@article {
author = {Fazeli, Meysam and Asgari, Moeen},
title = {Three-dimensional numerical simulation of landslide-induced waves in dams reservoirs (Case study: Siyah bishe dam)},
journal = {Journal of Hydraulics},
volume = {15},
number = {4},
pages = {1-15},
year = {2020},
publisher = {Iranian Hydraulic Association},
issn = {2345-4237},
eissn = {2645-8063},
doi = {10.30482/jhyd.2020.209432.1422},
abstract = {Introduction Large landslides can cause overtopping and consequently demolish the dams and other substructures and facilities. The landslide stabilization is very costly due to their large size and considerable extent. Hence proper estimation of the wave height because of sliding into the reservoirs in order to determine the risk of overtop is inevitable. In this study, 3D simulation of the SM5 sliding landslide into the upper reservoir of the Siyah Bisheh is conducted to calculate the height of the waves generated by this phenomenon. Methodology For landslide modeling, the assumption of rigid mass is assumed and mass motion is considered as a combination of transitional and rotational motion. First, Heinrich's (1992) laboratory model was used to evaluate the performance of the Flow-3D numerical model (calibration and validation). For this purpose, the sliding mass was introduced into the reservoir by prescribed motion and the changes in water level at different points were compared with the experimental results. The results showed that there is an appropriate matching between the experimental and numerical results. The purpose of this comparison was to evaluate the accuracy of the software used to estimate water level. Although in some cases, the trend of changes in water level is significantly different from laboratory results, the maximum level obtained in numerical model is in relevant agreement with laboratory results. In the numerical simulation of the mass movement in the Siyah-Bisheh Dam, the mass range and the shape of the slide circle are first determined. The mass has a volume about 425,000 cubic meters and is about 100 meters long. The slide radius is estimated to be 200 meters. About 250,000 cubic meters of this mass lies beneath the reservoir water level, which 150,000 cubic meters moves during landslide. In this case, the center of mass moved 20 meters downwards and can generate a velocity between 1 to 10 meters per second. For the modeling of motion, different scenarios are considered based on the mass movement velocity. Due to the low width of the river at the mass location (about 60 m), the mass movement is limited at this distance so all masses cannot enter to reservoir. Topography of reservoirs with 1/ 2000 scale were used to model reservoir and SM5 mass. Because of the narrow width of the valley, the mass hits the opposite wall and stops. As mentioned before, mass movement is considered a set of rotations and translations. The main reason of using this type of movement is the lack of ability to consider mass deformation. In terms of mesh size, meshes of 5 and 10 m in plan and 1 and 2 m in height are used. The results of convergence test show that there is no significant difference between the meshes of 5 m in the plan and 2 m in the depth and finer one. Different scenarios with various velocity of mass (velocity of 1, 3, 6 and 10 m / s) are considered for the simulation process. The mass is assumed to have reached maximum speed in a short time and stopped shortly at the end of the opposite wall. Results are presented for the 5 specified points in the reservoir with an appropriate distribution on its surface. Results and discussion The results are presented for 90 seconds after the mass enters the reservoir and it has been attempted to take into account the impact of the distance and time when the peak occurred. The wave height near the mass reaches to 10 meters where the mass has 10 meters per second and reaches to around 3 meters as it departs from the entry point. The maximum wave height near the dam site has been obtained around 2.5 m. According to the laboratory results, the wave caused by the landslide moves in the direction of mass entry into the reservoir. The mass direction is perpendicular to the river and parallel to the dam axis