PROBING INTO THE EFFECTS OF CAVITATION ON HYDRODYNAMIC CHARACTERISTICS OF SURFACE PIERCING PROPELLERS THROUGH NUMERICAL MODELING OF OBLIQUE WATER ENTRY OF A THIN WEDGE

The current paper investigates flow around a blade section of a surface piercing hydrofoil. To this end, a thin wedge section is numerically modelled through an oblique water entry. The flow is numerically studied using a multiphase approach. The proposed numerical approach is validated in two steps. First, pressure and free surface around a wedge entering water are simulated and compared against previously published analytical results. Subsequently, cavitation phenomenon around a submerged supercavitating hydrofoil is modelled and analyzed. It is observed that cavity length, pressure, and lift force are accurately predicted. Subsequently, the main problem has been studied for two different cavitation numbers for a range of advanced ratios equivalent to fully, transition and partially ventilated conditions in order to investigate the effect of ambient pressure on hydrodynamics of the water entry of the foil. The numerical findings reveal that, when the cavitation number decreases, the start of transition mode is postponed and this mode is expanded for the larger range of velocity ratios. This implies that fully ventilated velocity ratio modes are expanded, too. However, in the transition mode, the cavitation number plays an essential role and may lead to a decrease in the pressure difference across the surface piercing hydrofoil which yields a decrease in the resultant force

Analysis of Ventilation Regimes of the Oblique Wedge-Shaped Surface Piercing Hydrofoil During Initial Water Entry Process

The suction side of a surface piercing hydrofoil, as a section of a Surface Piercing Propeller (SPP), is usually exposed to three phases of flow consisting air, water, and vapour. Hence, ventilation and cavitation pattern of such section during the initial phase of water entry plays an essential role for the propeller’s operational curves. Accordingly, in the current paper a numerical simulation of a simple surface piercing hydrofoil in the form of an oblique wedge is conducted in three-phase environment by using the coupled URANS and VOF equations. The obtained results are validated against water entry experiments and super-cavitation tunnel test data. The resulting pressure curves and free surface profiles of the wedge water entry are presented for different velocity ratios ranging from 0.12 to 0.64. Non-dimensional forces and efficiency relations are defined in order to present the wedge water entry characteristics. Congruent patterns are observed between the performance curves of the propeller and the wedge in different fully ventilated or partially cavitated operation modes. The transition trend from fully ventilated to partially cavitated operation of the surface piercing section of a SPP is studied and analyzed through wedge’s performance during the transitional period

PROBING INTO THE EFFECTS OF CAVITATION ON HYDRODYNAMIC CHARACTERISTICS OF SURFACE PIERCING PROPELLERS THROUGH NUMERICAL MODELING OF OBLIQUE WATER ENTRY OF A THIN WEDGE

The current paper investigates flow around a blade section of a surface piercing hydrofoil. To this end, a thin wedge section is numerically modelled through an oblique water entry. The flow is numerically studied using a multiphase approach. The proposed numerical approach is validated in two steps. First, pressure and free surface around a wedge entering water are simulated and compared against previously published analytical results. Subsequently, cavitation phenomenon around a submerged supercavitating hydrofoil is modelled and analyzed. It is observed that cavity length, pressure, and lift force are accurately predicted. Subsequently, the main problem has been studied for two different cavitation numbers for a range of advanced ratios equivalent to fully, transition and partially ventilated conditions in order to investigate the effect of ambient pressure on hydrodynamics of the water entry of the foil. The numerical findings reveal that, when the cavitation number decreases, the start of transition mode is postponed and this mode is expanded for the larger range of velocity ratios. This implies that fully ventilated velocity ratio modes are expanded, too. However, in the transition mode, the cavitation number plays an essential role and may lead to a decrease in the pressure difference across the surface piercing hydrofoil which yields a decrease in the resultant force

Study the Efficiency of Clinoptilolite Zeolite for Lead Removal from Aqueous Solutions and Determining Adsorption Kinetics and Isotherms

Recently the low-cost adsorbent for heavy metals removal such as Lead in recent years has been noticed by researchers. In this study, lead removal by clinoptilolite has been investigated. Non-continuous lead absorption from aqueous solution was carried out by using clinoptilolite. The zeolite characteristics were analyzed with SEM and XRD. The effect of pH variables (1, 3, 5, 7, 10), contact time (15, 30, 45, 60, 90 min), clinoptilolite adsorbent dosage (1, 3, 5, 7, 10 g) and lead concentrations (10, 20, 40, 50, 60, 70, 80 & 100 mg/L) were studied on lead removal efficiency and adsorption isotherms and kinetics in constant temperature and stirrer speed of 250 rpm. According to the results, optimum conditions of lead removal by natural zeolite were pH of 8, adsorbent dosage of 5 g/L and contact time of 45 min., the highest removal efficiency of 89.6 achieved. By increasing metal concentration, the amount of removed lead was decreased while absorption capacity increased. Of the two studied models, the Langmuir isotherm had better conformity for lead adsorption (R2=0.99) than other isotherms. Also the pseudo second order kinetics model had better conformity with achieved data than other models. Results of this study indicated that natural clinoptilolite zeolite can be considered as an efficient and cost effective adsorbent for lead removal from aqueous solutions

Study the Efficiency and Effective Factors on the Application of Clinoptilolite Zeolite for Removal of Zn from Aqueous Solutions, Determination of the Adsorption Kinetics and Isotherms

