Electric ducted fans (EDFs) have emerged as promising propulsion systems due to their compact design, high thrust density, and enhanced operational safety. Accurate prediction of aerodynamic thrust is essential for EDF design and performance evaluation; however, existing numerical studies have not yet provided a systematic comparison of the thrust-prediction capability of different k-ω-based turbulence models in micro-EDF applications. In this study, a dedicated thrust-measurement platform was developed for a 120 mm EDF, and experimental thrust data were obtained under three representative hover operating conditions. Based on these measurements, six turbulence models, including SST, SKω, BSL, GEKO, EARSM, and SST-γ(alg.), were evaluated using three-dimensional CFD simulations. The numerical model was assessed through thrust validation, centerline velocity comparison, power-consistency analysis, grid independence verification, and qualitative flow-field interpretation. A two-factor full-factorial analysis was further conducted to quantify the effects of rotational speed and turbulence model on prediction accuracy and computational cost. The results show that the turbulence model has a stronger influence on the normalized thrust-prediction error than the rotational speed factor over the investigated operating range. The SST-γ(alg.) model achieves the highest thrust-prediction accuracy, with an average relative deviation of 0.47%, but requires the highest computational cost. In comparison, the SST model provides a favorable balance between accuracy and efficiency, with an average relative deviation of 1.79% and an average computation time of 184.33 min, approximately 33% lower than that of the SST-γ(alg.) model. The centerline velocity and power-consistency results further support the comparative model assessment. Overall, this study provides an experimentally validated comparative reference for turbulence model selection in simulations of similar 120 mm EDF under hover conditions. Considering both prediction accuracy and computational efficiency, the SST model can serve as a practical turbulence model choice for engineering parameter optimization of similar micro-EDF configurations.k−ω
Pressure losses in heating, ventilation, and air-conditioning (HVAC) duct elbows significantly increase fan power requirements and reduce overall system efficiency. This study presents a comprehensive computational fluid dynamics (CFD) investigation aimed at identifying effective strategies for reducing pressure losses in 90° HVAC duct elbows. The numerical methodology was first validated against published experimental measurements, demonstrating excellent agreement and providing confidence in the predictive capability of the CFD model. The validated model was then employed to evaluate the influence of duct geometry, inlet velocity, guide vane configuration, inter-vane spacing, perforated guide vanes, and duct material roughness on aerodynamic performance using the SST k–ω turbulence model. The results show that round elbows reduce pressure losses by approximately 50% compared with hydraulically equivalent rectangular elbows, highlighting the strong influence of duct geometry on flow separation. Among the flow-control strategies investigated, curved guide vanes produced the greatest improvement, with an optimized three-vane arrangement and a non-dimensional spacing of s/Dh≈0.15 (corresponding to 150 mm for the specific geometry tested) reducing pressure losses by approximately 31% relative to the baseline elbow without guide vanes. In contrast, the investigated perforated guide vane provided only marginal improvement, indicating that its geometry requires further optimization to minimize blockage and mixing losses. The material roughness study showed that smooth, rigid duct materials produced only minor differences in pressure loss, whereas flexible ducts generated noticeably higher losses because of their increased surface roughness. These findings demonstrate that optimizing elbow geometry and guide vane design is considerably more effective than modifying duct material or using the investigated perforated vane configuration. The study provides practical design recommendations for improving the aerodynamic performance and energy efficiency of HVAC duct systems.
M. Fouad, Mostafa Rizk, Anoud Nagaf et al.· Machines· 0 citations
The propulsion performance and propeller design of ships have traditionally been evaluated mainly under calm-water conditions. However, under actual sea conditions, waves can increase added resistance, change the stern wake distribution, reduce propulsive efficiency, and affect cavitation behavior. This study evaluates the propulsion performance and designs a propeller for an 1800 TEU container ship under regular wave conditions using computational fluid dynamics. Resistance and self-propulsion simulations are conducted for eleven wavelength ratios in the range of 0.5≤λ/LPP≤2.0, with a fixed wave steepness of H/λ=0.01. The results show that the required power increases significantly in the resonance wavelength range because of the combined effects of added resistance, wake variation, and reduced propulsive efficiency. The Brake Horsepower (BHP) transfer function obtained from the regular wave simulations is combined with representative sea-state spectra using the spectral method to estimate the Daily Fuel Oil Consumption (DFOC) under actual operating sea states. The total long term DFOC is estimated as 37.084 t/day. For the propeller design, the wake distribution at the propeller plane is analyzed at λ/LPP=1.1, as a representative wave condition where the ship motion and propulsion performance variation become significant. The wake analysis shows that the instantaneous inflow changes considerably according to the wave phase, which can affect blade loading and cavitation. Based on this analysis, a new propeller geometry is designed with the cavitation performance as the primary consideration while also improving the propulsion performance. The designed propeller reduces the cavity volume over the selected wave phases and decreases the delivered power by approximately 2.1% in calm water and 3.4% in wave conditions. These results demonstrate the importance of considering wake variation and cavitation characteristics in practical propeller design under actual operating conditions.
