مجله هیدرولیک
سال هشتم شماره 4 (زمستان 1392)

In this study، the effect of non-uniformity of sediment particles، on progression and pattern of delta through passing flood was investigated at various times of progressing the delta. For this purpose، 5 particle size distribution curves were used. All the curves had the same normal distribution and average particle size diameter. The effect of non-uniformity of sediment particles on progression of delta was also investigated using a physical model of river connected to the reservoir، by a gradual divergence angle. In the range of experimental observations، results show that increasing the impact time of flood causes the delta to progress more quickly after passing the flood flow. On the other hand، increasing the geometric standard deviation of the particles makes the power of the developed equation to vary between 2 to 3. 5. The amount of scouring the delta created due to the flowing flood was also reduced up to 20%، while increasing the geometric standard deviation of the sediment particles increases from 1. 2 to 2. 6.

Application of mathematical models of pollution transport in rivers is very important. It is necessary to utilize analytical solutions for verification of numerical methods. The purpose of this study is to determine 1-D analytical solution of the pollution transport equation (ADRE [1]) with constant velocity and dispersion coefficient for arbitrarily time patterns of multiple point sources using Green''s function method (GFM). General solution of ADRE equation was determined in semi-infinite domain. Final explicit solution depends on the existence of Green’s function related to the original problem. In order to find the Green’s function of each problem، a powerful tool called “Adjoint Operator” was employed. By locating the Green’s function in the general solution associated with the main boundary value problem، the final solution of ADRE equation was specified. Verification of the proposed solution was achieved by comparing the present results to the ones of Van Genuchten and Alves (1982) for the same conditions of flow and time step pattern of entrance for the pollution loading. The results obtained from both solutions were completely consistent. To generalize the proposed solution، the concentration resulting from two point sources with irregular time pattern was determined using GFM. Due to the lack of analytical solution in these cases، the result were compared with the results obtained from MIKE11 model. The Final graphs and statistical analysis show good agreement between the results of MIKE11 and the proposed solution. The main innovation aspect of this research is determining the analytical solution of ADRE equation for multiple active point sources with irregular and arbitrary time pattern.

Spur dikes، as hydraulic structures، are used to protect river banks against scouring. Spur dike in river bends، where secondary flow causes more erosion around outer bank، can be used as a protection mean. When spur dikes are installed in a bend، a complicated flow pattern is formed، especially around the spur dike. Geometrical parameters of spur dike and bend plus hydraulic parameters of flow، affect flow pattern resulting from interaction of spur dike and bend. Understanding the effects of different parameters on spur dike operation and flow pattern will help the effectiveness of the spur dikes. In this paper، flow pattern around spur dike in a bend was simulated numerically by variation of length and location of spur dike at different hydraulic conditions. Then، considering hydraulic operation and structural stability of spur dike، GRA method was used for optimizing composition of length and location of spur dike at different Froude numbers. The results show that the length of spur dike is more effective than its location on spur dike operation. If stability of spur dike is taken into consideration، spur dike will have better operation when it is installed at any location with length of 25% of the channel width.

Accurate measurement of flow in open channels، water transmission and sewage networks is accounted as an important issue in operational management of hydraulic structures. So far، various types of structures such as weirs، orifices، flumes and slide gates have been used to measure the discharge in conveyance structures. Meanwhile، proportional weirs، a type of sharp-crested weirs، have high accuracy، because of their low sensitivity to upstream depth. In the linear type of proportional weirs، the relationship between discharge and head is linear، while in quadratic and logarithmic types، linear relationships are established between discharge and square head، and between discharge and logarithm of head، respectively. In this research، based on theoretical criteria for proportional weirs and also dimensionless design method، three types of linear proportional weir; i. e. chimney cross section، inverted triangle، and inverted two triangles، and two types of quadratic proportional weir; i. e. one-piece and two pieces linear edge، were designed، constructed and installed at the end of a rectangular channel. In this research، about 600 experiments were carried out with discharge range of 2 to 10 l/s to find experimentally the relationships between head and discharge in the above mentioned proportional weirs. Results of experiments showed that discharge coefficient is a function of dimensionless ratio of the head to the weir height، and the dimensionless ratio of the weir crest length to the weir height. Using some of the experimental results، a relation between discharge and flow coefficient obtained for each weir. Comparison of the results obtained from the relationships with the rest of the results from experiments، showed that the average error of the proposed equation is equal to 1. 5 percent، indicating high accuracy of the proposed equations.

Estimation of the flow resistance is one of the most important parameters in the planning، design and operation of water resources projects، including water transfer and river system management. Bed forms، such as ripple، have significant effects on total roughness. In this paper، the effects of two types of ripples on the Manning coefficient was investigated. Experiments were performed in the Hydraulic Laboratory of Shahrekord University. Some relationships were obtained based on the geometric characteristics of the ripple bed forms and flow conditions using SPSS software. It was also observed that in the case of parallel ripple bed form، the roughness was about 47% more than that of plane bed and in the case of flake ripple bed form، the increasing rate was 43%. It was concluded that the Manning coefficient was significantly affected by the parallel shape of ripple bed form compared with the flake shape.

In this paper، numerical investigation of flow and scour pattern around T-shaped spur dike located in a 90 degree bend with live bed was carried out using SSIIM software. The channel under investigation was a 90 degree channel with radius of curvature of 2. 4 meters، and a T-shaped spur dike was located in a 45 degree position in proportion to the outer bank for determination of flow pattern، with the ratio of wing to web equal to 1. For determination of scour pattern، the ratio of wing to web was considered to range from 0. 25 to 1. 25. Comparison between the results of experimental data and numerical modeling using SSIIM software indicated good agreement between the two. Changes in lateral velocity، profile of the bed due to the effect of the ratio of the wing to the web of the spur dike، 3D velocity components as well as changes in the maximum scour depth were also compared. The results indicated that the amount of scour was minimum for the ratio of wing to web equal to 1. 25. Changes in the maximum scour depth occurred in the range of 1. 29 to 1. 42 times the upstream depth. It was also observed that two vortexes were formed at the downstream side of the spur dike، one clockwise and the other counterclockwise