4:10 pm Presentation
“Wall-Modeling in Curvilinear Coordinates: Implementing Wall Shear Stress as Boundary Condition”
Presented by GHANESH NARASIMHAN (Profs. Zaki & Meneveau)
Wall-modeled Large Eddy Simulations (WMLES) determine instantaneous wall stress from a given filtered velocity. This wall stress is applied as a boundary condition (BC) in the LES solver that solves the filtered Navier-Stokes equations. TransFlow is a conservative Navier-Stokes solver in general curvilinear coordinates using volume flux formulation. Performing WMLES in TransFlow requires applying wall shear stress as boundary condition on a curvilinear grid. To this end, expressions for wall shear stresses in curvilinear coordinates are obtained from general coordinate free definition of the velocity gradient tensor. Since the grid is normal to the boundaries, expressions for wall shear stresses are derived for an orthogonal curvilinear coordinate system. Direct Numerical Simulation (DNS) of channel flow is performed with no-slip BC and wall stresses are computed using the obtained expressions. A separate DNS is run by applying the evaluated stresses as the boundary condition. Validation of implementation is done by comparing the velocity fields from DNS with no-slip and wall stress BC. The relative errors between the velocity fields from these two DNS are shown to be accurate to machine precision for at least 25 viscous time units.
4:35 pm Presentation
“Extending a Row-Averaged Model to a Turbine-Specific Model for Wind Farm Control”
Presented by GENEVIEVE STARKE (Profs. Gayme & Meneveau)
This study builds upon a recently proposed model-based receding horizon control approach that enables wind farms to follow a reference power signal. The wake model used in the controller is extended from a one-dimensional row-averaged model to encompass more two-dimensional effects such as wakes. This enables the control of individual turbines which generalizes the application to arbitrary wind farm configurations. The wake model is also adjusted to incorporate the changes in the freestream velocity across the spanwise component of the farm, which allows the wind turbines to be more responsive to local rather than aggregate wind conditions.