During flooding, flow enters floodplains and extremely affects the hydraulics of river flow. In this case, estimation of flood discharge with traditional or commonly used methods leads to high errors (up to 40 percent). The most significant method for modifying traditional methods is Shiono and Knight quasi 2-D model which has numerous applications in laboratory and field compound cross sections. In this paper, based on this 2-D model, suitable dimensionless equations for secondary flow effects have been presented for solving the velocity lateral distribution in straight flume and river compound channels. Results of main channel flow velocity of this method have been compared with Shiono and Knight and Ervine et al., models, for some flume and river compound channels. This comparison showed that the proposed equations and Ervine et al. model had the highest and lowest accuracy, with determination coefficients of 0.99 and 0.71 percent, respectively. Also Ervine et al. method may lead to high error in case of asymmetrical compound cross sections and hence, it is not recommended.

Meandering has attracted the attention of scientists and engineers since a long time. In river bend, high variations of flow depth, velocity and shear stress across the river produce a spiral flow and hence, bank erosion in outer bank and sedimentation in inner bank. Such situation is very complicated in rivers with floodplains. In this condition, flood flow enters the floodplains and changes the direction of secondary flow because of momentum transfer between main channel and floodplains. In this paper, using a quasi-two dimensional mathematical model, the lateral distribution of velocity in overbank meandering rivers is simulated. This mathematical model combined with dimensionless relationships for secondary flow term is solved numerically in curvilinear system. The most important result of this research indicates that the maximum and minimum magnitudes of velocity are occurred in inner and outer banks, respectively, which is in the opposite sense with the flow structure at the inbank meandering channels. This finding agrees well with the experimental data in overbank meandering channels. Furthermore, the numerical results have higher accuracy compared with Ervine et. al. method. The mean relative error of proposed and Ervine et al. methods for predicting the main channel velocity are 6 and 10 percents, respectively.

Reliable prediction of boundary shear force distributions in open channel flow is crucial in many critical engineering problems such as channel design, calculation of energy losses and sedimentation. During floods, part of the discharge of a river is carried by the simple main channel and the rest is carried by the floodplains located to its sides. For such compound channels, the flow structure becomes complicated due to the transfer of momentum between the deep main channel and the adjoining floodplains that magnificently affects the shear stress distribution in floodplain and main channel sub sections. In the present study experiments were conducted in a compound rectangular section with different discharges and 3 different aspect ratios. The results showed that in each aspect ratio, shear stress increases by increasing the water level. It is also shown that by increasing the aspect ratio, shear stress is decreased significantly.

In the river, velocity parameter is one of the most important hydraulic variables and is effectively used in many river engineering fields like development of stage-discharge curve and sediment transport. In some river engineering schemes, the calculation of average flow velocity is sufficient. However, for some other projects, such as designing hydraulic structures in the river, stable channel design, flood calculations in rivers and floodplains, the lateral and vertical distributions of flow velocity should be calculated. To calculate the two-dimensional distribution of the velocity of flow (in transverse and vertical directions) many mathematical models have been presented with many complexities from practical point of view. In this research, a simple and practical mathematical model of Kean et al in combination with eddy viscosity equation as well as Einstein's law of the wall velocity was used to determine the two-dimensional flow velocity distribution in the smooth and rough compound channels. By numerical solution of this mathematical model, using finite differences method, isovel curves data were calculated for some experimental compound channels with different flow depths and floodplain's roughness coefficients and then they were compared with the experimental data. Also, transverse distributions of the flow velocity were calculated in these channels and compared with the measured profiles. These comparisons showed that the proposed mathematical model with coefficient of determination (R2)=0. 92, root-mean-square error (RMSE)=0. 036 and mean absolute percentage error (MAPE)= 2. 8% had an acceptable accuracy. The proposed mathematical model was developed with steady and uniform flow assumption, neglecting the secondary flow effect.

