شبیه‌سازی عددی تأثیر جریان غلیظ بر آشفتگی جریان در تخلیه‌کننده تحتانی سدها

نویسندگان

چکیده

استفاده از فعالیت‌های حفاظت آب و خاک برای کنترل رسوب‌زایی حوضه‌های آبریز در همه شرایط موفق نبوده و به نظر می‌رسد تخلیه رسوبات ته‌نشین شده در مخزن از طریق تخلیه‌کننده‌های تحتانی تنها راه حل مؤثر و موفقیت‌آمیز خواهد بود. با توجه به اهمیت انرژی آشفتگی جریان از لحاظ ورود هوا به جریان و پتانسیل وقوع کاویتاسیون،‏ در این مقاله سعی شده تا با شبیه‌سازی عددی این فرایند،‏ گامی در جهت بهینه‌سازی عملکرد این سازه‌ها برداشته شود. در این پژوهش ابتدا جریان دو فاز آب و هوا شبیه‌سازی و نتایج با مشاهدات و اندازه‌گیری‌های آزمایشگاهی مقایسه شد. سپس دو جریان با غلظت 300 و 500 گرم در لیتر به‌صورت سه‌ فاز اولری آب و هوا و رسوب،‏ جهت بررسی تأثیر غلظت بر پروفیل‌های آشفتگی و انرژی آشفتگی سطحی شبیه‌سازی شد. نتایج نشان داد که در غلظت‌های بالای رسوب،‏ انرژی آشفتگی جریان در مقایسه با حالت آب خالص بسیار ناچیز بوده و فقط در سطح جریان و در فواصل نزدیک دریچه تأثیرگذار است. ورود ذرات جامد رسوب به جریان سبب کاهش شدت و نرخ آشفتگی در مقاطع مختلف جریان در تونل شده به گونه‌ای که افزایش غلظت جریان به 300 گرم بر لیتر سبب کاهش 50 درصدی حداکثر انرژی آشفتگی می‌شود.

کلیدواژه‌ها


عنوان مقاله [English]

Numerical simulation of density current effects on turbulence characteristics of flow in bottom outlets

نویسندگان [English]

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  • m k
چکیده [English]

Water and soil conservation activities cannot limit sediment production on watersheds, completely and it seems that the only practical way to remove the sediments from the reservoir is to flush it out by bottom outlets. Because of the importance of turbulence energy in air entrainment to flow and cavitation occurrence, in this paper numerical simulation of sediment transport through the bottom outlet of the dam is performed. For this purpose, first, the air-water mixture in bottom outlet is simulated and the results are compared with experimental measurements. Then, a three phase flow with two sediment concentrations of 300 and 500 gr/lit are simulated to investigate the effect of sediment concentration on flow turbulence and its energy. The results show that the turbulence energy is negligible in flow with high sediment concentration in comparison with clear water and only affects on the flow surface and near the gate. Adding sediment particles to the flow leads to reduce the turbulence intensity of flow through bottom outlet tunnel, so that, increasing its concentration to 300gr/lit reduces the maximum of turbulence energy about 50%.Water and soil conservation activities cannot limit sediment production on watersheds, completely and it seems that the only practical way to remove the sediments from the reservoir is to flush it out by bottom outlets. Because of the importance of turbulence energy in air entrainment to flow and cavitation occurrence, in this paper numerical simulation of sediment transport through the bottom outlet of the dam is performed. For this purpose, first, the air-water mixture in bottom outlet is simulated and the results are compared with experimental measurements. Then, a three phase flow with two sediment concentrations of 300 and 500 gr/lit are simulated to investigate the effect of sediment concentration on flow turbulence and its energy. The results show that the turbulence energy is negligible in flow with high sediment concentration in comparison with clear water and only affects on the flow surface and near the gate. Adding sediment particles to the flow leads to reduce the turbulence intensity of flow through bottom outlet tunnel, so that, increasing its concentration to 300gr/lit reduces the maximum of turbulence energy about 50%.Water and soil conservation activities cannot limit sediment production on watersheds, completely and it seems that the only practical way to remove the sediments from the reservoir is to flush it out by bottom outlets. Because of the importance of turbulence energy in air entrainment to flow and cavitation occurrence, in this paper numerical simulation of sediment transport through the bottom outlet of the dam is performed. For this purpose, first, the air-water mixture in bottom outlet is simulated and the results are compared with experimental measurements. Then, a three phase flow with two sediment concentrations of 300 and 500 gr/lit are simulated to investigate the effect of sediment concentration on flow turbulence and its energy. The results show that the turbulence energy is negligible in flow with high sediment concentration in comparison with clear water and only affects on the flow surface and near the gate. Adding sediment particles to the flow leads to reduce the turbulence intensity of flow through bottom outlet tunnel, so that, increasing its concentration to 300gr/lit reduces the maximum of turbulence energy about 50%.Water and soil conservation activities cannot limit sediment production on watersheds, completely and it seems that the only practical way to remove the sediments from the reservoir is to flush it out by bottom outlets. Because of the importance of turbulence energy in air entrainment to flow and cavitation occurrence, in this paper numerical simulation of sediment transport through the bottom outlet of the dam is performed. For this purpose, first, the air-water mixture in bottom outlet is simulated and the results are compared with experimental measurements. Then, a three phase flow with two sediment concentrations of 300 and 500 gr/lit are simulated to investigate the effect of sediment concentration on flow turbulence and its energy. The results show that the turbulence energy is negligible in flow with high sediment concentration in comparison with clear water and only affects on the flow surface and near the gate. Adding sediment particles to the flow leads to reduce the turbulence intensity of flow through bottom outlet tunnel, so that, increasing its concentration to 300gr/lit reduces the maximum of turbulence energy about 50%.

کلیدواژه‌ها [English]

  • Turbulence-Bottom outlet-Numerical simulation-Sediment concentration-