Abstract:
Throughout the planning and design of hydraulic structures, engineers and researchers are
increasingly integrating computational fluid dynamics (CFD) into the process. Despite reports
of success in the past, there is still no comprehensive assessment that assigns ability to CFD
models to simulate a wide range of different spillways configurations.
The complementary spillway of Salamonde dam, located in the north of Portugal, is controlled
by an ogee crest and two radial gates, followed by a free surface flow tunnel, with a rather
complex geometry, and a terminal ski jump which directs the jet into the river bed. The present
paper analyses the ability of a CFD model (FLOW-3D) to simulate the flows along this
spillway.
The spillway was primarily tested and developed in a physical model built in the National
Laboratory for Civil Engineering (LNEC), where discharges and flow depths were measured in
ten defined cross-sections for four different gate openings conditions. These results were used
to calibrate the numerical model and to analyze the differences between physical and
numerical models results.
It is shown that there is an accurate agreement between physical and numerical model
discharges. Concerning the flow depths, the FLOW-3D represents reasonably well the flow
behavior, but slightly underestimates the flow depth in some points of the cross-sections. A
sensitivity analysis for the conditions and parameters of the numerical model (e.g., 1st vs 2nd
order momentum advection, turbulent mixing length TLEN, mesh size) was carried out.
According to FLOW-3D results, for a certain reservoir level, spillway discharge and flow depth
are highly dependent on mesh size.
Conclusions about the most adequate FLOW-3D options to adopt are presented. The calibrated
model was used to simulate the spillway design discharge and to assess the hydraulic behavior
of the outlet structure and of the jet impingement characteristics. The pressure distribution in
specific cross-sections was also assessed.
