Print ISSN: 1813-0526

Online ISSN: 2220-1270

Main Subjects : Dams and Water resources Engineering


Surrogate Worth Trade - Off (SWT) Method and the Decision-Making Process in Water Resources Planning and Management

Mohammed Awni Khattab; Kamel Ali Almohseen

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 118-126
DOI: 10.33899/rengj.2020.127592.1049

Multi-objective decision-making methodologies are one among widely researched areas in recent years. As a result, many technologies have been developed. Among these, is Surrogate Worth Trade - Off (SWT). SWT has emerged in the areas of water resource planning and management, and is one of the multi-objective analysis methods described as an interactive method. This study includes reviewing and applying (SWT) method to optimally operate the Mosul Dam Reservoir. This operation policy sought to achieve two contradictory objectives: diverting water from the reservoir for irrigation purposes and releasing water from it for the purpose of hydropower generation. A comparison was also made of the results that were nominated from the application of this method, namely (allocating million cubic meters/ year for irrigation and generating 1572 GW-hour/year for power generation) with the results of the research [3] which four methods for solutions have been implemented. These are: weights, constraints, goal attainment, and step method. The results reveal that the used methods gave the optimal solution by (allocating 5906 million cubic meters/ year for irrigation and generating 1,600 GW-hour/year for power generation), (6236 ,1555) , (6188 ,1558) and (6121 , 1568) respectively. from the comparison It can be concluded that (SWT)  is an efficient and promising method in identifying an operating policy for a single reservoir system with competing objectives.

Analysis of Rainfall Data for a Number of Stations in Northern Iraq

Ihsan F. Hasan; Younis N. Saeed

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 105-117
DOI: 10.33899/rengj.2020.127531.1044

This study aimed to analyze the rainfall time series data for 9 stations in the north of Iraq, namely (Sulaymaniyah, Darbandikhan, Dokan, Duhok, Erbil, Kirkuk, Mosul, Sinjar, Tal-Afar) from 1979 until 2014 using the Multiplicative model of time series, this is for the purpose of identifying the reality of the time series variables (general trend, seasonal, periodic, random) which affected by the rains, and the prediction of monthly rainfall data for the  selected stations. The rainfall characteristics of the northern region of Iraq were also studied in terms of daily, monthly and annual distribution of rainfall rates and a relationship between intensity-Duration-Frequency (IDF) at different return periods (2, 5, 10, 15, 25, 50, 100) years has been found to identify the reality of rainstorms and provide solutions  to a number of design problems related to management and treatment of water for Basins in general and ungauged Basins in particular such as surface runoff discharge and erosion control.

Effect of Nozzle Angel & Cyclic Pressure Head Variation on Water Distribution Uniformity for Stationary Sprinkler Systems

Esraa Ali Younis; Haqqi Ismail Yasin

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 93-104
DOI: 10.33899/rengj.2020.127209.1040

The present  research included studying the effect of the sprinkler nozzle angle and cyclic variation of the operating pressure head on the uniformity of water distribution for many sprinkler heads spacing with rectangular  and triangular sprinkler heads arrangement for different sprinkler heads. The research conducted 40 tests to measure a single sprinkler water distribution pattern under similar climatic operating conditions by adopting the water distribution pattern along a beam that represents the radius of the wetting circle which its center is a sprinkler head for different sprinkler nozzle angles (Ɵ + 5 °, Ɵ + 3.5 °, Ɵ, Ɵ -3.5 °, Ɵ -5 °) and the constant-cyclic operating pressure head conditions for different sprinkler heads. 320 patterns were found for field water distribution pattern and uniformity coefficient for four different spacing  with  a rectangular and triangular sprinkler heads arrangement for   the sprinkler heads and  the measured water distribution patterns.
The research revealed that 70% of the uniformity coefficients in the rectangular arrangement are greater or equal to its value in a triangular arrangement. The increase in the nozzle angle results in increasing the uniformity coefficient of 1.4% for each degree, an increase in the nozzle angle, and can reach 2.4% for each degree for a specific spacing, arrangement, and sprinkler head. Also, the difference between the two water distribution patterns in the case of operating with constant pressure head  and variable pressure head is slight, but it shows in the values of the uniformity coefficient, where the maximum difference reaches 10%, and in general, the best in the values of the uniformity coefficient requires determining the nozzle angle, the spacing and the arrangement of sprinkler head as well as the case of operating pressure head constant or variable.

