Showing 19 results for Irs
Z. Khosravani, S. J. Khajeddin, A. Soffianian, M. Mohebbi, A. H. Parsamehr,
Volume 16, Issue 59 (4-2012)
Abstract
LISS IV sensor's data from IRS-P6 satellite was used to produce land use map of eastern region of Isfahan, the studied part of which has an area of 22121 hectares. Its three band data, namely band 2 (Green), band 3 (Red) and band 4 (Near infra red) of LISS-IV sensor images with 5.8 m ground resolution were georeferenced by nearest neighbor method and first-order polynomial model to the DEM map of 1:25000, where the RMSE was equal to 0.3 pixel. To analyze the satellite data, various image processing methods such as supervised and unsupervised classification methods, principal component analysis, NDVI vegetation index and filtering were applied to the satellite data. Finally, the land use map was produced with hybrid method. The final map detected 6 land uses very clearly, which are: Agricultural lands, barren lands, disturbed lands, cultivated Haloxylon amodendron, roads, residential areas and industrial locations. The kappa of land use map is 0.89 and the overall precision is 0.92. The barren lands have a very poor natural vegetation and are considered as natural deserts. Disturbed lands have been formed because of brick kiln activities, and the vegetation cover of these areas has disappeared completely The LISS IV data has a high ability to detect the various studied land-uses especially to digitize the roads. They can be used to update the 1:25000 topographic maps, as well.
T. Honar, S. Mazloom Shahraki,
Volume 18, Issue 69 (12-2014)
Abstract
Cylindrical and semi-cylindrical weirs are used in water distribution systems for flow measurement in open channels and for control of water surface. Review of literature shows that cylindrical and semi-cylindrical weirs are not widely used in practice. Because of their low construction cost and simplicity, an investigation was done to study cylindrical and semi-cylindrical weirs in terms of their hydraulic characteristics such as discharge coefficient, energy loss and flow depth over the spillway crest. The research was done for 128 models in the hydraulic laboratory of water engineering department, Shiraz University. According to the results, due to flow separation from body of the weirs, flow coefficient increases in the cylindrical and semi cylindrical weirs by 57%. It was found that discharge coefficient increases by increasing the total head of upstream. Therefore, construction of cylindrical and semi-cylindrical weirs and side weir is recommended due to reduction in weir length, increased hydraulic efficiency, and reduced administrative costs compared to other wide edge side weirs.
S. Samiee, M. Heidarpour, S. Okhravi,
Volume 19, Issue 73 (11-2015)
Abstract
Side weir is the structure to evacuate extra water from a canal when level of water rises. This structure is mounted on the wall of canal. It is used predominantly to set flow in irrigation and drainage systems or urban wastewater harvesting systems. Implementing guide vanes is a simple way to increase side weir efficiency. In this study, the effect of using guide vanes on discharge and discharge coefficient of rectangular sharp-crested side weirs was investigated. ADV instrument was applied for recording vertical velocity over the crest of side weir. Local discharge was calculated by vertical velocity data for both conditions of presence and no presence of guide vanes. Results showed that in both cases, increasing the Froude number results in the decrease of passing discharge and discharge coefficient of the rectangular sharp-crested side weir. Data analysis also showed that by increasing the Froude number, guide vanes have more effect on increasing discharge coefficient and local discharge. The local discharge increased along the crest and the most passing local discharge occurred near the end of the side weir. Analysis indicates that using guide vanes leads to the increase of discharge coefficient by about 32%.
H. Azarpeyvand, A. R. Emadi, M. Sedghi Asl,
Volume 23, Issue 1 (6-2019)
Abstract
Labyrinth weirs are the economic structures to increase the weir output efficiency in limited widths, which can be seen in the plane f trapezoidal and triangular forms. These weirs with a hydraulic load and fixed width pass the more discharge in comparison to other type of weirs. In this study, labyrinth weirs trapezoidal in plane form were investigated. The experiments were performed on 27 laboratory models with 9 different discharge rates and a total of 243 tests. The results showed that, in all of the composite trapezoidal labyrinth weirs, the ratio of discharge coefficient to Ht/p (Ht: Total hydraulic load and p: weir length) weir length was increased at first; after reaching the maximum rate, it started to decrease. According to the suggested general relation, the utmost impact on discharge coefficient resulted from the cycle number and Ht/p relation. Creating new labyrinth on the wing of the weir led to the increase of the effective length; as a result of it, the discharge rate increased in a specific amount of Ht/p. Also, the discharge through a trapezoidal labyrinth weir with the semicircular planform was better than the square; the square, in turn, was better than the simple trapezoidal weirs.
