خصوصيات پرش هيدروليكي روي بستر زبر با آب پايه در چاهك آدم رو با شيب شكن

چكيده انگليسي :

Characteristics of hydraulic jump on rough beds with a sill in a drop manhole Seyed Mostafa Nabavizadeh m nabavizadeh@cv iut ac ir 2019 Department of Civil Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M ScLanguage FarsiSupervisors Dr M R Chamani Mchamani@cc iut ac ir and Dr M N Moghim Moghim@cc iut ac ir AbstractHigh velocity and supercritical speed of downstream flow at many hydraulic structures lead to destructionand erosion of downstream structures One of the main approaches which is used by researchers to decreasethe velocity of flow increase the energy loss and improve the performance of such structures is to applyhydraulic jump phenomena In order to form and stabilize the hydraulic jump the jump control structuressuch as sill sharp and broad crested weirs as well as positive and negative steps can be used The aim of this study is to experimentally investigate the hydraulic conditions of upstream flow in thehorizontal channel at two bedding modes Smooth and Rough beds The experiments are carried out on fivesill models with different lengths of 20 50 and 200 mm and heights of 42 50 and 60 mm in a horizontalsmooth channel and on two sill models with a constant length of 200 mm and variable height of 50 and 60mm in a rough channel To roughen the channel bed natural materials gravel and sand with mean diameterof 3 5 and 7 mm were used Using previous experiments certain experiments were carried out in alaboratory to create critical hydraulic jump It should be mentioned that significant differences were observedbetween the results of most of the studies due to the fact that they ignored the effect of parameters like therelative length of the spillway relative distance and roughness of the channel bed Therefore we weremotivated to do more experiments in this regard in order to make the results of this study more reliable The experimental results show that parameters such as roughness of the channel bed length height anddistance of the sill affect the formation conditions of a hydraulic jump For example in the MS1 model inwhich the relative height of the sill equaled 2 75 the initial Froude number of the critical jump was 5 29 Decreasing the relative height of the sill by 2 29 the initial Froude number of the critical jump is 4 67 According to the results decreasing the relative height of the sill from its critical relative height causes theflow to pass over the sill and the hydraulic jump does not form Under these conditions increasing therelative height of the sill provides the conditions for re forming the hydraulic jump Experimental resultsshow that under identical hydraulic conditions if the sill length increases from 20 mm in MS1 model to 200mm in MS2 model the initial Froude number of the critical jump approximately increases 0 6 to 0 7 units Increasing the sill distance from the compression section reduces the initial Froude number of the criticaljump For example under similar conditions of MS1 model and the relative height of sill equaled 2 75 increasing the sill distance from 600 mm to 700 mm reduced the initial Froude number of the critical jumpfrom 5 29 to 5 12 According to the laboratory results considering the constant value of the geometricproperties of the sill the hydraulic jump length will not change if the valve opening and inlet flow rate areincreased to reform the hydraulic jump but increasing the length and height of the sill reduces the hydraulicjump length and improves the stabilization of the end of the jump Key words Hydraulic jump Jump control structures Sharp crested weirs Broad crested weir

نبوي زاده، مصطفي

خصوصيات پرش هيدروليكي روي بستر زبر با آب پايه در چاهك آدم رو با شيب شكن

پرش هيدروليكي , سازه هاي كنترل كننده ي پرش , سرريزهاي لبه تيز , سرريزهاي لبه پهن