مجله هیدرولیک
سال چهاردهم شماره 2 (تابستان 1398)

The result of 40 experiments in the field of scouring by three dimensional wall jets were conducted in this paper. Experiments were carried out at the different values of densimetric Froude number that ranges was 3.9 to 6.6, a range of tailwater condition was 4 to 15 times the dimensions of the jet and for the three same cross-section nozzle with different dimensionless axial distance from the channel wall in ranges of 0.5 to 17.3. At first in this paper the scour mechanism caused by the wall jets was described. The effect of jet distance to the channel side wall was also investigated. The results of the paper verified with the previous studies. Laboratory observations and results show that the nozzle distance from the channel side wall caused the jet deviation towards the near wall and asymmetric in flow regimes. The factors has significant influence on scour due to jets as the maximum scour depth increased by decreasing of the distance of the nozzle to the side wall. Also in most cases the scour longitudinal parameters decreases by increasing the distance of the nozzle to the side wall. It was found that tailwater depth has an influence on scour longitudinal parameters. According to the results it can be note that the effect of jet location on scour is significant and can be considered as an effective parameter in scour cause by wall jets.

sedimentation in reservoirs is a great problem, especially around the outlet gates during their operation. sediment flushing efficiency from outlet gates is very low too. in this paper a new method to increase the efficiency of sediment flushing is prepared. in this method a structure namely SFM (Sediment Flushing Motivator) consisting of two rows of piles installed inside the reservoir on upstream of gates is introduced. one to six pairs of piles with a permeability of 0%, 28.6%, 37.5%, 42.9%, 50% and 60% at two parallel rows at a distance of eight cm from each other were installed. uniform non-cohesive sand material with mean particle sizes of 0.67 mm was utilized as the bed packed sediments. the results show that at the best condition (permeability of 37.5% and row distance of eight cm) the mean flushed sediment volume increases by 161% compared to the reference test (the situation in which no SFM structure is utilized).

Spillway is a hydraulic structure that is used to cross overwaters and floods from upstream to downstream of dams. Side weirs are a variety of hydraulic structures that are designed for various purposes in water transfer systems. The side weirs is constructed with an elevation less than the wall height of the canal, and when the water level rises, spillway will regulate the flow rate and control the water level in the main channel. This research done, in a laboratory review, a canal with a length of 10 meters 0.6m wide, 0.6 height and 16 types of piston cluster type A trapezoidal piano key side weir with different tripods 10, 15 and 20 cm. The above-mentioned overflows are under consideration. The results show that the overflow with a base of 15 cm in both cases has a maximum flow rate coefficient in the ratio of the0.2> H/P> 0.4and has a fluctuation ratio of 0.5

A clear understanding of the interaction of bed-form and flow characteristics in natural streams is essential for a variety of ecological and river engineering projects such as river rehabilitation, pollution control, and stable channel design. The present study deals with the logarithmic layer of double-averaged (in time and space) streamwise velocity profiles in non-uniform flows, decelerating flow, in coarse-bed Rivers. The streamwise velocity profiles were obtained from field measurements conducted in the Haraz and Rostam Abad Rivers. Velocity measurements were collected at 200 Hz and 120 seconds by using ADV. Both riverbeds composed of coarse gravel and cobble, with relative submergences ( ) from 4.4 to 10.4. Due to the limit application of the double-averaging method in Iranian Rivers, the validity of this method was investigated by using the logarithmic law and the boundary layer characteristic method. From the observations, the flow may be divided into two different layers: the inner layer (logarithmic layer) and the outer layer. In the inner layer ( ) the double-averaged velocity profiles confirmed the logarithmic law, however, the velocity data deviated from the logarithmic law in the outer region without a particular pattern. The results of this study can help a better estimation of hydraulic parameters in coarse-bed streams, decreasing the cost of hydraulic plans in rivers.

The impact of submerged vegetation patch on hydraulic processes such as flow resistance and sediment transport is significant. However, a few researches have been reported for this issue in literature. Flow within and just above vegetation behaves similar to mixing layer rather than the boundary layer. This study applies the mixing layer theory to quantify the interaction between flow and submerged vegetation patch, emphasizing the effect of developing flow over small patches in the canonical mixing layer theory. Accordingly, it is essential to combine a canonical mixing layer model and modified equations to quantify evolving area along the patch. Field experiments were conducted over vegetation patch with three different densities in Beheshtabad cobble-bed River located in Chaharmahal-Bakhtiari province. The results reveal that there are reasonable agreement between the measured values of velocity and Reynolds stress profiles and the estimated ones by evolving mixing layer equations. However, the spreading coefficient of this model decreases by increasing the canopy density thanks to the limitation of vertical development of eddies. Quadrant analysis over vegetation patch shows the dominate event under the crest of canopy is “ejection” and over it is “sweep”. Moreover, the contribution of “sweep” event increase slightly at downstream of vegetation patch.