R. Gharibvand, M. Heidarnejad, H. A. Kashkouli, H. Hasoonizadeh, A. Kmanbedast,
Volume 24, Issue 1 (5-2020)
Abstract
The flow fields over a trapezoidal labyrinth weir (two-cycle) and a piano key weir were simulated using Flow3D, studying the impact of each model on the flow field in the weirs and the coefficient of discharge in comparison with the available experimental data. Moreover, the models were investigated experimentally in a 12.5 m long, 0.3 m wide, and 0.4 m high rectangular flume under clear-water conditions. The results showed good agreement between the data from the numerical and experimental models. The piano key weirs had a higher coefficient of discharged compared with labyrinth weirs. The coefficient of discharge was observed to increase by 26 percent as the height of the PKW was increased by 50 percent (from 5 to 7.5 cm). This increase was 24 percent for labyrinth weirs.
. M. Karimaei Tabarestani,
Volume 25, Issue 1 (5-2021)
Abstract
One of the most common and practical methods in controlling the local scour around bridge pier is to place a protective riprap layer. Due to various uncertainties in the design of this countermeasure method, in the present study, the reliability analysis method was applied for the design of a riprap size around a real bridge pier as a case study. Therefore, four different methods including First Order Second Moment, First Order Reliability Method, Spread Sheet and Monte Carlo Simulation Technique were used to quantify the uncertainties and design of riprap size. The results showed that the probability of riprap size failure, which was calculated by the empirical equation and the use of the mean value of effective parameters in the case study, was very high, nearly 34%. In the following, the relationship between safety factor and the reliability index at the site of this case study was determined. Finally, in order to achieve more realistic results, the hydraulic correlation coefficient between depth and flow velocity parameters and its effect on the probability of the riprap failure were studied. It was shown that the correlation coefficient between these two hydraulic parameters was very high and more than 90%, and its maximum effect on the probability of the riprap failure was less than 10%.
Prof. J. Abedi-Koupai, S. Rahimi, S. Eslamian,
Volume 25, Issue 3 (12-2021)
Abstract
Changing the date of the first fall frost and the last spring frost is an important phenomenon in agriculture that can be one of the consequences of global warming. Using general circulation models (GCMs) is a way to study future climate. In this study, observations of temperature and precipitation were weighted by using Mean Observed Temperature-Precipitation (MOTP) method. This method considers the ability of each model in simulating the difference between the mean simulated temperature and mean precipitation in each month in the baseline period and the corresponding observed values. The model that had more weight, selected as the optimum model because it is expected that the model will be valid for the future. But, these models are not indicative of stationary climate change due to their low spatial resolution. Therefore, in this research, the outputs of GCM models are based on the three emission scenarios A2 and B1 and A1B, downscaled by LARS-WG for Isfahan station. The data were analyzed by SPSS software at a 95% confidence level (P<0.05). The results indicated that in the Isfahan in the future period 2020-2049 based on the three scenarios, as compared with baseline period 1971-2000, the first fall frost will occur later and the last spring frost will occur earlier. The first fall frost will occur later for 2 days (based on the A1B emission scenario) to 5 days (based on the A2 emission scenario) and the last spring frost will occur earlier for 2 days (based on the and B1 emission scenario) to 4 days (based on the A2 emission scenario). Finally, the best distribution functions for the first fall frost and the last spring frost for the baseline period and under climate change were selected and compared using the EasyFit software.
H. Elahifar, O. Tayari, N. Yazdanpanah, M. Momeni,
Volume 25, Issue 4 (12-2021)
Abstract
The discharge coefficient of labyrinth weirs increases with increasing the crest length in a certain width range. The present research was carried out in a laboratory flume with a length of 8 m, a width of 0.6 m, and a height of 0.6 m. The discharge coefficient of two-cycle symmetric and asymmetric rectangular labyrinth weirs was experimentally measured. The dimensional analysis by the Buckingham π theorem indicated that the discharge coefficient was dependent on Se, B/Wavg, Ht/P, and WL/WR. According to the results, the discharge coefficient decreased with increasing the hydraulic head in the symmetric and asymmetric labyrinth weirs and the linear weir. Asymmetric labyrinth weirs with a WL/WR of 2.05 outperformed symmetric labyrinth weirs with a WL/WR of 1. Quantitatively, the discharge coefficient of the labyrinth weir with a B/Wavg of 3.1 was respectively 21% and 94% higher than that with a B/Wavg of 2.93 and 2.76. The discharge coefficient of the labyrinth weir with a WL/WR of 2.05 was 10-27% higher than that with a WL/WR of 1. The discharge coefficient of the linear weir was 60-250% higher than that of labyrinth weirs.
