary layer, these wind turbines undergo the same changes as the speed of the wind in a wind farm. In this context comes our study for the effect of the atmospheric boundary layer on the energy production for a single wind turbine, then generalize it to all the wind turbines of the farm. Using the logarithmic profile of wind speed in the atmospheric boundary layer, data from two types of wind turbines; NREL-V and ENERCON-E2 are introduced in a computer program for the calculation of the developed power. The results obtained are compared and discussed.

This paper presents a comprehensive numerical analysis of the impact of dynamic stall on the aerodynamic performance of a Darrieus H three-bladed vertical axis wind turbine. The study employs Reynolds-averaged Navier-Stokes (RANS) simulations with k-ω SST turbulence modeling. Different rotor configurations are studied to assess the influence of dynamic stall on the flow field characteristics and rotor performance. Torque and rotor power are analyzed for various velocity ratio values. Two critical parameters, mesh resolution, and time step size, are carefully examined for their effects on result accuracy. The findings indicate that dynamic stall significantly affects energy production, leading to decreased blade performance during stall conditions. Wind turbines should be designed to operate within dynamic stall limits. Moreover, the power coefficient of the rotor is compared with experimental data, showing an 8% error in this comparison.

The present study focuses on the effect of turbulence models on the aerodynamic performance of Darrieus-H vertical axis wind turbines with symmetric airfoil NACA0021. Simulations were performed by two different turbulences models, k-ω SST and DESS-A. The results show that the power coefficients predicted by Delayed Eddy simulations (DES) are closer to the experimental data available in the literature than those of the k-ω model of shear stress transport. It is demonstrated that the Delayed Detached Eddy Simulation is regarded as a reliable model to analyze the aerodynamic performance of vertical axis wind turbines.

A 3D numerical investigation is carried out to analyze film cooling of gas turbine blades. The FLUENT v12 computer code based on the finite volume method is used. The SST turbulence model is implemented in the present work. Our study focuses on the effects of injection ratio and the angle of inclination of the jet on the cooling efficiency. The first results concern the use of turbulence model SST on a NACA0012 airfoil with five holes of 5 mm diameter and spacing between two adjacent holes equal to 4d. The holes are inclined 30°, 45° and 90° in the plane (x, y). The results of the distribution of the static temperature contours depict the uneven distribution on the surface of the profile for a jet inclination angle equal to 90° (detachment of the film just above the hole). The best results are obtained with an angle equal to 30° where it is noted that the air film fits better to the wall to be protected. In second part we have performed the effect of blowing ratio (Ra=0.6, 0.8 and 1.2) on film cooling efficiency on the same NACA profile and with same data. The results show that the best efficiency is obtained for Ra=0.6.

An experimental and numerical studies of the transverse flow/Row of Jets (R1) are performed. Discrete jets are arranged across a surface exposed to a wall boundary layer of parallel stream, as occurs in discrete-hole cooling systems for turbine blades. The coolant flow characteristics at the hole exits of a film-cooled blade are derived from an earlier analysis where the hole pipes and coolant plenum were also discretized. The experimental model chosen is the ENSMA tunnel facility using flat plate with several staggered rows of holes. A three-dimensional FLUENT code is used to compute the velocity field of mainstream/jets characteristics in interaction on the flat plate. Simulation results are presented for both flat plate and cambered plate represented by three cambered NACA profiles with the key emphasis in this paper on the accuracy of the averaged results and on the film-cooling flow physics to show if the Reynolds averaged equations with turbulence models need anisotropy and realizability corrections to provide correct predictions for the cooling effectiveness. The calculations are performed by solving the governing equations, with turbulence modeling effects, with considering, three-dimensional external flow structure, free-stream turbulence and stream curvature effects. Comparisons between experimental and numerical calculations results are made and discussed for two turbulence models. Some discrepancies are observed in the flow near the wall. These differences are identified and discussed.

This article presents an analysis of the complex and unsteady flow a ssociated with the functioning of the rotor of a vertical axis wind turbine Darrieus - H. In this study, the influence of different numerical aspects on the accuracy of the simulation of the flow around a rotor of three straight blades in rotation is performed, which are the effect of the turbulence modeling, and the effects of the mesh and the time step. The Delayed Detached Eddy Simulation (DDES) approach is used. The aim of this article is to describe and analyze the unsteady flow in 3D predicted numerically considering the effects of arms like blade-arms interference, blade-wake interactions around the Darrieus rotor and the effect of tip vortices. Two-dimensional simulations are used in a preliminary numerical configuration. Then, three-dimensional simulations a re performed t o p recisely determine the characteristics of the complex aerodynamic flow associated with the operation of the wind turbine rotor. The flow field around the rotor is studied for several values of the tip speed ratio, dynamic quantities, such as the torque and the power of the rotor that are presented and analyzed. From the results obtained, it is clear that the approach of the Detached Eddy Simulation with the SST K-ω model can be considered as a reliable prediction. A comparison of the performance of the results showed that the predicted coefficients of performance are very close to the experimental data from the bibliography.

