mehdi karami moghadam; tooraj sabzevari; mehdi nourzadeh hadad
Abstract
Introduction: The study of flow diversion in open channels which has been, since long, under consideration by hydraulic engineers, is much used to divert flow from a main channel or from a river into an irrigation or hydropower channel. When a water intake with an angle is installed at one side of the ...
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Introduction: The study of flow diversion in open channels which has been, since long, under consideration by hydraulic engineers, is much used to divert flow from a main channel or from a river into an irrigation or hydropower channel. When a water intake with an angle is installed at one side of the channel, the streamlines of the flow deflect towards the intake. As a result, a separation zone is produced in the lateral channel. The separation zone develops in the lateral channel and reduces the discharge capacity and efficiency of water intake by delimiting the channel width available for the flow. Therefore, determination of water intake geometry and flow conditions to produce minimum separation zone is very important and they are the focus of this study. The majority of previous studies was conducted on sharp edged water intake entrances. Therefore, in this study, to find the optimum radius for a round edged entrance water intake, a comprehensive experimental program was carried out in a laboratory flume and the separation zone dimensions and Alpha and Beta coefficients were measured.
Materials and Methods: The experimental model was built in hydraulics laboratory. The water intake was installed at 55 degrees to the main channel. The main channel consisted of a rectangular cross-section with a base width of 0.5 m, height of 0.4 m and a length of 15.80 m. The lateral diversion channel was 0.25 m wide, 0.40 m high. According to previous experiments that performed by Keshavarzi and Habibi (2005), radii of 10, 15 and 20 cm were selected for the edges of the intakes, upstream of the 55 degree water intake. The velocities of the flow in transverse and flow directions were measured using an electromagnetic velocity meter at three distances Z= 3 cm, 6 cm and 12 cm, in which Z is the distance from the bed. Then the size of the separation zone, Alpha and Beta coefficients were determined.
Results and Discussion: To find a relationship between the radius of the round edge entrance in the 55 degree water intake and the size of separation, the geometry of the separation zone must be determined. To find the geometry and pattern of separation zone for different flow conditions, the particle traces technique was employed using Tec plot Software version 8.0. In open end flow condition, for discharge ratios of 0.2, 0.4, 0.6 and 0.8, and for the radii of 10, 15 and 20 cm, flow separation occurs at 3 cm and 12 cm distance and only upstream of the intake inlet. The separation size in r=20 cm is less than for other radii. Also, the separation size for Qr = 0.8 is minimized and for Qr =0.2 is the maximum and for r/Wb=0.8, the length and width of separation are minimum. In close end flow condition and for radii of 10, 15 and 20 cm, the size of separation zone at upstream of water intake is much larger than that in downstream. Comparing with the separation length downstream of the intake it can be concluded that with increasing the inlet radius, the separation length upstream of the intake inlet decreases. Therefore, in close end conditions, rounding of the intake inlet is effective to decrease separation length at upstream side of water intake. Also, in close end conditions, flow separation occurs at downstream side of water intake. Furthermore, the separation size for r=20 cm is less than for other radii, therefore, r/Wb=0.8 is the optimum radius ratio with a minimum separation size at the 55 degree water intake.
Conclusions: When a water intake with an angle is installed at one side of the channel, the streamlines of the flow deflect towards the intake. As a result, a separation zone is produced in the lateral channel. The separation zone development in the lateral channel and reduces the discharge capacity and efficiency of water intake by delimiting the channel width available for the flow. In this study, to find the optimum round inlet radius, the experimental tests were carried out at a water intake installed in a rectangular channel with rounded edge with 10, 15 and 20 cm inlet radius. Then separation zone dimensions and alpha and beta coefficients determined. These experiments were carried out in close end and open end flow conditions for diversion flow ratio 0.2, 0.4, 0.6 and 0.8. Using particle trace plot for different flow pattern, the values of length and width of flow separation upstream and downstream of the intake were determined. The result showed that the separation size for Qr = 0.8 is minimized, whereas it is maximum for Qr =0.2. Furthermore, the separation size for r=20 cm is less than for other radius, therefore, r/Wb=0.8 with a minimum separation size was selected as the optimum radius ratio.
mehdi nourzadeh haddad; Akbar hasani; mehdi karami mighadam
Abstract
Introduction: Water shortage in arid and semiarid regions is the most serious factor in limiting agricultural activities as it leads to the rapid reduction of yields from both a quantitative and qualitative perspective. Under conditions of water scarcity, leaf temperature rises, which causes plant wilting ...
