https://www.hydrophysics.ir/ Hydrophysics en daily 1 Wed, 19 Feb 2025 00:00:00 +0330 Wed, 19 Feb 2025 00:00:00 +0330 https://www.hydrophysics.ir/article_729029.html The objective of this study is to evaluate the accuracy of CMIP6 models in simulating precipitation in the Lake Urmia Basin (Iran) over the past three decades, based on the Kling-Gupta Efficiency (KGE) statistical index. Data from five synoptic meteorological stations were analyzed using four AOGCM models: AIM-ESM1-2-HR, AIM-CM5-0, AIM-CSM2-MR, and EC-EARTH3-CC. The historical period considered spans from 1985 to 2014. Raw model outputs were downscaled using CMHyd software. Taylor diagrams were generated using both linear scaling and distribution mapping methods to identify the most suitable bias correction technique. Model performance was assessed using the KGE index at each station. According to the results, the highest and lowest KGE correction values were observed at Maragheh and Mahabad stations, respectively, while the maximum and minimum KGE values after calibration occurred at Tabriz and Maragheh stations. The calculations indicate that the MPI model provides the most accurate precipitation simulation across all selected stations in the Lake Urmia Basin, whereas the BCC model performs the weakest. The findings also reveal that raw model outputs contain significant errors and cannot be used directly. The linear scaling method was found to improve GCM outputs effectively. Considering the KGE index values of the MPI model (greater than 0.03 at all five stations after scaling), the model demonstrates reliable capability for assessing precipitation in the Urmia Basin. https://www.hydrophysics.ir/article_729673.html This study investigates the improvement of Eddy Kinetic Energy (EKE) simulations in the Caspian Sea using the Princeton Ocean Model with two reanalysis datasets: ERA-Interim and ERA5. The simulations were conducted at a horizontal resolution of 3 km with 35 vertical layers over a 10-year period (2009–2018). Results indicate that ERA5 substantially enhances the representation of EKE, with an annual mean value of 0.117 m²/s²—approximately twice that obtained from ERA-Interim (0.06 m²/s²). Seasonal analyses reveal the highest eddy activity in summer (peaking at 0.15 m²/s² in ERA5) and the lowest in winter. Spatially, the southern Caspian basin, characterized by greater water volume and deeper bathymetry, exhibits the most pronounced EKE variations, whereas the northern basin, despite reaching comparable peak values (0.15 m²/s²), shows minimal variability due to its shallower depth and smaller volume. The enhanced spatial resolution (from 0.79° to 0.25°) and improved physical parameterizations in ERA5 are identified as the primary factors contributing to these differences. These results align with findings from other semi-enclosed basins and highlight the importance of advanced reanalysis products for realistic ocean modeling. Overall, the outcomes of this study offer a valuable foundation for future research on current prediction, ecosystem management, and pollutant monitoring in the Caspian Sea. https://www.hydrophysics.ir/article_732929.html The investigation and understanding of sedimentation and erosion regimes along coastal zones are crucial for the design and development of ports. Identifying the sources of river sediments is essential for effective decision-making and dredging management. Sediments may originate from upstream tributaries or from marine processes. In the rivers of northern Iran, water discharge to the sea is often restricted during summer to store water upstream, which can lead to sediment transport from the sea toward river estuaries. Several factors affect sediment deposition in river systems, including river geometry, in-channel structures, and the presence of breakwaters at the river mouth. This study investigates the effect of geometric modifications to the breakwater at the Babolrud River mouth on sediment deposition patterns. Topographic, wind, and wave data from the study area were collected. Based on field observations, two scenarios were defined for the first six months of the Iranian year 1402 (March–September 2023) to analyze sedimentation behavior using the MIKE (Sediment) model. In Scenario 1, the sediment deposition rate at the river mouth during spring and summer reached approximately 60 centimeters, creating significant navigational challenges for recreational vessels and kilka fishing boats. Within the river channel, the sedimentation rate was much lower, ranging from 2 to 5 centimeters. In Scenario 2, which considered sediment inflow from the sea into the river and port basin, the rate of sediment deposition and bed-level rise near the mouth increased considerably compared to Scenario 1. These results indicate that continuous dredging at the river mouth is necessary to maintain navigability and efficient port operations. https://www.hydrophysics.ir/article_733094.html In the Persian Gulf, information on