Sung-Koo Kang

Abstract Laboratory experiments have yielded evidence suggestive of large-scale meandering motions in the wake of an axial flow hydrokinetic turbine in a turbulent open channel flow (Chamorro et al. , J. Fluid Mech. , vol. 716, 2013, pp. 658–670). We carry out a large-eddy simulation (LES) of the experimental flow to investigate the structure of turbulence in the wake of the turbine and elucidate the mechanism that gives rise to wake meandering. All geometrical details of the turbine structure a

[1] Large-eddy simulation of turbulent flow through a natural-like meandering channel with pool-riffle sequences installed in the St. Anthony Falls Laboratory Outdoor StreamLab is carried out to elucidate the hydrodynamics at bankfull flow condition. It is shown that the shallow flow in the riffle is dominated by the presence of large-scale roughness elements that enhance turbulent mixing; increase turbulence anisotropy; and induce multiple, streamwise secondary cells driven by turbulence anisot

Abstract Flume experiments were conducted to investigate the three‐dimensional flow structure and turbulent flow mechanisms around a nonsubmerged, sidewall‐attached rectangular spur dike with a low length‐to‐depth ratio. Velocity measurements show that the wake of the spur dike in the middepth region consists of a single, large recirculation zone, while that in the near‐bed region is composed of a horizontal recirculation zone and a corner vortex with its axis perpendicular to the flume sidewall

The predictive capabilities of an isotropic, eddy viscosity turbulence model for closing the unsteady Reynolds‐averaged Navier‐Stokes (RANS) equations are systematically investigated by simulating turbulent flow through a field‐scale meandering channel and comparing the computed results with the large‐eddy simulation (LES) of the same flow recently reported by Kang and Sotiropoulos (2011). To facilitate the comparison of the two turbulence models, both RANS simulation and LES are carried on exac

Summary An improved near‐wall modeling for large‐eddy simulation using the immersed boundary method is proposed. It is shown in this study that the existing near‐wall modeling for the immersed boundary (IB) methods that imposes the velocity boundary condition at the IB node is not sufficient to enforce a correct wall shear stress at the IB node. A new method that imposes a shear stress condition through the modification of the subgrid scale‐eddy viscosity at the IB node is proposed. In this meth

The three-dimensional flow structure and turbulence characteristics around a non-submerged rectangular obstacle in an open channel are explored using numerical simulation. In particular, a low length-to-depth ratio condition, shown to be associated with three-dimensional flow features in our previous study, is considered. To sufficiently resolve all the important details of the three-dimensional turbulent flow around and in the entire wake of an obstacle, high-resolution large-eddy simulation (L

We investigate the flow dynamics around a rock vane, a widely used instream structure for stream restoration, by conducting laboratory flume experiments, and carrying out high-resolution Large Eddy Simulation (LES) taking advantage of parallel computing. The flume experiments are conducted under fixed- and mobile-bed conditions, where the velocities and bed elevations are measured, respectively. The LES is carried out for the fixed-bed experiment by directly resolving the details of the rocks th

Large-eddy simulation (LES) of a three-dimensional, turbulent free surface flow past a stream restoration structure with arbitrarily complex geometries is presented. The three-dimensional, incompressible, spatially filtered Navier-Stokes and continuity equations are solved in generalized curvilinear coordinates. For the solution of mixed air-water flows, the curvilinear immersed boundary (CURVIB)–level set method developed previously is used and extended to carry out LES. Complex solid geometrie