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Abstract Although many desalination plants have been built in the countries around the Persian Gulf (PG) over the past decade, there exist crucial water demands in this region. Considering the limited water exchange between PG and the open seas, effluents more than the natural capacity of the PG will increase the sea-water salinity continuously. This excess salinity, in addition to threatening the marine ecosystems, endangers the water supply for many population centers. This study provides a comprehensive numerical analysis of the impact of existing and new desalination plants on the PG’s salinity. In addition, the water residence time and pollutant extension have been investigated in the PG. There exist several concerns, especially in recent years about the probable threat of desalination growth in semi-enclosed seas such as PG. The effect of desalination plants on the mean salinity of PG is one the questions investigated in this research. Results demonstrate that the water residence times in the southern and northwestern regions are more than five years. This time is reduced to nearly 26 to 45 months in the eastern regions near the Strait of Hormuz. Generally, the desalination plants have a negligible effect on the salinity of PG in comparison with the climate conditions such as evaporation and water exchanges. Based on the results, a 50% increase in effluent discharge of existing desalination plants increases the average salinity of the PG by only 0.01 psu. However, the annual volume of net evaporation (that exits the clean water directly) is nearly 36 times more than the effluent discharge from the existing desalination plants. Furthermore, this value is almost 0.2% of the amount of water that enters the PG through the Strait of Hormuz. In spite of these findings, the regional effects can be significant in some parts of the PG. For example, the southern and western coasts of PG are generally more vulnerable to pollution than other areas. The main reason is the shallow water depth in these areas and the water recirculation pattern. Some sensitive local areas have been also addressed in this study. Among the studied regions, the coastlines at the northwest of PG and at the north the Qeshm Island are two susceptible areas. The findings of this study underscore the importance of considering a new integrated viewpoint in developing desalination plants within PG.

Abstract The objective of this investigation is to obtain a more profound understanding of the effective parameters of the velocity caps for bottom intake systems, utilizing particle image velocimetry (PIV) and OpenFOAM. Observations indicate a higher probability of surface vortex formation in square types compared to circular ones, with the vortex being formed downstream of the caps. Additionally, the flow pattern reveals that the flow whirls in a more favorable path into the circular caps as opposed to the square ones. Through both experimental and numerical comparisons of three shapes (rhombus, square, and circle), it becomes evident that the circular type outperforms the other types in terms of discharges through the intake, showing an improvement of about 8%. The results indicate that flow depth and height of the velocity caps are positively effective parameters for the flow rate, with respective influences of 90% and 30%. In contrast, the interaction between the flow and caps intensifies with an increase in the distance of the intake opening from the bed, which plays a negative influence on the flow rate. Enhancing the number of blades in caps proves to be the optimal approach for generating a smoother flow with minimal impact on the flow rate. Numerical simulations show a 50% reduction in cap height leads to a significant 33% decrease in flow rate. Additionally, rotating the square cap by 45° into a rhombus aligned with the flow direction results in a 7% discharge flow rate increase.