the characteristics of mesoscale eddies is limited, even though these currents can significantly affect ship performance. The aim of this study is to investigate the impact of mesoscale eddies on the Energy Efficiency Existing Ship Index (EEXI) and the Carbon Intensity Indicator (CII) for oil tankers. Four mesoscale eddies, identified using oceanographic data, were analyzed. A numerical model was implemented with appropriate boundary conditions and seasonal current fields, and a westward current with an average speed of about 0.1 m s⁻¹ was extracted for different months of the year. The effect of these currents on the speed, fuel consumption, and environmental performance indicators of a representative tanker was then evaluated. The results show that following routes influenced by mesoscale eddies increases fuel consumption by approximately 8–12% and leads to higher emission indices because of the longer sailing distance, whereas conventional shipping routes are shorter, more energy-efficient, and more cost-effective. Nevertheless, knowledge of the location and characteristics of these eddies can support better route planning, help anticipate ship drift, and reduce risks during emergencies such as loss of propulsion or steering. https://www.hydrophysics.ir/article_732214.html Hydroacoustic types represent the dominant sound speed profile structures in the water column and vary according to the number of layers and the presence of sound channels, making them highly important for understanding sound propagation in the sea. These profiles are primarily controlled by temperature variations. The aim of this study is to investigate the effect of time of day as a controlling factor on sound speed profiles across three time periods and different regions in the Gulf of Oman using ARGO data from 2003 to 2023.​ In this research, ARGO float data were processed using MATLAB to derive individual sound speed profiles, regional mean profiles, monthly means for three daily time periods, and data frequency distributions. The results show that the lowest data density in all regions occurs during the morning period, while the highest density is observed from sunset to sunrise. A comparison of mean sound speed profiles in five regions indicates that the influence of longitude on profile shape is stronger in the morning than in the afternoon and from sunset to sunrise.​ The highest frequency of surface sound channel formation occurs in the morning, indicating that the hydroacoustic types during this period predominantly correspond to positive-type surface channels. From March to May, no surface channel forms in any of the three time periods, and the absence of this channel from sunset to sunrise appears to be related to the residual effect of increased afternoon surface temperature and the resulting stratification. https://www.hydrophysics.ir/article_722771.html Iran, with more than six thousand kilometers of coastline along the Caspian Sea, Persian Gulf, and Gulf of Oman, ranks among the leading countries worldwide in terms of coastal extent and thus requires effective coastal monitoring and management. Determining and quantifying the coastline position is one of the most important tasks in coastal engineering and management programs. Traditional, field-based shoreline mapping is time-consuming and expensive and cannot meet the demand for continuous monitoring, so there is a growing need for fast, low-cost, and large-area methods such as satellite remote sensing. One effective solution is the extraction of coastlines from satellite imagery using advanced image processing and classification techniques.​ The aim of this study is to extract the coastline of Bandar Laver using three approaches—Canny edge detection, fuzzy logic, and supervised object-oriented classification with the random forest algorithm—and to compare their accuracy in shoreline identification. Sentinel‑2A satellite images were used, and the wet/dry boundary was taken as a proxy for the coastline. Edge detection was applied using the Canny algorithm, while fuzzy logic and object-oriented classification with random forest were implemented to generate shoreline maps, from which the coastline of Bandar Laver was derived for all three methods.