Study of Scour Around Cylindrical Bridge Piers with Circular Openings

Mays Ibrahim Alsaidi; Ghania Abd Al-Majeed Hayawi; Mena Ahmed Alsawaf

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 66-74
DOI: 10.33899/rengj.2020.126863.1029

            To reduce the local scour around bridge piers and ensure their safety, an experimental study was conducted to examine the effect of a single tubular hole that faces the flow direction through three successive cylindrical bridge piers. In order to reduce the local scour, occurred because of the collision of the flux. Two groups of successive piers were used, both had diameters of 5, 11, 16 cm. First group of piers with internal tubular opening which had 20% diameter of the pier and located at half the water depth. The second group just solid pier for comparison. The spacing between them was varied to be 30, 40 or 50 cm for each group. As well as the discharge was varied. The used moveable bed material classified as non-uniform coarse sand, which had 0.5 mm mean diameter. The results showed that the presence of the openings helps effectively to reduce the depth of scour and its effect increases as the diameter of the opening increases, as the highest reduction reaches 55.56%, 53.33% and 10% for diameters 16, 11 and 5 cm, respectively. The scour depth increases when the diameter of the pier the increase of and the short distance between the successive piers.

Studying The Effect of Intake Channel Angle on the Sediment Transport Branching Channels

Ehsan Elewy Salman; Mwafaq Younis Mohammed

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 60-65
DOI: 10.33899/rengj.2020.126731.1018

An experimental investigation was conducted to observe the connection angle effect of the branched channel front with the main channel on the entering sediments amounts into the branched channel. Three angles were taken to the branched channel inlet (60°,45°,30°), that connected with the main channel from the left side with two concentrations of sand at a granular diameter rate (D50=0.5mm). The concentration flow rates were 1.8 and 2.22(g/s), respectively. The sand was fed and organized by a speed regulator to main channel to obtain the concentrations. The results showed that the 60° was better than the rest in the sediment numbers. Compared to the 30° and 45° angles, the reduction at the 60° was at (32-40)% of 40% of the discharge rate. Besides, at the 30% discharge rate, the reduction was (16-19)%. Within the study limits, it has indicated that the greater angle is the better and it reduces sediments.
 

Slope Stability Study of Al-Qaim Dam that Proposed to be Constructed on Khosar River – Case Study

Farah K. Saeed; Kamel A. Almohseen; Abdulwahab M. Yunis

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 75-83
DOI: 10.33899/rengj.2020.127023.1034

It is extremely significant during the design stage of an earth dam is to analyze the seepage and slope stability. The proposed Al-Qaim dam on  Al Khoser river was used as a case study to apply Geo-Studio 2012 program and its appendices Seep/w and Slope/w. Some minor modifications to the original design suggested by SOGREAH company have been proposed. The Geo-Studio 2012 program was used to analyze three states of Al-Qaim reservoir i.e. (end of construction، steady-state، and rapid drawdown). Seep/w and Slope/w have used to analyze the seepage and the stability of the slopes، the results reveal a good agreement between this analysis and the design company's results. Moreover، the present analysis achieves the requirement of safety with less volume of embankment which reduces the cost of construction substantially.
 

Modelling of Wetting Front Advance and Discharge Change of Subsurface Line Source

Abdulghani Kh. Mohammed; Entesar M. Ghazal

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 84-92
DOI: 10.33899/rengj.2020.127221.1042

Sub-drip irrigation is one of the most important and the latest high-performance irrigation systems that are characterized by a high ability to reduce losses of deep percolation and evaporation from the soil surface. Twelve laboratory experiments were carried out to study the effect of soil texture, dripper depth and initial water content on the wetting pattern, dripper discharge. Further, non-linear regression approach was applied to predict empirical relationships for estimation the wetting pattern dimensions and actual dripper discharge. The results showed a significant match between the observed and estimated values ​​of the wetting front advance and the dripper discharge change. At a specific volume of water application, the size of wetting soil increased (8-20%) with the initial water content increase and (2.5-6.25%) with dripper depth increase and this size decreased (4.5-36%) with the clay content increase. The rate of vertical upward advance decreased with increasing the initial water content. The dripper discharge gradually decreased with the continuation of water application due to positive pressure increase at the dripper opening, and this decrease increased with increasing dripper depth, clay content and the initial water content of the soil.

