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Showing 24 results for Masjedi
Numerical and experimental study of the combination of labyrinth weir with orifice and its effect on discharge coefficient
A. R. Bahrebar, M. Heidarnejad, A. R. Masjedi, A. Bordbar,
Volume 25, Issue 2 (Summer 2021)
Abstract
The combination of a labyrinth weir with an orifice is a proper solution for floating material to pass over the weir and transfer sediment through the orifice. Additionally, creating a slot in the overflow wing leads to higher discharge. This study examined four discharges (5, 10, 15, and 20 liters per second) with channel width and height of 30 and 40 cm in trapezoidal-orifice, square-orifice, and triangular-orifice labyrinth weirs in the laboratory and using Flow3D with RNG k-epsilon (k-ε) turbulence model, the results were compared with one another. Comparing the discharge flow over weirs and measuring the discharge coefficient among the mentioned models showed that the triangular-orifice labyrinth weir had the highest discharge rate. Moreover, the increased Ht/P ratio (Ht represents total hydraulic head; P denotes weir height) for all models resulted in the increased discharge coefficient. Due to the efficiency of this type of weirs, the highest discharge coefficient was obtained at low Ht/P ratios. At lower ratios, since there was free flow, the coefficient of weir discharge increased, and as the ratio increased, the weir was partially submerged. Furthermore, for the weir design, the best Ht/P ratio was between 0.13 to 0.41, and the maximum discharge coefficient (Cd = 1.2) was within this range.

Experimental Study of the Effect of Geometric Dimensions of Rectangular Piano Key Overflow Crest on the Flow Intensity Coefficient
M. Dorfeshan, A.r. Masjedi, M. Heidarnejad, A. Bordbar,
Volume 27, Issue 3 (Fall 2023)
Abstract
Piano key overflows have a high discharge capacity. Proper design of these overflows requires sufficient accuracy in predicting the type of overflows. In this study, experiments were performed in a rectangular laboratory flume made of Plexiglas to investigate the effect of the relative length and width of the two-cycle piano switch overflow crest on the discharge coefficient. In present research, the flow intensity coefficient was investigated by installing a rectangular piano switch overflow with relative crest lengths of 0.8, 1, and 1.2 and relative crest widths of 0.2, 0.3, and 0.4 in 10 flow intensities in the channel. The results of this study showed that by increasing hydraulic load, the flow intensity coefficient first increases and then decreases. Also, by increasing the relative length of the crest by 50%, the current intensity coefficient increases by 43% in the overflow. Increasing the relative width of the overflow crest by 50% increases the current intensity coefficient by 25% in the overflows. Also, an equation was presented to determine the maximum relative scour depth, and the correlation coefficient of the results of this equation with the laboratory results is about 0.90.

Investigating the Effect of Slot Dimensions in Bridge Abutments on the Scour Hole’s Depth
M. Sehat, A. Bordbar, A.r. Masjedi, M. Heidarnejad,
Volume 27, Issue 4 (Winter 2023)
Abstract
Today, abutments disrupt the normal flow of rivers and cause scouring and erosion of sedimentary materials around them, creating holes and resulting in much damage every year. Researchers have proposed various methods to reduce the power of water erosion. One of the essential methods in this regard is creating slots in abutments. Since the expansion of the scour hole endangers the stability of the bridge structure, this study examined the effect of slot dimensions in the support on the scour hole dimensions. The findings demonstrated that the presence of slots in abutments effectively reduces the dimensions of scour holes. With the slot, the volume of the scour hole can be reduced by up to 50%. Furthermore, as the relative speed of scouring increases by 75%, the depth of the scour hole also increased up to 140%. An increase in slot depth leads to a decrease in scour hole depth of up to 85%.

Laboratory Investigation of the Effect of Sill Length in Flip Bucket Spillway on Scour at the Bottom of Downstream
S. Abdollahi, A. Masjedi, M. Haidarnejad, A. Afros, M. Asadilor,
Volume 28, Issue 1 (Spring 2024)
Abstract
The use of structures has economic and safety advantages compared to other energy-consuming structures. In this research, to investigate the effect of the length of the sill of the flip bucket spillway on the scour downstream, experiments were conducted in a rectangular laboratory flume made of Plexiglas. The scouring downstream of the flip bucket spillway was investigated using a flip bucket spillway with four relative sill lengths and four threshold angles at four current intensities in the channel in this research. The results of this research showed that by the increase in the length of the sill in the flip bucket spillway, the energy consumption in the spillway increased and the scour depth downstream decreased. Also, increasing the relative length of the sill by 70% at the sill angle of 45 degrees, the scouring depth is reduced by about 88%. Also, a relationship was presented to determine the maximum depth of relative scour, and the correlation coefficient of the results obtained from this equation with the laboratory results is about 0.92.

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