​ For validation, the shorelines obtained from the image processing methods were compared with a reference shoreline digitized by an expert interpreter. The overall accuracies were 88% for the Canny method, 90% for the fuzzy logic approach, and 93% for the object-oriented random forest classification, demonstrating the superior performance of the random forest method for coastline extraction in the study area. These results confirm the suitability of object-based machine learning techniques for operational, cost-effective coastal monitoring in Iran. https://www.hydrophysics.ir/article_727893.html Human societies and the environment are facing major challenges due to climate change. Global warming, indicated by the projected rise in Earth’s surface temperature, is not uniform across the planet, making regional assessments essential for understanding local impacts and developing adaptation strategies. This study employs the CanESM5.0 climate projection model, based on the Coupled Model Intercomparison Project Phase 6 (CMIP6), to analyze the effects of climate change on meteorological parameters and future drought conditions at the Selseleh synoptic station in Lorestan Province, Iran. To simulate meteorological parameters, recorded temperature and precipitation data for the period 1997–2022 were used. Future climate projections for the period 2023–2043 were evaluated under three Shared Socioeconomic Pathway (SSP) scenarios: an optimistic scenario (SSP1–2.6), a moderate scenario (SSP2–4.5), and a pessimistic scenario (SSP5–8.5). The results show that the CanESM5.0 model demonstrates good performance in simulating temperature but performs less effectively for precipitation. Future projections indicate that the Selseleh region will experience the impacts of global warming, with an overall increase in mean annual temperature and a decrease in mean annual precipitation across all three scenarios. Seasonal analysis reveals that the highest precipitation and lowest temperatures occur in winter, while the lowest precipitation and highest temperatures are recorded in summer. These findings provide valuable insights for future water resource management, the development of adaptation strategies, and evidence-based planning to mitigate the effects of climate change in the region. https://www.hydrophysics.ir/article_721202.html In this paper, the dielectric and piezoelectric properties of Mn: 25PIN-40PMN-35PT piezoceramic samples with different steps of adding excess PbO was investigated. For this purpose, 4 samples were synthesized by two-step columbite precursor method. Structural and piezoelectric characterizations of samples were done. The results showed that the sample which additional excess PbO was added after calcination of the powder and its re-calcination, has optimal properties (Ec=20.95 kV/cm, TC=218 ℃, ε⁄ε0=1650 and d33=177 pC/N) compared to other samples. After determining the optimal step of adding excess PbO, its weight percentage was evaluated to have a composition with optimal properties. In this regard, 5 samples containing 1 to 5 Wt% excess PbO were synthesized and investigated. The comparison of the data obtained from these samples showed that the sample containing 1 wt% excess PbO has optimal properties compared to other samples. The results of optimizing the percentage of excess PbO and how to add it to the composition can also be applied to other lead-containing piezoelectric compositions. https://www.hydrophysics.ir/article_732211.html By employing acoustic emissions from surface or subsurface naval platforms, sonar systems (encompassing both active and passive modalities) are tasked with the detection, identification, and localization of such assets. A sonar simulator, as a software construct, emulates the functionality of a physical sonar system. Beyond its pedagogical applications, it offers significant cost efficiencies in the research and development lifecycle of defense systems and serves as a valuable tool in operational planning and the representation of tactical scenarios. The implementation of a sonar simulator model necessitates addressing two key phases: the reconstruction of observational signals and the subsequent inversion process for target rendering. These phases can be modeled through disparate or integrated methodologies. This research addresses the dual challenges of a paucity of observational signal datasets across diverse vessel types and the imperative for real-time simulation. To this end, a novel approach to passive sonar operational simulation is proposed, drawing inspiration from the Analytic Hierarchy Process (AHP), an established optimization and decision-making framework within management science. This methodology operationalizes the simulation by mapping the domain expertise and experiential insights of sonar operators onto an interconnected hierarchical network of salient criteria and influential alternatives. https://www.hydrophysics.ir/article_732828.html Hot water discharge in marine environments, especially semi-enclosed seas and bays, has significant impacts on hydrophysical properties and the marine environment. The discharge of hot water leads to an increase in the surface temperature of the water and, as a result, a decrease in its density. These temperature changes and subsequent salinity changes affect the distribution of nutrients, such as nitrogen and phosphorus, and oxygen. Reduced oxygen levels, especially in areas near hot spring discharges, can lead to reduced water quality and the loss of marine life. In the Persian Gulf, where the depth is shallow and evaporation rates are high, these changes are more severe and will have more destructive effects on marine ecosystems. These environmental