Emitter is the key component in drip irrigation system; it is designed to let out the water in pipe to drop into the soil slowly and uniformly. Uniformity of emitter discharge is dependent on some parameters such as water temperature. Temperature variations influence water properties, especially viscosity. This may be a significant factor affecting flow through emitters. Field and laboratory study on this object is time-consuming and expensive. Computational fluid dynamics provides a promising tool to help in study of flow behavior of water passing through the channel of labyrinth. In this study, the flow in labyrinth channels was simulated by using the method of Computational Fluid Dynamics (CFD) to calculate temperature effect on emitter discharge for three sample of one type emitter. For this purpose, emitter discharge for the six pressures: 2, 4, 6.1, 9.2, 12.25 and 16.33 mH20 and six temperature: 5, 15, 20, 25, 35, 45 and 55oC was simulated. Samples were destroyed and longitudinal and latitudinal cuttings for the samples were obtained and sizes of the channels were calculated by photography with Scanning Electronic Microscope (SEM). To simulate pressures and temperature effect on rate of discharge using CFD, laminar flow model and turbulence model was applied. Verification of Results showed that the simulated data had a good agreement with the experimental data and also emitter discharge is insensitive to temperature variations and CFD provides a promising tool to reduce the cost and time of study on emitters.

Wetted front position is important in optimal drip irrigation system design. Wetted pattern depends on parameters such as emitter discharge, applied water volume, soil texture and structure and land slope. This field study was conducted in four slopes (0, 5, 15 and 25%) and 3 discharge rates (2, 4, and 8 lit /hr.) in three application times (1, 2 and 4 hours). Soil texture was silt clay loam. Wetted pattern dimensions were measured by excavation sections parallel to the surface; moisture was measured in these sections 24 hours after finishing irrigation. It is recommended that if to consider changing wetted pattern position in sloping lands and moisture distribution, emitter position toward plant has to be improved. This can be determined by the demonstrated equations.

Emitter is the key component in drip irrigation system. It is necessary to have a comprehensive understanding of the flow mechanisms within drip irrigation emitters to design emitters that have a high performance. The use of computational fluid dynamics (CFD) to research the flow characteristics is appropriate because the labyrinth flow path is narrow and its boundary is complex. In this study, the flow in labyrinth channels was simulated by using the method of computational fluid dynamics (CFD) to calculate the distributions of pressure and velocity of the flow, and to calculate the relationship between pressure and rate of discharge for three sample of one type emitter. The emitters were destroyed and sizes of those channels were calculated by photography with Scanning Electronic Microscope (SEM). To calculate the relationship between pressure and rate of discharge as well as simulation of flow in emitters' channels, laminar flow model and turbulence model were applied. Verification of the results obtained from the CFD simulation was conducted in laboratory, according to the ISO9261 standard.The results of simulation for the labyrinth channel well matched the measured data in laboratory Computational fluid dynamics provides a promising tool to help in the design of labyrinth channels used in drip emitters.

Introduction: Drip irrigation in which water is only available to the plant, is increasingly used in recent years. Since the flow behavior inside the emitter is difficult due to their complex structure and small size, in present study an attempt was made to assess the flow behavior of the emitters using mathematical and physical models. It needs to be mentioned that analysis of flow behavior of water in labyrinth channels is difficult because of micro-characteristics of the emitter. In this context Zhang et al. (2007) modeled the emitter’ s flow path using fluent software. In this investigation two physical models namely: laminar and turbulent were used to simulate the flow. Also numerical models that have been tested in experimental conditions, were used in the hydraulic analysis of Emitters. Next, Fluent software was used to simulate the behavior of the flow inside the two long-path emitters for calculating the discharge-pressure relationship of the models and results were compared with results obtained from experimental results...

The semi-empirical model proposed by Schwartzman and Zur for estimating width and depth of the wetted soil volume under a single emitter was tested by field observations. As the model was developed from data resulted from only two emitter discharges in two soil types, field experiments were conducted in six different soil types and twenty two emitter discharges. A linear regression with zero intercept was performed to verify the validity of the model. The slope of the line of best fit and its coefficient of determination were 0.99 and 0.98, respectively. Relative error and root of mean squared errors (RMSE) were used to check the discrepancies between observed and estimated values of the maximum diameter of the resulting wetted bulbs. The amount of RMSE, maximum and minimum values of relative errors were 10 cm, 30%, and 0%, respectively. Regarding the statistical results, the validity of the model is confirmed.  