and it is expected that the generated wave will hit the opposite wall. The generated wave due to landslide collides to the opposite bank and dispersed. As a result, the height of the generated wave is reduced and therefore the possibility of overtopping falls dramatically. Based on the results, it can be said that the wave height will not exceed 2.5 m near the dam body. However, the maximum wave height produced in the reservoir exceeds 10 m at high velocities. At the end, the surface wave height due to landslide has been calculated using the issue number 53 of Iranian Commission on Large Dams (IRCOLD). In this calculation, the slide mass is estimated to be 150,000 cubic meters and the mass velocity is 13 m/s. Conclusion According to the empirical tables and relationships, the wave height is obtained at 400 and 800 m far from the dam body at 2.5 and 1 m respectively. This value is compatible with the results obtained from the numerical model. Keywords: Landslide, 3D numerical modeling, wave height, overtopping, Siyah Bishe},
keywords = {Landslide,3D numerical modeling,wave height,Overtopping,Siyah Bishe},
title_fa = {شبیه سازی عددی سه بعدی تولید امواج ناشی از زمین لغزش در مخازن سدها ( مطالعه موردی سد سیاه بیشه)},
abstract_fa = {زمین لغزشهای بزرگ میتواند باعث ایجاد روگذری و به تبع آن تخریب سدها و تاسیسات وابسته به آن شوند. هزینه پایدارسازی این تودهها به علت بزرگی و گستردگی آن بسیار بالا بوده بطوریکه تخمین مناسبی از ارتفاع امواج ناشی از لغزش این تودهها به منظور تعیین ریسک روگذری امری اجتناب ناپذیر است. در این تحقیق با استفاده از مدلسازی سه بعدی توده لغزنده به داخل مخزن سد بالای سیاه بیشه با استفاده از نرم افزار Flow-3D، ارتفاع امواج ایجاد شده ناشی از این پدیده بدست می آید. برای مدلسازی توده لغزشی فرض صلب بودن توده لحاظ شده و حرکت توده بصورت ترکیبی از حرکت انتقالی و دورانی در نظر گرفته شده است. با توجه به عرض کم رودخانه در محل توده (حدود 60 متر)، حرکت توده در این فاصله محدود بوده بطوریکه تمام توده وارد آب نخواهد شد. در مقابل موج بوجود آمده ناشی از لغزش به علت برخورد با دیواره مقابل مستهلک می شود. بر اساس نتایج به دست آمده میتوان گفت ارتفاع موج ایجاد شده، در نزدیکی بدنه سد از 5/2 متر تجاوز نخواهد کرد. این در حالی است که بیشترین ارتفاع موج تولیدشده در مخزن در سرعتهای بالای توده از 10 متر تجاوز می کند. با استفاده از نشریه 53 کمیته ملی سدهای بزرگ ایران ارتفاع موج سطحی ناشی از لغزش توده محاسبه شده است. با توجه به جداول و روابط تجربی، ارتفاع موج در فاصله400 و 800 متری از بدنه سد حدود 2.5 و 1 متر بدست آمده است.},
keywords_fa = {زمین لغزش,مدلسازی عددی سه بعدی,ارتفاع موج سطحی,روگذری,سد بالای سیاه بیشه},
url = {http://jhyd.iha.ir/article_114670.html},
eprint = {http://jhyd.iha.ir/article_114670_234b74b0cada866ba7375276a3a537d3.pdf}
}
@article {
author = {Farhani, Foad},
title = {Numerical Modeling of Effects of Geometrical Parameters on Amount of Torque Produced by a Floating Water Turbine in a Rectangular Open Channel},
journal = {Journal of Hydraulics},
volume = {15},
number = {4},
pages = {17-30},
year = {2020},
publisher = {Iranian Hydraulic Association},
issn = {2345-4237},
eissn = {2645-8063},
doi = {10.30482/jhyd.2020.238803.1469},
abstract = {Introduction In this research work, the maximized transmitted torque due to the impulse from flowing water in an open channel has been studied for five types of cylindrical turbines to find the best water turbine in terms of maximum produced electrical energy. For this purpose, using numerical finite volume method, a set of turbine and blades, consisting of a 3-dimensional cylindrical water turbine of equal diameter and length (1m), with five different blade configurations, has been simulated in a 10 m long and 3 m wide rectangular open channel with no inclination, subjected to a water flow of 2 m/s velocity. Considering the weight of various elements, the set of turbine and blades has been designed so that it remains floating in the channel at various immersion depths. Furthermore, with change in flow depth, the immersion depth remains constant. Considering the magnitude of the flowing water impulse in the channel, the corresponding torque transmitted from the water to the blades of the five types of turbines was determined and the maximum torque value was obtained. Methodology In the present research, five types of blades, attached