impacts can lead to ecological crises. In order to investigate the fluctuations in the hydrophysical properties of seawater and to accurately manage wastewater discharge in industrial units, it is necessary to optimally design and model the hot water discharge process to reduce negative impacts on the environment. Solutions such as using closed cooling systems, preventing water discharge in sensitive areas, and proper design for more uniform mixing and distribution of warm water can help reduce environmental damage and maintain the balance of marine ecosystems. In the present study, the MIKE software model was used to investigate and analyze the hydrophysical fluctuations occurring at the hot industrial wastewater discharge site in the Persian Gulf. https://www.hydrophysics.ir/article_731986.html In recent years, energy absorption from sea waves as a renewable resource has received much attention. In this study, the smoothed particle hydrodynamics (SPH) numerical method is used to investigate the oscillatory behavior of a rotating wave energy converter. This converter is placed at the end of a slope connected to a reservoir that is affected by a solitary wave. The slope can represent the seashore, where waves are deformed near it and their energy absorption has its own considerations. In this study, the effect of various parameters on the energy absorption rate of the converter, such as wave height, stiffness of the torsion spring connected to the converter at the bottom, the moment of inertia of the converter, and the angle of inclination of the surface have been investigated. The results showed that by reducing the moment of inertia of the converter, the energy absorption rate decreases, but the value of this parameter must be greater than a critical value for the converter to be able to withstand the wave impact. It was also found that the spring stiffness at a moderate level leads to the desired performance of the converter. The amount of period, as an important factor in the oscillatory motion of the converter, is significantly dependent on the spring stiffness. Also, the optimal performance of the energy converter occurs at a certain slope, regardless of wave height, spring stiffness, and moment of inertia, which is related to the process of wave deformation on an inclined surface. https://www.hydrophysics.ir/article_732879.html The hull form design of underwater vehicles significantly influences their hydrodynamic performance. The three main sections—nose, midbody, and tail—play a crucial role in optimizing the hull of autonomous underwater vehicles (AUVs) from a hydrodynamic perspective. In this study, the simultaneous effects of nose and tail geometry on hydrodynamic performance and surrounding flow characteristics of a fixed-length AUV hull were investigated. Mairing’s equations were employed to design the hull profile, and the control parameters were adjusted to generate variations in the hull form. Numerical simulations were performed using STAR-CCM+ based on the RANS equations. Optimization was conducted via a full factorial design of experiments in Design Expert at a flow velocity of 1.1 m/s. The optimal hull form was selected to minimize drag force while maintaining a volume variation within 2% of the initial model. Among 15 conducted experiments, five models with the highest desirability were identified, and model 12 was chosen as the optimal configuration, achieving a 1.12% reduction in drag compared to the initial design. Notably, model 7 exhibited the lowest drag, with a 3.2% reduction relative to the baseline. Flow analyses were performed over velocities ranging from 0.3 to 1.4 m/s, and the effects of Reynolds number, drag coefficients, and volume-dependent resistance were evaluated. Results indicate that variations in the curvature and slope of the nose and tail sections significantly affect the drag force of the submerged vehicle. https://www.hydrophysics.ir/article_725257.html In this paper, the performance and vibration characteristics of an electromagnetic boomer as a source of high-power acoustic waves have been studied. The system under study consists of a 45-turn tape coil with two circular diaphragms with a diameter of 508 mm and a thickness of 12.7 mm, which are restrained from the sides by 6 springs. For this purpose, the boomer operation was formulated using the relations governing diaphragm vibrations, eddy currents, and their mutual effects. Since it is difficult to solve these equations analytically, the finite element method was used to solve these equations simultaneously. The results show that with increasing diaphragm thickness from 5 to 18 mm, the diaphragm displacement amplitude initially increases rapidly, but gradually approaches a constant value at 18 mm with increasing thickness. At the same time, the diaphragm displacement frequency decreases from 22 to 14 Hz with increasing thickness. On the other hand, studies show that if the spring constant increases by a similar ratio