S. Lee, K. Paik, S. Jeong et al.· Journal of Marine Science an...· 0 citations
The aerodynamic efficiency of small wind turbines (SWTs) depends strongly on airfoil selection, yet the balance between aerodynamic, structural, and sustainability factors under low-Reynolds-number conditions remains insufficiently explored. This study proposes a sustainability-driven, multi-criteria framework integrating aerodynamic performance, structural reliability, and material efficiency. Thirty airfoils from NACA, Selig, Eppler, and NREL families were analyzed over Re = 100,000–500,000 using an in-house MATLAB viscous panel-based solver coupling potential-flow formulation with viscous boundary-layer and transition corrections. Four criteria—glide ratio, maximum lift coefficient, stall stability, and Material Efficiency Index (MEI)—guided the selection of BW-3, E-216, and SG6041 for genetic-algorithm blade optimization. BEM and aeroelastic simulations, supported by preliminary ULS and FLS checks, identified SG6041 as the best compromise between aerodynamic performance, startup behavior, structural safety, fatigue resistance, and material mass. The framework supports lightweight, sustainable SWT blades using date-palm-fiber composites.
A. Bouhelal, Belkacem Agagna, Abdelhafid Brima et al.· Wind Engineering : The Inter...· 0 citations
This study addresses the current gap in predicting the aerodynamic environment encountered by scramjet-propelled hypersonic vehicles during flight. Correlation analyses between key simulation parameters and numerical accuracy were conducted based on wind tunnel date. Based on these insights, an optimized aerodynamic environment simulation scheme is proposed. The predicted aero-acoustic, vibrational, and thermal conditions are shown to be extreme, with values reaching 147 dB, 182 g, and 2130 K, respectively. During structural design, the airfoil leading edge directly faces more intense aerodynamic heating and therefore requires materials with excellent heat resistance. Vibration-resistant design should prioritize the airfoil trailing edge. Adopting new high-performance materials like Inconel alloys significantly enhances structural reliability and durability. In environmental testing, the test scope must comprehensively cover the extreme limits of the aforementioned aerodynamic conditions, with thermal tests requiring a rapid temperature rise rate of 83°C/s to simulate thermal stresses under extreme flight conditions. Furthermore, as flow velocity increases, the impact of aerodynamic heating on structural vibrations becomes more pronounced, further validating the critical importance of combined thermal-vibration testing.
For transport unmanned aerial vehicles, selecting propulsion characteristics is a key consideration. A distinction must be made between lift propulsors, which must provide sufficient thrust within limited dimensions, and cruise propulsors, which primarily require high efficiency in both hover and forward flight. The results of developing a numerical simulation methodology for isolated propellers and ducted fans are presented, including the selection of turbulence models under conditions of a potential laminar-turbulent transition. The studied objects include K184V propellers and VK1 ducted fans, developed at the Central Aerohydrodynamic Institute (TsAGI) for hovercraft propulsion systems. The one-equation Spalart-Allmaras model and two-equation models based on k-ε and k-ω variables are investigated. The turbulence models are verified against benchmark data to account for the laminar-turbulent transition and the presence of separation bubbles on the blade and duct surfaces. One method for dividing the flow region into laminar, turbulent, and transitional zones is introducing the intermittency parameter γ into the turbulence model equations, where γ is equal to unity in fully developed turbulent flow and zero in laminar flow. The Langtry-Menter k-ω SST Reθ-γ transition model is one such turbulence model that uses the intermittency parameter and accounts for the laminar flow region effect. A geometric multigrid method is used to solve the difference equations. The numerical simulation yields pressure and velocity fields both in the computational domain and directly on the blade and duct surfaces, allowing the determination of aerodynamic characteristics of the ducted fan under various operating conditions. For hover and forward-flight conditions, the calculated dependencies of thrust and power coefficients, as well as propulsive efficiency, are obtained for a wide range of rotational speeds and engine power inputs. The results are compared with benchmark experimental data from TsAGI. Accounting for the laminar-turbulent transition and the associated formation of thin laminar separation bubbles significantly improves the agreement between the computational results and experimental data.
P. A. Arkhipov, P. V. Bulat, S. Y. Dudnikov et al.· Aerospace Engineering and Te...· 0 citations
Improving the performance of radial inflow turbines under coupled aerodynamic and mechanical constraints remains a key challenge in high-speed Organic Rankine Cycle (ORC) systems. In magnetically supported configurations, turbine design is restricted by axial thrust limitations, while maintaining the target mass flow rate is essential for stable system operation. To address these challenges, this study develops a physics-guided design approach for a high-speed ORC radial inflow turbine by integrating one-dimensional preliminary design, three-dimensional CFD-based optimization, and enthalpy gradient magnitude (EGM)-based flow diagnostics. The numerical model is validated against experimental data of a baseline turbine. Three key geometric parameters are optimized under coupled axial thrust and mass flow constraints. The optimized design increases the total-to-total isentropic efficiency from 74.7% to 87.1% while maintaining acceptable axial loading. EGM analysis shows that high-efficiency configurations exhibit more uniform spatial distributions of energy gradients within the impeller passages, whereas low-efficiency cases are characterized by localized high-gradient regions associated with flow separation and secondary flow structures. A volumetric average EGM parameter is further introduced for quantitative evaluation and exhibits a clear negative correlation with turbine efficiency. The optimized efficiency reported herein is a numerical prediction requiring future experimental validation. The results demonstrate that improved internal flow organization contributes significantly to turbine performance enhancement and provides diagnostic insights for design evaluation of high-speed ORC turbines.
Bochen Wan, Wang Zheng, Yueyang Wang et al.· Energies· 0 citations