In rivers with a compound section, typically the relatively high roughness of floodplains, as compared with the main channel, grounds the speed difference in these two ( main channel and floodplains). The velocity dissimilarity also creates shear layers at the interface point of the main channel and the floodplain. The development of shear layers will also cause turbulence in the mutual plane of the main channel and the floodplain. In such conditions, the average flow speed cannot be applied to compute parameters such as shear stress, bed-load discharge, and so forth. Laboratory experiments was carried out to investigate the effects of floodplain divergence on flow hydraulic and the rate of sediment transport through roughness and different divergent angles. This research 36 tests were done at a concrete flume with compound channel cross section (9 and 27 tests with prismatic and Non-prismatic cross section respectively). By using a micro-propeller and ADV (with 200 Hz frequency) in different sections the velocity were measured. For depth ratio of 0.15 0.25 was used the micro-propeller and depth ratio 0.35 was used the ADV. The results reveal that the increase in all three factors of roughness, divergence angle, and relative depth cause dramatic changes in hydraulic of flow and sediment transport.

The present paper investigated the simultaneous effect of the density and pattern of bed roughness with obstacle on the control of a dense current head. The tests were run in a flume (length 720 cm, width 35 cm, and height 70 cm) using two roughness patterns (parallel and zigzag), and with four roughness densities (0%, 10%, 30%, and 50%). In all tests, the dense fluid was assumed to be of the salt type with a density of 20 g/lit. Two series of tests were performed using rough surfaces with and without obstacle. In total, 56 tests were conducted. The results showed that in all of the tested sloped, for the zigzag pattern, the highest control for the head of the dense current occurred at a density of 30%; while this density value was 10% for the parallel pattern. Moreover, using an obstacle in addition to roughness increased the control of the density current head. The mean control percentage in the tested slopes was 97% for the zigzag pattern at a density of 30% compared to the mode without roughness and with a zero percent slope; however this mean control percentage increased to 163% by implementing an obstacle. Further, in the parallel pattern with a density of 10%, the mean control percentage for the modes without and with an obstacle were respectively 44% and 74%.

The wave impact is the most important force to the marine structures. Breaking waves makes the most severe forces to the marine structure. Due to the turbulence and strong mixing behavior of the breaking waves, its analysis is difficult and complicated. In this paper, first a solitary wave is numerically modeled. Then the propagating of the solitary wave plunging breaker is simulated on the slope beach. The finite volume method and the two-phase VOF model have been implemented for free-surface modeling. The simulation was performed in an unsteady-state. Furthermore the k-w SST turbulence model was applied. The shape of the free surface of water is quantitatively and qualitatively in good agreement with analytical and experimental results. All of the different stages of wave breaking including the beginning, the tip-wave collision to the bed, the jet of water formation and its further breaking, are relatively in good agreement with the experimental tests. Finally, three-dimensional simulations of a solitary wave impact to a rigid column have been performed. These simulations were separately implemented for two states of breaking and without wave breaking. The results showed good agreement with experimental data.

Sea level rise and groundwater extrapolation lead to freshwater head changes at boundaries of coastal aquifers and causes further intrusion of seawater into aquifers. In the present study, the behavior of unconfined coastal aquifer to instantaneous sea level rise and freshwater head decline is investigated by physical and mathematical dispersive modellings. Three laboratory models have been conducted in a sand tank and salt wedge shape has been photographed over time. Salt wedge toe position, area of transition zone and volume of intruded seawater are measured for this purpose. The numerical results are in good agreement with experimental observations. The outputs derived by both modellings indicate that the instantaneous rise of head in sea boundary or significant decline of freshwater head in landside deforms the wedge shape of saline water, so that the seawater encroachment velocity at its tip will be faster than other regions. Moreover, establishment of an inverse hydraulic gradient (hydraulic gradient from sea to land) causes significant seawater delivery from sea into the aquifer. As a result, the salt wedge can even be stretched up to land boundary. Results of dispersive simulations demonstrate that when the velocity of saline water rises inside the aquifer, the advection role will be highlighted rather than dispersion. However, the longitudinal and transverse dispersivity will also increase and that consequently will widen the transition zone. Nevertheless, the increase rate of saline water volume has been achieved much higher than the growth rate of toe position and transition zone area.