to a hollow cylindrical turbine of 1 m length and 1 m diameter, have been used. The turbine floats on water at a particular depth in an open channel. The water speed in the open channel determines the torque due to the impulse from the flowing water. Considering the various blades, the resultant torque has been studied numerically using two-phase flow finite volume method. The material for the construction of the cylindrical turbine and the blades is dense polyethylene having a density of with 950 kg/m3. Moreover, the fluids considered in the finite volume numerical computations are water with a density of 998 kg/m3, and air with a density of 1 kg/m3 at a constant temperature of 20° Celsius. The hollow turbine cylinder has a volume of 0.78 m3 and is filled with air. The three-dimensional flow channel, in which the turbine is placed, is a rectangular concrete channel of 10 m length and 3 m width, through which water flow at a depth of 35 cm. To avoid the effect of surrounding walls on the transfer of the flow impulse to the turbine, width of the channel has been considered slightly oversized. The roughness values for the bottom surface of the concrete channel and the turbine walls and the blade set is 1 mm and 0.01 mm, respectively. The depth of the channel is constant at 1 m, which is equivalent to the average depth of most city open channels. Results and Discussion The difference between type 1 and type 2 turbines is in the blade’s angle along the turbine rotational axis. As a result, the produced torque by type 1 turbine is more than that of type 2. On one hand, increase in contact area between the blades and the flowing water in the channel results in higher torques. On the other hand, the angular shape of the increases the slip between the flow and the blades, which reduces the conversion of kinetic energy into static energy. Ultimately, the result of the above two phenomena in type 2 turbine is a reduction in the produced torque to about 15 N/m. In type 3 turbine, an increase in the produced torque was achieved through the increase in the number and shape of the turbine blades. Hence, the implementation of the aforementioned changes relative to type 2 turbine resulted in an increase in the produced torque to about 56 N/m. Therefore, increase in the number of blades and change in the blade shape in this type of turbine compensated for the effects of blade angle elongation in type 2 turbine. Furthermore, in type 4 turbine, the internal diameter of the blades was reduced, while the number of blades was increased, blades distribution angle was changed from 45° to a straight configuration, and the contact area also decreased. Consequently, the amount of flow slip along the blades also decreased. Specifically, the result of all the above mentioned changes in type 4 turbine was to reduce the produced torque to about 14 N/m compared to type 3 turbine. Therefore, the combined effect of reduction in the contact area and reduced internal diameter of the turbine blades is more dominant than the combined effect of increased number of blades and reduced flow slip on the blades. In type 5 turbine, number of blades was reduced by 10 and the blades internal diameter was tripled relative to type 4 turbine, which resulted in a significant increase in the produced torque. Therefore, type 5 turbine, as a floating turbine, may be recommended for production of electric energy in open channels. Conclusion Considering the results of the calculations, type 5 turbine with 21 semicircular shape blades, 11 cm in external diameter and 10.5 cm internal diameter, has a higher capacity to produce more torque compared to other types of turbine studied. The factors affecting the final produced torque include the contact area between the blades and the flowing water in the channel, the length of the blades along the turbine axis, the extent of slip of flow when facing the turbine blades, and the number of blades. The produced torque by type 5 turbine is 458.96 N/m, which is the highest among the turbine types studied in this research.},
keywords = {Hydraulic Turbine,Computational Fluid Dynamics,Open channel flow},
title_fa = {مدلسازی عددی تاثیر پارامترهای هندسی توربین آبی شناور بر میزان گشتاور تولیدی در کانال روباز مستطیلی},
