Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Jianting Du (1) F P Xiaoli Larsén (1) Rodolfo Bolaños (2)
(1) Technical University of Denmark, Roskilde, Denmark (2) Technical University of Denmark, Roskilde, Denmark (3) DHI, Hørsholm, Denmark (4) DHI, Hørsholm, Denmark
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Mr. Jianting Du is currently a Ph.D. student at the Technical University of Denmark. He obtained Master Degree in Physical Oceanography in 2012 at the First Institute of Oceanography, SOA, China, where he continued working as a research assistant for 1 year on the topic of atmospheric and wave model coupling.
A coupled atmospheric and wave modeling system for storm simulations
This study is part of an on-going research project X-WiWa that aims at improving the simulation of wind and waves during storms for wind turbine design and operations in coastal areas.
For this particular purpose, we investigated the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System which couples the Weather Research and Forecasting (WRF) Model with the third-generation ocean wave model (SWAN).
Main body of abstract
The current COAWST system allows non-nested domain in WRF and structured grids in SWAN. We improve the COAWST system by enabling nested domains in WRF and unstructured meshes in SWAN, thus better representing coastal areas that are characteristic of complex boundaries and bathymetries. During the coupling, WRF transfers 10 meters wind velocity to SWAN and SWAN feedbacks roughness length (z0) to WRF. To understand the impact of z0, several approaches for parameterization z0 were first tested in ideal cases and evaluated by the non-dimensional wind-wave growth curves. The study is extended to real storm cases, followed by validation with wind and wave observations. The technique of online coupling (exchange data at every time step) and offline coupling (exchange data after each run) were investigated and corresponding results were compared.
It is found that the simulation of offshore wind and waves during storm conditions are strongly impacted by the parameterization of z0 as well as the model resolution.
The use of online coupling, together with nesting and unstructured meshes is recommended for modeling storms (wind and wave) in coastal zones.