Purpose -The purpose of this paper is to numerically investigate the influence of corner radius on flow past a square cylinder at a Reynolds number 500. Design/methodology/approach -Six models were studied, for R/D ¼ 0 (square cylinder), 0.1, 0.2, 0.3, 0.4, and 0.5 (circular cylinder), where R is the corner radius and D is the characteristic dimension of the body. The transient two-dimensional (2D) laminar and large eddy simulations (LES) models were employed using finite volume code. The Strouhal number, mean drag coefficient (C D ), and root mean square (RMS) value of lift coefficient (C L,RMS ), for different R/D values, were computed and compared with experimental and other numerical results. Findings -The computational results showed good agreement with previously published results for a Reynolds number, Re ¼ 500. It was found that the corner effect on a square cylinder greatly influences the flow characteristics around the cylinder. Results indicate that, as the corner radius ratio, R/D, increases, the Strouhal number increases rapidly for R/D ¼ 0-0.2, and then gradually rises between R/D ¼ 0.2 and 0.5. The minimum values of the mean drag coefficient and the RMS value of lift coefficient were found around R/D ¼ 0.2, which is verified by the time averaged streamwise velocity deficit profile. Originality/value -On the basis of the numerical results, it is concluded that rounded corners on a square cylinder are useful in reducing the drag and lift forces generated behind a cylinder. Finally, it is suggested that with a rounded corner ratio of around R/D ¼ 0.2, the drag and oscillation of the cylinder can be greatly reduced, as compared to circular and square cylinders.

This paper presents the results of a field study undertaken all over the Punjab, Pakistan, to evaluate the socio-economic and climatic impact of photovoltaic-operated high-efficiency irrigation systems (HEIS), i.e., drip and sprinkler irrigation systems. Nearly half of the rural population relies on agriculture for a living, and the recent energy crisis has had a negative impact on rural communities. Farmers’ reliance on fossil fuels for the operation of irrigation systems has increased exponentially, resulting in the high costs of agricultural production. Primary data regarding on-farm agriculture and irrigation practices used in this study were collected through an intensive on-farm survey, while secondary data were taken from published reports and statistics. The results of the current investigation show that the installation of PV systems has resulted in the increased adoption of high-efficiency irrigation systems, a reduction in the high operational costs incurred on account of old diesel-powered pumping systems (with an annual saving of 6.6 million liters of diesel), a 100% increase in farmer’s income, a reduction of 17,622 tons of CO2 emissions per annum, and 41% savings in water. The unit cost of PV-powered HEIS was found to be 0.1219 USD/kWh, which was 4% and 66% less than subsidized electricity cost and diesel cost, respectively.

No abstract

This paper presents the optimal design of a photovoltaic (PV) drip irrigation system. Designing a PV system is based on calculated motor power, solar irradiance level and other meteorological parameters at a certain geographical location. Therefore, a simulation study of the designed PV system were performed by a PVGIS simulation tool. The PVGIS simulation tool analyzes the potential of power generation with optimal PV modules tilt angle and orientation on a monthly and annual basis, and an analysis of the overall shading situation (horizon) as well as the internal shading between the PV module rows. The selection of water pump and motor depends upon the depth of water table and desired discharge and head to operate the irrigation system. Furthermore, a locally developed Solar-Drip Simulation Tool (SoSiT) was used for load and supply optimization. Based on ambient temperature, solar irradiation and water requirements, SoSiT calculates net generation by a PV system and resultant water output of the irrigation system. The particular drip irrigation site has two zones; the maximum water requirement for zone 1 (row crop) is 50,918.40 Liters/day and for zone 2 (orchards) is 56,908.80 L/day. From PVGIS simulation results, the maximum daily energy production of the designed PV system was 6.48 kWh and monthly energy production was 201 kWh in the month of May. SoSiT results showed that the PV system fulfilled the required crop requirement by only using 28% of the potential water supply, and 72% of the potential water supply from a solar-powered pump was not used. This value is high, and it is recommended to grow more or different crops to utilize the fuel-free electricity from the PV system. The unit cost of PV-powered drip irrigation is USD 0.1013/kWh, which is 4.74% and 66.26% lower than the cost of subsidized electricity and diesel, respectively.