abstract_fa = {در این تحقیق، میزان گشتاور انتقالیافته بهینه، از تکانه جریان آب جاری در یک کانال روباز، به پنج نوع توربین استوانهای، مورد بررسی قرار گرفتهاست. هدف از انجام پژوهش، یافتن توربین آبی مناسب، جهت تولید انرژی الکتریکی بیشینه میباشد. برای انجام این کار، یک توربین استوانهای سهبعدی، بهقطر و طول 1 متر، با پنج نوع پره، به شکلهای مختلف، با کمک روش عددی حجم محدود، شبیهسازی گردید. مجموعه توربین و پرهها، در یک کانال مستطیلی روباز بدون شیب، به طول 10 متر و عرض 3 متر، و سرعت جریان 2 متر بر ثانیه، قرار گرفتهاند. مجموعه توربین و پرهها، به طریقی طراحی شدهاند که با توجه به وزنشان، بهصورت شناور در عمقهای استغراق مختلف، داخل کانال قرارگیرند، و با تغییر عمق جریان، عمق استغراق مورد نظر ثابت بماند. با توجه به مقدار تکانه جریان آب جاری در کانال، میزان گشتاور انتقالیافته از جریان به پرههای پنج نوع توربین مورد نظر، محاسبهشده و مقدار بیشینه آن بدست آمد. نتایج نشان میدهد که، بکارگیری توربین نوع پنج، با پرههایی گسترشیافته به شکل نیمدایره در امتداد محور توربین، به تعداد 21 عدد، و قطر داخلی 10.5 سانتیمتر، بیشترین مقدار گشتاور، برابر 458.96 نیوتن در متر را، حاصل میآورد. لذا میتوان بهکمک آن، ضمن استفاده از یک مولد الکتریکی مناسب، انرژی الکتریکی بیشینه را تولید نمود.},
keywords_fa = {توربین آبی شناور,دینامیک سیالات محاسباتی,جریان کانال روباز},
url = {http://jhyd.iha.ir/article_114719.html},
eprint = {http://jhyd.iha.ir/article_114719_5b8461917721b47e13f7fdfdb7f095d9.pdf}
}
@article {
author = {mohseni, marzieh and Tavakoli nezhad allah abadi, Fatemeh},
title = {Experimental Study of Vertical velocity profiles in compound channels with vegetation on floodplains},
journal = {Journal of Hydraulics},
volume = {15},
number = {4},
pages = {31-45},
year = {2020},
publisher = {Iranian Hydraulic Association},
issn = {2345-4237},
eissn = {2645-8063},
doi = {10.30482/jhyd.2020.245051.1474},
abstract = {Introduction: Vegetation has traditionally been viewed as a nuisance and obstruction to channel flow by increasing flow resistance and water depth. However, in recent years, vegetation has become a major component of erosion control and stream restoration. Most of research efforts focus on describing vegetation roughness , determining drag coefficients and empirical formulas for resistance under various vegetation configurations. While the development of experimental solutions for vegetative resistance is important, it is also important to understand the detailed characteristics of flow through vegetation. Yang et al.(2007) conducted flume experiments with different types of vegetation, and found that, in the cases of non vegetated floodplains, all measured streamwise velocity distributions followed the logarithmic distribution, but for vegetated floodplains, they followed an S-shaped profile Nezu and Sanju(2008) have investigated turbulence structures and coherent motion in vegetated canopy open-channel flows. They divided the whole flow region into three sub-zones, i.e., the emergent zone, the mixing-layer zone and the log-law zone. In the present study, some experiments were undertaken herein under different conditions to elucidate the flow structure. The main focus is to examine how the vertical velocities, are affected by simulated vegetation arranged in emergent and submerged conditions. In addition, the effect of dowel density, configuration, and relative depth are examined. Methodology: The experiments were conducted in a fixed bed rectangular flume, 9 m long and 0.6 m high and 0.8 m wide. The slope of bed flume was 12 ×10-5. The main channel and floodplain had widths of 24 and 28 cm, respectively, and the main channel had a side slope, s, of 0. The bankfull height, h, was 6 cm. Vegetation were simulated by wooden dowels. The wooden dowels were 140 mm tall and 7 mm in diameter. The dowels were attached to a PVC sheet bolted to the bottom of the flood plain in linear and staggered arrangement. The spacing of the dowels varies from 2.5-10 cm in both lateral and streamwise directions forming stem density of 0.41, 1.64%, 6.04%. The flume was operated under a uniform flow condition, and measurements of discharge, point velocity and flow depth were taken. Flow depths were measured by means of a pointer gauge, discharges were measured by a digital flowmeter, installed