This paper describes the experimental study of a behavioural barrier consisting of a bubble curtain placed near an ecological river water intake, aiming to assess the bubble curtain’s influence on the velocity field of water flowing in the water intake proximity. The scientific novelty is given by the water intake solution operating in tandem with the dedicated bubble curtain generator used for avoiding fish entrapment. The water intake solution used in the present research is based on a run-of-river intake without a dam in the riverbed, maintaining the mountain rivers longitudinal connectivity. An experimental setup was designed and built to study the behavioural barrier for ecological water intakes in different operating conditions. Thus, tests were performed for two water velocities (0.33 m/s and 0.535 m/s) in the experimental setup, two water depths (92 mm and 119 mm) and two air flow rates (10.5 LPM and 15 LPM). The results were compared with the case when no air is injected through the bubble curtain generator. The assessment of the bubble curtain influence on the water flow inside the channel was made by measuring and analysing the velocity variation in vertical and horizontal direction. The results showed a significant velocity gradient in the bubble curtain proximity, which can contribute to influencing the behaviour of the fish by deterring them from the water intake area.

Different scenarios of an arch-dam breach and their impact on the time-space evolution of flood waves are analysed using numerical modelling. As the accidents involving this type of dam are among the most catastrophic ones, the 108 m in height Paltinu arch-dam, Romania, was chosen as a case study due to its problems in the past. Three dam breach magnitudes and two inflow hydrographs for the worst-case scenario of Normal Operating Pool elevation in the reservoir were chosen as variable parameters, to assess their influence on the dam break wave characteristics and downstream flooded areas. The flood was routed along the 18 km reach of the Doftana River down to the confluence with the Prahova River. A 2D numerical model was set up with the help of HEC-RAS software, which was also used to analyse the resulting hazard maps under a GIS environment. Comparison of inundation boundary, maximum depths and velocities, as well as the arrival time at control sections allow for conclusions to be drawn. These predictive results of shape, magnitude, and time to peak of the flood waves are essential for flood risk management to obtain the risk maps, estimated damage costs, and possible affected areas.

Wind energy represents one of the main sources of renewable energies. Innovation in wind turbine technology tends to focus on increasing energy production, especially at low wind velocities. Vertical axis wind turbines could have a greater expansion because they have many advantages, such as the capacity to start at low wind velocities and no need for orientation to the wind direction. The present paper analyses numerically and experimentally, a Savonius-Darrieus hybrid wind system on a common vertical shaft. CFD modeling and simulation show a slight instability at low velocities, up to entering the nominal working regime of 2-3 m/s, but also the separation of vortices and the fluid-blade interaction at over 9 m/s. At higher velocities, the performances and the power coefficients decrease, observations demonstrated also experimentally within the study. The optimal wind velocity for the Savonius-Darrieus vertical turbine is 6 m/s.

A small Savonius wind turbine of helical type was tested in an open jet wind facility for identifying the optimum position of the rotor blades aiming the maximization of static torque. The two blades of the wind turbine of U shape were twisted up to 180⁰ from bottom to top and three values for blade overlap were considered i.e. 0.35, 0.2 and 0.0. The turbine torque was measured for no load conditions and wind velocities between 2-8 m/s. In the same time the air flow through Savonius rotor was observed by using a visualization setup aiming to identify the correlation between the torque and the flow pattern inside the returning blade at rotating angles where the torque has highest values. Best results for the torque coefficient of 0.72 and power coefficient of 0.265 were obtained at a wind velocity of 5.8 m/s and low overlap ratio of 0.2. By measuring the overall torque of the rotor for each case study, the positive effect of pressure recovery was explained as a result of air flow through the blade overlap from the concave side of the advancing blade to concave side of the returning blade for a certain interval of the rotating angle a = 50-60°.

The paper is concerned with experimental studies and numerical modelling of the air flow around blunt bodies (cylinder, aerodynamic profile) inside a wind tunnel. The range of the investigated Reynolds numbers is 12000<Re<35000. The main goal of the work is to establish a CFD procedure to analyse the flow pattern in the vicinity of the bodies and to predict the position of the boundary layer detachment. The computations are performed with several turbulence models implemented in the ANSYS Fluent code. The direct visualizations and the numerical results are corroborated, with the aim to investigate the positions of the separation points and the flow spectrum developed downstream the bodies.

Dam failures are low-probability but high-consequence events which require hydraulic modelling studies for hazard assessment. A hypothetical failure of the 127 m Bicaz gravity Dam, Romania, is investigated using a 2D model developed in HEC-RAS along a 115 km reach of Bistrita River, in Romania. Six failure simulation scenarios are considered during incoming flood and normal-flow conditions, combined with three rectangular shape breach areas (for a various number of monoliths failure) in case of a sabotage event. The main purpose of the study is to analyse the flood wave dynamics downstream of an area with multiple other smaller dams, dykes, and reservoirs. Peak flow attenuation and arrival times of the front were mainly investigated down to Piatra Neamț and Bacău cities. In the downstream full reservoirs, the velocity and flow hazard increase and water spills over the contour dikes, whereas in an empty reservoir, the flood wave is attenuated, and the same hydraulic parameters decrease. A new reservoir filling time parameter also shows higher values in the empty reservoir. Maximum flood depths, velocities, hazard, and inundation boundaries are examined along the river. A preliminary assessment of hazard and exposure of buildings, performed in QGIS for Piatra Neamț city, shows that the impact of such a flood wave would be catastrophic. The results of this study are very useful to provide information for such a catastrophic failure and to support emergency planning.