7667

7139

كارشناسي ارشد

سازه هاي آبي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده كشاورزي

1391

هشت،72ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

حسين افضلي مهر

اسماعيل لندي

4/2/92

محمد شايان نژاد، احمد ميره اي

مهندسي كشاورزي

ID7139

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Influence of unfavourable pressure gradient on flow structure in a channel with vegetated bed and smooth walls Ali Keshavarz a keshavarz@ag iut ac ir Department of Water Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi HosseinAfzalimehrhafzali@cc iut ac ir Abstract Vegetative covers in rivers and river banks have different physical chemical ecological and environmental functions and affect river processes like sediment nutrient and pollution transport oxygen production aquatic life and etc Through the years inappropriate use of rivers has caused vegetation destruction and many environmental problems In recent years developed countries have tried to restore the rivers This subject shows the significance of studies about hydrodynamic of flow in the presence of vegetation in different conditions Since most of the studies in the field of interaction between flow and vegetation have carried out in the case of uniform flow thus in the present study the objective is investigation of flow structure velocity profile Reynolds stress and turbulence intensity distributions in a decelerating flow over bed vegetation The experiments carried out in a flume 8m long and 40cm wide with a 2 percent bed slope and in the presence of grass on bed with 2 discharges and 2 water depths 4 experimental series and totally 120 velocity profiles measured For each experimental series the measurements carried out in 5 sections and 4 profiles with different distances from the wall for each section The results show that the velocity profiles shift to the left along the flume Also there are 3 distinct regions with different characteristics in velocity profile distributions The first region is in higher regions of the canopy In the first region the velocity values as well as the velocity gradients are low The next region is above the crest of vegetation and the most important characteristic of this region is high velocity gradient and validation of the log law The third layer is located above the second layer and its characteristic is low velocity gradient and is nearly vertical The log law cannot be used for this region but with some modification by pi parameter in Coles law It is usable for this region too Using different methods like Clauser and Rotta methods shows the flow is in equilibrium that means the measured sections are in a distance from the flume entrance that the boundary layer has formed completely The distributions of Reynolds stress and turbulence intensity are nearly similar The values of Reynolds stress and turbulence intensity are low near the water surface and if we move toward the bed the values increase and the region with maximum turbulence occur above the vegetation coverand this region is coincident with the region with high velocity gradient Key Word Vegetation velocity profile Reynolds stress turbulence intensity

حسين افضلي مهر

اسماعيل لندي

محمد شايان نژاد، احمد ميره اي