Lakes provide a wide range of ecological, cultural, and economic benefits and prime opportunities for recreation, tourism, and livelihoods in the Upper Indus Basin (UIB). In the wake of growing anthropogenic actions and climate change impacts, an appraisal of the lake water quality is essential to determine the health of the ecosystem and assist resource conservation initiatives in the region. An attempt has been made to establish a preliminary physicochemical baseline for eight high-altitude lakes in the UIB, Pakistan, to characterize their spatial hydrochemical variability and identify potential water quality concerns in the region. At the time of sampling, the lakes exhibited a slightly alkaline condition with pH ranging between 7.7 and 8.2 (mean 8.0). The lower alkalinity detected in the lakes, like Sheosar (42 mg/L), may indicate limited buffering capacity and more sensitivity to nutrient pulses or potential acidification. Nitrate-N concentration was low in most lakes, with many below detection limits. The Gibbs diagram indicated seven samples in the rock dominance zone, i.e., chemical weathering of rocks as the major factor contributing ions to the lake water, while in one sample, i.e., Borith Lake, evaporation-crystallization was the main source of dissolved chemical ingredients. The Spearman correlation analysis indicated a higher positive relationship (r > 0.9) between Ca and Mg, likely due to carbonate rock weathering. The observed variations in the water quality parameters may have significant effects on both the ecosystem and human health, necessitating further research and future attention. In-depth research on glacio-hydrological dynamics and limnology can support sustainable management and conservation of the freshwater ecosystems in the region.
Turbulent transition refers to the complex flow phenomenon of laminar flow evolving into turbulence, and the criteria for judging transition constitute a core research topic in fluid mechanics, computational fluid dynamics, flow experiments, and engineering applications. This study systematically reviews the evolutionary framework of transition criteria over the past century, ranging from the empirical Reynolds number rule, linear stability theory, and the engineering en method, to semi-empirical correlations, the intermittency factor γ model, energy gradient theory, and state-of-the-art numerical criteria based on direct numerical simulation (DNS) and large eddy simulation (LES). Specialized stability criteria for non-parallel flows such as Taylor–Couette flow and Dean flow are sorted out, and the evolutionary paths, theoretical foundations, and applicable working conditions of low-turbulence natural transition and high-disturbance bypass transition are clarified. The progress of existing research is summarized, with critical bottlenecks identified, including high-Reynolds-number transition, three-dimensional coupled complex flows, and poor generalization of data-driven models. The applicable scopes and inherent defects of diverse transition theories are compared: energy gradient theory explains the instability mechanism of finite-amplitude perturbations; the intermittency factor model dominates industrial numerical simulations; and high-fidelity numerical simulation serves as the core tool for uncovering micro transition mechanisms. Four major future research directions are proposed: unified multi-scale theoretical frameworks, efficient computational fluid dynamics (CFD) algorithms, data-driven prediction models, and engineering applications for novel fluid machinery, delivering theoretical support for transition prediction and flow control.
The literature documents the economic and environmental evaluations of conventional phase change materials (PCMs), such as paraffin wax, used in photovoltaic-thermal (PV-T) systems. Nonetheless, there is limited evidence of bio-based PCM applications within PV-T systems. This study investigates the economic and environmental aspects of employing shea butter as a bio-based PCM in a PV-T setup. The photovoltaic-thermal system integrated with shea butter was designed using the Transient Simulation System (TRNSYS). The shea butter system showed superior economic performance, with a levelized cost of energy (LCOE) of US$0.131/kWh, compared with US$0.146/kWh for the paraffin wax system. Its energy costs were also lower than those of the grid and diesel generation in Nigeria. However, the payback period was longer than that of traditional PV systems. Environmentally, shea butter has a global warming potential (GWP) of 0.615 kg CO2e, significantly lower than that of paraffin wax (3.75 kg CO2e).
The influence of mooring system parameters on the hydrodynamic characteristics of waves of the Fishery-Photovoltaic complementary integrated platform formed by installing aquaculture cages on the Huaneng ‘Huanghai No.1’ floating photovoltaic platform is studied. It systematically investigates the influence of mooring system parameters on the wave-induced hydrodynamic performance of the integrated platform. A fully coupled numerical model for the integrated platform-mooring system is established using the OrcaFlex11.4c software. The reliability of the proposed numerical method is validated against the Cylindrical Floating Production, Storage and Offloading (CFPSO) wave basin model test and the net cage flume test. Through 17 simulation cases with gradient mooring radius settings, this study elucidates the response pattern of the mooring system as it transitions from a catenary configuration to a taut configuration. The results indicate that a relative mooring length of approximately 0.73 corresponds to the critical threshold. At this threshold, mooring stiffness rises abruptly, platform motion responses are markedly suppressed, cage volume variation is mitigated, and mooring line tensions remain within a controllable range. This mooring radius achieves an optimal trade-off among platform motion performance, mooring tension safety, and aquaculture stability. Further increasing the mooring radius yields only marginal improvements in motion response and cage volume performance, while causing a notable rise in mooring tension and a sharp decline in system cost-effectiveness. This study provides a theoretical foundation for the design of mooring systems for deep-sea fishery-photovoltaic complementary integrated platforms.