In this paper, a detailed numerical analysis of the effect of dynamic stall on the aerodynamic performance of a Darrieus H three-bladed vertical axis wind turbine is performed. To do this a series of simulations based on the Reynolds averaged Navier–Stokes (RANS).with turbulence modeling by the k-ω SST model is used. In order to quantify the influence of the dynamic stall on the aerodynamic performance of the rotor, the characteristics of the flow field around the rotor in different configurations are studied. For different velocity ratio values, dynamic magnitudes such as torque and rotor power are presented and analyzed. Also, two parameters are carefully studied: the mesh resolution and the size of the time step. In the analysis, it seems that these parameters affect the accuracy of the results. The numerical results show that dynamic stalling directly affects energy production. The results obtained show that the blades performance decreases when the profile is stalled, it is therefore important to design wind turbines that operate within the limit of dynamic stall. Finally, the numerical results of the power coefficient of the rotor are compared with the experimental data from the bibliography. An error of 8% is observed in this comparison.

In this article we present an experimental and numerical study of the behavior of the boundary layer type viscous flow in the presence of the thermal effect. The flow was held in a three-dimensional field with a uniform infinite velocity in the case of an adiabatic wall with heat input. The presented experimental work was performed in the Thermal Laboratory (LET) of the Prime Institute of Poitiers (France). It describes the analysis of a turbulent boundary layer created in a wind tunnel on the surface of a flat plate covered with epoxy resin. An HP 6012A power supply system was used to provide circulating heat flux to heat the flat plate to 80°C by the Joule effect. The numerical result shows a clear difference in the evolution of the thermal boundary layer between the three temperatures of the wall.

Inspired by the functioning of neurons in the brain, neural networks are tools widely used in
artificial intelligence in solving statistical problems. To this end, in wind energy, the wind is in perpetual variation, in order to model it and predict its intensity from its average annual speed, we present in this study a method based on the use of artificial neural networks.
Using the accumulation of a period of 10 years of measurements of the average annual wind speed of a site in the region of Kaberten, a computer program has been developed under MATLAB to estimate the wind in the years to come. This program makes it possible to predict the wind speed at 10 m from the ground in the year following the measurement period. The results obtained by this method on the Kaberten site are analyzed and discussed.

La fonction du moteur est de produire une énergie mécanique, en transformant l’énergie chimique grâce à une combustion interne Le moteur thermique reçoit de l’essence, combustible du système d’alimentation carburation. Il réalise une énergie grâce à une compression. Cette combustion est
déclenchée par le système d’allumage. Il produit une énergie mécanique disponible au volant moteur. Il rejette des gaz brûlés.

L’énergie est un élément fondamental de nos sociétés, elle est extraite de ressources primaires, transportées, transformées, stockées… Depuis l’aube de l’humanité, les ressources primaires exploitées ont été le bois, puis les fossiles (charbon, pétrole, gaz), transformées via des combustions et, plus récemment, l’uranium à travers la fission nucléaire ; l’énergie mécanique des cours d’eau et du vent a également été mise à contribution. Des transformations stellaires aux transformations d’énergie terrestres : les conversions d’énergie sont au cœur de nos vies.
Dans ce cours on va essentiellement apprendre dans un premier temps, les différentes formes d’énergie naturelles (Solaire, biomasse, géothermie, éolienne, thermique, hydraulique et nucléaire) ainsi que leurs méthodes de leurs transformations en énergie électrique. On montrera comment on établit une chaîne énergétique traduisant des conversions d’énergie. Définir la notion de rendement énergétique. Donner des exemples de conversion de l’énergie dans le domaine de l'électricité.
Dans un deuxième temps on va entamer les différents cycles thermodynamiques et leurs utilisations dans les turbines pour la production de l’électricité.

Les moteurs à combustion interne transforment l'énergie chimique du carburant en énergie thermique après combustion de celui-ci. Cette dernière énergie est transformée en énergie mécanique directement utilisée sur les roues des véhicule. De nombreuse techniques modernes sont utilisées afin d'am&liorer le rendement du véhicule et afin de diminuer les polluants nocifs. Parmi ces technique on cite:
Technique du sous dimensionnement
Techniques d'injection d'essence.
Technique de diminution de la formation de polluants.
Technique de l'utilisation de la suralimentation des MCI par turbocompresseur

Numerical and experimental studies of the transverse flow/Row of Jets are performed. Comparisons between experimental and numerical calculations
results are made and discussed for three turbulence models (k-epsilon, SST and RSM). The reduced axial velocity is under predicted by the three models in
comparison with experiment (PIV). Nevertheless, RSM and SST models are the best to reproduce the behavior of experimental results.

The blades in a gas turbine engine are exposed to extreme temperature levels that exceed the melting temperature of the material. Therefore, efficient cooling is a requirement for high performance of the gas turbine engine. The present study investigates film cooling by means of 3D numerical simulations using a commercial code: Fluent. Three numerical models, namely k-ε, RSM and SST turbulence models; are applied and then prediction results are compared
to experimental measurements conducted by PIV technique. The experimental model realized in the ENSEMA laboratory uses a flat plate with several rows of staggered holes. The performance of the injected flow into the mainstream is analyzed. The comparison shows that the RANS closure models improve the over-predictions of center-line film cooling velocities that is caused by the limitations of the RANS method due to its isotropy eddy diffusivity.