JOURNAL OF AGRICULTURAL ENGINEERING RESEARCH
Year:2011 | Volume:11 | Issue:4|Papers Count:9

Flow passing through lateral intakes and channel junctions is turbulent. Sediment flow and bed forms are affected by these flow patterns and vice versa. In this research, a laboratory study was carried out to explore a possible method for sediment control for a set of submerged vanes and a single spur dike simultaneously. Since a larger portion of the near-bed flow was diverted, the intake received a relatively large amount of bed load material; thus, appropriate and reliable methods were needed to minimize the amount of diverted sediment materials into the intake channel. The submerged vane creates a tip vortex and then the helical flow downstream reduces movement of bed sediment into the diversion. In this study, the optimum dimension, number and array of vanes were selected as determined by the regular design method. To guide flow into the diversion and increase vane performance, a single spur dike was utilized at the opposite side of the intake channel. The location, length and angle of the spur dike were optimized using the results of previous testing. The flow patterns for three diversion ratios (13%, 18%, and 24%) and a 25 cm spur dike positioned 80 cm from the intake at a 45o angle. The flow depth was measured using a point gauge and three dimensional velocities (u, v, w) at five levels above the bed as measured by ADV. After the sediment flow reached equilibrium, the channel bed was fixed. The length of separation at the intake channel was decreased by increasing the diversion ratio. By setting a spur dike opposite to the intake channel, the width of the separation line decreased at the channel bottom and increased at the surface, decreasing the amount of sediment ingestion in the intake channel.

Pressurized irrigation is a recent development that consumes more energy for the pressure produced. In this study, energy consumption, waste and efficiency were investigated at a diesel and electrical sprinkler irrigation pumping plant in some fields in Hamadan province during 2007-8. Nebraska performance criteria (NPC) were used to compare sprinkler irrigation pumping plant performance. The results showed that the average overall energy efficiency for 17 fields for the electrical pumping plants was 46.6% (70.6% NPC) and 12.7% for the diesel pumping plants (52.9% NPC). Average fuel wastage for the diesel and electrical pumping plants was 3.9 l diesel per h and 12.1 kWh, respectively. The average electromotor and pump efficiency were 92.4% and 42.2%, respectively, at the sprinkler irrigation pumping plant that did not connect directly to a well. Only the average electromotor efficiency was greater than the NPC. Factors affecting the overall energy efficiency reduction were improper pump or motor size, a worn-out pump or motor, and incorrect installation of a pump or motor.

An assessment of irrigation networks shows that their utility is less than expected because of poor design and operation, lack of sufficient maintenance and poor management. Poor performance of irrigation networks is partly because of old components that require rehabilitation. Rehabilitation of irrigation systems are done case-by-case, which lacks integration and a systemic approach and has not led to appreciable improvement. The involvement of so many components in irrigation rehabilitation and their complex interactive relation on system performance requires a system dynamics approach. Simulation techniques must be explored that represent complex dynamic systems in a realistic way. System dynamics, a feedback-based object-oriented simulation approach, was used to model the rehabilitation of irrigation networks. The ease of model modification in response to changes in the system and the ability to perform sensitivity analysis make this approach attractive for modeling the rehabilitation. In this paper, the proposed approach was applied to rehabilitate irrigation networks where the main elements affecting the network utility were efficiency, adequacy, equity, flexibility and stability in water delivery. Several rehabilitation scenarios were considered and their effects on the performance element (efficiency) were investigated. The long-term impact of the system utility was determined using system dynamics modeling and the appropriate policies were selected. The Qazvin Irrigation Network was selected as a case study. The three scenarios for network rehabilitation were fixing the area under cultivation, decreasing drawdown of groundwater and increasing investment in rehabilitation projects. The effect of the scenarios on the efficiency of the system was calculated and the final impact on the system utility was determined. The results showed that all three scenarios improved system utility, however, fixing the area under cultivation showed the best improvement.