Water Management under Deficit Irrigation

Haqqi Ismail Yasin; Entesar M. Ghazal

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 1, Pages 32-40
DOI: 10.33899/rengj.2020.126551.1011

Depending on the production function, irrigation water cost function and the sale price of yield, previously, lengthy mathematical expressions have been developed to estimate the optimal levels of water used in deficit irrigation, that would maximize yield (Wm), under water limiting (Ww), and under land limiting (Wl) and the amount of water that leads to income equal to income of Wm when land is limited (Wel), and that leads to farm income equal to farm income of Wm when water is limited Wew . Therefore, in this paper, firstly the previous lengthy expressions for (Wel) and (Wew) were simplified. Secondly, simple expressions for both (Wel) and (Wew) were derived under presence of rainfall. Thirdly, very simple mathematical relations between (Wm & Wl) and (Wm & Ww) were derived in order to determine much easier expressions than those previously derived for Wel, and Wew respectively, with and without rainfall.

Testing of the Homogeneity of Precipitation Time Series in Selected Regions of Iraq

Samah Mohammed Qasim; Abdulwahab Mohammad Youns; Omar M. Mahmood-Agha

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 1, Pages 126-137
DOI: 10.33899/rengj.2020.127033.1035

Precipitation data are subject to many tests and assessments before being used for studies in the field of water resources, hydrological processes, and climate change research to ensure their reliability and quality. Homogeneity tests are considered as a useful tool to control the reliability and quality of data. In this study, a homogeneity test was performed for the monthly rainfall data distributed over different regions of Iraq. Homogeneity was examined using four tests: Pettit, SNHT, BRT and VNRT at a confidence level of 5%.The results showed that the time series for the winter months of the Ramadi, Baghdad, Hilla, Khanaqin and Karbala stations were heterogeneous, while the time series of the Al-Nakhaib, Wetba, Baghdad and Tal Afar stations during the spring months were statistically heterogeneous according to the SNHT test. While the Pettitt test showed heterogeneous results for the stations of Nasiriyah, Basra, Khanaqin and Kirkuk for the winter months. Al-Rutba, Khanaqin, Tal Afar,Sinjar,Mosul and Karbala for the spring months. The data for all stations were homogeneous, using the BRT test for the winter and spring months. VNRT test showed the heterogeneity of the data for the Samawah stations for the months of winter, Ramadi, Nakhab, Tal- Afar and Najaf for the months of spring. The current study also showed that the precipitation of all stations are classified as useful, with the exception of the Al-Nukhaib and Najaf stations, which have been classified as doubtful .

Planning and Decision Making Under Uncertainty (Mosul Reservoir Optimal Operating Policy- Case Study)

Mohammed Awni Khattab; Kamel A. Al-Mohseen

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 1, Pages 85-96
DOI: 10.33899/rengj.2020.126885.1032

This study is concerning the planning and decision making process of water resources projects under uncertainty. It includes a mathematical analysis to optimize the operation of the Mosul reservoir sought to achieve two conflicting goals, diverting water from for irrigation and releasing water for hydroelectric generation. Four methods of solutions have been implemented. These are: weights, constraints, goal attainment, and step method. The results reveal that the used methods gave the optimal solution by allocating 5906 million cubic meters/ year for irrigation and 1600 Gw-hour/year for power generation ),(6236, 1555), (6188, 1558),and (6121,1568) under the given inflow conditions . The current study suggested that the average value of these solutions i.e (6113, 1570) can be taken as a compromise solution to the problem. It is believed that this solution has a good chance to be selected by the decision-maker, because it contains the least possible degree of subjectivity.

