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Dans le champ des pratiques artistiques, les notions de coopération et d’interaction ne sont pas nouvelles. Elles étaient même consubstantielles à l’acte de création dans les ateliers de la Renaissance par exemple où il s’agissait de produire à plusieurs en réponse à des demandes formulées par de puissants commanditaires. L’ampleur de l’œuvre à venir et sa technicité justifiaient alors le processus collectif. Au cours du XXe siècle, la création à plusieurs a souvent eu affaire avec une ligne de pensée qui interrogeait la question de l’auctorialité, de la conscience individuelle, de l’intentionnalité et du hasard. Les surréalistes, les dadaïstes et les adeptes du Bauhaus testaient volontiers des pratiques ludiques à plusieurs, tel que le célèbre cadavre exquis. Les avant-gardes, qui portaient en elles des manières d’être et de vivre la relation à l’art, et au cœur desquelles se discutait la notion d’engagement, s’essayaient volontiers au partage de la conception et de la diffusion. Une nouvelle vision du monde s’inscrivait dans le collectif. La notion d’œuvre d’art y était ainsi redéfinie : la technique d’un medium, le style propre à un·e artiste, la suprématie auctoriale étaient malmenés, interrogés.

À l’aube des premières élections libres en Tunisie, l’affaire de la Manouba a fait le tour des médias nationaux et internationaux. Alors qu’un groupe salafiste occupe la faculté de lettres de la Manouba, les universitaires s’engagent dans une lutte pour la défense des libertés académiques. Cet article retrace l’usage des différents supports médiatiques dans la construction de cette affaire en problème public capable d’attirer l’attention politique, jusqu’à introduire les libertés académiques dans la nouvelle Constitution, en écriture à l’époque. En partant de cette affaire, nous aborderons les enjeux de l’usage des supports numériques par les réseaux salafistes, afin de diffuser leur propagande, face à l’usage d’une multiplicité de supports pour institutionnaliser une cause, à l’image de ce qui a été fait par les universitaires. Nous aborderons également les travaux sur le cadrage de la cause réalisés par les deux partis opposés dans l´affaire, ainsi que l’influence de l’usage de certains supports et de certains cadrages dans la mise en circulation internationale des discours sur le genre et du danger islamiste. This article analyzes how media have been used to build this case as a public problem. This case has been able to catch the political attention until the addition of the academic freedom in the Constitution, still ongoing at the time. Starting from this case, we will examine the reasoning behind the use of digital media in the Salafist network in order to diffuse their propaganda. Facing this Salafist system, the scholars have used a multiplicity of media to institutionalize their cause. We will also focus on the researches about the case’s framing made by both of the interested parties, but also the influence the use of some media and some framings in the International diffusion of the gender speech and the danger of Islamism.

This paper presents an investigation into the effect of area ratio parameter of diffusers on its energy output through power coefficient C p . This parameter has effect both on diffusers’ energy yield, besides diffuser’s size for architectural integration prospects. A systematic increase in diffusers area ratio is adopted following standardized diffuser profile presented by NACA 1244 aerofoil. A series of area ratios were investigated (i.e., 1.25, 1.5, 1.75, 2, 2.5, 3 and 3.5). Area ratio of 1.5 (i.e., outlet/inlet, 0.75 m/0.50 m) exhibited the highest power coefficient C p of 4.2, in addition to achieving highest resulting velocity of 25.8 m/s under incident velocity of 16m/s. Considerable wind separation inside inner walls of diffusers occurred from area ratio 1.75 onwards, which impacted resulting velocities. Simulations performed with ANSYS CFD Academic to standalone diffusers. A series of incident velocities employed from 1 to 16 m/s that resulted in velocity increase by 120–156% respectively.

In this research, the flow around a hydrokinetic turbine within a channel is controlled with a diffuser. A simulation model for a channel width and height of 150 mm is developed and experimentally validated. For a flow speed of 0.33 m/s the diffuser was found to experimentally augment the available power within the flow by a factor of 1.96. A turbine was modelled as a 1-dimensional actuator disk model and several diffuser-turbine variables were studied. Tip gap, nacelle cover size as well as drag distribution along the actuator disk model were studied and observations were made on differences in pressure, theoretical power, and disk loading at a channel speed of 0.5 m/s. The theoretical maximum power for the optimized diffuser that could be extracted from the flow was found to be 0.26 W at a minimal pressure difference of 238.29 Pa, and a disk loading of 1.46 N.

Computational analysis is performed on a centrifugal compressor fitted with tapered vaneless diffuser in order to increase the rate of diffusion. The main parameter involved in the present study is the wall taper angle of the diffuser, which is varied from 1° to 6° in the interval of 1°. Simulations are performed for the stationary as well as rotating diffuser at a speed of 79,000rpm, by using ANSYS CFX 17.2. By considering the geometry with stationary parallel wall diffuser as the base case, the performance enhancement in the characteristics such as static pressure recovery coefficient, stagnation pressure loss coefficient, isentropic efficiency, energy coefficient and torque coefficient are reported. The flow features in the compressor having various diffuser geometries are studied with the help of static pressure, radial velocity, static entropy, and contours of velocity streamlines at the design point. Of all the cases of stationary tapered diffusers, the diffuser with 3° taper angle showed optimum performance: the increase in isentropic efficiency (η) is by 1.5%, the increase in static pressure recovery coefficient (CP) is by about 9% and the decrease in stagnation pressure loss coefficient (CPOL) by 10.7%. On the other hand, it was found that in the case of rotating diffuser optimum performance: an increase of about 40% in CP and decrease of about 32% in CP0L occurred for a taper angle of 6°. However, its efficiency decreased by 2.9% with rotating diffuser in comparison with the base case, due to increased energy losses.

