مقالات رزومه دکتر زهرا قربانی

Due to the measurement problems related to direct methods for estimating discharge, indirect methods based on the concept of surface velocity have been recently developed. In the present research according to the limited number of studies and the lack of appropriate relations between river geometric and hydraulic parameters with velocity index, the effect of dimensionless parameters including dimensionless Manning roughness coefficient, relative depth, Froud number and bed slope on the velocity index has been experimentally investigated. The results showed that by increasing the parameters of relative depth, dimensionless Manning roughness coefficient and Froude number the velocity index decreases. Meanwhile the influence of the bed slope is not clear. The mean value of the velocity index in rectangular channels was 0.92 and the its average error was estimated to be about 4.9%. Also, the analysis of the analytical models of the vertical velocity distribution showed that in the case of a smooth bed, the power law model with 4.5% average error and in the case of the bed with metal mesh, the logarithmic law with 10% average error have the best estimate of the velocity index.

Determining the discharge in rivers using the cross-sectional area-velocity method, especially under flood conditions, is associated with serious challenges. Due to advances in measurement techniques, many researchers have strongly suggested the use of non-contact methods. The non-contact method that use surface velocity radar to determine the discharge are becoming more and more popular especially in flood conditions. This method is to use the concept of index velocity based on the generalization of surface velocity to mean velocity and discharge. Also index-velocity method was used for discharge monitoring or recording at streamflow- gaging stations with flow reversals, backwater effects, hysteresis effects and channel-roughness changes that the use of conventional "stage-discharge rating" method impractical or impossible. During floods, natural rivers appear in the form of a compound cross-section in their middle and end sections. Due to momentum exchange between main channel and flood plains, the flow hydraulic in compound channels is complicate. Most studies in index-velocity method are focused on prediction of the discharge in simple channels. Due to the hydraulic difference between the flow of simple and compound cross-sections, the velocity index (ratio of surface velocity to average velocity) for compound channels is still unknown.

The purpose of this study is how to apply the index velocity method in flood conditions (compound sections) and actually determine the optimal velocity index in compound sections and the highest percentage of its location in the width of the compound section. Also, by performing dimensional analysis, the influence of relative roughness parameters, Froude number, relative depth and relative width on the velocity index in compound channels was investigated. In order to build a laboratory compound channel, a channel with a rectangular cross-section with a width and height of 60 cm with a metal frame and glass walls was used. The height of the flood plain in all tests is constant and equal to 7 cm and three different widths of the flood plain 40, 45 and 50 cm in the smooth state and also one state of the flood plain with a width of 40 cm with metal mesh in compound form was made. Velocity distribution measurements were made in the compound channel, in the main channel and floodplain at 7 or 8 transverse points. In the present study, the velocity index in compound channels at a fixed bed slope of 0.1% and for the relative depth of the main section is 4.2-6.12 relative roughness 0.0003-0.0031 and Froude number 0.14-0.79 has been studied.

By examining the velocity index values across the compound cross-section it was found that the range of average of the velocity index in the width of the compound channels is 0.76-0.98 and with 63% relative frequency is in the range of 0.87-0.93. By fitting between all surface velocity and average velocity data in the entire compound cross-section, it was determined that the optimal value of the velocity index (with R2=0.95) for compound channels is 0.88 with value of absolute relative error of about 0.01-10.06% and an average relative error of 3.3%. The results showed that the increase in the relative roughness and Froude number of the approaching flow and the decrease in the relative depth in the floodplain cause a decrease in the velocity index. The relative error values of discharge estimation showed that in flood conditions (overbank), the velocity index value is different from the normal conditions (inbank) of the river and considering the same velocity index value for both normal and flood conditions will cause more error in the discharge estimation. By examining the location of the optimal value of the velocity index of 0.88 in the entire width of the compound section, it was determined that 71% of the density of points is located on the border of the compound channel and in the last quarter of the flood plain and the first half of the main section. Also, the velocity index is 0.92 in the main channel and 0.86 in flood plain, and if use them, a better estimate of the discharge in the compound channel is obtained. Analytical models of velocity distribution also showed that the velocity power law provides the best estimation of the velocity index than other models if the power index is chosen correctly.