UNIFORMITY FOR PORTABLE GRID SPRINKLER SYSTEMS

Ahmad Thamer Ibrahim; Haqqi Ismail Yasin

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 2, Pages 25-38
DOI: 10.33899/rengj.2019.164333

The proper size and diameter of the lateral sprinkler pipe is associated with the variations of pressure head along the pipeline; the greatest pressure head variations, the smallest pipe size and thereby an increase in the required pressure head at the inlet of lateral pipe and the pumping power unit.  The pattern of water distribution of sprinklers operating with different operating pressure will accordingly varies and may leads to variations in uniformity of water application along the lateral pipe. The research purpose is to study the effect of pressure head variation on the uniformity of the water distribution along the lateral pipe by adopting different values of the friction head losses that expressed as a fraction of average operating head, and linking with spacing between sprinkler heads. Furthermore, this study aims to compare between the increase in pumping power cost to ensure operating head at the lateral inlet associated with increase in the fraction of friction head losses, and decrease in the cost of the pipe. 18 tests were carried out to obtain the water distribution pattern for single sprinkler under different pressure heads and for five different type sprinklers,the water distribution pattern of a single sprinkler was estimated as a function of distance from the sprinkler and the pressure head with non-physical formulas and high determination coefficients. Fractions of head losses due to friction were chosen to be (10, 20, 30, 40, and 50) % of the sprinkler operating head. A computer program was developed to compute the pressure head at each sprinkle, water distribution pattern, and water application uniformity of the sprinkler network system using different sprinkler head spacing and three levels of operating heads. Also, the economics of pipe size and pumping operation cost using the selected fractions of the friction head losses was studied.
The results show that the water distribution uniformity increases when the pressure head at sprinkler head increases and this increase varies according to the sprinkler type and spacing; there is no observable change between the system water distribution uniformity and uniformity coefficient of application at the average operating pressure head for all sprinkler spacings and friction head looses fractions except the case of friction head loose equal to 50% of the operating head that showed very small differences. Also, the annual pumping cost to ensure required pressure head at lateral pipe inlet using same average operation head is constant for all used sprinkles. The total annual cost increases when the adopted friction head loose in the design of lateral sprinkler pipe increases stating that the economic pipe size is associated with low friction.

Effect of Irrigation Scheduling Using CROPWAT on Water Use Efficiency and Grain Yield and Components for Maize (Zea mays L.) in Semi Arid Regions

Ahmed Azhor Thanoon

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 2, Pages 130-137
DOI: 10.33899/rengj.2019.164329

Irrigation scheduling is determining the appropriate time and quantity of irrigation to reach maximum production. In this research the irrigation scheduling was determined using a computer program CROPWAT , developed by FAO . The program used the climate , crop , and soil data for calculation the irrigation scheduling .The climate data represents average years (1971-2007) of pan evaporation to Mosul city for calculating the reference evapotranspiration , maize crop and light soil data , were used to input data . The program was used cases include three different irrigation timing levels are 100%, 70% and 50% of the readily soil moisture depletion(critical depletion and belowcritical depletion) with refill soil moisture content to field capacity . The results of  irrigation scheduling from the program were applied to the field experiment in the Mosul Technical Institute during the summer of 2010. The grain yield and components were measured at harvest to improve the best irrigation scheduling for maize crop in semi arid regions .
The results showed that the depth of irrigation added to three different irrigation levels 100% and 70% and 50% of the readily soil moisture depletion reached 860 and 881 and 900 mmrespectively, the number of irrigations 15, 21, 29 . The results also showed that the best irrigation scheduling for higher water use efficiency was0.55 kg/m3 and highest production356g/m2 for the treatment of 70% of  the readily soil moisture depletion. Therefore the CROPWAT is aneffective tool for planning and management of irrigation maize in semi arid regions .

Investigation of Local Scour Around Group Bridge Pier with Different Shapes

Tahseen A. GELMIRAN; Khalil I. Othman; Mustafa GUNAL

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 2, Pages 10-22
DOI: 10.33899/rengj.2019.164355

In this study, the establish on laboratory experiments for computing the depth of local scour (ds) around group bridge pier. For this purpose, fifteen models of bridge piers were constructed and tested, divided into five groups, of each group containing three bridge piers with the same specifications. The diameter of upstream bridge piers (D1) was varied to 2, 4, 6, 8, and 10 cm, and diameter of downstream bridge piers (D2) 10 cm for all. The spacing (S) between the bridge piers was varied three times 20, 30, and 50 cm for all groups. Considering the effectiveness study of upstream flow conditions, the size of diameters of bridge piers, the spacing between bridge piers and medium size of bed material on the maximum scour depth and scour pattern around bridge piers. The study was conductedby employing a physical hydraulic model for bridge piers operated below subcritical flow, clear-water condition and exploitation uniform cohesionless sand as bed material. The experimental results showed the scour depth (ds) increasing whenever increasing the upstream diameter (D1) of bridge pier and decreasing whenever decreasing the spacing (S) between bridge piers. The dimensional analysis techniques and statistical program were used for locating a new empirical formula with the facilitate of the experimental information; this formula is for calculating the maximum scour depth at bridge piers.