In rivers with non-prismatic compound cross-sections, due to the change in cross-section along the channel, mass exchange between the main channel and floodplains. Therefore, discharge distribution in non-prismatic compound channels is an important task for river and hydraulic engineers. In this paper, some results of experiments performed in non-prismatic compound channels with skewed and inclined floodplains have been explained. Two skew angles of 3.81o and 11.31o and three discharges were investigated. The effects of relative depth and relative distance on percentage discharge distribution in each sub-section of the skewed compound channels are presented. The experimental results show that the percentage discharge in each sub-section relies upon the parameters like relative depth, relative distance, skew angle, and floodplain side slope. By using the experimental results, multivariable regression models have been developed to estimate the percentage of discharge in the main channel and on the floodplains. Investigations indicate that the regression models presented in this research, in the validation range, can predict the percentage of discharge in each sub-section of the skewed compound channel fairy well. So that for the results used in this research, the coefficient of determination (R2) for predicting discharge regression model in the main channel is 0.96, on the diverging floodplain is 0.92, and on the converging floodplain is 0.91. Also, the mean absolute percentage errors (MAPE) between the calculated and measured value of percentage discharge in the main channel, on the diverging floodplain, and the converging floodplain are equal to 1.47%, 14.29%, and 21.7%, respectively.

In this research, using FLOW3D software, the flow velocity distribution and shear stress of the bed in meandering compound channels due to the change of floodplain width and relative depth were investigated. For this purpose, four sections of meandering compound channels with floodplain width having 3. 3, 4. 31, 5. 32 and 6. 33 meters and three relative depths of 0. 26, 0. 35 and 0. 45 have been used. The results of numerical simulation show that by increasing the floodplain width, the depth averaged velocity and bed shear stress are reduced. So that with a 92% increase in floodplain width, the maximum flow velocity in the main channel decreases by 24%, and the depth averaged velocity at relative depths 0. 45 and 0. 26 are reduced by 17% and 21%, respectively; and the rate of change of depth averaged velocity is more noticeable due to a change in the width of floodplain for low relative depths. The effect of changing the floodplain width on the bed shear stress has the highest value in the mid-section between two apexes (CS3 section); so that by 92% increase in the floodplain width in the mid-section (CS3), the bed shear stress is reduced by 35%. Also, the amount of boundary shear stress in the inner arch wall in all channels which is higher than the boundary shear stress in the outer arch wall; and the maximum amount of wall shear stress occurs near the bankfull level of the main channel and by increasing the relative depth, the wall shear stress increases.

One of the obvious reasons for most disorders in network service provisioning is network path congestion. Congestion avoidance in today's networks is too costly and sometimes impossible. With the introduction of SDN, centralizing the equipment's control plane has become possible. This paper presents an enhanced method named ESV-DBRA to avoid congestion in multi-tenant SDN networks. At first, ESV-DBRA monitors the traffic load and delay of all network paths for each tenant individually. Then, by merging the parameters obtained from the monitoring, the Service Level Agreements (SLA), and a novel proposed cost function, it calculates the cost of the network paths per tenant. As a result, traffic for each tenant is routed through the path/paths at the lowest possible cost from the tenant's perspective. Next, the bandwidth quotas will be calculated and assigned to the tenants over their optimal routes. Afterward, whenever congestion is likely to occur in a path, ESV-DBRA automatically changes the route or bandwidth of the tenants' traffic related to this path to avoid congestion. Related algorithms are also proposed.Eventually, simulations show that the proposed method effectively increases bandwidth utilization by 10.76%.

Different types of contact, including contact between node pairs, any-contact of nodes, and contacts of the entire network, are used to characterize social relations in mobile social networks. Different modes of routing, from the point of view of message delivery semantics, encompass unicasting, multicasting, any-casting, and broadcasting. Studies have shown that using probability distribution functions of contact data, which is mainly assumed to be homogeneous for nodes, improves the performance of these networks. However, there exists an important challenge in studies on distributions. A lot of works apply the distribution of one type of contact to other types. Hence in routing applications, it causes to use of the distribution of one type of contact for any mode of routing. This study provides a complete solution to model each type of homogeneous contact data distribution and to use them in different modes of routing. We propose a routing algorithm that uses this new model. Results show that our solution improves the average latency of comparing methods Epidemic, TCCB, and DR about 3.5-times, 30%, and 45%, respectively. It achieves a delivery rate of about 5% and 6%, and average latency about 6% and 8% better than that of DR and TCCB, respectively.