upstream of the channel, and a micro propeller current meter were used to velocity measurements. Within the measurement cross section, located at 5.6 m, the authors arranged ten verticals, where the lateral values of y from the first vertical to the last were 0, 4, 8, 12, 12.2, 26 and 34 cm. When the vertical distance from the measurement point to the bed was less than 175 mm, the measurement interval was 10 mm and 5mm in the main channel and floodplain, respectively. Results and discussion: The experimental results are presented in three parts, flow through non-vegetated floodplain first, flow through emergent vegetation second, followed by the submerged case. The effects of density and dowel configuration are included in each of the sections. Each section ends with a discussion on the effects of rigid dowels on logarithmic profile. In the cases of nonvegetated floodplains, all measured streamwise velocity distributions followed the logarithmic distribution, but for vegetated floodplains, they followed an S-shaped profile. It is seen that after implanting the vegetation over the floodplain, the velocity over the floodplain decreases whereas it increases in the main channel. Also, as the vegetation density, λ, increases, velocity increases in the main channel and decreases in the floodplain. In the presence of emergent vegetation on floodplain, logarithmic profile does not exist even in the main channel, however it seems that the formation of the S-shaped profile in the main channel is under the bankfull height and above the bankfull height the vertical velocity profile takes on a logarithmic profile again. Under Submerged flow conditions, the velocity characteristics in all locations above the dowel array are well illustrated by the semi-logarithmic expression that has a slip velocity initially near the inflection point. On the basis of the present experimental results, the whole flow region is divided into the following three sub-zones: (1) Emergent zone (0 ≤ z ≤ hp), (2) Mixing-layer zone (hp < z ≤ hlog), (3) Log-law zone (hlog < z ≤ H). In the present study, hp was equal to 0.2 H and hlog was equal to 0.5 H. In the emergent zone (0 ≤ z ≤ hp) the velocity is almost constant due to strong wake effects of vegetation stems although it may behave slightly in a counter-gradient fashion. In the second zone (hp ≤ z ≤ hlog), the vertical velocity profile are similar in both submerged and emergent conditions, and the effect of bed roughness is completely eliminated and the velocity gradients are reduced and almost fixed. The velocity in the third zone (hlog < z ≤ H) is significantly higher than the velocity in the second zone. In the log-law zone (hlog < z ≤ H), the log-law of velocity distribution for rough beds is reasonably applied even to vegetated flows. Comparison the longitudinal velocity profiles for linear and staggered dowel arrangements indicates an increase in the resistance due to the linear arrangement compared to the staggered arrangement. Conclusion: In the cases of non vegetated floodplains, all measured streamwise velocity distributions followed the logarithmic distribution, but for vegetated floodplains, they followed an S-shaped profile. However, in the main channel, higher than the bankfull height the velocity profile is logarithmic. The results shows that as the vegetation density, λ, increases, the velocity increases in the main channel and decreases in the floodplain. Linear arrangement resulted higher resistance compared to staggered vegetation arrangement. The velocity profile at all locations above the dowel array are very well represented by the following semi logarithmic expression. In fully submerged vegetation, the whole flow region was divided into three sub-zones, i.e., the emergent zone, (0≤z≤hp) the mixing-layer zone (hp < z≤hlog), and the log-law zone(hlog=35%, Layout1 did not affect the value of the anti-sediment coefficient. That is, if the intake’s width is large, it is necessary to install submerged vanes in front of the intake to be able to affect the amount of sediment entering the intake. In general, by changing the levels of the parameters θci/θc, αi, and hs/hm, Layout1 has led to an average increase of 59% in the anti-sediment coefficient. Layout2, on the other hand, has resulted in an average 148% increase in the anti-sediment coefficient compared to the case where no submerged vanes are used in the bend. Keywords: Lateral intake, bend, numerical simulation, SSIIM.},