It is essential obtain adequate data on the physical and mechanical properties of a crop to reduce crop loss and maintain the quality of crops at and after harvest and to design and optimize machines for post-harvest processing. In this investigation, the physical and mechanical properties of nectarines (var. Independence) from the Takestan region of Qazvin province were studied. The largest diameter (61 mm); mean diameter (59 mm); smallest diameter (57 mm); mass (97.74 g); volume (1123.17 cm); density (0.99 g/N); geometric mean diameter (59.10 mm); surface area (102/30 cm2); and sphericity coefficient (97%). The chemical properties showed acidity for Independence nectarines to be 1.3% and sugar to be 11%, making it tart. The coefficient of friction for multi-layer materials (wood, aluminum, galvanized sheet metal) showed a static friction coefficient varying from 0.321 for an aluminum surface to 0.389 for a wood surface layer. In addition, the break force was 58.9 N, deformation was 10 mm, and fracture energy at break point 0.3 J and 1.34 kJm-3.

After harvesting, pistachio nuts are generally kept in storage before being exported. During handling, the nuts are exposed to external forces that cause mechanical damage to them. The increase of the mechanical damage is a function of storage conditions, especially temperature. This research investigated the effect of storage temperature (25, 5, -5, -15oC), on the mechanical properties of pistachio kernels. The kernels were kept at the four storage temperatures for three months. Durability, impact, compression and comminution tests were then performed on the kernels. The statistical analysis of the data indicated that the negative temperatures had lower durability damage, but caused the kernels to become brittle, which increased impact damage. In the compression test, the modulus of elasticity of the kernels at 25, 5, -5, -15oC were 64.17, 63.11, 37.70 and 26.56 MPa, respectively. This also indicated that the power required to cause biological yield in the kernels increased as storage temperature increased. The commination test showed little difference in the distribution of broken kernels on different sieves.

The high cost of direct planters is a limitation in the development of no-till planting for row crops. Attaching appropriate coulters to conventional row crop planters can adapt existing tilled soil planters for a no-till system. In this study, two types of commonly-used disk coulters for no-till planters (plain and fluted (waved) were tested for installation at the front of a common vacuum planter with runner openers. The performance of the coulters was first compared under different vertical loads and forward speeds and for two soil moisture contents (dry and moist). The results showed that the plain coulters cut the residues, but could not produce a strip of fine soil wide enough for the runner openers at an appropriate depth. However, the fluted coulter in dry soil cut the residues properly as well as loosening a strip of soil 25-34 mm wide to a depth of 24-40 mm. Thus, in dry soil at a forward speed of less than 1.35 m/s, applying a vertical load equal to one-fourth the weight of a conventional vacuum row planter on a fluted coulter created a 31 mm wide strip of fine soil to a depth of 35 mm. The installation of four fluted coulters on the tool bar of a four row vacuum planter (in front of each planting unit) sufficiently distributed the machine weight on the drive wheels and coulters to create the vertical load required for both soil-wheel contact and penetration of the coulters into hard soil. This allowed adequate uniform placement of seeds at the desired depth. Maintaining a forward speed of 1.35 m/s guaranteed 95% soil coverage for an emergence rate of 83%. In moist soil, the fluted soil threw the soil outside the planting strip and, thus, is not recommended.

This research was conducted with two varieties of almond kernel (thin shell and semi stone shell) for five moisture levels (5%, 10%, 15%, 20%, 25% d.b.) with five replications using completely randomized base factorial design. The results showed increases with increasing moisture content from 5% to 25% for the thin shell almond for the following variables: true density (851.12 to 1138.94 Kg/m3); porosity (35.69 to 54.45%), terminal velocity (4.81 to 6.18 m/s); static friction coefficient on Plexiglas (0.471 to 0.591); static friction coefficient on galvanized iron (0.417 to 0.552); projected area (1.45 to 1.67 m2); repose angle (18.26° to 27.59o). Corresponding values for the semi stone shell almond were: true density (897.18 to 1123.84 Kg/ m3); porosity (32.09 to 47.22%); terminal velocity (5.35 to 6.53 m/s); static friction coefficient on Plexiglas (0.368 to 0.458); static friction coefficient on galvanized iron (0.356 to 0.447); projected area (1.36 to 1.53 m2); repose angle (16.33° to 22.45o). The results also showed that bulk density decreased as moisture content increased from 5% to 25% for the thin shell (547.26 to 518.76) and semi stone shell (609 to 592.94 Kg/m3).