The results showed that the use of the velocity index value of 0.88 for compound channels has an average relative error of about 3.3% in flow estimation. Therefore, by adjusting the default value, it is possible to improve the accuracy of flow estimation in flood conditions. In situations where the possibility of direct measurement in open channels (flood conditions) is not available, it is possible to use the cross section, the surface velocity at the border of flood plain and the main channel and the optimal velocity index of 0.88 can be accurately estimated.

Today, the construction of dams is one of the most important solutions for the storage of surface water. Due to fresh water limitations, the construction of reservoir dams to control the surface water resources in Iran is inevitable and necessary. In dam reservoirs, the turbidity current is usually the cause of sediment transfer and deposition. If the current is completely stopped in the middle areas of the reservoir, the amount of sedimentation will be reduced at the bottom of the dam wall and, as a result, the main functions of the dam will not be disturbed. Therefore, it is necessary to study this phenomenon. One of the methods for hydraulically changing the turbidity current is to roughen it or to use a barrier in the bed. Several studies have been carried out on the velocity of the turbidity current so far, and controlling it by roughening and barriers. However, it seems that no studies have been made on the effects of the angle and location of impermeable submerged plates on the turbidity currents.

Here, 42 experiments were made on the effects of the impermeable submerged plates on the head velocity and the height of the turbidity current head. For this purpose an experimental, flume with 30cm width, 10m length and 46cm height was used. The turbidity current entered the flume with concentrations of 20 and 40 g/l and bed slopes of 1 and 2%. In order to investigate the effects of the angle of the impermeable submerged plates, impermeable plates which came into seven different angle of mounting of the plates with respect to the current axis (0, 15, 30, 45, 60, 75, 90 degrees) and also, impermeable plates with eight locations were located across the current. Measurements of velocity and height of the head turbidity current were made on 6 sections with 50cm distances. Then, based on the data obtained, and by dimensional analysis of Edgar Buckingham’s method (Buckingham π methodology), the non-dimensional graphs of velocity, height and Densimetric Froude Number of the head of turbidity current were plotted.

According to the performed experiments, the results of this study are presented in two sections. In the first section, the results are related to the effect of the plate angles; in the second, the results are related to the effect of the plate positioning. Generally, due to the collision of the turbidity current with the plates, the non-dimensional velocity was reduced along the mounting route. Also, the Densimetric Froude Number was decreasing along the current route. The results showed that with increasing the angle of the plates, the decreasing gradient of the dimensionless velocity increases along the dimensionless route. Therefore, the plates with angles of 75° and 90° which are in the vertical and near-vertical position relative to the current axis, are affecting the current flow velocity more than plates at other angles. In general, the flow velocity of the turbidity current decreased by 8.6 to 27.1% with respect to the control state in case of different angle of mounting of the plates with respect to the current axis. With a concentration of 20 g/l and the slope of 1%, the plates with the mounting angles of 75 and 90° relative to the horizontal axis of the turbidity current flow provide the most significant decrease in the velocity compared to the control, with 26.4% and 27.1%. The analysis of the position of the plates showed when the plates are mounted across the total width of the canal, they provide the most significant reduction in the velocity compared to the control. In general, in different conditions, the flow velocity of turbidity current increases to 6.3% in the worst location and decreases 45.1 percent in the best location relative to the control state (in bed without submerged impermeable plates). With a concentration of 20 g/l, the plates at the position of 2, with 45.1% and the slope of 1%, and 29.5% at the slope of 2%, made the biggest decrease in the current head velocity compared to the control. Also, with the concentration of 20g/l at the slopes of 1 and 2%, the position 5 made the biggest decrease in the velocity with 33.9 and 38.3%. Slope investigations showed that with the concentration of 20 and 40 g/l, the slope increase will reduce the effect of the plates on the velocity.