keywords = {Lateral Intake,bend,numerical simulation,SSIIM},
title_fa = {مطالعه عددی تأثیر تغییر پارامترهای هندسی آبگیر و آرایش صفحات مستغرق بر ضریب پادرسوبی آبگیر},
abstract_fa = {آبگیرهای جانبی برای انحراف آب از مسیر اصلی به کار میروند. از موارد مهم در طراحی آبگیرها، تأمین شرایطی است که حداکثر آبگیری به همراه حداقل رسوب فراهم شود. علاوه بر آبگیری از قوس خارجی رودخانه، استفاده از صفحات مستغرق به منظور منحرف کردن بار بستر از دهانه آبگیر توصیه شده است. در پژوهش حاضر 27 مطالعه عددی به منظور بررسی تأثیر استفاده از صفحات مستغرق در مقدار ضریب پادرسوبی آبگیر صورت گرفته است. مطالعات در سه دسته 9 تایی انجام شده است. دسته اول بدون صفحات مستغرق، دسته دوم دو ردیف صفحه مستغرق در بالادست آبگیر نصب شدند (طرح 1) و در دسته سوم، چهار ردیف صفحه مستغرق هم در بالادست و هم درمقابل دهانه آبگیر (طرح 2) قرار داده شدند. در هر دسته پارامترهای نسبت عرض آبگیر به عرض آبراهه اصلی، موقعیت آبگیر در قوس، زاویه آبگیری و نسبت ارتفاع آستانه به عمق جریان تغییر داده شد. نتایج نشان داد طرح 1 منجر به کاهش 15 درصدی مقدار رسوب وارد شده به آبگیر نسبت به حالت بدون صفحه شده است، در حالیکه طرح 2 به طور متوسط کاهش 46 درصدی مقدار رسوب وارد شده به آبگیر را نسبت به حالت بدون صفحه به همراه داشته است. همچنین بیشترین ضریب پادرسوبی آبگیر مربوط به طرح 2 و در حالتی است که در آن عرض آبگیر 0.15 عرض آبراهه اصلی، موقعیت آبگیر در فاصله 0.65 زاویه مرکزی قوس از ابتدای قوس، زاویه آبگیری ◦70 و نسبت ارتفاع آستانه به عمق جریان 0.234 باشد.},
keywords_fa = {آبگیر جانبی,قوس,شبیه سازی عددی,SSIIM},
url = {http://jhyd.iha.ir/article_119403.html},
eprint = {http://jhyd.iha.ir/article_119403_5df63f65cbdd725aa78e0fd5939bdd6e.pdf}
}
@article {
author = {Nabipour, Mostafa and Salehi Neyshabouri, S.A.A. and Souri, Farhad and Mohajeri, Seyed Hossein},
title = {Experimental study of bed particle motions in the floodplain of rectangular compound channel},
journal = {Journal of Hydraulics},
volume = {15},
number = {4},
pages = {113-124},
year = {2020},
publisher = {Iranian Hydraulic Association},
issn = {2345-4237},
eissn = {2645-8063},
doi = {10.30482/jhyd.2020.252605.1482},
abstract = {Introduction: Sediment transport is one of the most basic and important characteristics in river hydraulics and bed morphology. The prediction of sediment transport path in rivers and also artificial laboratory channels is absolutely complicated, and mostly conducted with semi-empirical methods. In such cases, the Lagrangian method is essential for exploring the physics of individual sediment particles. The investigation of the flow pattern in the compound channels originated from 1960s and followed by the exploration of turbulence structures of overbank flows. However, studies on the characteristics and processes of sediment transport in the compound channels are rarely conducted. For completion this gap, in this experimental study, the rolling and sliding motions of individual bed particle in the floodplain of a rectangular compound channel have been experimentally investigated. Specifically, the mechanical parameters of particle motions such as velocity and acceleration are investigated. In this regard, different statistical distributions, especially Gaussian or normal distribution, are employed to introduce the properties of bed sediment motions in the floodplain. Methodology: The experiments were conducted in the hydraulic laboratory of Tarbiat Modarres University in a straight open channel with length of 10 m, width of 1 m and height of 0.7 m (Fig. 1). The laboratory flume is a wide rectangular channel with a compound section (Fig. 2), where the side wall and bottom of the channel are made of glass. The main channel is 0.4 m wide and the floodplain is 0.6 m wide. To control the water depth, an adjustable weir was used at the end of channel. The discharge at the inlet of the channel was controlled using a regulating valve downstream of pump and measured by an electromagnetic flow-meter. The hydraulic conditions of the experiments are summarized in Table 1. According to the calculations, the Reynolds and Froude numbers are 