Similarity Between Inside and Outside in Architecture A Comparative Study Between Mies Van der Roh& Robert Venturi Trends

Shaimaa AL-Dabbagh; Dr. Asma AL-Dabbagh

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 1, Pages 46-55
DOI: 10.33899/rengj.2019.163115

The relationship between inside and outside is considered as the principal one in architecture as it is one of its most important relationships in architecture’s history. Human had tended, from the very creation of being, to withhold a part of the outside space in order to form a special inside space of the building.
This is done through containment as in making the cave as a refuge or through designation as in setting a space by using vertical or horizontal elements. This process is called “inside and outside” which might be the leading generated term of building construction. Human firstly and the architect secondly aim at finding, unceasingly, a relationship between interior and exterior spaces. And, as they do so; they manipulate the outer mass, inner space and mutual boundaries in-between through shaping them in a way yielding a relationship between both interior and exterior spaces; thus, to find similarity or dissimilarity between the shapes of the outer mass and the inner mass of the interior space. The present study attempts to study the similarity characteristic by studying its contrast as a characteristic of the relationship between interior and exterior to determine the differences between the architects' trends (Mies and Venturi) regarding to the relation of inside and outside. this relationship will be having a big role in determining the patterns of buildings, their trends, and intellectual and spatial affiliations.
In order to achieve the objectives of the research, in the practical side, three (3) single residential houses were chosen for each architect, and After applying difference variables to the selected sample, throughout the study  a vision had been put into words expressed in that: the difference between inside and outside is what is known as the (In between), Which is the resultant of, basically, pro forma purposes, which are adapted to perform particular functions later as in Mies Architecture, or any strict functional purposes as in Venturi Architecture.

Deriving Equation to Estimate Movement of Water in Soil for Subsurface Drip Irrigation

Dheyaa Mohamed Taha; Dr. Younis Mohamed Hassan

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 1, Pages 39-45
DOI: 10.33899/rengj.2019.163114

Subsurface drip irrigation is an efficient irrigation method because it applies water directly to the crop root zone, but one of the disadvantages of this method is the positive pressure which is formed in the soil at dripopening especially in fine soils where the drip discharge is larger than the soil infiltration capacity which leads to decrease the discharge rate because the positive pressure will reduce the operation pressure of the drip. In this study, water was applied to ahole surface which filled with gravel to a needed depth,than distributed from the holebottom to all direction through the soil. Wetting front  was observed during water supply and redistribution periods .
Eighteen laboratory experiments for watching advance of wetting front at different times, by using cuboid-shaped container, dimensions (50*50*70) cm. two side of this container are plastic sheets, soil was compacted in the container to achieve bulk density. Two soils were used in the experiments, sandy loam with initial water content (3% and 6%), discharge (0.5, 1.04 and 2.14) L/hr, and silty clay with initial water content (5% and 8.5%), discharge (0.54 and 1.08) L/hr. For the both soils (5 and 10)cm radius of gravel container  with 20cm depth was used, the container have holes from bottom and side at 5cm high to water exit. The volume of water applied was 4.5 L.
The study presents equation to estimate fully shape of wetting pattern,by using dimensional analysis techniques, the effective variables on wetting front movement had been transfered to dimensionless groups, and by using the (SPSS)software  a relationship was found between distance from center of hole to wetting front and time for all direction.

Wetting Pattern for A Two-Line Trickle Source

Qamar Moayad Bakir; Haqqi Yasin

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 1, Pages 56-65
DOI: 10.33899/rengj.2019.163116

The laboratory tests carried out 12 tests to follow the advance of wetting front at appropriate times during the wetting and redistribution phases as a resulting of water application from a single linear trickle source or two linear trickle sources with a certain spacing to soil profile. These data are used to express with an estimating relationships for the wetting pattern produced by single linear trickle source and two linear trickle sources during wetting and redistribution phases. The study showed that there is a significant correspond between the wetting pattern of the measured and the estimated by the experimental equations. The wetting pattern increases with the decreasing of spacing between the two linear trickle sources, and this increase is regular along the wetting front or the surrounding of the wetting pattern, and this increase in the vertical direction of the wetting pattern is more in sandy loam soil than in silty clay soil and vice versa in the horizontal direction, when compare among the wetting patterns at the end of the wetting phase and the redistribution phase at a total time of 72 hours.

