PYSICAL MODEL STUDY OF FLOOD PROPAGATION DUE TO DAMBREAK ON A VARIETY OF BUILDING CONFIGURATION PATTERNS

• Main Author: Pratiwi, Vitta
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/51359
• Institution: Institut Teknologi Bandung

The importance of dam safety was emphasized by two dam failures that occurred in Indonesia, namely the Gintung Dam (Banten Province) in 2009 (previously known as Situ Gintung) and the Way Ela Natural Dam (Maluku Province) in 2012. These two incidents have prompted the government to increase its preparedness for disasters and planning to minimize the potential impacts associated with dam failures. This phenomenon is very important to be investigated further because flow problems due to dambreaks like this have occurred in many residential areas and cause significant material and non-material losses. To reduce this risks, a better understanding of dambreak phenomenon is needed. Information regarding the flow profile that occurs in the built-up area can be analyzed based on the dambreak flow that occurs around the building which is simplified through a physical model. Therefore, it is necessary to study the physical model of flood propagation due to dambreak in various patterns of building configurations as energy absorbers. Thus it can be seen that the special treatment on the physical model is related to the influence of the building structure in providing the greatest damping effect. To model conditions similar to conditions in the field, a physical model is made using a flume, which uses a sudden opening mechanism as a simulation of the flow due to dambreaks. In this study, a physical model of flood propagation due to embankment collapse will be developed at the ITB Hydraulic Laboratory, with a channel size of 10 m long and 1 m wide, then the reservoir size is 4 m long and 2 m wide. The flood flow is modeled as a flash flood due to the movement of large water masses with the sudden opening of the floodgates. As an analogy for a simple energy-absorbing building using 10x10x40 wooden blocks. The numerical model to be used is a 3D model, 3D Flow modeling based on the three-dimensional Navier Stokes equation consisting of the continuity equation, the momentum equation and the three-dimensional fluid energy equation. The modeling results are in the form of surface flow characteristics which include height, velocity of propagation, energy attenuation and froude number. The shape of the building greatly affects the water level where for the water level profile, the highest depth for the comparison of all building configurations at the point in front of the building occurs in the configuration of 3 square buildings. Barriers with a rhombus shape have a bigger shadow zone influence behind the building so that the flow has a longer lag time and distance than the rectangular shape before the flow depth rises again after hitting the building. The velocity that occurs is influenced by the depth of the reservoir for a configuration without a building, where the velocity at the observation point increases with the increase in the volume of storage and this increase in velocity is linear with the depth of the reservoir. However, when the flow on the reservoir depth does not have a significant effect as seen in the velocity profile graph against time. The highest velocity for all configurations at the observation point near the door occurs in the configuration of 3 rhombus buildings while the far point behind the building occurs in 2 longitudinal buildings. square. The largest energy change for the configuration without buildings is seen in the first 2 seconds after that the energy change is not too large as seen in the longitudinal profile graph. In the longitudinal profile energy graph, it can be seen in the image above where the reservoir depth affects the value of the graph. The amount of energy that occurs looks different for the observation points in front of and behind the building. The building effect causes a significant reduction in the amount of energy that occurs behind the building. The depth of the reservoir has a very significant effect in causing changes in flow in the configuration without buildings, but after construction the depth of the reservoir does not really affect the Froude number. In the first 5 seconds most of the flow is supercritical due to the effect of the sudden opening of the door after the 5th second the flow that occurs is subcritical. The novelty resulting from this study is the relationship between the influence of the arrangement (layout) of energy damper buildings on the flow characteristics of wave propagation due to dambreak, namely the depth of flow, velocity of propagation, energy that can be damped and Froude's number to determine the type of flow that occurs. In addition, in the data processing method, the image processing method (imaged processing) is used by using the Python model which helps facilitate reading of the results of running water levels. The benefit of this research is to provide information on the influence of flood propagation due to dambreak which is useful for assessing the feasibility of reservoirs, reservoirs and ponds with dense buildings in their vicinity. This assessment can be used to take considerations to redesign reservoirs, reservoirs and ponds and surrounding settlements as part of disaster mitigation. This research application can also be used to determine the spread of flooding in settlements in urban areas.