The effects of various corrugated geometries on the aerodynamic performance of bio-inspired airfoils are investigated under pure plunging motion at a low Reynolds number. Following a comprehensive review of previous studies on corrugated insect-inspired airfoils under gliding, pitching, and flapping motions, the present work addresses their unexplored aerodynamic behavior under plunging motion. Three corrugated cross-sections of the dragonfly Aeshna cyanea, along with their corresponding profiled airfoils, are considered and compared with a flat plate and a NACA0012 airfoil to examine the influence of their geometrical characteristics on aerodynamic forces. The unsteady Reynolds-Averaged Navier–Stokes equations, closed by the k–ω SST-SAS turbulence model, are solved using ANSYS Fluent at α = 0° and a Reynolds number of 7600. Validation against two-dimensional (2D) experimental data for a plunging flat plate shows maximum deviations of 0.9% and 1.9% in the lift and drag coefficients, respectively. The results indicate that the third corrugated airfoil achieves a maximum lift-to-drag ratio that is 27% and 30% higher than those of the flat plate and NACA0012 airfoil, respectively.
Unidirectional fiber-reinforced thermoplastic composite (FRTC) tapes combine continuous-fiber load carrying with the toughness and processability of thermoplastics. However, their durability under thermal and aqueous exposure remains a concern. This study evaluated the aging response of glass fiber-reinforced polypropylene (GF-PP) and polyethylene (GF-PE) tapes subjected to dry thermal aging and distilled-water (DW) immersion at 95 °C for up to 4 weeks. Longitudinal tensile properties (ASTM D3039) and water uptake (ASTM D5229M) were measured. The GF-PP tape exhibited a higher saturation water absorption (0.530%) and apparent diffusion coefficient (20.4×10-14 m2/s) than the GF-PE tape (0.206% and 9.63×10-14m2/s, respectively). After 4 weeks of dry thermal aging, GF-PP and GF-PE retained 91.5% and 81.2% of their tensile strength, compared with 68.7% and 51.0% after hydrothermal aging. Although GF-PE absorbed less water than GF-PP, it exhibited greater mechanical degradation, indicating that water uptake alone does not govern tensile durability. The results suggest that dry thermal aging primarily promotes fiber-matrix weakening and reduces stress-transfer efficiency, whereas hydrothermal aging accelerates matrix plasticization, interfacial deterioration, debonding, and progressive damage accumulation. These findings demonstrate that the durability of FRTC tapes depends on the combined effects of temperature, moisture transport, matrix type, and fiber-matrix load-transfer efficiency.
To improve the disturbance rejection performance of valve-controlled cylinder electro-hydraulic servo systems under external disturbances and load variations, this paper proposes a fractional-order sliding mode control (FOSMC) strategy. A system model with dual-inertia compensation is established, and a fractional-order sliding surface with the corresponding control law is designed to improve convergence and reduce chattering compared with conventional sliding mode control. Unlike conventional SMC, the proposed method combines fractional-order sliding surface design with dual-inertia-compensated modeling to enhance tracking robustness. A physical test bench is constructed, and both simulations and experiments are conducted under different disturbance and load conditions. In representative cases, FOSMC reduced the Root-Mean-Square Error (RMSE) under white-noise disturbance by 14.3% and lowered the maximum tracking error in experiments by 72.9% compared with PID. The results verify the effectiveness of the proposed method in improving tracking accuracy, disturbance rejection, and robustness.
Fault signals of wind turbine bearings have nonlinear and non-stationary characteristics, and the fault features are weak under actual noise interference conditions, leading to difficulties in fault feature extraction and identification. This paper proposes a novel fault diagnosis model synergizing weighted health indicator with feature-enhanced Transformer for wind turbine bearing to improve the fault recognition ability. Firstly, a lens opposition-based learning strategy is introduced to enhance the electric eel foraging optimization (EEFO) algorithm. The improved EEFO (IEEFO) is then used to optimize multivariate variational mode decomposition (MVMD), enabling efficient signal decomposition. The signal is reconstructed by constructing a new health indicator to amplify fault feature distinctiveness. Then, the continuous wavelet transform (CWT) is applied to convert the reconstructed signal into a 2D image, preserving its time-frequency characteristics. Finally, an improved Swin Transformer model incorporating linear deformable convolution (LDConv) is designed to further enhance feature extraction and classification performance. The proposed method is validated using bearing data from Case Western Reserve University (CWRU) and a wind turbine bearing simulation test bench. Comparative experiments demonstrate that this approach achieves higher diagnostic accuracy for wind turbine bearings compared to other methods.
This study investigates incorporating a partial copper wire mesh within a phase change material (PCM)-based battery pack to enhance heat dissipation. Nine series-connected 21700 lithium-ion cells (5000 mAh) were discharged at 1C to 3C (5–15 A) at an ambient temperature of 22 °C. A thermodynamic energy balance framework quantified heat generation, dissipation, and latent heat utilization. Experimental results indicate that integrating the copper mesh significantly improved heat dissipation, lowered peak cell temperatures, and reduced latent utilization. Compared to the baseline pure-PCM hybrid system, the mesh-PCM configuration decreased maximum mean cell temperatures by 3.7, 2.6, and 4.8 ± 0.6 °C at 1C, 2C, and 3C discharge rates, respectively, while increasing heat dissipation by 20%–40%. However, a specific thermophysical design trade-off was observed at the 3C rate, where the spatial temperature non-uniformity increased from 1.2 to 1.8 ± 0.1 °C. At moderate discharge rates (1C and 2C), the mesh-PCM system effectively managed heat without requiring macroscopic latent heat utilization, while at 3C, the bulk PCM melting fraction was reduced from 15.3% to 9.9%. This extends safe operational limits up to 3C. These findings highlight the partial mesh integration to enhance the performance of PCM-based battery thermal management system, offering a lightweight and effective upgrade for conventional pure-PCM hybrid cooling methods.