Improvement Water Productivity for Wheat Crop at Mosul Area

Rand Saadi Huseen; Dr. Younis Mohamed Hassan; Dr.Eman H. Sheet

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 1, Pages 24-30
DOI: 10.33899/rengj.2019.163112

This study aimed to optimize the yield of wheat crop under rainfed Agriculture at Mosul zone in Iraq . this can be reached by the selection of proper time of seeding time which gives the best crop yield for rainfed Agriculture or by adding one supplementary irrigation of selected depth and time which gives the maximum yield or best economical return.
In this study we generated data base using program (Aquacrop) for wheat yield with rainfall depth during the season for rainfall agriculture with rainfall depth +supplementary irrigation by using one irrigation during the season with depth (25,50,100)mm adding to one week of the season which is 23 week with initial water content between field capacity and wilting point with three date to begin the agriculture season the results showed that the optimal seeding time for the rainfed Agriculture is 15 December which gives 257.5 kg/ha yield and the next is 15 November 250.5 kg/ha and 15 January 89 kg/ha, For supplementary Agriculture the best time of the irrigation is the first week of the season with a depth change inversely with rain depth and the best seeding time is 15 November.

Effect of Roughened Flood Plain of Symmetrical Compound Channel on The Resistance of Flow

Aws Younes Hamed; Mwafaq Younes Mhammad

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 1, Pages 31-38
DOI: 10.33899/rengj.2019.163113

This research deals with the experimental study of the effect of roughened the flood plain of symmetrical compound channel (having 18 cm main channel and 29 cm flood plain width from both sides) on the resistance of flow using different size of gravel roughness (D50=6.8 ,16.8, 24,47) mm, as well as the flood plain is smooth.
 Five discharges (34,27.8,19.35,12,7.87)L/sec were carried out for each case, The compound channel was divided to 3 sections  perpendicular to the direction of flow  and each of them divided to 7 sections , 4 in flood plain and 3 in main channel . Pitot static tube used for velocity measurements and point gage for water surfacelevel measurement as well as the temperature of water was measurement, From the measurements it can be concluded that  the velocity over the flood plain was reduced clearly up to 40 – 70 % when the flood plain roughened by course roughness compare with that of smooth one  , while the velocity in the main channel increased to satisfy the continuity equation . Empirical equations were developed to combine the resistance coefficient n with other variables include the flow and geometry characteristics

Experimental Study of the Scour Depth at Downstream Weirs Has Different Holes

Mariam Khder Mohammad Alhealy; Ghania Abd Al Majeed Hayawi

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 1, Pages 18-23
DOI: 10.33899/rengj.2019.163111

An experimental study was carried out  to deal with using a weir with circular holes to control the scour occurs behind it. The holes are located near the bed of the channel, their geometric details had been changed in its size, number and their distance from the bed of the channel. The channel bed was lined by crushed gravel with average diameter 11.1 cm. The thickness of the crushed gravel layer was 22 cm and its length was 4 m. There is 18 cases were conducted. Which the diameter of the holes were 1.6, 2.3, 3 cm, and for each size of them, the distance of the holes was 0, 0.25 or 0.5 cm, their number was one or three. These cases were compared with the case of using weir with no hole. The main hydraulic variable was the discharge, which five different discharges were  flowed for each case. The total number of the experiments was 95. The dimensions of the scour hole behind the weir was measured as well as the water surface elevation in the upstream of the weir.
The analysis indicated that the discharge plays the main role to increase the size of the scour hole. Using the weir with holes helps to decrease the scour occurs behind it, because the flow from holes interrupted the flow fallen from over the weir then some of its energy was dissipated. The diameter of the weir's hole that caused the smallest scour was 0.115 cm, while the most effective distance of the this hole to cause the same effect was 0.5 cm, among all the studied cases. Due to its height increases the dissipation of the energy of the falling flow.