Since the sixties, most of numerical studies that model the rotary lip seal lubrication have been restricted by assuming that one of the two opposing surfaces is smooth: either the lip or the shaft. This hypothesis, although it is verified only for a shaft roughness ten times smaller than that of the seal, is the best solution to avoid the transient term “∂h/∂t” in the deterministic approach. Thus, the subject of the present study is twofold. The first part validates the current hydrodynamic model with the international literature by assuming the asperities on the lip and shaft as a two-dimensional cosine function. In the second part the Reynolds equation for rough surfaces with relative motion is solved. The numerical results show that the relative motion between rough surfaces impacts significantly the load support and the leakage rate, but affects slightly the friction torque.

Recent research has focused on energy recovery and storage technologies. One of the materials allowing the recovery of dissipated energy is the piezoelectric material (PE). These functional materials perform reversible energy conversion, transforming electrical energy into mechanical and vice versa. In this study, we investigate the recovery of vibratory energy in vehicle suspension systems—energy traditionally dissipated by conventional shock absorbers—using piezoelectric materials to capture this wasted energy and redirect it to the vehicle’s auxiliary power supply network. We propose an integrated electromechanical model incorporating piezoelectric actuators in parallel with the suspension mechanism. The collected energy is processed and stored for later use in powering accessories such as windows and mirrors. The idea is to integrate renewable energy sources to optimize the performance of the vehicle. We proposed a Multiphysics model of the system under a software used to this type of modeling (Simcenter AMESim v1610_student). The simulation results of the system and its various sub-systems are presented for studying the piezo-actuator response to reduce consumption and increase energy performance in a vehicle. These findings will undergo experimental validation in the project’s subsequent phase.

In the last years, the new research papers piezoelectric energy harvesting from vortex-induced vibration (PEH-VIV) are focused on indirect contact between airflow and piezoelectric transducer. Where some researchers have noticed that is difficult to establish an accurate analytical model that could describe precisely the behavior of the piezoelectric generator including the indirect interaction with airflow. Due to these difficulties, new studies are concentrating directly on the experimental investigations to get results of energy harvesters of the indirect-contact piezoelectric wind energy harvesters (IC-PWEHs). However, this paper presents an analytical model that can provide good results according to experimental tests. The obtained results concern the displacement of the piezoelectric transducer indirectly excited by a vortex-induced vibration (VIV) and the generated voltage according to a different mass of cylindrical shell. The numerical results of the model show a significant agreement with the experimental results due to the good estimation of the system’s parameters, where the computing is done numerically using the MATLAB Simulink. Additionally, the optimal mass value of the piezoelectric transducer was determined approximately by the proposed analytical model. Where this mass is equivalent to the highest voltage amplitude according to the experimental tests.

It is generally agreed that radial lip seals are used in systems with a rotating shaft and a stationary lip. However, according to previous work, it was demonstrated that relative motion between the shaft and the lip has substantial effects on the hydrodynamic lifting load and sealing performances. Nowadays, new generations of textured shafts have emerged in order to reduce friction torque and improve reverse pumping, but no study has confirmed the effect of the relative motion between the rough lip and the shaft grooves on the rotary lip seal performances. In this work, an isothermal hydrodynamic lubrication was performed in transient conditions to investigate the effect of the relative velocity between an oblique grooved shaft and a rough lip. After confirming the validity of the current model with respect to previous works, simulations have underlined the effect of the grooved shaft with relative lip motion on the rotary lip seal performance. Indeed, by keeping the same relative velocity between surfaces, it is shown that moving the shaft with a rate higher than that of the lip surface could produce an important reverse pumping and reduce the friction torque significantly, in comparison with cases where the shaft velocity is weaker.

Solar photovoltaic (PV) systems play a pivotal role in sustainable energy generation, yet their efficiency declines with elevated operating temperatures caused by solar irradiance and environmental factors. To address this, hybrid, active, and passive cooling technologies have emerged as effective solutions, offering the dual benefit of temperature regulation and waste heat recovery for secondary applications. This paper presents a comprehensive review of recent advancements in PV cooling methods, analyzing their working principles, thermal performance, advantages, and limitations. Special emphasis is placed on hybrid cooling systems, which integrate multiple techniques to maximize efficiency, alongside active and passive approaches. Furthermore, the study explores the integration of heat recovery systems , such as heat pumps and thermal storage tanks , to repurpose waste heat for domestic, industrial, or space-heating applications, thereby enhancing overall energy utilization. The review concludes by identifying critical research gaps and future directions for optimizing PV cooling and heat recovery systems.