and simultaneously with increasing diaphragm thickness, the diaphragm displacement will have a maximum value with a thickness of 9 mm. Examination of the diaphragm material also shows that the displacement range of the aluminum diaphragm is significantly greater compared to other metals due to its lower density and higher conductivity. https://www.hydrophysics.ir/article_732829.html This study aimed to analyze the relationship between the phases of the ENSO phenomenon and the 30-year autumn precipitation in Kermanshah province using the ONI index. Autumn precipitation plays an important role in providing water resources and agricultural management in Kermanshah province, and its changes under the influence of atmospheric fluctuations such as ENSO can have significant economic and social consequences. Two sets of data were used, including monthly data from the Kermanshah synoptic station and seasonal data from the ONI index received from the NOAA website for 1994-2023. Pearson correlation coefficient was used to determine the relationship, and based on the phase detection criterion, the El Nino and La Nino phases were separated and the different intensities of both El Nino and La Nino phases were extracted and examined. The relationship between precipitation in the study area and the aforementioned distance index in the autumn season is direct, which was significant at the 99% confidence level (R=0.51 and P<0.01). The average precipitation in the moderate El Niño phase has dominated the other intensities of this phase, and the average precipitation in the mild El Niño phase has been higher than the other levels of this phase. The lowest precipitation at the mentioned station during the study period was at the average level of the El Niño phase with a value of 23.33 mm, and the highest precipitation in the 30-year period was at the average level of the El Niño phase with a value of 427.88 mm. https://www.hydrophysics.ir/article_733095.html Plasma, recognized as the fourth state of matter, exhibits unique properties that make it highly suitable for laboratory investigations and technological applications. In this study, key plasma parameters, including expansion velocity, temperature, and density, were experimentally measured using shadowgraphy. The experiments were conducted with a Nd:YAG laser at pulse energies of 140 and 200 mJ in two different environments: air and water. Plasma formation was induced with a fundamental wavelength of 1064 nm, while shadowgraphy employed the second harmonic at 532 nm. Temporal imaging over 1–10 μs intervals allowed detailed analysis of plasma front propagation. The results indicate an average plasma expansion velocity of 3.54 km/s in air and 2.74 km/s in water. The plasma temperature was measured at 3435 K in air and 2008 K in water, while the density values for 140 and 200 mJ pulses were 5.04 and 5.35 kg/m³ in air, and 4.91 and 4.95 kg/m³ in water, respectively. Temporal evolution of these parameters revealed a gradual decrease in temperature, velocity, and density after plasma formation. This study demonstrates that shadowgraphy provides an effective tool for precise plasma diagnostics and comparative analysis across different environments. Moreover, the high sensitivity and dynamic characteristics of laser-induced plasma offer potential applications in optical cryptography and sensitive environmental monitoring, where spatial and temporal plasma patterns can function as secure data channels or environmental indicators, responsive to subtle changes in the surrounding medium. These findings may contribute to the development of advanced laser-based systems for information encoding and environmental surveillance. https://www.hydrophysics.ir/article_733576.html Automatic rain detection from digital images, especially in regions lacking traditional equipment, is a low-cost and effective tool for weather monitoring and rapid warning. In this study, the Farneback optical flow algorithm was used to identify motion caused by rain in consecutive video frames. This method analyzes vertical pixel motion and can detect rain, serving as a simple and relatively robust approach in real-world conditions. To evaluate, a set of rainy and non-rainy videos was selected, and results were compared with manual labeling. The algorithm’s average accuracy is 78.72%, indicating a reasonable capability to detect rain, particularly in videos with fixed frame rates and relatively higher brightness. The results suggest that this method can achieve more favorable outcomes when combined with other methods and trained further, and it is cost-effective in terms of implementation. This approach is suitable for real-time and surveillance applications and can serve as a low-cost substitute for traditional equipment. Given the importance of rain detection in natural disaster management and climate change, this area has become a vital focus in recent research, and future improvements could increase efficiency and accuracy.