Electromagnetic Reduction of Plasma Density During Atmospheric Reentry and Hypersonic Flights

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76341/1/AIAA-32147-259.pd

OC6 Phase I: Investigating the underprediction of low-frequency hydrodynamic loads and responses of a floating wind turbine

Phase I of the OC6 project is focused on examining why offshore wind design tools underpredict the response (loads/motion) of the OC5-DeepCwind semisubmersible at its surge and pitch natural frequencies. Previous investigations showed that the underprediction was primarily related to nonlinear hydrodynamic loading, so two new validation campaigns were performed to separately examine the different hydrodynamic load components. In this paper, we validate a variety of tools against this new test data, focusing on the ability to accurately model the low-frequency loads on a semisubmersible floater when held fixed under wave excitation and when forced to oscillate in the surge direction. However, it is observed that models providing better load predictions in these two scenarios do not necessarily produce a more accurate motion response in a moored configuration.The authors would like to acknowledge the support of the MARINET2 project (European Union’s Horizon 2020 grant agreement 731084), which supplied the tank test time and travel support to accomplish the testing campaign. The support of MARIN in the preparation, execution of the modeltests, and the evaluation of the uncertainties was essential for this study. MARIN’s contribution was partly funded by the Dutch Ministry of Economic Affairs through TKI-ARD funding programs. This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36- 08GO28308. Funding provided by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Wind Energy Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes

Verification of a Numerical Model of the Offshore Wind Turbine From the Alpha Ventus Wind Farm Within OC5 Phase III

The main objective of the Offshore Code Comparison Collaboration Continuation, with Correlation (OC5) project, is validation of aero-hydro-servo-elastic simulation tools for offshore wind turbines (OWTs) through comparison of simulated results to the response data of physical systems. Phase III of the OC5 project analyzes the Senvion 5M wind turbine supported by the OWEC Quattropod from the alpha ventus offshore wind farm. This paper shows results of the verification of the OWT models (code-to-code comparison). A subsequent publication will focus on their validation (comparison of simulated results to measured physical system response data). Based on the available data, the participants of Phase III set up numerical models of the OWT in their simulation tools. It was necessary to verify and to tune these models. The verification and tuning were performed against an OWT model available at the University of Stuttgart - Stuttgart Wind Energy (SWE) and documentation provided by Senvion and OWEC Tower. A very good match was achieved between the results from the reference SWE model and models set up by OC5 Phase III participants

Sensitivity Analysis of Limited Actuation for Real-time Hybrid Model Testing of 5MW Bottom-fixed Offshore Wind Turbine

The present paper studies the effect of limited actuation for real-time hybrid model testing (ReaTHM® testing) of a bottom-fixed offshore wind turbine in operational, parked, and fault conditions. ReaTHM® testing is a new approach for conducting small-scale experimental campaigns and has recently applied to test a braceless semisubmersible floating wind turbine in MARINTEK ocean basin [1, 2, 3]. The aerodynamic loads on the wind turbine were applied based on simultaneous simulations coupled to the experiments while the wave loads and floater response were physically tested. The effects of actuation limitation on the ReaTHM® testing setup for the semisubmersible wind turbine were investigated previously [4] using numerical simulations, by not including some components of the aerodynamic loads or by inducing error (for example in the direction of the force actuation). In this paper, the same approach is used to investigate the sensitivity of a bottom-fixed 5MW offshore wind turbine to limited actuation. The consequences of limited actuation are also considered for fault conditions (grid loss, and blade seize with and without shutdown) due to the potential importance of fault events for the ultimate and accidental limit state analysis. For the operational turbine, most responses of interest were not strongly dependent on the studied limitations in actuation, but the aerodynamic pitch and yaw moments were important for fault cases.publishedVersio

Point Absorber Design for a Combined Wind and Wave Energy Converter on a Tension-Leg Support Structure

A combined wind and wave energy extraction device is stud-ied, consisting of a single column tension leg platform (TLP) which supports a 5MW wind turbine (WT) and 3 point absorber wave energy converters (WECs). Two variations of the WECs are considered: one that is constrained to purely heave motion relative to the TLP hull, and a hinged device which moves in cou-pled surge and pitch as well as heave. The effects of both types of WECs on the WT power takeoff; on structural loads in the tur-bine tower and blades, WEC supporting structure, and tendons; and on the platform motions are examined for operational and 50-year extreme environmental conditions

Multipurpose platforms

A multipurpose platform is an offshore system designed to serve the purposes of more than one offshore industry. Indeed, a number of industries have expanded, or are expanding, from onshore to offshore locations, adapting to the harsh environment in order to extract energy (conventional or renewable) or useful materials (deep mining), to produce food (aquaculture), nutraceuticals, and pharmaceuticals (blue biotechnology), to expand the urban areas, or to simply develop the local tourism, to name a few. This process starts to appear like, and certainly has the potential to become, a further `agricultural/industrial revolution', characterised by: (a) a substantial shift from `gathering of resources where available' to the systematic, settled use of the resources offered by the ocean, (b) a shift from offshore facilities of a specific industry operating independently to an `ecosystem' of offshore industrial activities, and (c) the resulting development of new technologies. Expanding the above-mentioned industries towards this new frontier can help to respond to two of the main challenges facing mankind: the sustainable, safe, and reliable production of energy and food, driven by an increasing population and rising prosperity. For these reasons, and also due to the huge potential to create jobs and revenues, many countries around the world are proposing and implementing strategies to develop the so-called Blue Economy

COMPARISON AND VALIDATION OF HYDRODYNAMIC LOAD MODELS FOR A SEMI-SUBMERSIBLE FLOATING WIND TURBINE

In global aero-hydro-servo-elastic analyses of floating wind turbines (FWTs), the hydrodynamic loads are usually found from potential flow theory and applied in a single point of a rigid hull. When the hull is relatively stiff, this approach ensures correct behaviour for the six rigid body degrees-of-freedom (DOFs), but provides no information about the internal loads in the hull. The current work considers a simplified method to include distributed, large volume hydrodynamics in the global analysis, where frequency-dependent loads from potential theory are applied on a finite element (FE) model of the hull in a strip-wise manner. The method is compared to conventional load models for a braceless 5MW semi-submersible FWT, and validated against experimental results from model tests with focus on internal loads and rigid body motions in the main wave-frequency range. The global motions are accurately predicted by the distributed model for all investigated load cases. Good agreement with experimental results is also seen for the column base bending moment in wave-only conditions, although extreme values are not captured correctly due to limitations in linear theory. In combined wave-wind conditions, the measured bending moments are significantly increased because of the wind-induced mean angle of the platform. This effect is not considered in the numerical model, which therefore underestimates the moment response. However, an approach which calculates the loads in the actual mean configuration of the hull is found to give reasonably accurate results, at least in moderate wave conditions.publishedVersionCopyright © 2018 by ASM