P. Fattah, Kh. Hosseini, A.a. Hashemi,
Volume 26, Issue 3 (12-2022)
Abstract
Splash (raindrop) erosion plays an significant role in soil loss, especially in arid and semi-arid regions with poor vegetation. In this paper, by analyzing the pattern of rainfalls that occurred during 26 years in four basins located in Semnan County, their effect on the pattern of eroded sediments from the basin was investigated. Sedimentary layers from the sampling of retarding reservoir sediments in 2017 were related to the corresponding precipitations. Due to the occurrence of the highest amount of rainfall in each quarter of rainfall, rainfall hyetographs were divided into four categories. Cumulative precipitation curves with similar quartiles were drawn in one shape and compared with sediment curves and vice versa taking into account the physical characteristics of the basin. The results showed that the Aliabad basin (with less slope and more elongation) with an effective quarter of type 3 had the highest similarity in precipitation and sediment patterns. Also, the Western Soldereh basin (with the highest slope and the least elongation) with an effective quarter of type 2 had the least similarity in precipitation and sediment patterns. The results indicate the vital role of rainfall patterns on the resulting sediment patterns, which show up to 85% similarity.
M. Majedi Asl, T. Omidpour Alavian, M. Kouhdaragh, V. Shamsi,
Volume 27, Issue 3 (12-2023)
Abstract
Non-linear weirs meanwhile economic advantages, have more passing flow capacity than linear weirs. These weirs have higher discharge efficiency with less free height upstream compared to linear weirs by increasing the length of the crown at a certain width. Intelligent algorithms have found a valuable place among researchers due to their great ability to discover complex and hidden relationships between effective independent parameters and dependent parameters, as well as saving money and time. In this research, the performance of support vector machine (SVM) and gene expression programming algorithm (GEP) in predicting the discharge coefficient of arched non-linear weirs was investigated using 243 laboratory data series for the first scenario and 247 laboratory data series for the second scenario. The geometric and hydraulic parameters were used in this research including the water load (HT), weir height (P), total water load ratio (HT/p), arc cycle angle (Ɵ), cycle wall angle (α), and discharge coefficient (Cd). The results of artificial intelligence showed that the combination of parameters (Cd, H_T/p, α, Ɵ) respectively in GEP and SVM algorithms in the training phase related to the first scenario (Labyrinth weir with cycle wall angle 6 degrees) were respectively equal to (R2=0.9811), (RMSE=0.02120), (DC=0.9807), and (R2=0.9896), (RMSE=0.0189), (DC=0.9871) in the second scenario (Labyrinth weir with a cycle wall angle of 12 degrees) it was equal to (R2=0.9770), (RMSE=0.0193), (RMSE=0.9768), and (R2 = 0.9908), (RMSE = 0.0128), (DC = 0.9905), which compared to other combinations has led to the most optimal output that shows the very favorable accuracy of both algorithms in predicting the coefficient the Weir discharge is arched non-linear. The results of the sensitivity analysis indicated that the effective parameter in determining the discharge coefficient of the arched non-linear Weir in GEP and in SVM is the total water load ratio parameter (HT/p). Comparing the results of this research with other researchers revealed that the evaluation indices for GEP and SVM algorithms of this research had better estimates than other researchers.
M. Majedi Asl, T. Omidpour Alavian3, M. Kouhdaragh,
Volume 27, Issue 4 (12-2023)
Abstract
Weirs of the labyrinth have some advantages including the high coefficient of the irrigation of weir and the low fluctuation of water when the flow passes over the crest of the weir. In this research, the flow rate coefficient has been investigated by changing the weir geometry in terms of wall slope, arc cycle angle, and nose length change in the upstream and downstream of each cycle of the trapezoidal arc labyrinth weir. A total of 240 tests have been performed on 16 different physical models in a channel with a width of 120 cm and a narrowing of 20 cm from each wall. All models have been compared with the control model (normal labyrinth weir) (80A). The results showed that the 80B weir with an arc cycle angle of 20 degrees and without wall slope has a better performance than other weirs. Also, the weir with an arc cycle angle and a wall slope of 20 degrees in a divergent form (D20B) in the area (Ht/P) <0.31 has a better performance than other weirs with an arc cycle angle of 20 degrees, and after this area, the weir with a wall slope of 10 degrees has performed better in divergent form (D10B). In weirs with different cycles at an arc cycle angle of 20 degrees, the labyrinth weir with 5 cycles (N5) has performed better up to the point (Ht/P)=0.36. Also, at the maximum point, the difference is 13 and 17%, respectively, compared to the 4-cycle and 3-cycle weirs.
