Large-eddy simulation of a hydrokinetic turbine mounted on an erodible bed

Marine and hydrokinetic (MHK) energy from free-flowing waves, tides and currents comprises an important source of clean and renewable energy. The development of technologies for harnessing MHK energy and assessing its environmental effects is still at early stage. In this work, we develop a computational model for simulating hydrokinetic turbines with bed-load sediment transport under clear-water scour conditions. Turbulent flow is simulated using large-eddy simulation (LES). The bed surface elevation is simulated by solving the non-equilibrium continuity equation, the so-called Exner-Polya equation. The turbine blades are parameterized as actuator lines. The developed model is applied to simulate the flow past an axial-flow hydrokinetic turbine mounted on an erodible bed in an open channel. A good agreement with measurements is obtained. The effects of turbine operating conditions and sediment particle sizes on the bed-load sediment transport are then examined. Finally the turbine wake characteristics are investigated for a rigid flat bed and the eroded bed under different turbine operating conditions.

[1]  Fotis Sotiropoulos,et al.  Sand waves in environmental flows: Insights gained by coupling large-eddy simulation with morphodynamics , 2016 .

[2]  F. Sotiropoulos,et al.  Numerical simulation of sand waves in a turbulent open channel flow , 2014, Journal of Fluid Mechanics.

[3]  Fotis Sotiropoulos,et al.  Computational and experimental investigation of scour past laboratory models of stream restoration rock structures , 2013 .

[4]  Tim Stallard,et al.  Modelling a Tidal Turbine in Unsteady Flow , 2008 .

[5]  E. Foufoula‐Georgiou,et al.  Marine-hydrokinetic energy and the environment: Observations, modeling, and basic processes , 2012 .

[6]  Xiaolei Yang,et al.  A smoothing technique for discrete delta functions with application to immersed boundary method in moving boundary simulations , 2009, J. Comput. Phys..

[7]  Jørgen Fredsøe,et al.  Sediment Ripples and Dunes , 1982 .

[8]  J. Roberts,et al.  Simulating environmental changes due to marine hydrokinetic energy installations , 2010, OCEANS 2010 MTS/IEEE SEATTLE.

[9]  F. Sotiropoulos,et al.  High-resolution numerical simulation of turbulence in natural waterways , 2011 .

[10]  F. Porté-Agel,et al.  Simulation of Turbulent Flow Inside and Above Wind Farms: Model Validation and Layout Effects , 2012, Boundary-Layer Meteorology.

[11]  C. Meneveau,et al.  Large eddy simulation study of fully developed wind-turbine array boundary layers , 2010 .

[12]  Fotis Sotiropoulos,et al.  Experimental and computational investigation of local scour around bridge piers , 2012 .

[13]  I. Bryden,et al.  Laboratory-scale simulation of energy extraction from tidal currents , 2008 .

[14]  Jens Nørkær Sørensen,et al.  Tip Loss Correction for Actuator/Navier–Stokes Computations , 2005 .

[15]  Fotis Sotiropoulos,et al.  Curvilinear immersed boundary method for simulating fluid structure interaction with complex 3D rigid bodies , 2008, J. Comput. Phys..

[16]  K. Rados,et al.  Wake Effects in Tidal Current Turbine Farms , 2002 .

[17]  P. Moriarty,et al.  A large-eddy simulation study of wake propagation and power production in an array of tidal-current turbines , 2013, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[18]  Markus Uhlmann,et al.  Interface-resolved direct numerical simulation of the erosion of a sediment bed sheared by laminar channel flow , 2014, 1409.0339.

[19]  F. Sotiropoulos,et al.  Numerical simulation of large dunes in meandering streams and rivers with in-stream rock structures , 2015 .

[20]  Jens Nørkær Sørensen,et al.  Tip loss corrections for wind turbine computations , 2005 .

[21]  L. Chamorro,et al.  On the interaction between a turbulent open channel flow and an axial-flow turbine , 2013, Journal of Fluid Mechanics.

[22]  C. Hill,et al.  Interaction between instream axial flow hydrokinetic turbines and uni-directional flow bedforms , 2016 .

[23]  Fotis Sotiropoulos,et al.  Simulation-Based Approach for Stream Restoration Structure Design: Model Development and Validation , 2014 .

[24]  F. Sotiropoulos,et al.  On the onset of wake meandering for an axial flow turbine in a turbulent open channel flow , 2014, Journal of Fluid Mechanics.

[25]  Yi-Ju Chou,et al.  A model for the simulation of coupled flow-bed form evolution in turbulent flows , 2010 .

[26]  F. Sotiropoulos,et al.  Effects of a three-dimensional hill on the wake characteristics of a model wind turbine , 2014 .

[27]  Fotis Sotiropoulos,et al.  Curvilinear immersed boundary method for simulating coupled flow and bed morphodynamic interactions due to sediment transport phenomena , 2011 .

[28]  F. Sotiropoulos,et al.  Initial stages of erosion and bed form development in a turbulent flow around a cylindrical pier , 2011 .

[29]  Fotis Sotiropoulos,et al.  Numerical simulation of 3D flow past a real-life marine hydrokinetic turbine , 2012 .

[30]  Paul Mycek,et al.  Numerical simulation of the wake of marine current turbines with a particle method , 2012 .

[31]  Jesse D. Roberts,et al.  Sandia National Laboratories environmental fluid dynamics code. Marine Hydrokinetic Module User's Manual , 2014 .

[32]  F. Sotiropoulos,et al.  Computational study and modeling of turbine spacing effects in infinite aligned wind farms , 2012 .

[33]  P. Moin,et al.  A dynamic subgrid‐scale eddy viscosity model , 1990 .

[34]  Xiaolei Yang,et al.  Large‐eddy simulation of turbulent flow past wind turbines/farms: the Virtual Wind Simulator (VWiS) , 2015 .

[35]  Leonardo P. Chamorro,et al.  Local Scour around a Model Hydrokinetic Turbine in an Erodible Channel , 2014 .

[36]  Jens Nørkær Sørensen,et al.  Numerical Modeling of Wind Turbine Wakes , 2002 .

[37]  Fotis Sotiropoulos,et al.  A numerical method for solving the 3D unsteady incompressible Navier-Stokes equations in curvilinear domains with complex immersed boundaries , 2007, J. Comput. Phys..

[38]  V. Voller,et al.  A generalized Exner equation for sediment mass balance , 2005 .