Background and objective: The industrial wastewaters are considered to be one of the main sources of heavy metal impurities. The removal of toxic heavy metals from wastewaters is of great importance from an environmental point of zn are the most concerning heavy metals in aqueous solutions due their high toxicity in low concentrations and bioaccumulation in live tissues. Among various removal methods, adsorption through inexpensive adsorbents has been highly considered by researchers. The zn removal by natural clinoptilolite zeolite was defined as the main purpose of the current study. Methods: The experiments were carried out in batch mode operation with natural zeolite. The zeolite characteristics were analyzed with SEM and XRD. The effect of pH (5, 6, 7, 8, 10), contact time (15, 30, 45, 60,90min), adsorbent dosage (1, 3, 5, 7, 10) and pb and zn concentrations (10, 20, 40, 50, 60, 70, 80 and 100 mg/L) on removal efficiency of zn, adsorption isotherms and kinetics were studied in constant temperature. Results: Based on the findings, optimum conditions of zn removal by natural zeolite, included pH, 7, adsorbent dose of 5g/L and contact time of 30 minutes. The metal removal was decreased along with metal concentration, but the absorption capacity was increased. Of the two studied models, the Langmuir isotherm was better fitted Freundlich for zn (R2=0.98). Also for Zn, the pseudo second order kinetics was consistent with results. Conclusion: The results of current study indicated that natural clinoptilolite zeolite can be considered as an efficient and cost effective adsorbent for zn removal from aqueous solutions

Temporal distribution and zoning of nitrate and fluoride concentrations in Behbahan drinking water distribution network and health risk assessment by using sensitivity analysis and Monte Carlo simulation

International audienceThe present study aimed to investigate the spatial distribution and zoning of nitrate and fluoride concentrations in the drinking water distribution network of Behbahan city and the health risk caused by their concentration using sensitivity analysis and the Monte Carlo simulation during 2018 to 2019.In this cross-sectional study, 90 samples were collected from 45 points of the city's drinking water distribution network in the two high-rainy and low-rainy seasons.Nitrate and fluoride concentration was measured byDR 5000 spectrophotometer and its non-carcinogenic impacts were calculated using EDI and HQ.The results showed that the average nitrate concentrations in high and low rainy seasons in the study area were 15.05 and 13.35 mg l(-1), respectively.Also, the average concentrations of fluoride in high and low-rainy seasons were 0.67 and 0.76 mg L-1, respectively.The fluoride concentration in the high-rainy season showed a decreasing trend from north to south.The nitrate concentration decreased from north to south and southwest.The amount of nitrate HQ in the age groups corresponding to children, adolescents, adults and infants were 0.5, 0.4, 0.34, and 0.07, respectively.The fluoride HQ levels in the age groups corresponding to children, adolescents, adults and infants were 0.7, 0.5, 0.05, and 0.1, respectively.These results showed that children were the significant at-risk group due to these ions.According to the Monte Carlo simulator, 95th percentile caused by exposure to nitrate and fluoride ions in all age groups was more than one.Based on the sensitivity analysis, the most efficient factor in the health risk caused by nitrate and fluoride ions was the concentration of these ions in the drinking water distribution network

Comprehensive health risk analysis of heavy metal pollution using water quality indices and Monte Carlo simulation in R software

Abstract Rapid urbanization, population growth, agricultural practices, and industrial activities have led to widespread groundwater contamination. This study evaluated heavy metal contamination in residential drinking water in Shiraz, Iran (2021). The analysis involved 80 groundwater samples collected across wet and dry seasons. Water quality was comprehensively assessed using several indices, including the heavy metals evaluation index (HEI), heavy metal pollution index (HPI), contamination degree (CD), and metal index (MI). Carcinogenic and non-carcinogenic risk assessments were conducted using deterministic and probabilistic approaches for exposed populations. In the non-carcinogenic risk assessment, the chronic daily intake (CDI), hazard quotient (HQ), and hazard index (HI) are employed. The precision of risk assessment was bolstered through the utilization of Monte Carlo simulation, executed using the R software platform. Based on the results, in both wet and dry seasons, Zinc (Zn) consistently demonstrates the highest mean concentration, followed by Manganese (Mn) and Chromium (Cr). During the wet and dry seasons, 25% and 40% of the regions exhibited high CD, respectively. According to non-carcinogenic risk assessment, Cr presents the highest CDI and HQ in children and adults, followed by Mn, As and HI values, indicating elevated risk for children. The highest carcinogenic risk was for Cr in adults, while the lowest was for Cd in children. The sensitivity analysis found that heavy metal concentration and ingestion rate significantly impact both carcinogenic and non-carcinogenic risks. These findings provide critical insights for shaping policy and allocating resources towards effectively managing heavy metal contamination in residential drinking water

Removal of turbidity and organic matter from car wash wastewater by electrocoagulation process

Car wash effluent is one of the important threats that can contaminate water resources for drinking, agriculture and industrial uses in Iran. The purpose of this study was assessment and analysis of the efficiency of the electrocoagulation process in the removal of turbidity and organic matter from car wash effluent. Data were taken through laboratory scale and sampling from different car wash sewages of Ahvaz, Iran. In this experimental study, we used a bipolar method to convert alternative electricity to direct current. The important factors of our study were pH, electrical potential, voltage and reaction times. Results show that the percentage of turbidity removal in the electrocoagulation (EC) with an aluminum electrode (E) with an optimum pH = 7 were 75 and 99.59 in 10 and 30 voltages, respectively. According to results, the percentage of chemical oxygen demand (COD) removal in the electrocoagulation with an iron electrode with an optimum pH = 3 were 67 and 94 in 10 and 30 voltages. Consequently, electrocoagulation is a comparatively suitable process for turbidity and organic matter removal from car wash wastewater