Coupled physical-numerical analysis of flows in natural waterways

The recent digital-electronic revolution has helped experimental hydraulics benefit from a new generation of acoustic-, laser-, and imaging-based inst rumentation. These newly developed techniques are not only of superior accu racy, but they have also expedited data collection. Powerful visualization software has been used increasingly to present and interpret experimental r esults. In addition, numerical models have become increasingly available in some cases providing turnkey solutions to complex flows. The outcome of th is intensive development is powerful computer-based research tools that all ow an unprecedented interaction between physical and numerical experiments. This integrated approach is considerably improving our understanding of nu merous aspects and practical consequences of flow mechanics and allows a co mprehensive treatment of space-time processes in fluid flows which is diffi cult to obtain using alternative means. This holistic experimental-numerica l approach is readily available for integration as expert-systems or decisi on-making programs in hydroinformatics systems. The present paper discusses the beneficial synergy between laboratory measu rements and computational models of different levels of complexity. A study , conducted at the Iowa Institute of Hydraulic Research (IIHR) is presented herein as an example to demonstrate the interaction among the three invest igation components, namely, laboratory measurements, the kinematic model, a nd the hydrodynamic model, as well as the benefits and limitations of each of them. The laboratory velocity measurements were made using three-compone nt Acoustic-Doppler Velocimeters. A simple numerical model based exclusivel y on flow kinematics was used to empower results visualization and to provi de insight in several flow features. The kinematic model feedback was used to optimize the data acquisition scheme for the ensuing measurements. The d etailed hydrodynamic flow analysis for regions with complex three-dimension al flows was obtained by a numerical model that solves the Reynolds Average d Navier-Stokes (RANS) equations in general curvilinear coordinates.