كليدواژه :
پرش هيدروليكي واگرا , بلوك قائم , بلوك منحني , مدل آشفتگي k-ԑ , نرم افزار FLOW-3D
چكيده فارسي :
يكي از سازه هاي متداول جهت استهلاك انرژي جريان هاي پر سرعت، حوضچه آرامش مي باشد. بررسي محققين نشان مي دهد كه واگرايي و زبري هاي مصنوعي حوضچه هاي آرامش هر يك باعث كاهش نسبت عمق ثانويه به اوليه، طول پرش و افزايش افت نسبي انرژي نسبت به پرش كلاسيك مي شود. در اين تحقيق با استفاده از نرم افزار FLOW-3D و مدل هاي آشفتگي k-ԑ استاندارد و RNG k-ԑ شبيه سازي عددي پرش هيدروليكي در مقاطع مستطيلي واگرا انجام شده است و با نتايج بدست آمده از بررسي هاي آزمايشگاهي مورد مقايسه قرار گرفت، درادامه اثرات بلوك قائم و منحني بر مشخصات پرش هيدروليكي مورد ارزيابي قرار گرفت. نتايج نشان داد كه مدل آشفتگي k-ԑ استاندارد براي پيش بيني پروفيل سطح آب در پرش هيدروليكي در مقاطع مستطيلي واگرا مناسب بوده و انطباق قابل قبولي دارد. بررسي ها نشان داد كه در مقايسه ميان بلوك ها، بلوك هاي منحني، اثر گذارتر عمل مي كنند، طوري كه بلوك هاي منحني باعث كاهش عمق ثانويه و طول پرش هيدروليكي به ترتيب 70 و 35 درصد نسبت به پرش كلاسيك شده است و بلوك هاي قائم، باعث كاهش عمق ثانويه و طول پرش هيدروليكي به ترتيب 46و 18 درصد نسبت به پرش كلاسيك شده است.
چكيده لاتين :
The hydraulic jump phenomenon is one of the most common phenomena in open channels. Hydraulic jump is a transition state from supercritical to subcritical flow regime, which normally occurs in conjunction with hydraulic structures, such as spillways, weirs, and sluice gates. A hydraulic jump phenomenon serves a variety of purposes, for instance, to dissipate the energy of flow to prevent bed erosion and aerate water or to facilitate the mixing process of chemicals used for the purification of water. Stilling basins are one of the most common structures for energy dissipation of flow with high velocities. The stilling basin has been accepted to be the most powerful hydraulic structure for the dissipation of the flow energy. The size and geometry of the stilling basin affect the formation of flow patterns, which can be influential for hydraulic performance of the whole system. The depth of water after the jump is related to the energy content of the flow, and any reduction in energy content with increased energy dissipation in the jump will reduce the required depth of flow after the jump. Sometimes these basins are supplied with appurtenances that increase the overall roughness of the basins. This in turn increases the energy dissipation, decreases the sequent depth, and requires a shorter basin for the full development of the hydraulic jump. There are plenty of research studies in the literature regarding the classical hydraulic jump in the usual rectangular straight stilling basin, but less for the hydraulic jump in other cross section shape of basins. Expanding gradually basin with the rectangular cross section acts as two separate hydraulic structures including stilling basin and transition. In this type of structures not only the transition can be eliminated, but the length of the basin will be also much smaller than what is designed for the usual straight basins. Researchers’ studies show that divergence in stilling basins reduce the sequent depth and the length of the jump while increasing the energy losses compared to the classic jumps. In this research, numerical simulation of the hydraulic jump was performed in divergence rectangular sections, and compared with the results of the laboratory, making use of the FLOW-3D software and the standard k-ԑ and RNG k-ԑ turbulence models. The effects of Vertical and Curve blocks on the specification of hydraulic jump were evaluated. The results showed that the standard k-ԑ turbulence model was able to predict the water level profiles in the hydraulic jump in divergence rectangular sections with appropriate and acceptable coincidence. Results showed that the mean relative error of water surface obtained from numerical model and measured values is about 3.55 percent. Also the numerical model showed the vortices that were accrued because of diverging walls as well as experiment investigations. The results show that creating the vertical blocks, reduces the sequent depth as much as 46.27 % and the length of the hydraulic jump as much as 17.64%, while increasing the energy loss as much as 31.57%, compared to the classic hydraulic jumps. The results also show that creating the Curve blocks, reduces the sequent depth as much as 69.76 % and the length of the hydraulic jump as much as 35.29%, while increasing the energy loss as much as 32%, compared to the classic hydraulic jumps.
