Depth of tillage and its effect on field watershed size in Ejigbo zone, Osun State, Nigeria

The study investigated effects of different depths of tillage on flow of runoff in watersheds on fields tilled and planted with maize (Zea mays) hybrids and open pollinated variety (OPV) of maize. Twelve 1 m × 1 m × 2 m pits were dug and overlaid at all sides and at its bottom with impermeable membrane to accumulate watershed’s runoff from the fields. Twelve compartmental plots of 400 m2 each comprising 2 depths of tillage (0-15 cm and 0-30 cm) and 2 varieties of maize (hybrids and open pollinated) were used. Each of the treatments was replicated thrice to make 2 × 2 × 3 factorial design. Each plot measured 4 m × 10 m at 2 m apart. Among the data collected were the volume of water accumulated in the small earthen pits dug, flow velocity (v m/s) of water in runoff channels/collectors that fed earthen pits, slopes of the collectors, cross-sectional area of collectors and wetted perimeter. Results revealed that average infiltrometer values of 15.00±0.24 mm/h and 16.50±0.40 mm/h respectively in the upper part and the lower part were recorded. The 0-15 cm depth of tillage accumulated more volume of runoff water than the 0-30 cm depth of tillage in the pits and it was 23.33% higher in the lower depth of tillage used on the field than the 0-30 cm depth of tillage. Implying that 0-30 cm tillage depth retained more water from the rainfall compare to the water retained by the 0-15 cm depth. Even though, volume of runoff water of 0-15 cm depth of tillage was higher than that of the 0-30 cm depth of tillage, 0-15 cm depth of tillage had the highest yield of maize (9.30±4.26 t ha-1).

Assessment of environmental water requirement for rivers of the Miankaleh wetland drainage basin

The Miankaleh wetland, one of the richest ecosystems in the north of Iran, has experienced an unprecedented environmental degradation caused by overexploitation of the water resources and climatic changes in recent years. This research aims to estimate the environmental water requirement (EWR) for the rivers that drain into the wetland. For this purpose, comprehensive data were collected through physiographic, climatic, hydrologic, ecologic, and field studies of the wetland and its drainage basin. To estimate the EWR, we applied several methods including the Tenant, the Eco-deficit, the flow duration curve, the Wetted-Perimeter method, and the physical habitat simulation model (PHABSIM) and the results were evaluated based on the natural discharge of the rivers before retrogression of the Miankaleh wetland. Further, the results showed that the consideration should be given to the Wetted-Perimeter and the PHABSIM Model for estimation of the EWR for the rivers of the Miankaleh wetland given the seasonality of the rivers and hydroclimatic condition of the study area. The mean annual EWR of the rivers was estimated between 0.12 and 2.03 m3/s, which is close to the values of the bank full flows. The current discharge of the rivers are less than the estimated EWR, showing the discharge rates do not meet the water requirement for aquatic species of the Miankaleh wetland

Heat Transfer Enhancement of Double-Tube-Type Heat Exchanger by Petal-Shaped Tube (Study on Optimum Tube Shape)

Heat exchangers are used widely in many fields, and various kinds of exchanger have been developed according to the requirement of the practical applications. Recently, heat exchangers that are highly efficient or compact have become more desirable from the viewpoint of energy conservation, and several new types have been developed, such as a compact fin tube type and a double tube type having an inner pipe with a special geometry. In this study, the flow and heat transfer characteristics of a petal-shaped double tube with a large wetted perimeter of six and five petals and five shallow petals and the effect of tube shape on the heat transfer and heat transfer efficiency were examined experimentally. The heat transfer of the double tube with a petal-shaped inner tube was increased because of the large wetted perimeter, but the pressure loss by friction increased. The optimal shape of the petal-shaped double tube with a high heat transfer performance and the greatest efficiency is discussed.

Topological and fractal aspects of the main hydraulic parameters

The traditional concept of wetted cross-section, wetted perimeter and hydraulic radius seems fairly simple and clear, especially in the case of smooth boundaries of the flow. However, for the rough boundary surface covered with randomly arranged roughness the definition of the wetted cross-section as a normal to all elementary streams becomes notably problematic. More controversial seems the concept of wetted perimeter. This issue is of particular importance for the beds with high-dimensional roughness for which the geometric dimensions of the flow and the roughness elements are of the same order. The article shows that topological features of the boundary surfaces for the natural channels allow definitely refer them to fractals. Further study of the bed roughness based on its fractal nature can form a new approach to methodological soundness of main hydraulic parameters and open up new opportunities for their description.

New and improved three and one-third parabolic channel and most efficient hydraulic section

Several parabolic-shaped open channel sections are available in the literature, including quadratic and semi-cubic parabolic sections. This paper presents a three and one-third parabolic cross-section that has superior characteristics compared to those of previous parabolic-shaped sections. The section characteristics, including two approximate formulas for the wetted perimeter and a simple iterative formula for the normal water depth are presented. The exact solution for the most efficient hydraulic section is derived. The results show the width–depth ratio for the most efficient hydraulic section is 2.1273. Practical applications of the proposed most efficient hydraulic section are presented, including direct formulas for the discharge and explicit formulas of normal and critical depths. The results show that the proposed section improves the hydraulic characteristics compared with other parabolic sections and trapezoidal section.