Introduction: Oxygation is a variant of subsurface drip irrigation in which ambient air is injected through the system via a venturi, thereby plant roots receive air and water simultaneously. The objective of this research was to study the effect of two surfactants and certain ratios of them on the uniformity distribution of emitter air flow rates along lateral pipes in an oxygation system. Matherials and Methods: Two non-ionic surfactants, namely, Triton X-100 and Tween 80, and three mixtures of them with different ratios including 2: 1, 1: 1, and 1: 2 were added to irrigation water and the results were compared to the case where no surfactant was used. For statistical analysis of data, the Kolmogorov–, Smirnov and Friedman tests along with Christiansen Uniformity Coefficient were used. Findings: In the absence of surfactants, Christiansen uniformity coefficient (CUC) for emitter air flow rates was-67 percent. The relative increase in CUC, when Triton X-100, Tween 80, and the ratios 2: 1, 1: 1, and 1: 2 were applied, amounted to 211, 162, 210, 213, and 206 percent, respectively. Conclusion: The results of this research clearly indicates that application of surfactant mixtures with synergic interaction will effectively enhance distribution uniformity of emitter air flow rates.

This study was designed and carried out to determine the effects of operating pressure and irrigation water salinity on the performance of common pressure- compensating emitters in irrigation systems. The study evaluated three commercial brands, namely, “Netafim”, “Eurodrip,” and “Peresi Zalvan”. These emitters were tested at flow rates of 8 and 24 L/h under operating pressures of 0.5, 1.5, and 2.5 bars. Additionally, two levels of water salinity (5 and 12 dS/m) were considered. The results revealed that increasing operating pressure from 0.5 to 2.5 bars and raising salinity from 5 to 12 dS/m led to either increased or unchanged coefficient of discharge variations in different emitters. Comparing pre-test (new) emitters with post-test (used) ones showed variations due to various factors, including pressure changes, salinity effects, and inherent emitter characteristics. Notably, the impact of salinity did not result in significant differences in emitter performance under varying pressure conditions. However, for the Netafim and Eurodrip emitters (8 L/hr), averaging the results across all three operating pressures indicated that increased salinity led to reduced discharge. Specifically, the reduction was approximately 3.8% for Netafim and 2.6% for Eurodrip. Also, it was concluded that the application of 2.5 bar pressure led to the entry of parts and solid objects in the irrigation pipes or passed through the filtration system into the emitters, resulting in a decrease in flow rate. However, this problem can be solved to a large extent by washing the pipes before starting the system. Netafim emitters (8 L/hr), despite the lack of significant entry of these objects, had a diaphragm adhesion problem, and showed the greatest decrease in flow rate due to this reason. A detailed examination of the destroyed samples showed that the reason for these differences was the different shape and structure of the water inlet. Accordingly, the smallness of the cross-sectional area of water inlet, reduces the entry of solid parts. Therefore, application of 2.5 bar pressure resulted in the highest rate of solid parts entry into the Peresi Zalvan with the largest cross-sectional area and the lowest rate of entry in the Netafim (8 L/hr). However, this problem can be solved to a large extent by washing the pipes before starting the system.

Background: The formalism recommended by Task Group 60 (TG-60) of the American Association of Physicists in Medicine (AAPM) is applicable for b sources. Radioactive biocompatible and biodegradable 153Sm glass seed without encapsulation is a b- emitter with a short half life and delivers a high dose rate to the tumor in the millimeter range. In this work the dosimetry parameters of the seed for brachytherapy were evaluated.Materials and Methods: Using MCNP4C code data, the Dosimetric parameters of AAPM TG-60 recommendations including the reference dose rate, the radial dose function and the anisotropy function were obtained. Two dimensional dose distributions were also calculated.Results: The dose rate at reference point was estimated to be 9.41 cGy.h-1.mCi-1 for 153Sm.153Sm with its relatively low energy beta component falls off the most rapidly of the other beta emitters. The calculated data was compared with that of several beta and photon emitting seeds.Conclusion: The results showed the advantage of the beta emitting 153Sm source in comparison with the other beta emitting sources, Because of its rapid dose fall-off of beta-ray and high dose rate at the short distances of the seed. The results would be helpful in development of the radioactive implants using 153Sm seeds for the brachytherapy treatment.

In the present study, field experiments were carried out at the research fields of the Agricultural Faculty of the University of Tabriz in a sandy-loam soil in order to determine the wetting pattern dimensions and soil moisture distributions in the vicinity of an emitter and also in a domain between the two adjacent emitters in a subsurface drip irrigation system. The obtained data from experiments were compared to the results from HYDRUS two-dimensional and three-dimensional simulations. Results showed that HYDRUS-3D was more efficient than HYDRUS-2D in simulating wetting pattern dimensions on the constructed soil profiles one just at the emitter location and the other between the two adjacent emitters with RMSE values of 2.54 and 3.96, respectively. Comparison of the obtained values from the two and three dimensional simulations showed that the two models had acceptable accuracy in simulating the soil water distributions on the profile at the emitter location. Also, by increasing the irrigation duration from 1 hour to 4 hours, the value of RMSE between soil moisture values obtained from the two and three dimensional models decreased from 0.068 to 0.025. Considering the good accuracy of the three dimensional model, the calibrated model was run for three different emitter installation depths and the suitable emitter installation depth for sweet corn production in the studied soil was recommended to be 30 cm based on the plant maximum water need, minimum deep percolation and evaporation losses and the plant rooting system.