2012 Annual Report
1a.Objectives (from AD-416):
Perform hydraulic experiments specifically designed to validate the performance of numerical models used to predict the movement of a flood wave resulting from a dam break.
1b.Approach (from AD-416):
Numerical models are an important tool used in many areas of engineering and science that allow for rapid, inexpensive simulation of a variety of conditions. Accurate numerical modeling requires calibration by laboratory or field data. This helps to ensure that the model adequately captures the physics of the physical system and gives a standard to use in model testing and development. The need for calibration is especially relevant for hydraulic models, where bulk flow and turbulent quantities interact with structures such as streambeds, stream banks, dams, etc., in very complex ways. A new hydraulic model testing facility is to be constructed and housed at the National Sedimentation Laboratory. The facility will be designed and built for measuring transient flow during dam break scenarios. The design will also allow for convenient reconfiguration to meet future needs for model calibration and validation. High speed cameras and acoustic sensors will be used to record water surface profile data that will be compared to model results.
The three general configurations which the facility will be designed for are as follows: 1. Simple dam break—non channelized flow. The downstream area will be wide with respect to the breach and can be equipped with or without sidewalls. Both dry and wet downstream conditions will be possible. Allowances will be made to add obstacles to the flow such as positive cutlines that are high or overtoppable and negative cutlines (dips, cuts). 2. Simple dam break—channelized flow. Configurable with/without bends with a free overfall at the end of test section. Wet or dry downstream with obstacles such as positive cutlines that are high or overtoppable and negative cutlines. 3. 1D-2D coupling with channel in line with dam breach and with/without irregular sidewall heights.
Validation of numerical models is essential if physically realistic, reliable models are to be developed. There is a particularly strong need for validation and calibration for hydraulic models, where complex interactions between bulk flow and turbulent quantities are caused by the presence of structures such as streambeds, stream banks, dams, etc. A new hydraulic model testing facility, designed to calibrate and validate numerical models of transient flow during dam break scenarios, was constructed at the National Sedimentation Laboratory in Oxford, Mississippi. The design also allows for convenient reconfiguration to meet future needs for model calibration and validation. During FY 12, the design, construction, testing, and collection of performance data were completed. This includes the implementation of a system of high-speed cameras to capture transient flow and its topography, the construction of an automated rapid gate system, and development of processing algorithms to make use of the data collected during dam break experiments. Monitoring activities included site visits, emails, meetings, and telephone calls on at least a monthly basis.