Experimental and Numerical Study of a Turbulent Multiple Jets Issued from
                        Lobed Diffusers

Medaouar, W.; Loukarfi, L.; Braikia, Mohamed; Khelil, Ali; Naji, Hassane; Control, Testing

doi:10.29252/jafm.12.03.29476

Cited by 4 publications

(5 citation statements)

References 17 publications

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“…The ventilation system in vehicles plays a critical role in providing a steady supply of fresh air and removing the pollutants from the ambient air by diluting it. High-induction air diffusers with lobed orifices are a promising solution for improving IEQ in vehicles [27]. The same conclusion was pointed out in [28], where these air diffusers supply fresh air into the ventilated enclosure and mix it with the existing ambient air, thereby lowering pollutant levels and enhancing the overall IEQ.…”

Section: Introductionmentioning

confidence: 65%

Innovative High-Induction Air Diffuser for Enhanced Air Mixing in Vehicles and Personalized Ventilation Applications

Bode,

Joldos,

Sirbu

et al. 2024

Energies

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Thermal comfort is very important for the well-being and safety of vehicle occupants, as discomfort can elevate stress, leading to distracted attention and slower reaction times. This creates a riskier driving environment. Addressing this, high-induction air diffusers emerge as a significant innovation, enhancing indoor environmental quality (IEQ) by efficiently mixing cool air from the heating ventilation and air conditioning (HVAC) system with the cabin’s ambient air. This process ensures uniform airflow, diminishes temperature discrepancies, prevents draft sensations, and boosts overall air quality by improving air circulation. In addition to enhancing thermal comfort in vehicles, the novel air diffuser also offers significant potential for personalized ventilation systems, allowing for individualized control over airflow and temperature, thereby catering to the specific comfort needs of each occupant. This study introduces a novel air diffuser that demonstrates a 48% improvement in air entrainment compared to traditional diffusers, verified through Ansys Fluent simulations and laser Doppler velocimetry (LDV) measurements. At a fresh airflow rate of 31.79 m3/h, the total air entrainment rate at 0.6 m for the standard air diffuser is 73.36 m3/h, while for the innovative air diffuser, it is 109.26 m3/h. This solution has the potential to increase the level of thermal comfort and air quality within vehicles, and also signals potential applications across various enclosed spaces, underscoring its importance in advancing automotive safety and environmental standards.

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Section: Introductionmentioning

confidence: 65%

Innovative High-Induction Air Diffuser for Enhanced Air Mixing in Vehicles and Personalized Ventilation Applications

Bode,

Joldos,

Sirbu

et al. 2024

Energies

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“…Some scholars have proved the practicability of this model in numerical simulations. 38,39 In this study, the Schiller-Naumann model is chosen for the drag force between the gas and liquid phases, which is the earliest and most famous among the commonly used drag force models. The drag force coefficient between the gas and liquid phases is calculated by dividing the relative bubble Reynolds number into two ranges, as done by Niu et al, 40 Feng et al, 20 and Liu et al 21 in their numerical simulations and experiments.…”

Section: Numerical Methods and Settingmentioning

confidence: 99%

“…The SST k ‐omega turbulence model is used in the liquid phase. Medaouar et al 39 pointed that the SST k ‐omega model considers the transfer effect of turbulent shear stress at the wall, and can better predict the flow separation near the wall and the separation region in fluid mechanical equipment, especially in multiphase mixing pumps. The dispersed‐phase zero‐equation model is used for the gas phase.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…The advantage of the zero‐equation model is that it is intuitively simple and suitable for flows, such as jets and shear layers. Some scholars have proved the practicability of this model in numerical simulations 38,39 . In this study, the Schiller–Naumann model is chosen for the drag force between the gas and liquid phases, which is the earliest and most famous among the commonly used drag force models.…”

Section: Numerical Simulationmentioning

confidence: 99%

See 1 more Smart Citation

Dynamic characteristics of the tip leakage vortex in an oil–gas multiphase pump based on vorticity decomposition theory

