پديد آورندگان :
محمدزاده، پيمان دانشگاه رازي - گروه مهندسي عمران، كرمانشاه , جوان، ميترا دانشگاه رازي - گروه مهندسي عمران، كرمانشاه , اقبال زاده، افشين دانشگاه رازي - گروه مهندسي عمران، كرمانشاه , مروتي، خسرو دانشگاه رازي - گروه مهندسي عمران، كرمانشاه
كليدواژه :
كانال مركب , سيلاب دشت , همگرايي , شبيه سازي عددي , فلوئنت
چكيده فارسي :
كانال‌هاي مركب، مقطع عرضي بسياري از رودخانه‌ها خصوصاً در بازه‌هاي مجاور مناطق مسكوني و زراعي را تشكيل مي‌دهد. بررسي رفتار هيدروليكي آن‌ها، در طرح‌هاي كنترل سيلاب و ساماندهي رودخانه‌ها اهميت فراواني دارد. در تحقيق حاضر، الگوي جريان و سطح آزاد آب در يك كانال مركب همگرا با بهره‌گيري از مدل آشفتگي RSM و روش VOF شبيه‌سازي شده است. مقايسه تغييرات طولي تراز سطح آب، سرعت متوسط گيري شده در عمق و ظرفيت انتقال دبي توسط سيلاب‌دشت‌ها با نتايج آزمايشگاهي نشان دهنده قابليت مدل عددي در شبيه‌سازي الگوي جريان دركانال مركب همگرا مي‌باشد. با مقايسه الگوي جريان در كانال مركب همگرا براي عمق نسبي‌هاي مختلف مشخص گرديد، اختلاف سرعت ايجاد شده بين سيلاب‌دشت و كانال اصلي باعث بروز ساختار جريان پيچيده در عمق نسبي‌هاي كم مي‌شود، اين اختلاف سرعت باعث به وجود آمدن جريان‌هاي ثانويه در مقطع عرضي كانال شده و با افزايش عمق نسبي جريان‌هاي ثانويه حذف مي‌شوند. جريان‌هاي ثانويه ايجاد شده باعث افت انرژي شديد در عمق نسبي‌هاي كم مي‌شوند. همگرايي در كانال مركب، ظرفيت انتقال دبي توسط سيلاب‌دشت‌ها را كاهش مي‌دهد چنانچه در عمق نسبي 1/0، سيلاب‌دشت‌ها كم ترين مقدار دبي را انتقال مي‌دهند.
چكيده لاتين :
Flooding of rivers is accompanied with a threat on the population living on their floodplains and on the neighboring settlements. Accurate modeling of such flows is thus imperative to assess flood risks, perform real-time flood routing, or estimate the impact of a mitigation schema.The converging of the compound channel causing the flow become even more complicated. The flow patterns in converging compound channel and free-surface profile has been simulated by using RSM turbulence model and VOF method, respectively. The comparison of the experimental results including longitudinal free surface profiles, depth-averaged velocity distribution and the ratio between floodplains and total discharge confirmed that the numerical simulation can be used to model the flow pattern in converging compound channel. Furthermore, Absolute Percentage Error (APE) for each of these parameters was amounted to 3.25%, 4.66% and 9.72%, respectively. Respectto the numerical simulation capability in anticipating the flow field parameters, we investigated the effect of relative depth on the flow patterns in a converging compound channel. Moreover, the flow parameters including velocity distribution, depth-average velocity, secondary flows, ratio between floodplain and total discharge, bed sheer stress and energy dissipation were investigated in different relative depths h* (0.1, 0.2, 0.3, 0.4 and 0.5). By evaluating and comparing the flow results in the different relative depths, we came to conclusion that the longitudinal-average velocity in the main channel increased as the cross section was narrowed. However, the longitudinal-average velocity in the floodplains decreased in the relative depths of 0.1 and 0.2 as the cross section was narrowed. In contrast, this parameter increased in the relative depths of 0.3, 0.4 as well as 0.5 the floodplains narrowed. Velocity gradient between the main channel and floodplains in the relative depth of 0.1 was strong and in the relative depth of 0.5 was insignificant. In the smaller shallow depth, this velocity gradient has been resulted in secondary flow in the cross section of converging compound channel. Accordingly, in the relative depth of 0.1 and 0.2 four cells of secondary flows were formed and in the relative depth of 0.3 just two cells of secondary flowswere formed. The secondary flows in the relative depths of 0.4 and 0.5 was eliminated. Convergence in the length of main channel get the discharge conveyance copacity of floodpland to decrease.furthemore by decreasing the relative depth the capability of floodplains to conveance the discharge was significantly dicreasead. This decrease was evident in the depth of 0.1 in which the ratio between floodplain and total discharge was amounted to 2.52%. Sheer stress in channel bed increased when the relative depth of the main channel increased and the maximum amount of bed shear stress was happened at end of the channel. On the other hand, in the floodplains, this parameter decreased along with the converging in the lower relative depths (0.1, 0.2) and for the other relative depths the bed sheer stress increased along with converging. In channel inlet the maximum and minimum amount of energy dissipation was resulted at the relative depth of 0.1 and 0.5 repectively