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Introduction: Water shortage in arid and semiarid regions is the most serious factor in limiting agricultural activities as it leads to the rapid reduction of yields from both a quantitative and qualitative perspective. Under conditions of water scarcity, leaf temperature rises, which causes plant wilting and premature senescence of leaves and, eventually, severes reduction of dry matter production. Use of high-efficient irrigation practices, improvement of soil's physical properties, and use of soil amendments such as superabsorbent polymers are some ways of compensating for water shortage, especially during the growing season. Some materials such as plant residues, manure, various types of compost, and superabsorbent polymeric hydrogels can store various amounts of water and thus increase water retention and storage capacity of soils. Superabsorbent hydrogels, which are also called superabsorbent polymers (SAPs) or hydrophilic polymeric gels, are hydrogels that can absorb substantial quantities of water. Hydrogels are a class of polymeric materials having network structures (with physical or chemical crosslinks) that are very capable of swelling and absorbing large amounts of water. These materials are formed from water-solublepolymers by crosslinking them either using radiation or a crosslinker. Superabsorbents are widely used in many products such as disposable diapers, feminine napkins, soils for agricultural and horticultural purposes, gel actuators, water blocking tapes, medicine for the drug delivery systems and absorbent pads where water absorbency or water retention is important. Water is a major constraint for crop growth in arid and semi-arid regions, as the precipitation is low and uncertain in these areas. Efficient utilization of meager soil and water resources necessitates the adaptation of appropriate water management techniques. Suitable soil moisture increases the biological activities as result of physical and chemical condition of soil improving the crop production finally.
Material and Methods: This experiment was conducted under greenhouse conditions in Shushtar city at northern Khuzestan Province using the randomized complete block design using 13 treatments and with 3 replications. Soil samples were taken from a field in the study area, air dried, and passed through a 2 mm sieve. Seven concentration (0, 0.25, 0.5, 0.75, 1.0, 1.25, and 1.5 percentage) of superabsorbent polymers (Aquasorb and Accepta) were used in greenhouse condition. Superabsorbent and 10 Kg soil thoroughly mixed in each pot. All treatments were irrigated when the plants at control showed sign of wilting. There were three replications of each treatment. NPK fertilizers were applied as urea, diammonium phosphate (DAP) and potassium sulphate (K2SO4) based the soil test. Soil samples were again collected which were analyzed for nitrate-N, total organic carbon (TOC), phosphorus and potassium, bulk density, particle density and saturation percentage.NPK of plant samples were also determined. Data were statistically analysed by Duncan test using SPSS.
Results and Discussion: Results had shown that the highest bulk density (1.515 gr/cm3) seen in control treatment and with increasing the polymer, bulk density decreased significantly to 0.91 gr/cm3 in treatment No.2. Also the treatments No. 4 and 11 shown decreasing EC significantly from 0.9 in control treatment to 0.68 in No.4. Adding superabsorbent had significant effect on Potassium amount of soil. Using superabsorbent had no significant effect on real density, pH, N amount, Phosphorous, soil organic carbon after yield harvesting in soil and amount of Phosphorous in plant. Significant increasing in number of leaves, branches, fresh weight of plant, and fruit weight with using superabsorbent polymers and the highest used polymer level (treatments No. 7 and 13) had the highest effect on fresh weight of plant which reported 47.2 g for No.7 and 90.47 g for No.13. Also using 1 percentage of Accepta superabsorbent (No.12) caused the significant increasing of fruit weight (502.9 g) instead of control (73.5 g). Based on the presented results No. 2 and 9 had the most effects on N of plants, which the N amount in control was 1.31 percentage and in No.2 and 9 were 2.88 and 2.82 measured respectively. Treatments No. 7, 8, 9, and 11 had the most measured plant potassium. Final results had shown the number of bacteria and fungi increased significantly using superabsorbent and the number of bacteria increased to 215 × 104 in No.13 and the number of fungi to 176500 in each gram of soil.
Conclusion: The overall results of this research had shown the promotion of physical, biological, and finally increase the yield as results of using superabsorbent especially Accepta type. Using these superabsorbent polymers in farms need more studies because of more effective climate parameters.