Presentation on theme: "Wind Modeling Studies by Dr. Xu at Tennessee State University"— Presentation transcript:
1 Wind Modeling Studies by Dr. Xu at Tennessee State University Guanpeng XuTennessee State UniversityCenter of Excellence in Information System,Engineering & Management
2 Overview of Presentation Wind ProjectsMethodologiesResults and Conclusions
3 Wind Modeling StudiesComputational Studies of Horizontal Axis Wind TurbinesFull NSHybrid MethodologyOverset Grid (CHIMERA)2D/3D Icing Simulation2D Icing3D IcingThe first project is a part of my Ph.D. research. My advisor is Lakshmi Sankar at School of Aerospace Engineering, Georgia Institute of TechnologyProjects were supported byNational Renewable Energy Laboratory (NREL), DOE
4 Mathematical FormulaReynolds Averaged Navier-Stokes Equations in Finite Volume Representation:Where q is the state vector. E, F, and G are the inviscid fluxes, and R, S, and T are the viscous fluxesA finite volume formulation using Roe’s scheme is used.The scheme is third order or fifth order accurate in space and second order accurate in time.
5 The Hybrid Methodology N-S zonePotential Flow ZoneTip VortexThe flow field is made ofa viscous region near the blade(s)A potential flow region that propagates the blade circulation and thickness effects to the far fieldA Lagrangean representation of the tip vortex, and concentrated vorticity shed from nearby bluff bodies such as the towerThis method is unsteady, compressible, and does not have singularities near separation lines
6 The Overset Grid Methodology Inclusion of tower effects requires modeling non-rotating and rotating components.Georgia Tech CHIMERA methodology has been modified for tower shadow effects of HAWT :Body-fitted grids are used for rotating blades and tower.Each grid block is simulated using either a Navier-Stokes or hybrid method.The flow fields among the grid sets are linked by 3-D interpolation.
7 The Icing SimulationPorous ice with liquid water content and air/vapor is assumed.The flow field and icing/melting are calculated using a modular approach.Grid is deformed with on-the-fly ice shape; NS solver is used for outer flow.
8 Configuration Studied NREL has collected extensive performance data for three rotor configurations:A rotor with rectangular planform, untwisted blade and S-809 airfoil sections, called the Phase II RotorA twisted rotor, with rectangular platform and S-809 sections, called the Phase III RotorA two bladed, tapered and twisted rotor, called the Phase VI Rotor. Best quality measurements (wind tunnel) are available.
9 Results and Discussion --Sample GridSize 11043402(380,000)Viscous zone 6043202 (100,000)Body fitted grid on Phase II rotor
10 OVERSET GRIDA very coarse grid was used for Proof of Concept
20 Tower Shadow Causes 15% Variation in Wind Speed 10m/sPortion of the Rotor Disk exposed to the tower wake~8.5m/sCode predicted this loss in dynamic pressure, but not the vortex shedding effects due to the sparse grid employed.
21 Improvement to a Tip Loss Model and a Stall Delay Model Using CFD as a Guide Effects of Corrigan’s Model with Different values of n
22 ConclusionsThe Hybrid method, which solves the HAWT flow using a zonal approach, has been developed for efficiently simulating fully three-dimensional viscous fluid flow around an HAWT. Good results have been obtained.A full Navier-Stokes methodology has also been developed. Two turbulence models and two transition prediction models have been integrated into above solvers. Consistent results have been obtained for above two solvers. An overset grid based version that can model rotor-tower interactions has been developed.
23 ConclusionsThe physics studied includes turbulence models, transition prediction models, yaw (unsteady) simulation, tower shadow, wind turbine flow states, stall delay, and tip losses.The complete research activities have been documented in Guanpeng Xu’s doctoral thesis, Journal of Solar Energy Engineering, and in AIAA papers, , , , , and are omitted here.