ضريب شدت جريان دريچه ي كناري در قوس 180 درجه

Discharge Coefficient of Side Sluice Gate in 180O Curved Channel

چكيده- براي تنظيم ميزان جريان ورودي از كانال انتقال اصلي به كانال فرعي مي توان از دريچه هاي كناري استفاده كرد . براي تخمين دبي عبوري از زير دريچه، نياز به تعيين ضريب شدت جريان آن است. اين ضريب را مي توان به صورت تجربي ب ه دست آورد. براي ضريب شدت جريان دريچه كناري در مسير مستقيم، محققان روابط اندكي ارايه داده اند؛ اما در قوس 180 درجه تا كنون مطالعاتي در اين مورد انجام نشده است. از پارامترهاي موثر بر دبي جريان مي توان به ارتفاع آب در بالادست دريچه؛ عدد فرود بالادست ، ميزان بازشدگي دريچه و موقعيت دريچه كناري در قوس 180 درجه اشاره كرد. براي بررسي پارامترهاي موثر بر ضريب شدت جريان دريچه كناري در قوس 180 درجه آزمايش هايي انجام شد . در اين مقاله با استفاده از داده هاي آزمايشگاهي و به كارگيري فرمول عمومي دريچه ها ، ابتدا پارامترهاي بدون بعد موثر بر ضريب شدت جريان تعيين مي شود ؛ سپس روابطي براي تعيين ضريب شدت جريان دريچه هاي كناري ، در موقعيت هاي مختلف قوس 180 درجه ارايه مي شود.

Side sluice gates are flow metering structures, which are used for controlling the flow from the main channel to the side channel. It is usually required to determine the discharge coefficient for estimation of the side sluice gate discharge. In order to study the influence of some important parameters on the discharge coefficient of side sluice gate, extensive experiments were conducted. The experiments were conducted in a re-circulating channel having a central angle of 180o, a centerline radius of RC = 2.6 m, and the width and height of 0.6 m. The ratio of radius of centerline of the channel to the width of the channel Rc/B was 4.33. The bend was connected to two straight upstream and downstream reaches. The upstream one was 7.2 m in length while the length of downstream one was 5.2 m. The bed and sides of the channel were made of glass and supported with metal frames. The side channel was set at different locations of bend (i.e. at the sections 53, 65, 90, 115 and 135 degree). The side sluice gate was made of Plexiglas and was set at the entrance of the side channel. The experiments were carried out for different gate openings, upstream depth of flow and location of the side sluice gate under free flow condition. The upstream discharge was measured by a digital flow meter, while the downstream discharge was measured using a calibrated triangular weir. The difference of upstream discharge and downstream discharge resulted to the sluice gate discharge. The results of experiments on a side sluice gate located in a 180 degree curved channel are reported. The variation of flow depth along the side sluice gate was studied. The influence of different parameters like: depth of flow, approach Froude number, side sluice gate opening and location of side sluice gate on discharge coefficient were investigated. It was found that increase of approach Froude number increases the discharge coefficient. Moreover, increase of relative flow depth h1/a increases the discharge coefficient. Here, h1 is the approach Froude number and a is the sluice gate opening. Maximum discharge coefficient was observed when the sluice gate was located at the section 150 degree in the channel bend. New equation for discharge coefficient of a side sluice gate in a 180 degree curved channel was developed. The discharge coefficient was found to be related to approach Froude number, location of sluice gate in the channel bend and the relative flow depth.