مطالعه‌ي آزمايشگاهي تاثير ضريب شكل مخزن در خصوصيات سيلاب ناشي از شكست سدها

Experimental Study of the Effect of Reservoir Shape Factor on Dam-Break Flow Characteristics

هدف از اين پژوهش، يافتن ارتباط بين ضريب شكل مخزن سدها و خصوصيات جريان سيلاب به‌ويژه عدد فرود در پديده‌ي شكست سد به‌وسيله‌ي يك مدل فيزيكي است. به اين منظور، آزمايش‌‌ها بر روي يك مدل فيزيكي شبيه‌سازي پديده‌ي شكست سد در آزمايشگاه هيدروليك دانشگاه صنعتي اميركبير انجام شده است. اندازه‌گيري سرعت در نقاط مختلف كانال به وسيله‌ي سرعت‌سنج ADV و اندازه‌گيري تغييرات سطح آب به وسيله‌ي حس‌گرهاي آلتراسونيك انجام شده است. با داشتن تغييرات سرعت و تغييرات تراز سطح آب، دبي ناشي از شكست سد محاسبه شده و هيدروگراف مربوط براي هر يك از ضرايب شكل مخازن ترسيم شده است. آنگاه رابطه‌ي بين عدد فرود و ضريب شكل مخزن سد به‌دست آمده است. نتايج آزمايشگاهي در مقايسه با نتايج داده‌هاي شكست واقعي سدها در گذشته، نشان داده است كه روند تغييرات سازگاري مناسبي با نتايج جمع‌آوري ناشي از شكست سدها دارد.

Flooding induced by large dam breaks causes severe and heavy damages to human lives and civil facilities. Knowing the volume and direction of the flood spreading, due to the breaking of a certain dam, in advance, may allow us to specify the areas prone to flood damage and help the institutions in charge to be on full alert before catastrophe occurs. The main aim of this research is to study the influence of the shape factor of a dam reservoir on a flood hydrograph, induced due to a dam break, by means of a physical model in the laboratory. Thus, the sudden dam break phenomenon has been modeled in the hydraulic laboratory of Amirkabir University of Technology. Different tests have been planned and carried out in the laboratory for shape factors ranging from 0.040 to 0.557. Hence, 7 series of reservoir with different dimensions and geometry have been built and tested. To measure the flow velocity and also the variations of water level at different points of the channel, the ADV speed meter and Ultrasonic and Micro sonic sensors were used, respectively. Having the variations of velocity and water level, the flow rate, due to dam break, is calculated and the corresponding hydrograph for each reservoir shape factor is obtained. Finally, the obtained hydrographs are evaluated and compared, and a correlation between the reservoirs shape factor and the Froude Number is developed. The experimental data were compared with those obtained from different actual dam break case histories. Although good agreement between the trends was found, large deviations from actual cases were observed. This may be due to several simplified procedures applied to the physical model developed in the laboratory to study the phenomenon. Thus, more sophisticated models with larger capabilities are needed to reach more accurate and reliable results in future research.