List of Articles roughness coefficient

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  1 - Laboratory Study of The Effect of V-shaped Structure on Changes in Fishway Roughness
  maryam shahabi Javad Ahdiyan Marjan Narimousa Mehdi Ghomeshi Hossein Azizi Nadian
  10.30495/wsrcj.2022.64329.11268
  Background and Aim: In this study, a new overflow with a v-shaped structure was used as a barrier in the culvert. The main purpose of the present study was to investigate its performance on changes in flow resistance properties such as the square root of the Modi fricti More

  Background and Aim: In this study, a new overflow with a v-shaped structure was used as a barrier in the culvert. The main purpose of the present study was to investigate its performance on changes in flow resistance properties such as the square root of the Modi friction coefficient and the Manning roughness coefficient.Method:The present study experiments were performed on the physical model available in the hydraulic laboratory of the Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz. This physical model includes a laboratory flume 10 meters long, 0.25 meters wide, and 0.5 meters high. At the beginning of each experiment, the structures were glued to the flume bed at specified relative distances. After 24 hours of gluing the systems, the flume's flow rate and slope were adjusted. The desired flow rate was adjusted using a triangular overflow with an angle of 53 degrees located downstream of the flume and the slope through the jack. A point gauge with an accuracy of 0.1 mm was used to remove the water surface profile.Results: By increasing the dimensionless flow in a relative distance between structures and a certain slope, the manning roughness coefficient of the structure decreases. So that at a slope of 10%, the relative distance between the structures was 1.3, the value of the Manning roughness coefficient of the system from dimensionless flow decreased from 0.20 to 0.43 by 30%. By increasing the relative distance between structures at a certain flow rate, the manning roughness coefficient of the structure decreases, which is similar to the effect of the relative distance between structures on the square root of the friction drop coefficient of the structure.Conclusion: In examining the impact trend of the V-fish structure, it was found that dimensionless flow has an inverse effect on the flow friction coefficient and the manning roughness coefficient of the structure. On the other hand, the inverse relationship between landing number and flow friction coefficient, and manning coefficient of the structure was determined. It was found that the relative distance between the structures also has an inverse effect on the flow friction coefficient and the manning coefficient of the structure. The inverse effect of the Reynolds number on current resistance parameters was also extracted. The best condition of the fish road structure with v-shaped overflow occurs in the relative distance between the 1.3 and 10% slope structures. Manuscript profile
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  2 - پیش بینی تأثیر پوشش گیاهی بر ضریب زبری هیدرولیکی کرانه و بستر رودخانه خشک شیراز
  محمدرضا نیک منش
  مدیریت منابع آب و خاک در رودخانه‌ها، بدلیل ارتباط مستقیم با سیستم‌های مختلف همچون زمین ، جامعه و مردم از اهمیت بالایی برخوردار است. طرحهای احیای پوشش گیاهی و بیومهندسی در رودخانه‌ها، همواره به عنوان یکی از روشهای مدیریتی منابع آب و خاک مد نظر بوده، اما اینگونه طرح‌ها، ع More

  مدیریت منابع آب و خاک در رودخانه‌ها، بدلیل ارتباط مستقیم با سیستم‌های مختلف همچون زمین ، جامعه و مردم از اهمیت بالایی برخوردار است. طرحهای احیای پوشش گیاهی و بیومهندسی در رودخانه‌ها، همواره به عنوان یکی از روشهای مدیریتی منابع آب و خاک مد نظر بوده، اما اینگونه طرح‌ها، علیرغم مزایای فراوانی که دارد، در صورت طراحی و روش‌های اجرایی نامناسب، می تواند مشخصات هیدرولیکی رودخانه را تغییر دهد. استفاده از پوشش گیاهی، کاهش میانگین سرعت جریان، کاهش عرض رودخانه، افزایش رسوب گذاری در بستر رودخانه و در نتیجه کاهش دبی جریان عبوری رودخانه را به همراه دارد و در مواردی ممکن است، باعث بالا آمدن سطح آب و افزایش عمق جریان گردد. در این مقاله ضمن معرفی جنبه‌های مختلف مدیریتی منابع آب و خاک در رودخانه‌ها و به طور خاص، رودخانه خشک، به عنوان یک عنصر تأثیرگذار مهم در شهر شیراز، طرحهای احیای پوشش گیاهی و بیومهندسی اجرا شده در این رودخانه و تأثیرات آنها بر هیدرولیک رودخانه، مورد بررسی قرار گرفته است. همچنین فواید این طرحها، در بازه‌هایی از رودخانه خشک که با روش‌های مناسب اجرا شده و باعث حفظ منابع آب و خاک گردیده اند و همچنین مضرات آنها، در بازه‌هایی که  با روشی نامناسب انجام شده و باعث افزایش ضریب زبری و کاهش دبی جریان عبوری می گردند، مورد تجزیه و تحلیل قرار می گیرد. بر اساس نتایج به دست آمده، اگرچه میزان فرسایش کناره‌های رودخانه  در مقاطع فاقد پوشش گیاهی به مراتب بیشتر از مقاطع دارای پوشش گیاهی، می‌باشد، اما به دلیل افزایش ضریب زبری و کاهش سطح مقطع، ناشی از وجود پوشش گیاهی، در برخی مقاطع، دبی عبوری به مقدار قابل توجهی کاهش می یابد. مقاطعی نظیر بالادست و پائین دست پل بلوار چمران،  بالادست پل غدیر و  پائین دست پل فضیلت، نمونه‌هایی از این مقاطع می باشند که نتایج آنالیز انجام شده با نرم افزار HEC-RAS در این مقاطع، برای دبی عبوری 100 تا 250 مترمکعب بر ثانیه، کاهش دبی عبوری به مقدار 10 تا 5/28 درصد را نتیجه می دهد. Manuscript profile
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  3 - Sensitivity analysis of Manning roughness coefficient of rivers in HEC-RAS model to determine flood zones (case study: Ker River- Fars province)
  vahid sohrabi Farshid Hashmipour Petkoi Hamid Sheikhpur Shahi
  Introduction: Rivers are one of the few natural phenomena that, despite the countless damages they have caused to humans since a long time ago, due to their special impact on human life and the formation of civilizations, humans have always been called to the lands alon More

  Introduction: Rivers are one of the few natural phenomena that, despite the countless damages they have caused to humans since a long time ago, due to their special impact on human life and the formation of civilizations, humans have always been called to the lands along the river. In Iran, due to its large size, multiple climates, and temporal and spatial density of rains in most watersheds, huge floods have been witnessed in most regions of the country every year, many of which cause a lot of human and financial losses.Methodology: In this research, 10 km long stretches of the Ker River (downstream of the Chamriz Hydrometric Station) were selected, and after preparing the statistics of the maximum instantaneous discharge of the river in two states before and after the construction of the Molla Sadra Dam, the effect of the construction of the dam on the river flow Checked out. Then, taking into account the river discharge per discharge with a return period of 25 years for two situations before and after the construction of the dam, the permanent flow model of the mentioned river was prepared by HEC-RAS software and then compared with each other. In the following, based on discharge with a return period of 25 years after the construction of the dam, the Manning roughness coefficient was changed to 50% of the initial value and the HEC-RAS model was implemented again. The construction of the said dam has caused some parameters such as water level, water flow speed, water flow area, flow rate in the river and also the flood of its plains to decrease.Results: The results of the sensitivity analysis of some parameters in relation to Manning's roughness coefficient showed that with the decrease of Manning's roughness coefficient, some parameters such as water level and flow area also decrease and parameters such as water flow speed, river discharge, river discharge on the right bank and the left increases and vice versa. Manuscript profile