بررسی پدیده کاویتاسیون روی سرریز سد ونیار با استفاده از مدل عددی FLUENT

نویسندگان

چکیده

در طراحی ساز‌ه‌های هیدرولیکی دارای جریان سریع،‏ معمولاً احتمال رخداد پدیده کاویتاسیون وجود دارد. برای جلوگیری از وقوع پدیده کاویتاسیون،‏ باید موقعیت نقاطی که در آن‌ها ممکن است با افزایش سرعت جریان،‏ فشار تا حد فشار بخار مایع کاهش یابد را شناسایی کرد. در این راستا برای دست‌یابی به یک معیار کمی،‏ از شاخص کاویتاسیون استفاده می‌شود. در این پژوهش ابتدا با روش عددی دینامیک سیالات محاسباتی (CFD)‎،‏ دو گزینه برای جریان بر روی سرریز سد ونیار طرح و شبیه‌سازی شد،‏ سپس شاخص کاویتاسیون برای هر یک از گزینه‌ها محاسبه و در‌نهایت برای صحت‌سنجی نتایج،‏ از نتایج مدل آزمایشگاهی استفاده شد. برای حل عددی معادلات سه بعدی ناویر- استوکس بر روی سرریز از نرم‌افزار Fluent و برای شبکه‌بندی سه‌بعدی سرریز از نرم‌افزار Gambit استفاده می‌شد. برای تعیین پارامترهای آشفتگی میدان جریان،‏ تعیین سطح آزاد جریان و مجزا‌سازی معادلات ممنتم،‏ به‌ترتیب از مدل آشفتگی (RNG)‎? – k،‏ روش VOF و روش بالادست مرتبه دوم استفاده شد. در انتها با بررسی نتایج حاصل از پژوهش،‏ هماهنگی مناسبی بین نتایج حاصل از Fluent و مدل آزمایشگاهی به دست آمد. همچنین مشخص شد که در هیچیک از گزینه‌های مطالعه شده کاویتاسیون رخ نداده و سرریز احداث شده در مقابل این پدیده ایمن است.

کلیدواژه‌ها


عنوان مقاله [English]

Investigation of cavitation phenomenon on Vanyar dam’s spillway using the FLUENT numerical model

نویسندگان [English]

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چکیده [English]

In designing the hydraulic structures with rapid flow, there is the probability of occurrence of cavitation phenomena. To prevent the occurrence of cavitation phenomena, the places where may pressure reduced to vapor pressure of liquid because of increase the flow velocity, should be identified. In this regard, to achieve a quantitative measure, the cavitation index can be used. In this study, two cases have been designed and simulated for Vanyar dam’s spillway using numerical models of computational fluid dynamics (CFD). Then the cavitation index was calculated for each case and finally for the verification, the results of laboratory model are used. For the numerical solution of the 3-dimensional Navier-Stokes equations and 3-dimensional gridding of the spillway, the Fluent and Gambit software are used, respectively. To determine the parameters of the flow field turbulence, the free-surface flow and the separation of momentum equations, the k – ? (RNG) turbulence model, the VOF method and the second order upwind method are used, respectively. The results indicated a proper agreement between the Fluent results and experimental model. Also it is found that in none of the considered cases, the cavitation didn’t occur and constructed spillway is safe against this phenomenon.

In designing the hydraulic structures with rapid flow, there is the probability of occurrence of cavitation phenomena. To prevent the occurrence of cavitation phenomena, the places where may pressure reduced to vapor pressure of liquid because of increase the flow velocity, should be identified. In this regard, to achieve a quantitative measure, the cavitation index can be used. In this study, two cases have been designed and simulated for Vanyar dam’s spillway using numerical models of computational fluid dynamics (CFD). Then the cavitation index was calculated for each case and finally for the verification, the results of laboratory model are used. For the numerical solution of the 3-dimensional Navier-Stokes equations and 3-dimensional gridding of the spillway, the Fluent and Gambit software are used, respectively. To determine the parameters of the flow field turbulence, the free-surface flow and the separation of momentum equations, the k – ? (RNG) turbulence model, the VOF method and the second order upwind method are used, respectively. The results indicated a proper agreement between the Fluent results and experimental model. Also it is found that in none of the considered cases, the cavitation didn’t occur and constructed spillway is safe against this phenomenon.

In designing the hydraulic structures with rapid flow, there is the probability of occurrence of cavitation phenomena. To prevent the occurrence of cavitation phenomena, the places where may pressure reduced to vapor pressure of liquid because of increase the flow velocity, should be identified. In this regard, to achieve a quantitative measure, the cavitation index can be used. In this study, two cases have been designed and simulated for Vanyar dam’s spillway using numerical models of computational fluid dynamics (CFD). Then the cavitation index was calculated for each case and finally for the verification, the results of laboratory model are used. For the numerical solution of the 3-dimensional Navier-Stokes equations and 3-dimensional gridding of the spillway, the Fluent and Gambit software are used, respectively. To determine the parameters of the flow field turbulence, the free-surface flow and the separation of momentum equations, the k – ? (RNG) turbulence model, the VOF method and the second order upwind method are used, respectively. The results indicated a proper agreement between the Fluent results and experimental model. Also it is found that in none of the considered cases, the cavitation didn’t occur and constructed spillway is safe against this phenomenon.

In designing the hydraulic structures with rapid flow, there is the probability of occurrence of cavitation phenomena. To prevent the occurrence of cavitation phenomena, the places where may pressure reduced to vapor pressure of liquid because of increase the flow velocity, should be identified. In this regard, to achieve a quantitative measure, the cavitation index can be used. In this study, two cases have been designed and simulated for Vanyar dam’s spillway using numerical models of computational fluid dynamics (CFD). Then the cavitation index was calculated for each case and finally for the verification, the results of laboratory model are used. For the numerical solution of the 3-dimensional Navier-Stokes equations and 3-dimensional gridding of the spillway, the Fluent and Gambit software are used, respectively. To determine the parameters of the flow field turbulence, the free-surface flow and the separation of momentum equations, the k – ? (RNG) turbulence model, the VOF method and the second order upwind method are used, respectively. The results indicated a proper agreement between the Fluent results and experimental model. Also it is found that in none of the considered cases, the cavitation didn’t occur and constructed spillway is safe against this phenomenon.

کلیدواژه‌ها [English]

  • Experimental model-CFD-Hydraulic parameters.-Cavitation index-