مطالعه تيوري و آزمايشگاهي جهش هيدروليكي واگرا با شيب كف معكوس

Theoretical and experimental investigation of diverging hydraulic jump on adverse slope

در اين تحقيق مشخصات جهش هيدروليكي واگرا در حوضچه مستطيلي با شيب كف معكوس به صورت تيوري و آزمايشگاهي بررسي شده است. بدين منظور با بسط مباني تيوري جهش هيدروليكي، روابط تيوري براي نسبت عمق ثانويه و افت نسبي انرژي استخراج و با آزمايش‌هايي بر روي يك مدل حوضچه آرامش واگرا با شيب كف معكوس، كه براي اين منظور طراحي و ساخته شده بود، عمق ثانويه، طول و ساير مشخصات جهش بررسي شد. آزمايش‌ها براي 4 زاويه واگرايي (3، 5، 7 و 10 درجه) به اضافه جهش مستقيم در مقطع مستطيلي و براي 4 شيب كف معكوس (27/2، 1/4، 61/5 و 8 درصد) به همراه شيب صفر و در دامنه اعداد فرود (9-5/2) صورت گرفت. مقايسه نتايج نشان داد كه مطابقت زيادي بين نسبت عمق ثانويه تيوري و تجربي وجود دارد. تجزيه و تحليل نتايج نشان داد كه بطور متوسط در هر زاويه واگرايي، افزايش شيب كف معكوس از صفر به 8 درصد باعث مي‌شود در مقايسه با جهش كلاسيك، نسبت عمق ثانويه 47 درصد و طول نسبي جهش 35 درصد كاهش و افت نسبي انرژي 20 درصد افزايش يابد.

To reduce the constructional costs of stilling basins, changes in geometries of cross section and plan of basin are sometimes used to adopt the basin with the upstream and downstream sections to eliminate transition structures. Any changes in the geometry of the basin would cause changes in the conditions and characteristics of the hydraulic jump. Hence, in this research, the effects of variation in both the adverse bed slope and the diverging angle of a gradually expanding stilling basin with rectangular section on the jump conditions were investigated both experimentally and theoretically. The experimental tests were conducted in a specially designed model for a wide range of bed slopes and longitudinal divergences of the basin walls. The important parameters of the jump, such as the length, sequent depth and the energy loss, were computed and compared to those in the classic jumps. Experiments was performed for 4 diverging angle (3, 5, 7 and 10°) and adverse bed slopes (2.27, 4.1, 5.61 and 8 percent) in addition to classic jump at wide range of Froude numbers (2.5-9). There is a good agreement between experimental and theoretical values of sequent depths of jump. The results show that for each diverging angle, increase in adverse bed slope from horizontal bed to 8 percent, caused approximately a decrease of the sequent depth and relative length of jump 47 and 35 percent respectively, and also an increase of the relative energy loss by 20 percents.