Shi,

Sun,

Wang

et al. 2024

Energy Science & Engineering

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The paper combines experimental and numerical simulation methods to investigate the tip leakage vortex (TLV) in an oil–gas multiphase pump. The study aims to understand the evolution and dynamic characteristics of the TLV. The vorticity decomposition theory is used to analyze the spatial–temporal evolution, transient behavior, and rigid vorticity of the TLV. The findings reveal that the TLV is formed near the pressure surface when the tip clearance jet passes through the shear layer. In one impeller rotation period, transient fluctuations of the TLV are attributed to pressure differences and velocity changes across the tip clearance, and the TLV undergoes two split–dissipation–recurrence processes within one impeller rotation cycle. The presence of the gas phase enhances the scale and strength of the TLV while prolonging its existence in the flow channel. Analysis based on the rigid vorticity transport equation shows that the growth of the TLV and collapse are primarily governed by the rigid vortex generation term. The Coriolis force term contributes to stabilizing the TLV, while the rigid vorticity stretching term affects its shape. Furthermore, the gas phase significantly increases the value of the Rigid vorticity Curl of pseudo‐Lamb vector Term (RCT), which plays a crucial role in the prolonged existence of the TLV under gas–liquid two‐phase conditions. From an inlet gas void fraction of 0%–20%, the RCT value increases by 4.8 × 106/s2, the entropy production value increases by 75.55%, and the hydraulic efficiency decreases by 16.29%.

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“…They concluded that the entrainment rate is due to the asymmetric shape of the nozzle and the strong convection of the turbulent structures induced by the lobes. Medaouar et al [8] performed a combined experimental and computational study of a central lobed jet surrounded by six equidistant peripheral lobed jets, and found that the interaction between the jets leads to velocity and temperature redistribution in the mixed zone. while allowing the propagation of the resulting jet.…”

Section: Introductionmentioning

confidence: 99%

Thermal and dynamic characterization of a multi-jet system with different geometry diffusers

Zahout,

Braikia,

Khelil

et al. 2024

Journal of Thermal Engineering

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This paper proposed to use the impinging jets mixing process to improve the quality of residential heating and air conditioning. The main objective is to meet the requirements of occupants in terms of thermal comfort and air quality by proposing an optimal solution for the thermal homogenization improvement in the rooms by changing of the diffusers geometry and their arrangement in the ventilation and air-conditioning devices in blowing systems. This study involves both experimental and numerical studies of a three diffusers configurations composed of four peripheral jet with similar geometries and a central jet with a different geometry. All the configurations consist of four equidistant peripheral swirling jets, only the central jet that makes the difference between them. The configuration 1 includes a swirling central jet, on the other hand a circular central jet for the configuration 2 and finally a lobed central jet for configuration 3. The velocity and temperature distributions of the three configurations are investigated experimentally and numerically. Experimentally, the multifunction thermo-anemometer have been used to measure flow temperature and velocity. The dynamic and temperature features are more radially spread and get better homogeneity in configuration 3 and this is due to the energy distribution on the radial plane, which is relatively better than configuration 1 and configuration 2. The second part deals with numerical predictions of the dynamics and thermal fields of the three configurations considered. The study was realized using a RANS-based turbulence model. The numerical results are in reasonable agreement with our experiments for the three configurations. With this study, detailed information on the structure of the resulting flow is very useful to deepen the understanding of the physics of jet interaction and to validate turbulence models. The turbulence simulation is realized by the k-ω-SST model. This model gives a satisfactorily predicts the axial drop in velocity and temperature over the entire study range, demonstrating its ability to handle the interaction between swirling and lobe jets. Our results show that the geometry of the central diffuser is essential. This allows the axial velocity to decrease faster than configurations 1 and 2. This increases lateral diffusion, resulting in better homogenization.

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Experimental and Numerical Study of a Turbulent Multiple Jets Issued from Lobed Diffusers

Cited by 4 publications

References 17 publications

Innovative High-Induction Air Diffuser for Enhanced Air Mixing in Vehicles and Personalized Ventilation Applications

Innovative High-Induction Air Diffuser for Enhanced Air Mixing in Vehicles and Personalized Ventilation Applications

Dynamic characteristics of the tip leakage vortex in an oil–gas multiphase pump based on vorticity decomposition theory

Thermal and dynamic characterization of a multi-jet system with different geometry diffusers

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