In this review, the factors affecting the transfer of oxygen in activated sludge processes using fine-pore diffusers for water resource recovery are critically discussed. In water resource recovery facilities, the energy required for aeration constitutes 50% to 80% of the total energy consumed by the plant. This critical review highlights the use of fine-pore diffuser aeration and emphasizes the significance of accounting for the following factors: diffuser aging and fouling, diffuser layout, diffuser type, selector benefits, local environmental conditions (temperature and atmospheric pressure), influent wastewater variability, dissolved oxygen control systems, and airflow rates. In our review, we were unable to find mathematical models that could be used to develop dynamic -factor predictions and diffuser fouling predictions. Although the development of a model that considers all the factors that affect oxygen transfer efficiency (OTE) in activated sludge systems would be extremely valuable, the creation of such a model is outside the scope of this review.

Vaned diffusers are widely used in centrifugal compressors due to their higher pressure-recovery coefficients compared to vaneless diffusers. In this study, the effects of the diffuser vanes’ wrap angle and number of vanes on the aerodynamic performance of an industrial Methane centrifugal compressor with a pressure-ratio of 1.288 are studied using high fidelity steady-RANS numerical simulations. Three wrap angles (WA = 19.3o, 22.3o and 25.3o) and three number of vanes (NDiff.= 16, 20 and 24) are examined, while all the other geometrical and operational parameters are kept constant. Results showed that decreasing the wrap angle can enhance the choke flow rate of the compressor, with slight reduction in pressure ratio at low flow rates. However, increasing the diffuser wrap angle, intensifies the flow separation over the diffuser vanes. On average, the best aerodynamic performance of the compressor occurred at WA=22.3o. Results also showed that reducing the number of diffuser vanes enlarges the operating range of the compressor, however, the pressure ratio will be lower at the flow rates less than the design point. Conversely, higher pressure ratios will be achieved at the flow rates greater than the design flow rate. The optimal aerodynamic efficiency of the diffuser, considering both the pressure ratio and the total-to-total efficiency, was achieved when the NDiff value was set to 20.

This study focuses on helico-axial multiphase pumps, conducting numerical and experimental analyses on three distinct models of pressureboosting units. Performance parameters were evaluated on a four-stage multiphase pump across various rotational speeds and gas void fractions for each model. A homogenizer was integrated upstream of the multiphase pump to ensure a uniform gas-liquid mixture distribution. The research provides theoretical and practical frameworks for the design of high-stability multiphase pumps utilized in offshore oil and gas applications.

Diffuser rotating stall (DRS) occurring in vaned diffusers significantly limits the operating range of industrial pumps, making the suppression of DRS a critical issue. As one countermeasure, it was experimentally demonstrated that a non-axisymmetric diffuser, formed by cutting the leading edge of every other vane, effectively suppresses the DRS in a mixed-flow pump. The authors applied this design to a centrifugal pump and investigated the suppression mechanism experimentally and numerically. In this study, the leading edges of three vanes in the base model’s eight-vane diffuser were cut by 14% in the vane axial direction. This process suppressed the DRS onset flow rate to 8% below the design flow rate. However, the effect of the short vane geometry on DRS suppression remains undiscussed, requiring further study to establish design guidelines. This study focuses on the inlet area ratio AP/AS, defined as the ratio of the inlet area on the pressure side AP to that on the suction side AS of a short vane. The diffuser with three leading edge cuts, which demonstrated the DRS suppression effect, has an AP/AS ratio of 2.61. As a comparison, the test diffuser was designed with an AP/AS ratio of 1/2.61, while maintaining the inlet and outlet vane angles. Experimental measurements show that at an AP/AS ratio of 1/2.61, DRS onsets at 68% of the design flow rate, significantly higher than at an AP/AS ratio of 2.61. To investigate the cause of this phenomenon, an unsteady RANS analysis was performed at the DRS onset flow rate, revealing that the decrease in AP promotes inlet blockage of the backflow generated on the vane suction surface, contributing to the propagation of the stall region.

The design of diffusers is a critical aspect of compressor performance, directly influencing pressure recovery, flow stability, and overall stage efficiency and operating range. This review paper provides an analysis of diffuser design principles, methodologies, and practical considerations in turbomachinery applications. The importance of diffusers in compressors is discussed, and the main types of diffusers are presented, highlighting, for each type of diffuser, their aerodynamic characteristics and operational advantages. Traditional empirical correlations and analytical models for diffuser geometry generation are reviewed, emphasizing their role in guiding preliminary design decisions. The integration of one-dimensional (1D) performance analysis methods with computational fluid dynamics (CFD) simulations is also discussed, illustrating how these approaches improve performance prediction and optimization accuracy. Design constraints are analyzed alongside performance trade-offs, highlighting the need to balance efficiency and stability. Overall, this review synthesizes existing knowledge on diffuser design in compressors, providing a structured framework for engineers and researchers to understand the key factors affecting performance and guiding the development of efficient, reliable diffuser configurations for real-world turbomachinery applications.