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Various CTD data obtained in the Oman Sea are analyzed to explain structural features of intrusive layering. Special attention is compensated to thermohaline intrusions observed in layers (depth ranges of 150 m to 450 m, 150 m to 350 m, 100 m to 350 m and 150 m and 400 m in the winter, spring, summer and autumn, respectively). The temperature and salinity profiles in thermohaline intrusion have sawtooth structure in all stations, while they have step structure in density field. Based on interpretations, detailed estimates of thickness are about 10 to 20 meters. The T-S diagrams show the positions of the outflow intrusion with different thicknesses and depths for all seasons in the Oman Sea. Vertical profiles of temperature and salinity show two boundaries in the upper and lower layers. They are prone to double diffusive convection. Salt fingering and diffusive convection can be seen in both the upper and lower boundaries, and salt fingering is stronger at the lower boundary. Diffusive convection also is visible from the surface to the mid-depth of the plume outflow, and the diffusive intrusion is more severe at the upper boundary than the surface and deep. The intensity of double diffusion in the bottom border is greater than the upper boundary. At the deeper parts, the stratification is completely stable. Variations of the positions of greatest salinities in different diagrams are due to changing water masses for different locations and depths and paths of intrusive flow.

The prediction of ocean waves is a highly challenging task in coastal and water engineering in general due to their very high randomness. In the present case study, an analysis of wind, sea flow features, and wave height in the southern coasts of the Caspian Sea, especially in the off-coast sea waters of Mazandaran Province in Northern Iran, was performed. Satellite altimetry-based significant wave heights associated with the period of observation in 2016 were validated based on those measured at a buoy station in the same year. The comparative analysis between them showed that satellite-based wave heights are highly correlated to buoy data, as testified by a high coefficient of correlation r (0.87), low Bias (0.063 m), and root-mean-squared error (0.071 m). It was possible to assess that the dominant wave direction in the study area was northwest. Considering the main factors affecting wind-induced waves, the atmospheric framework in the examined sea region with high pressure was identified as the main factor to be taken into account in the formation of waves. The outcomes of the present research provide an interesting methodological tool for obtaining and processing accurate wave height estimations in such an intricate flow playground as the southern coasts of the Caspian Sea.

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Combined cycle power plants are gaining more attention throughout the world and their usage is increasing. This is because their efficiency is higher than simple Rankine or Brayton cycles. However, their efficiency could still increase. In this article, the driving force plot and exergy analysis are used to study the behavior of heat exchangers of a heat recovery steam generator in base case and off-design conditions. Based on the obtained results, a new method is proposed to improve performance of a heat recovery steam generator during the summers in which higher ambient temperature results in lower efficiency of plant. In this new method, hot flue gas at the heat recovery steam generator inlet is split which results in higher steam production in heat recovery steam generator. The results showed that the new proposed method is very beneficial and increases net output power of the plant. When split ratio increases from 2.5% to 15%, the power produced in steam turbine increases from 0.15 to 0.9 MW. It also increases exergy destruction of the heat recovery steam generator. This is due to higher mass flow rate of the produced steam and higher temperature difference between hot and cold streams. It is shown that this new method can reduce the negative effects of consuming more fuel in duct burner during the summers.

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