اثر زبری سیلاب‌دشت بر هیدرولیک جریان در مقاطع مرکب با سیلاب‌دشت غیر‌منشوری

نویسندگان

چکیده

در این پژوهش،‏ اثرات زبری سیلاب‌دشت بر هیدرولیک جریان در مقاطع مرکب با سیلاب‌دشت واگرا بررسی شده است. آزمایش‌ها در سه عمق نسبی،‏ سه زاویه واگرایی سیلاب‌دشت و سه زبری سطح سیلاب‌دشت انجام شد. سرعت جریان در کانال اصلی و سیلاب‌دشت در طول منطقه واگرایی (ابتدا،‏ وسط و انتهای محدوده واگرایی)،‏ با سرعت‌سنج سه‌بعدی (ADV)‎ و میکرومولینه اندازه‌گیری شده است. با استفاده از داده‌های به دست آمده،‏ مقادیر تنش‌برشی،‏ متوسط عمقی سرعت جریان،‏ ضریب‌های زبری مکانی و منطقه‌ای،‏ مقادیر آشفتگی و نحوه تقسیم دبی بین کانال اصلی و سیلاب‌دشت‌‌ها محاسبه شد. نتایج نشان داد که در مقطع غیرمنشوری با افزایش زبری سیلاب‌دشت،‏ نسبت سرعت متوسط جریان در سیلاب‌دشت‌ها به کانال اصلی در حدود 31 درصد کاهش و در حدود 25 درصد مقدار آشفتگی جریان افزایش می‌یابد. همچنین با افزایش این عامل،‏ تنش‌برشی بستر در محل اتصال کانال اصلی به سیلاب‌دشت و در وسط واگرایی از 26 درصد به 48 درصد افزایش می‌یابد. با افزایش عمق نسبی از 15‎/0 به 35‎/0 مقادیر عددی پارامترهای مذکور به طور چشمگیری کاهش می‌یابد.

کلیدواژه‌ها


عنوان مقاله [English]

The effect of floodplain roughness on hydraulics of flow in compound channels with non-prismatic floodplains

نویسندگان [English]

  • Hojjatollah Yonesi
  • Mohammad Hosein Omid
  • Seyed Ali Ayyoubzadeh
چکیده [English]

This paper investigates the effects of roughness of the flood plain on hydraulic overbank flow in a compound channel with non-prismatic floodplains. Experiments are done using three depth ratio, three divergence angles and three-roughness size of the floodplain. The flow velocity was measured using a three dimensional Acoustic Doppler Velocimeter (ADV) and directional current meter in a lattice along the divergence channel in three sections of the flume (entrance, middle and end of the divergence) with a different depth ratio. Using the experimental data, the values of the shear stress, depth–averaged velocity, local and zonal roughness coefficients, turbulence parameters and divided discharge between the main channel and floodplain were calculated. The results show that with increasing the floodplain roughness, in non-prismatic section, the ratio of the velocity at floodplain to main channel decreased about 31% and turbulence flow increased about 25%. Also under these conditions, the shear stress at interface zone was increased from 26 to 48%. As well as with increasing depth ratio, the above mentioned values are markedly reduced.
This paper investigates the effects of roughness of the flood plain on hydraulic overbank flow in a compound channel with non-prismatic floodplains. Experiments are done using three depth ratio, three divergence angles and three-roughness size of the floodplain. The flow velocity was measured using a three dimensional Acoustic Doppler Velocimeter (ADV) and directional current meter in a lattice along the divergence channel in three sections of the flume (entrance, middle and end of the divergence) with a different depth ratio. Using the experimental data, the values of the shear stress, depth–averaged velocity, local and zonal roughness coefficients, turbulence parameters and divided discharge between the main channel and floodplain were calculated. The results show that with increasing the floodplain roughness, in non-prismatic section, the ratio of the velocity at floodplain to main channel decreased about 31% and turbulence flow increased about 25%. Also under these conditions, the shear stress at interface zone was increased from 26 to 48%. As well as with increasing depth ratio, the above mentioned values are markedly reduced.
This paper investigates the effects of roughness of the flood plain on hydraulic overbank flow in a compound channel with non-prismatic floodplains. Experiments are done using three depth ratio, three divergence angles and three-roughness size of the floodplain. The flow velocity was measured using a three dimensional Acoustic Doppler Velocimeter (ADV) and directional current meter in a lattice along the divergence channel in three sections of the flume (entrance, middle and end of the divergence) with a different depth ratio. Using the experimental data, the values of the shear stress, depth–averaged velocity, local and zonal roughness coefficients, turbulence parameters and divided discharge between the main channel and floodplain were calculated. The results show that with increasing the floodplain roughness, in non-prismatic section, the ratio of the velocity at floodplain to main channel decreased about 31% and turbulence flow increased about 25%. Also under these conditions, the shear stress at interface zone was increased from 26 to 48%. As well as with increasing depth ratio, the above mentioned values are markedly reduced.
This paper investigates the effects of roughness of the flood plain on hydraulic overbank flow in a compound channel with non-prismatic floodplains. Experiments are done using three depth ratio, three divergence angles and three-roughness size of the floodplain. The flow velocity was measured using a three dimensional Acoustic Doppler Velocimeter (ADV) and directional current meter in a lattice along the divergence channel in three sections of the flume (entrance, middle and end of the divergence) with a different depth ratio. Using the experimental data, the values of the shear stress, depth–averaged velocity, local and zonal roughness coefficients, turbulence parameters and divided discharge between the main channel and floodplain were calculated. The results show that with increasing the floodplain roughness, in non-prismatic section, the ratio of the velocity at floodplain to main channel decreased about 31% and turbulence flow increased about 25%. Also under these conditions, the shear stress at interface zone was increased from 26 to 48%. As well as with increasing depth ratio, the above mentioned values are markedly reduced.
This paper investigates the effects of roughness of the flood plain on hydraulic overbank flow in a compound channel with non-prismatic floodplains. Experiments are done using three depth ratio, three divergence angles and three-roughness size of the floodplain. The flow velocity was measured using a three dimensional Acoustic Doppler Velocimeter (ADV) and directional current meter in a lattice along the divergence channel in three sections of the flume (entrance, middle and end of the divergence) with a different depth ratio. Using the experimental data, the values of the shear stress, depth–averaged velocity, local and zonal roughness coefficients, turbulence parameters and divided discharge between the main channel and floodplain were calculated. The results show that with increasing the floodplain roughness, in non-prismatic section, the ratio of the velocity at floodplain to main channel decreased about 31% and turbulence flow increased about 25%. Also under these conditions, the shear stress at interface zone was increased from 26 to 48%. As well as with increasing depth ratio, the above mentioned values are markedly reduced.

کلیدواژه‌ها [English]

  • Bed shear stress-Angle of divergence-Non-prismatic compound channel-Roughness ratio.-