28000 and 0.34, respectively. Therefore, the flow in the compound channel in the present study has turbulent and subcritical regime. The flow depths in the floodplain and main channel are 5 and 20 cm, respectively. To capture high quality images from bed particle motions in short intervals, a camera with the speed of 24 frames per second and FullHD resolution was used (Fig. 3). To improve the quality of images, the floodplain and main channel bottoms were coated with black color in the measurement zone. Moreover, for detection of particle trajectories, the measurement zone was regularly meshed by the perpendicular lines with the distance of 10 cm. Several projectors were applied at different angles for illumination of the measuring plane. The spherical bed particle characteristics of the present study are mentioned in Table 2. Particle tracking were conducted at the distances of 5, 20, 40, and 50 cm from the floodplain side wall (Fig. 4), and repeated about 20 times for each one. Results and Discussion: Chi-Squared test were used to determine the appropriate distribution to describe the longitudinal and transverse velocity and acceleration of individual particles (Fig. 5). Also, skewness and kurtosis of data series are employed to investigate the fitness of velocity and acceleration data to the normal distribution (Eqs. 2 and 3). The skewness values for the particle longitudinal and transverse velocities are always close to zero and their kurtosis values are close to 3, in the case of sediment release at 20 cm from the floodplain side wall. This indicates that the particle longitudinal and transverse velocities follow the normal distribution. However, kurtosis of longitudinal acceleration diverges from 3, and consequently, does not follow normal distribution (Table 3). The averaged longitudinal and transversal velocities of the sediment particles increase, approaching to the interaction zone (Fig. 6). Also, the standard deviation of longitudinal and transverse velocity and acceleration values increase with the increase of distance from the floodplain side wall (Fig. 7 and 8). Kurtosis of streamwise and spanwise velocity and acceleration of sediment particles increase far from floodplain side wall (Fig. 9), duo to the uniformity of particle motions in the interaction zone. The linear relationship between the average particle velocity and flow shear velocity indicates that there is a good agreement between the results of the present study and previous researches. Conclusion: The results of this study show that the sreamwise and lateral velocity and spanwise acceleration histograms of spherical particles in the floodplain far from the interaction zone, could be fitted to the normal distribution. While the kurtosis of histograms increases considerably, approaching to the junction. The histogram of streamwise acceleration does not fitted by normal distribution. The histogram kurtosis of velocity and acceleration is enhanced approaching the interaction zone.},
keywords = {Compound channel,floodplain,Lagrangian Particle Tracking,Sliding and Rolling Motions},
title_fa = {مطالعه آزمایشگاهی حرکت ذره بستر در سیلاب دشت کانال مرکب مستطیلی},
abstract_fa = {بررسی انتقال بار رسوبی در رودخانهها و کانالهای روباز از اهمیت زیادی برخوردار است. در این تحقیق رفتار تکذره رسوبی بستر با حرکت لغزشی و غلتشی در سیلابدشت یک کانال مرکب مستطیلی (دارای دیواره میانی قائم) بهصورت آزمایشگاهی و براساس دیدگاه لاگرانژی مورد بررسی قرار گرفته است. به این منظور روش ردیابی ذرات منفرد در یک کانال مستطیلی مرکب مورد استفاده قرار گرفت. نتایج این تحقیق نشان میدهد که توزیع سرعت طولی و عرضی و شتاب عرضی ذرات رسوبی در نواحی دور از ناحیه اندرکنش از توزیع نرمال پیروی میکند. این در حالی است که با افزایش فاصله از مرکز سیلابدشت و نزدیکی به ناحیه اندرکنش، تبعیت پارامترهای مذکور از توزیع نرمال تضعیف میگردد. بررسیهای مطالعه حاضر نشان داد که هیستوگرام شتاب طولی ذره را نمیتوان با استفاده از توزیع نرمال برآورد نمود. همچنین مشاهده شد که مقدار کشیدگی هیستوگرام سرعت و شتاب با نزدیک شدن به ناحیه اندرکنش افزایش مییابد.},
keywords_fa = {کانال مرکب,سیلابدشت,ردیابی لاگرانژی رسوبات,حرکت غلتشی و لغزشی ذرات},
url = {http://jhyd.iha.ir/article_120318.html},
eprint = {http://jhyd.iha.ir/article_120318_9a3fda743c54eedcd3fb391f5be09ade.pdf}
}