تحلیل دینامیکی نیروی کشانه، تنش بیشینه کششی و محاسبه موقعیت برش در گیاهان منعطف غیرمستغرق

نویسندگان

چکیده

تحلیل رفتار متقابل گیاه و جریان برای تعیین درجه محافظت از سیل در بخش کشاورزی،‏ مهم است. در این مقاله یک روش تحلیلی برای بررسی منحنی خمش گیاهان منعطف و نقطه شکست آن‌ها در شرایط غیرمستغرق برای حالت دینامیک ارائه شده است. نتایج نشان داد که تحت شرایط یکسان هیدرولیکی نقطه شکست برای گیاهان منعطف با قطر ثابت،‏ در قاعده گیاه است ولی این نقطه برای گیاهان با قطر متغیر به سمت بالا حرکت می‌کند. همچنین میزان خم‌شدگی با افزایش قطر ساقه و ثابت بودن سایر عامل‌ها به‌دلیل افزایش نیروی کشانه،‏ افزایش می‌یابد. نتایج نشان داد برای گیاهان مخروطی،‏ خمش کل بیشتر از گیاهان با قطر ثابت است. همچنین برای گیاهان با قطر غیریکنواخت میزان خمش بیشتر است و هرچه گیاه منعطف‌تر باشد محل وقوع بیشینه خمش،‏ به سمت بالا منتقل می‌شود که این امر زبری جریان را تحت تأثیر قرار می‌دهد.

کلیدواژه‌ها


عنوان مقاله [English]

A dynamic analysis for determining the drag force, maximum tensile stress and rupture point of submerged flexible plants

نویسندگان [English]

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چکیده [English]

The investigation of plants behavior under different flow conditions, because of the interaction between "depth and flow velocity " and also "the amount and type of plant bending and its rupture point", is a complicated phenomena. In this research, a dynamic analytical method is introduced to investigate the bending curve of flexible plants, maximum tensile stress, critical rupture condition and the rupture point in submerged condition. The results indicate that the rupture point locates near the base of flexible plants with uniform diameter, while it shifts upward for the others with a non-nuniform diameter. In this regard, the rupture point will move toward the water surface when the difference between the plant diameter at the top and bottom of which increases. Moreover, when plant's stem diameter increases, the plant experiences more drag force; that is, the amount of bending will increase when other factors remains fixed. Plants with non uniform diameter have larger deflection, and an increase in the plant flexibility will move the position of maximum deflection upward, which in turn influences the flow roughness. Additionally for flexible plants, dimensionless drag force decreases strongly with the increase of the Reynolds number; that can be translated as the presence of a less hydraulic resistance.The investigation of plants behavior under different flow conditions, because of the interaction between "depth and flow velocity " and also "the amount and type of plant bending and its rupture point", is a complicated phenomena. In this research, a dynamic analytical method is introduced to investigate the bending curve of flexible plants, maximum tensile stress, critical rupture condition and the rupture point in submerged condition. The results indicate that the rupture point locates near the base of flexible plants with uniform diameter, while it shifts upward for the others with a non-nuniform diameter. In this regard, the rupture point will move toward the water surface when the difference between the plant diameter at the top and bottom of which increases. Moreover, when plant's stem diameter increases, the plant experiences more drag force; that is, the amount of bending will increase when other factors remains fixed. Plants with non uniform diameter have larger deflection, and an increase in the plant flexibility will move the position of maximum deflection upward, which in turn influences the flow roughness. Additionally for flexible plants, dimensionless drag force decreases strongly with the increase of the Reynolds number; that can be translated as the presence of a less hydraulic resistance.The investigation of plants behavior under different flow conditions, because of the interaction between "depth and flow velocity " and also "the amount and type of plant bending and its rupture point", is a complicated phenomena. In this research, a dynamic analytical method is introduced to investigate the bending curve of flexible plants, maximum tensile stress, critical rupture condition and the rupture point in submerged condition. The results indicate that the rupture point locates near the base of flexible plants with uniform diameter, while it shifts upward for the others with a non-nuniform diameter. In this regard, the rupture point will move toward the water surface when the difference between the plant diameter at the top and bottom of which increases. Moreover, when plant's stem diameter increases, the plant experiences more drag force; that is, the amount of bending will increase when other factors remains fixed. Plants with non uniform diameter have larger deflection, and an increase in the plant flexibility will move the position of maximum deflection upward, which in turn influences the flow roughness. Additionally for flexible plants, dimensionless drag force decreases strongly with the increase of the Reynolds number; that can be translated as the presence of a less hydraulic resistance.The investigation of plants behavior under different flow conditions, because of the interaction between "depth and flow velocity " and also "the amount and type of plant bending and its rupture point", is a complicated phenomena. In this research, a dynamic analytical method is introduced to investigate the bending curve of flexible plants, maximum tensile stress, critical rupture condition and the rupture point in submerged condition. The results indicate that the rupture point locates near the base of flexible plants with uniform diameter, while it shifts upward for the others with a non-nuniform diameter. In this regard, the rupture point will move toward the water surface when the difference between the plant diameter at the top and bottom of which increases. Moreover, when plant's stem diameter increases, the plant experiences more drag force; that is, the amount of bending will increase when other factors remains fixed. Plants with non uniform diameter have larger deflection, and an increase in the plant flexibility will move the position of maximum deflection upward, which in turn influences the flow roughness. Additionally for flexible plants, dimensionless drag force decreases strongly with the increase of the Reynolds number; that can be translated as the presence of a less hydraulic resistance.

کلیدواژه‌ها [English]

  • Rapture point-Dynamic analysis-Maximum tensile stress-Unsubmerged Flexible Plant.-Drage Force-