Arak University of Technology

Accurately predicting hydro/aero dynamic coefficients of vortex-induced vibration is crucial for designing and optimizing marine and oceanic structures exposed to fluid flows. In this study, we employ a long short-term memory network to predict lift and drag forces applied to an elastically-mounted circular cylinder vibrating freely in the x and y directions. The predictions are based on the response of the transverse and streamwise displacements at selected reduced velocities within the frequency synchronization region. We conduct fluid-structure interaction simulations for low mass damping (m*ζ=0.013 ) using 2D unsteady incompressible Reynolds-averaged Navier-Stokes equations with the finite volume method. The simulations cover a Reynolds number range of 1700–13000 (reduced velocities 2–14.9). The LSTM network architecture comprises 1 input layer, 3 hidden layers, and 1 output layer, with a previous data window of 20 and 32 neurons in each layer. We use the first 80 V_r=5.75 for training the LSTM network, while the remaining 20 V_r=5, and 6.5 , which were not part of the training process. The results demonstrate the LSTM model’s success in predicting lift and drag coefficients based on the time evolution of transverse and streamwise displacement amplitudes. At V_r=5.75 , the correlation factors for the lift coefficient are calculated as R=0.996 (training) and R=0.993 (test), while for the drag coefficient, they are R=0.973 (training) and R=0.940 (test). Overall, this study highlights the potential of the LSTM network in accurately predicting hydro/aero dynamic coefficients for flow-induced vibration, offering insights into the behavior of marine and oceanic structures under fluid flow conditions.

Human dermal fibroblasts (HDFs) play a vital role in skin regeneration, wound healing, and tissue remodeling, making their mechanical characterization essential for understanding skin physiology and pathology. This study investigates the elastic properties of primary HDFs under physiological conditions using atomic force microscopy (AFM) and analytical contact models. The Johnson–Kendall–Roberts (JKR) model and logarithmic friction analysis were applied to quantify cell stiffness and surface interactions. Experimental force–indentation data were compared with simulation results to determine the effective Young’s modulus, which ranged between 4 and 6 kPa. The findings align with previous reports and highlight the influence of extracellular conditions on fibroblast elasticity. This work enhances the understanding of skin cell biomechanics and provides a reliable mechanical reference for future studies in tissue engineering, disease diagnosis, and regenerative medicine.

Resistance spot welding (RSW) effectively joined Inconel 625 (IN 625) samples. This study examined how annealing heat treatment of cold-rolled sheets affects the microstructure and mechanical properties of resistance spot welded IN 625 joints. The microstructure and mechanical properties of the heat-affected zones (HAZ) of annealed sheets differed markedly from those of as-rolled sheets: fine recrystallized grains were absent in the HAZ of annealed sheets but present in the HAZ of as-rolled sheets. Furthermore, carbide accumulations were located closer to the weld button in annealed sheets than in as-rolled sheets. Microhardness measurements for annealed-sheet joints showed increased hardness in the fusion zone (FZ) and HAZ compared to the base metal (BM), while the HAZ hardness in as-rolled sheets was lower than in other joint regions. Pull-out fracture (PF) occurred in annealed sheets at low and moderate welding currents and in as-rolled sheets at high welding currents, whereas tearing failure (TF) occurred in annealed sheets under high welding currents. As the fracture mode shifted to TF in annealed sheets, as-rolled IN 625 exhibited a higher fracture load, while annealed IN 625 showed greater fracture energy under the same welding conditions.

This study predicts the performance of a concentrated photovoltaic system with a mini-channel and an elastic cylinder, using an Adaptive Neuro-Fuzzy Inference System and Sobol sensitivity analysis. The concentration ratio of CPV is 10. This study analyzed how different cylinder configurations (stationary vs. elastic) and shapes (circular, rhombus, and square) affect system efficiency under varying radiation intensities and Reynolds numbers (Re). ANSYS Fluent, which applies the finite volume method, was used for modeling. Utilizing a minichannel can augment the iel by approximately 3-7.1 % compared to the base case. The results indicate that an increase in radiation intensity raises the solar cell temperature, which leads to a decrease in electrical efficiency (iel ). An increment in the Re of the airflow in the mini-channel improves the iel by about 4.36 %. The presence of stationary and elastic cylinders can enhance electrical efficiency by 8-12.5 % compared to the base case. Using two elastic cylinders yielded a more even temperature distribution on the CPV. Changing the shape of the cylinder from circular to square and rhombus in the static and elastic states has improved the thermal and electrical efficiency compared to the circular state, and the greatest improvement is attributed to the rhombus-shaped cylinder. Additionally, the iel was estimated using the ANFIS neural network, and the obtained R-square value of 0.99374 indicates a good estimation of the iel.

This research investigates the impact of superhydrophobic surfaces on flow-induced vibrations (FIV) and convective heat transfer around elastically mounted square and circular cylinders. By leveraging superhydrophobicity, dual benefits are achieved: substantial suppression of two-degree-of-freedom FIV and enhanced heat transfer efficiency. Transient laminar flow around cylinders with varying slip lengths was simulated to explore these effects. The research demonstrates that superhydrophobic surface treatment significantly mitigates these oscillations, decreasing transverse oscillation amplitudes by as much as 80 % for the circular cylinder and 68 % for the square cylinder at reduced velocities of Ur = 4 and Ur = 5, respectively. Additionally, superhydrophobicity alters vortex-shedding patterns, weakening their intensity. At low slip lengths, classical vortexinduced vibration (VIV) behavior is observed for both cylinders; however, for the square cylinder, the synchronization is short-lived and transitions into a desynchronization regime. As slip length increased, the boundary layer became thinner and more stable, shear stress decreased, and the longitudinal and transverse spacing between vortices are reduced significantly. This resulted in a notable reduction in vortex size and strength, as well as an increase in shedding frequency for both cylinders. In terms of heat transfer, the Nusselt number exhibits significant enhancement across all reduced velocities, with maximum increases of 59.9 % at b* = 0.1 and Ur = 4 for the circular cylinder, and 141.8 % at b* = 0.1 and Ur = 6 for the square cylinder. The concurrent suppression of FIV and enhancement of heat transfer render these findings significant for engineering applications, particularly in heat exchangers, where it is essential to simultaneously manage flow-induced vibrations and thermal performance limitations.