Presently, physical modelling still plays a fundamental role in the analysis of the hydraulic structures behavior and as design support tool. Actually, water flows in hydraulic structures are highly turbulent and, in most of the cases, associated to significant air entrainment, its simulation being rather complex.
Therefore, the flow behavior analysis in hydraulic structures based on physical models is seen as a quite convenient approach, its use being clearly justified, namely, when dealing with projects involving important investment amounts. From the design point of view, these studies allow a suitable validation and optimization of the project solutions, allowing also ensuring or increasing the efficiency, economy and safety of the hydraulic schemes.

Although the use of physical models being widely used for the study of spillways, they are also quite often used to study the flow conditions of bottom outlets and hydraulic circuits, particularly the intakes and tailraces components. Presently LNEC is carrying out several hydraulic physical model studies of Portuguese large hydropower schemes, namely those included in the National Plan for Dams with High Hydroelectric Potential, as it is the case of Foz Tua dam Spillway and hydraulic circuit, Daivões, Alto Tâmega and Girabolhos dams’ spillways and both upstream and downstream dams’ spillways of Fridão scheme. 

Considering the involved flows complexity, experimental approach is still a key tool for the analysis and characterization of involved flows. In the meantime, considerable progress has been witnessed in the research field of hydraulic structures, mainly due to the increasing availability of powerful computing means and advancements on measuring and monitoring instruments. The new methodologies and instrumentation allowed incremental progress on quality and quantity of measured data, as well as the possibility to measure some parameters for which there weren’t any available measurement means until recently. Also, imagery data processing techniques coupled with robust computing means allowed an important leap in the flow visualization and characterization.  
Recent advances of the computational flow models and computers are opening new doors for the research on hydraulic structures by means of numerical models.