Nowadays, dams are one of the most important structures to store surface water. Turbidity currents are usually the reason of sediment transport and deposition in deep reservoirs. As the turbidity current is completely stopped in the middle regions of the reservoir, sediment deposition reduces near the dam wall and as a result the main tasks of the dam are not disrupted. So, it is important to study the phenomenon. Roughening up or using obstacle the bed is a technique for changing the turbidity current hydraulics or reducing of its velocity. Some researches have been studied at this field, however, it is necessary to evaluate the effect of submerged impermeable plates on turbidity currents.
In the present research, the head velocity and height of the turbidity current head were studied on the bed with submerged impermeable plates. For this purpose an experimental, flume with 30cm width, 10m length and 46cm height was used. The turbidity current was entered into the flume with concentration of 20 g.l-1 with 1 and 2 percent bed slopes and concentration of 40 g.l-1 with 1 and 2 percent bed slopes. Impermeable plates which came into two different areas (16 and 36 cm2) in five shapes (Square, rectangular, triangle, rhombus and trapezius) were located across the current. Also, square impermeable plates were placed as five arrays (parallel, plaid, converge, diverge and Z-shape) with an area of 16 cm2.
Flow velocity was measured in 6 sections with distance 50cm and the height of head in 21 sections with distance 15cm. Then, non-dimensional graphs of velocity, height, Froude number and Richardson number of turbidity current head were drawn by using the data which obtained by Buckingham dimensional analysis method. Dimensionless velocity during the installation significantly decreased due to collision turbidity current to with plates. Also, the height of turbidity current head in the along of flow path indicated that plates gradually reduced the height of head at the beginning of the route. Height of turbidity current head was increased and the current path Froude number was decreased at the end of the path.
Results showed that the development velocity of the turbidity current reduced between 25-48 percent proportion to smooth bed in the condition of plate’s installation with different shapes and also the height of head reduced between 5.1-18.4 percent. Also, development velocity was reduced between 11.2-45.1 percent and the height of head was reduced between 0.4-18.4 percent in different arrays. Converge array in the concentration of 20 g.l-1 and Parallel array in the concentration of 40 g.l-1 were determined as the best array. By changing the area of plates from 16 to 36 cm2 between different shapes, the shape of rhombus with 22.2 percent, showed the greatest effect in reducing velocity.

The role of groundwater has always been an important issue in order to provide drinking water especially in desert areas. However, studies and decision-making on water supply from the water source is more costly and difficult rather than surface water. Therefore, it is important to note the newest methods like zoning. Due to the effects of water chemical parameters on the quality, application of AHP, ANP, FAHP, and FANP methods lead to more accurate results. The aim of this research was to zone groundwater quality using ANP and FANP models and comparison of the results obtained by those achieved, by AHP and FAHP models.
For this purpose, the study was conducted to zone groundwater quality in Tabas aquifer located at the east of Iran with latitude between 33˚ 19’-33˚ 50’ and longitude between 60˚ 42’-63˚ 12’. In this study, the parameters studied were Mg, Ca, SO4, Cl, total dissolved solids (TDS), electrical conductivity (EC), and total hardness (TH). Raster maps for each parameter were prepared and these maps were converted to fuzzy maps. Then, the maps were integrated together using the weights from AHP and ANP methods.
The research indicated that the most weighted parameters using ANP method were Cl (0.172), Mg (0.161) and EC (0.159). Cl (0.457), TDS (0.163) and EC (0.141) were the most weighted parameters using AHP methods. In addition, the concentration of each parameter was increased from the east and southeast to the northeast.
Based on the results and groundwater flow path, water quality was reduced due to water flow in aquifer (from the east and southeast to northeast). Hence, the east and the southeast were the best location to provide drinking water. The area of these regions were 22.12, 25.08, 57.35 and 58.24% out of total area as determined using AHP, ANP, FAHP, and FANP, respectively.