The world is moving towards renewable energy sources rapidly and, at present, fossil fuels are reducing day by day. In this scenario, biofuels have become an attractive alternative to conventional diesel fuels. In the present work, the vaporization of Thumba biodiesel is numerically modeled using the finite volume-based approach in ANSYS Fluent and the results are compared with diesel fuel. Evaporation of fuels is governed by the conservation equations of energy, momentum, and mass. Owing to high temperature and pressure conditions, turbulence is present in the engine cylinder. To account for the turbulence effects, the Reynolds-averaged Navier–Stokes (RANS) turbulence model is used. Heat transfer to droplet and mass lost by the droplets is governed by the discrete phase model equations. The obtained results include the droplet lifetime, increase in temperature of a droplet, and velocity profiles. It is observed that the size and temperature of fuel droplets and ambient temperature have a significant effect on the evaporation time of fuel droplets in the engine cylinder. By reducing the droplet size, the complete evaporation of fuels can be achieved. Droplets having a high temperature have a short evaporation time and high evaporation rate. It is noted that, at a higher temperature, biodiesel evaporates more quickly than diesel fuel, thus producing complete combustion and hence giving maximum power output.

The purpose of this study is to investigate the potential of airborne particulate matter (PM10 and PM2.5) and its impact on the performance of the photovoltaic (PV) system installed in the Sargodha region, being affected by the crushing activities in the hills. More than 100 stone crushers are operating in this region. Four stations within this region are selected for taking samples during the summer and winter seasons. Glass–fiber papers are used as a collection medium for particulate matter (PM) in a high-volume sampler. The concentration of PM is found above the permissible limit at all selected sites. The chemical composition, concentration, and the formation of particulate matter (PM10 and PM2.5) layers on the surface of the photovoltaic module varies significantly depending on the site’s location and time. The accumulation of PM layers on the PV module surface is one of the operating environmental factors that cause significant reduction in PV system performance. Consequently, it leads to power loss, reduction of service life, and increase in module temperature. For the PV system’s performance analysis, two PV systems are installed at the site, having higher PM concentration. One system is cleaned regularly, while the other remains dusty. The data of both PV systems are measured and compared for 4 months (2 months for the summer season and 2 months for the winter season). It is found that when the level of suspended particulate matter (PM10 and PM2.5) increases, the energy generation of the dusty PV system (compared to the cleaned one) is reduced by 7.48% in May, 7.342% in June, 10.68% in December, and 8.03% in January. Based on the obtained results, it is recommended that the negative impact of PM on the performance of the PV system should be considered carefully during the decision-making process of setting solar energy generation targets in the regions with a high level of particulate matter.

Purpose – The purpose of this paper is to focus on the variation of wake structures and aerodynamic forces with changes in the cylinder corner radius and orientation. Design/methodology/approach – Numerical simulations were performed for flow past a square cylinder with different corner radii placed at an angle to the incoming flow. In the present study, the rounded corner ratio R/D=0 (square cylinder), 0.1, 0.2, 0.3, and 0.4 (where R is the corner radius and D is the characteristic dimension of the body) and the angle of incidence α in the range of 0°-45° were considered. Findings – The numerical model was validated by comparing the present results with results in the available literature, and they were found to be in good agreement. The critical incidence angle for the rounded corner cylinder – corresponding to the minimum mean drag coefficient (C D ), the minimum root mean square value of the lift coefficient C L,RMS), and the maximum Strouhal number – shifted to a lower incidence angle compared with the sharp corner square cylinder. The minimum drag and lift coefficient at R/D=0 were observed for the critical incidence angle αcri=12°, whereas for R/D=0.1-0.4, the minimum drag and lift coefficient were found to be within the range of 5°-10° for α. Originality/value – The presented results shows the importance of the incidence angle and rounded corners of the square cylinder for reduction of aerodynamic forces. The two parameters support the shear layer flow reattachment on the lateral surface of the cylinder, have a strong correlation with the reduction of the wake width, and hence reduced the values of C D and C L .

Power augmentation in a small-scale horizontal axis wind turbine, with its rotor encased in a flanged diffuser is explored. The power output of the wind turbine varies with changes in the diffuser design and the resulting back pressure. Reduction in this back pressure also results in early flow separation at the diffuser surface, which hinders turbine performance. The main aim of this study is to numerically investigate the local configuration of the wind turbine location inside the diffuser by varying diffuser angles and wind speeds. Therefore, shroud and flange were modeled and analyzed using the computational fluid dynamic (CFD) analyses and experiments were performed at two wind speeds 6 m/s and 8 m/s with and without the diffuser for model validation. The divergence angle of 4° was found to have no flow separation, thus maximizing flow rate. The proposed design shows wind speed improvement of up to 1.68 times compared to the baseline configuration. The corresponding optimum flange height was found to be 250 mm. However, increasing the divergence angle had a similar output. The dimensionless location of wind turbine was found to be between 0.45 and 0.5 for 2° and 4° divergence angle respectively. Furthermore, the maximum augmentation location varies with wind speed and diffuser’s divergence angle as described by dimensionless location of wind turbine, thus presenting a noteworthy contribution to the horizontal axis wind turbine area with the flanged diffuser.