7743

7208

كارشناسي ارشد

آبياري و زهكشي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده كشاورزي

1391

سيزده،114ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

حسين افضلي مهر

حسين سقائيان نژاد، اسماعيل لندي

1/3/92

محمد شايان مژاد، علي اسحق بيگي

مهندسي كشاورزي

ID7208

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

115 Interaction of vegetated walls slope grain size and Riffle on Turbulent flow Characteristics Narges kiani n Kiani@ag iut ac ir 2013 01 08 Department of Irrigation and Drainage Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiHossein Afzalimehr hafzali@cc iut ac ir AbstractRiver engineering seeks to preserve and optimize the natural rivers and their floodplains Rising in bedtopography called riffle These bedforms occurs in rivers with mild slop less than 5 percent andunconfined situation however riffles excite in developed floodplains Grains which cover thesebedforms are suitable places for salmons As a result a successful channel design needs studying thesebedforms at first Moreover vegetated walls have significant effect on stability and flow resistance inaddition these walls increase roughness coefficient in walls and flood plains In fact vegetationincrease channel walls stability and sediment transport threshold To sum up interaction of sediment flow and vegetation determinant morphodynamical river factors Many laboratory and analyticalresearches have done in several decades although the knowledge of interaction of bedform flow andtheir effects on hydraulic parameters such as shear stress is inadequate Among the objectives of thisresearch are to assess and understand the interaction of riffle and vegetated walls on acceleration flows study of bedform s slop effectiveness on turbulent flow characteristics analysis of flow patterns whengrain size near the crest of riffle is changed This study was conducted in Isfahan University agriculturalcollege Hydraulics Laboratory 3D measurement of flow was done by ADV Three dimensionalmeasurement of water flow velocity was measured using ADV In order to simulate riverbed testing twodifferent size 10 mm and 32 mm were used in different series To show the effect of changes in stoss andlee three different angle used to simulate bedform in the first three tests Influence of vegetation onturbulence flow through experiments conducted in the presence and lack of vegetation were studied Atotal of seven series of experiments were conducted to achieve the research goals velocity near the wall isIncreasing gradient along the channel leads to flow close to the bed and the case of recurring defectsoccur momentum changes in stoss and lee s angle then flow separation occurs in higher slope Mildslop prevent separation on lee and make a shear layer on deceleration part of bed form This shear layerextended on the crest Also the occurrence of maximum stress increases with increasing slope Steeprise in tensions on the bedform is the result of stoss and lee s angle Particles move through the bedformas suspended load and bedload with increases in angle Increased aggregation reduces the maximumspeed of the substrate is formed At a riffle with 10 degree in its stoss and lee angle the maximumvelocity happen at higher water depth with increasing in grain size But this increase don t havesignificant influence on tenssion Vegetated walls increased secondary patterns and decreased aspect ratio This kind of walls increased Drag forces and turbulence in flow Vegetated walls has an significantinfluence on deceleration and increased suspended load Key WordsRiffle angle of stoss and lee grain size of bedform vegetated walls Reynolds stress Turbulence intensities

حسين افضلي مهر

حسين سقائيان نژاد، اسماعيل لندي

محمد شايان مژاد، علي اسحق بيگي