فهرست مطالب mohammad mahmoodian shooshtari

Dust is created by wind erosion. In nature, based on the size of the particles, the movement of soil particles due to wind is carried out in three ways. Rolling, jumping and suspension. In the wind ranges that usually occur in nature, proportional to the diameter of the soil particles, these three modes of particle motion are somewhat separable. Particles smaller than 0.1 mm in diameter are usually suspended, soil particles with a diameter of 0.05 to 0.5 mm usually bounce, and soil particles with a diameter of 0.5 to 2 mm move in a crawling (rolling) manner. In the wind tunnel tests, which were conducted on the soil samples collected from the dust centers in the southeast of Ahvaz. It showed that at the reference point, when the wind blows, a lot of dust is formed in front of the soil mass.The obtained results show that the maximum amount of dust is formed in the first 150 seconds. The maximum amount of dust produced occurs in the first 85 seconds, which is about 7 times more than the dust after the first 150 seconds.

Side weirs are used to control water levels as well as water diversion for various uses in canals and rivers. Due to the complexity of flow conditions inside weirs, in this study, in order to simplify the calculations and increase its efficiency, this structure was investigated in convergent channel conditions. To investigate this issue, different geometric parameters of weir and hydraulic currents were investigated. Based on the geometric parameters of the side weir, experimental scenarios were considered. Based on the scenarios, 5 side weir lengths, 4 side weir heights, and 3 downstream channel widths were considered as side weirs that were tested at different discharges. Due to the fact that different geometric and hydraulic parameters were assumed to be variable in these experiments, the effect of each on the structure was analyzed and solutions for selecting the optimal dimensions in the channel were introduced. Based on the experimental results, it was found that for a fixed upstream water height with a 19% reduction in the width of the downstream channel, the ratio of the flow deflection to the lateral channel increases by 30%. It should be noted that the change in the flow section by converging the passage channel causes the longitudinal profile of the water surface to have a minimum height fluctuation along the entire length of the structure.

Although the spur dikes have appropriate performance to protect rivers bank, these structures are not immune from the local scour around their tips. Recent researches have shown that the bank attached triangular vanes has less scour depth at their tips toward the spur dikes because of their geometrical shape. One of the methods of flow pattern improvement around the structures is creating slot in structure to reduce maximum scour depth around the structures tips. In order to achieve the purposes of present study a rectangular slot (with opening percent equal to 10 percent of the effective surface vane and the location of the slot is parallel to the chord) has been created in the bank attached triangular vane. Then the effect of slot on bed topography was analyzed at different angles and hydraulic conditions (0.287, 0.304 and 0.322). Results showed that the average reduction of maximum scour depth by means of slot at the angles of 23, 30, 40 and 60 degrees have been 70, 20, 17 and 54 percent, respectively. Also the created slot in the vane caused the maximum scour depth to form away from the outer bank. By increasing the Froude number, the maximum scour depth has increased at sample-slotted vanes.

Beach-bound plates are used to control the erosion of the walls of rivers and beaches. The nose of the plates has always been subject to scour due to the flow contact with the structure. Different factors are effective in reducing the scour. Recent research has shown that coastal and beach-bound triangular slotted panels have played an important role in reducing the scour around the nose. In this study, in order to investigate the effect of the angle, the triangular slab (slit area = 10% of the effective surface area of ​​the plate) was used at different angles of (23, 30, 40 and 60 degrees) in arched flume. Experiments were conducted under different hydraulic conditions (landing numbers 287/0, 304/0 and 322/0). The results showed that the maximum scour depth at the 23 and 40-degree angles was the lowest and the highest, respectively. The maximum stacking height is proportional to the maximum scour depth. By increasing of the angle of the plates up to 40 degrees, the maximum scour depth is farther away from the outer curve and drops sharply at an angle of 60 degrees.
One of the issues in river engineering is erosion in the walls of rivers and coasts, due to the direct connection of the flow with the wall. The pattern of velocity distribution in the arc indicates the concentration of areas with maximum velocity in the lower arch and in the vicinity of the outer wall. Spoons are considered as protective structures that are used to reduce the erosion and improve the stabilization of the riverside wall. But, on the other hand, the location of the spillway in the flow path and the direct impact of the flow on the structure leads to local scouring around the nose of the spillway and, as a result, will eventually destroy the structure. It is noteworthy that the coastal triangular board of the modified state of the protective structures (in terms of appearance, degree of submergence, There is a gap in the page) for A. Judd minimum depth of scour around the nose page. . In a study by Boyan et al. (2010), in a single-seater survey of coastal triangles, the effective method for restoring river banks is to install these panels at low angles (20 and 30 degrees) and in the coastline. Therefore, due to the limited research done on the beach-bound plates, in a leading research with the installation of single-skeletal triangles attached to the coast at different angles, the angles of their placement on the topography of the bed in the 90-degree arc have been studied.

Triangular vanes attached to the bank are a new method to control erosion and help protection the bank in meandering rivers. This structure is subjected to scouring due to flow convergence at the tips of the structures. Therefore, countermeasure methods should be employed in order to prevent financial damages and life hazards. One of these methods is to use a slot. In this study, the series of triangular vanes that a parallel chord rectangular slot, with the opening of the full vane area of 10% and a ratio of a/b=4 (a and b are the length and width of the slot) the bed in which they are established position near has been used. The vanes angle is 30 degrees upstream of the bank. Experiments under different installation distances, 4, 6 and 8 times the effective vane length, hydraulic conditions are different (Froude number 0.287, 0.304, 0.322), and the clear water. In all experiments depth of flow is constant and equal to 14 cm. Then the results were compared with no slot. The results showed that the slot reduces the average depths of scour around the tips of vanes. In average, the reduce percent of the average scour depths around the tips of the structure in distances 4Le, 6Le and 8Le is equal to 9 percent, 17 percent and 18 percent respectively. The triangular vanes caused flow diversion from outer bank towards the center bend and thus the formation of thalweg. The slot reduces the maximum depth of scour thalweg. In average, the reduce percent of the maximum depth of scour thalweg in distances 4Le, 6Le and 8Le is equal to 22.6 percent, 46 percent and 30 percent respectively. The first of effective length of vanes was 1/5 flume wide. In start tests and erosion around the vanes increased the first of effective length of vanes. The slot reduces the effective length variation of vanes. In average, the reduce percent of average the effective length variation of vanes in distances 4Le, 6Le and 8Le is equal to 15.5 percent, 13.7 percent and 15.7 percent respectively.

In this research the effects of installed blades on the combined model of ogee spillway with lower bypass on energy loss of structure and downstream hydraulic jump characteristics has been experimentally investigated. In order to achieve the goal of this study, a physical model of ogee spillway with lower bypass was built, in which the output jet from the lower bypass (bottom outlet) was set to be at the angle of 30 degrees to the overflow of spillway. Installation of blades at the upstream of the lower bypass slit makes flow separation and more turbulence on spillway and as a result more energy dissipation on structure. In this research, two blades relative thickness including tb/ y1d= 0.07 and 0.14 were used and the results showed that the blades with the higher relative thickness (i.e. tb/ y1d=0.14) was found to be more effective in energy dissipation on structure and less values for the downstream hydraulic jump parameters. The measured values showed that the average energy loss on spillway, and the reduction length and secondary relative depth of hydraulic jump were 47.6%, 40% and 23.2%, respectively. According to the results obtained in this research study, the use of this structure is recommended for economical stilling basin construction at the downstream of small dams and spillways.