Application of simple and accurate routing models in the flood warning systems increases the capabilities of them. In the present study, it was attempted to fulfil the flood routing using ADZ model and its discrete time form which is named transfer function in the three river reaches, located between six hydrometric stations along the ZARINE and SIMINEH streams. Daily river’s discharges during 15 years (2001-2015) have been employed in the reach routing. Firstly, the numbers of the numerator and denominator terms have been obtained. These parameters are giving the numbers of the subzones in every river reach and also the conditions of the connections (series or parallel). The results of the present study revealed only one sub reach for every river. Therefore, any more analysis of the connection conditions has not been done. After that, the values of the transfer function’s coefficients have been derived using micro CAPTAIN toolbox. The statistical parameters of the mentioned toolbox as ((YIC), (Rt2), and (EVN) for the reaches of the DASHBAND BOUKAN-BOUKAN bridge, ALASAGGAL-SAFAKHANEH, and GESHLAGH bridge- ANIAN bridge have been determined as triple sets of (-5.241, 0.879, -10.86), (-3.954, 0.903, -9.43), and (-2.792, 0.920, -8.139) respectively. The outcomes exhibited a right corresponding between the theoretical graphs, obtained with the transfer function, and observed discharges. The transfer function method is more straightforward rather than the other accurate methods of flood routing like fully saint venant equations. Therefore, it can be used as an efficient method in the flood routing in the river reaches. Application of simple and accurate routing models in the flood warning systems increases the capabilities of them. In the present study, it was attempted to fulfil the flood routing using ADZ model and its discrete time form which is named transfer function in the three river reaches, located between six hydrometric stations along the ZARINE and SIMINEH streams. Daily river’s discharges during 15 years (2001-2015) have been employed in the reach routing. Firstly, the numbers of the numerator and denominator terms have been obtained. These parameters are giving the numbers of the subzones in every river reach and also the conditions of the connections (series or parallel). The results of the present study revealed only one sub reach for every river. Therefore, any more analysis of the connection conditions has not been done. After that, the values of the transfer function’s coefficients have been derived using micro CAPTAIN toolbox. The statistical parameters of the mentioned toolbox as ((YIC), (Rt2), and (EVN) for the reaches of the DASHBAND BOUKAN-BOUKAN bridge, ALASAGGAL-SAFAKHANEH, and GESHLAGH bridge- ANIAN bridge have been determined as triple sets of (-5.241, 0.879, -10.86), (-3.954, 0.903, -9.43), and (-2.792, 0.920, -8.139) respectively. The outcomes exhibited a right corresponding between the theoretical graphs, obtained with the transfer function, and observed discharges. The transfer function method is more straightforward rather than the other accurate methods of flood routing like fully saint venant equations. Therefore, it can be used as an efficient method in the flood routing in the river reaches. Application of simple and accurate routing models in the flood warning systems increases the capabilities of them. In the present study, it was attempted to fulfil the flood routing using ADZ model and its discrete time form which is named transfer function in the three river reaches, located between six hydrometric stations along the ZARINE and SIMINEH streams. Daily river’s discharges during 15 years (2001-2015) have been employed in the reach routing. Firstly, the numbers of the numerator and denominator terms have been obtained. These parameters are giving the numbers of the subzones in every river reach and also the conditions of the connections (series or parallel). The results of the present study revealed only one sub reach for every river. Therefore, any more analysis of the connection conditions has not been done. After that, the values of the transfer function’s coefficients have been derived using micro CAPTAIN toolbox. The statistical parameters of the mentioned toolbox as ((YIC), (Rt2), and (EVN) for the reaches of the DASHBAND BOUKAN-BOUKAN bridge, ALASAGGAL-SAFAKHANEH, and GESHLAGH bridge- ANIAN bridge have been determined as triple sets of (-5.241, 0.879, -10.86), (-3.954, 0.903, -9.43), and (-2.792, 0.920, -8.139) respectively. The outcomes exhibited a right corresponding between the theoretical graphs, obtained with the transfer function, and observed discharges. The transfer function method is more straightforward rather than the other accurate methods of flood routing like fully saint venant equations. Therefore, it can be used as an efficient method in the flood routing in the river reaches. Application of simple and accurate routing models in the flood warning systems increases the capabilities of them. In the present study, it was attempted to fulfil the flood routing using ADZ model and its discrete time form which is named transfer function in the three river reaches, located between six hydrometric stations along the ZARINE and SIMINEH streams. Daily river’s discharges during 15 years (2001-2015) have been employed in the reach routing. Firstly, the numbers of the numerator and denominator terms have been obtained. These parameters are giving the numbers of the subzones in every river reach and also the conditions of the connections (series or parallel). The results of the present study revealed only one sub reach for every river. Therefore, any more analysis of the connection conditions has not been done. After that, the values of the transfer function’s coefficients have been derived using micro CAPTAIN toolbox. The statistical parameters of the mentioned toolbox as ((YIC), (Rt2), and (EVN) for the reaches of the DASHBAND BOUKAN-BOUKAN bridge, ALASAGGAL-SAFAKHANEH, and GESHLAGH bridge- ANIAN bridge have been determined as triple sets of (-5.241, 0.879, -10.86), (-3.954, 0.903, -9.43), and (-2.792, 0.920, -8.139) respectively. The outcomes exhibited a right corresponding between the theoretical graphs, obtained with the transfer function, and observed discharges. The transfer function method is more straightforward rather than the other accurate methods of flood routing like fully saint venant equations. Therefore, it can be used as an efficient method in the flood routing in the river reaches.