Efficient mixing under laminar flow conditions remains a critical challenge in microfluidic systems because molecular diffusion alone is generally insufficient to achieve rapid and homogeneous species transport. In this study, the influence of obstacle orientation on mixing performance in passive micromixers was systematically investigated through numerical simulations. Inclined straight obstacles with orientation angles of 15°, 30°, 45°, and 60° were incorporated into microchannels under both leaky and leak-free configurations. Flow and concentration fields were solved using COMSOL Multiphysics, and the resulting mixing efficiencies and times were quantitatively evaluated. It was found that the introduction of inclined obstacles substantially enhanced mixing performance relative to a simple unobstructed microchannel. Superior mixing behavior was consistently achieved in the leak-free configuration, where stronger flow perturbations and more pronounced recirculation zones were generated within the central mixing region. For the leak-free configuration, mixing efficiency was observed to increase with decreasing obstacle angle. In contrast, no monotonic relationship between obstacle angle and mixing performance was identified for the leaky configuration. Among all investigated designs, the 15° obstacle configuration exhibited the highest overall performance, achieving mixing efficiencies of approximately 92% and nearly 100% in the leaky and leak-free configurations, respectively. To further evaluate the influence of geometric scale, the microchannel length was doubled for the 45° configuration. Enhanced concentration uniformity and reduced mixing time were achieved in the extended leaky microchannel, whereas no improvements were observed in the corresponding leak-free design. These findings demonstrate that obstacle orientation and channel configuration exert a strong influence on microscale transport phenomena and mixing enhancement. The proposed obstacle-based passive micromixer design provides an effective and energy-efficient strategy for improving mixing performance in microfluidic devices and offers valuable design guidelines for applications in biomedical analysis, chemical processing, and lab-on-a-chip systems.

Photovoltaic technology has become one of the most promising approaches for sustainable electricity generation; however, its performance is strongly influenced by environmental conditions, including dust accumulation and operating temperature. In this study, the combined effects of dust deposition and panel tilt angle on the thermal behavior and electrical performance of photovoltaic modules were experimentally investigated under controlled artificial illumination generated by light bulbs. Five irradiance levels (100, 200, 300, 400, and 500 W/m²) were employed to simulate different operating conditions, while various dust loading levels and panel tilt angles were systematically evaluated. The results demonstrated that the tilt angle significantly affected photovoltaic performance. As the dust loading increased, the panel's temperature rose. Although electrical power generation was successfully achieved through the bulbs, the output remained substantially low. Dust deposition reduced the amount of incident solar radiation reaching the photovoltaic modules, thereby decreasing electrical power generation and energy conversion efficiency. These findings provide valuable experimental evidence for optimizing photovoltaic system installation and maintenance in dusty environments and contribute to the development of more efficient and sustainable photovoltaic energy systems.