A physical hydraulic model is often a scaled-down version of the prototype (i.e., the full-scale structure). Engineers utilise physical hydraulic modeling as a design technique to improve the design of the structure, to guarantee the structure's safe functioning, and/or to simplify the decision-making process.
The Hydraulics Branch is staffed and equipped to study, by analytical methods, scale models, and field investigations, problems arising in connection with many types of projects. In the civil engineering field, the studies may include spillways, outlet works, canal chutes, drops, irrigation distribution systems, diversion works, sediment control works, river channels, ground-water flow, subsurface drainage of irrigated lands, reeration, and stratified flow in reservoirs. In the field of mechanical engineering, gates, valves, piping systems, penstocks, siphons, turbines, pumps, and closed-conduit features are studied. When an investigation is initiated by a design branch, the designers usually submit preliminary designs and specify which features are to be studied for hydraulic performance. In some instances, the request is general rather than specific. In either case, the studies, especially when a model is involved, are conducted to obtain the maximum amount of pertinent information.
Physical hydraulic models play a significant role in the planning and designing of almost all hydraulic and hydrologic structures. Whether they are stilling basins, barrage spillways, river training works, hydraulic syphons, or even basic bridges, they are often created, assessed, improved, and modified using physical hydraulic model studies. In order to ensure the accuracy and consistency of the findings, it is crucial to choose the proper scale ratios between the prototype and the model.
IRC:5 states that the “A model study may be required for bridging rivers having undefined cross section and huge flood plains”. Furthermore, in clause 106.5.1. “Hydraulic or Mathematical model studies may be required to ascertain the flow conditions, and design parameters for the training works and the required waterway”. A complete clause 106.11 in IRC: 5 is dedicated to the Hydraulic and Mathematical Model Studies.
IRC: 89 also suggested in the Clause 2.3 - For bridges across major rivers, the extent and configuration of the protective works should be decided with the help of physical models and the results obtained may be further checked on mathematical models.
Furthermore, in clause 5.2.7. states – “For guide bunds of bridges across major rivers, hydraulic model studies are recommended for deciding the various design i.e., Location, length, orientation and spacing etc.
Moreover, it is advisable to conduct physical hydraulic model studies in cases where the cost of a new bridge project or additional river training works for existing bridge is substantial followed by Mathematical hydraulic model studies (Clause 11).
The rules of similitude allow to extrapolate from experiments done with far less expensive models the expected performance of hydraulic prototype constructions. The fluid for the prototype need not be the same for the model. Through testing on small scale hydraulic models, we may be able to get worthwhile results at a low cost.
The model and the prototype hydraulic structure must adhere to the following similarities:
Model and prototype should have the same forms but only vary in size according to the specified scale ratio. This would ensure geometrically similar flows. In some circumstances, distorted models are used by using various scale ratios for the lateral, longitudinal, and vertical axes, but then the same must be taken into account when interpreting the findings.
To guarantee the same kinematics of flow, ratios of the velocities at all relevant sites on the model and prototype hydraulic structure should be the same.
To guarantee the identical dynamics of the flow, all forces acting on the corresponding places on the prototype and model should have the same quantum and direction.
The Froude Law, Reynolds Law, Mach Law, etc. may be used to assure similarity of the forces combined, which will also ensure dynamic similarity.
We perform a wide variety of operations in our lab, including the analysis and evaluation of hydraulic systems, the development of new hydraulic technologies, the improvement of current hydraulic systems, and the research-based investigation of fluid dynamics and related topics.
