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Conference date: November 30 - December 1, 2017

 

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Abstracts
[Wind Engineering] [Advanced Comput. Methods & Appl. in Marine Techn.] [Marine Operation for Cold Climate] [FEM, BEM & FVM and Design Optimization] [Structural Integrity and Health Monitoring]


Topic Area: Wind Engineering

COTech101: What scaling means in wind engineering
Complementary role of the reduced scale approach in a BLWT and the full scale testing in a large climatic wind tunnel

                Olivier Flamand
                  CSTB, Nantes, France

Abstract. Wind engineering problems are commonly studied by wind tunnel experiments at a reduced scale. This introduces several limitations and calls for a careful planning of the tests and the interpretation of the experimental results. The talk first revisits the similitude laws and discusses how they are actually applied in wind engineering. It will also remind readers why different scaling laws govern in different wind engineering problems. Secondly, the paper focuses on the ways to simplify a detailed structure (bridge, building, platform) when fabricating the downscaled models for the tests. This will be illustrated by several examples from recent engineering projects. Finally, under the most severe weather conditions, manmade structures and equipment should remain operational. What “recreating the climate” means and aims to achieve will be illustrated through common practice in climatic wind tunnel modelling.

 Keywords— boundary layer wind tunnel, climatic wind tunnel, experimental approach, scaling laws


COTech102: Implementation and application of the actuator line model by OpenFOAM for a vertical axis wind turbine

                      L Riva1*, K-E Giljarhus2, B Hjertager2 and S M Kalvig2
                      1Department of Engineering Sciences, University of Agder, Norway
                     2
Department of Mechanical and Structural Engineering and Material Science, University of 
                    Stavanger, Norway

Abstract. University of Stavanger has started The Smart Sustainable Campus & Energy Lab project, to gain knowledge and facilitate project based education in the field of renewable and sustainable energy and increase the research effort in the same area. This project includes the future installation of a vertical axis wind turbine on the campus roof. A newly developed Computational Fluid Dynamics (CFD) model by OpenFOAM have been implemented to study the wind behavior over the building and the turbine performance. The online available wind turbine model case from Bachant, Goude and Wosnik from 2016 is used as the starting point. This is a Reynolds-Averaged Navier-Stokes equations (RANS) case set up that uses the Actuator Line Model. The available test case considers a water tank with controlled external parameters. Bachant et al.’s model has been modified to study a VAWT in the atmospheric boundary layer. Various simulations have been performed trying to verify the models use and suitability. Simulation outcomes help to understand the impact of the surroundings on the turbine as well as its reaction to parameters changes. The developed model can be used for wind energy and flow simulations for both onshore and offshore applications.

Keywords. Vertical axis wind turbine, Computational fluid dynamic, Actuator line model, Openfoam, Atmospheric boundary layer, Built environment wind turbine


COTech104:3D WindScanner Lidar Measurements of Wind and Turbulence around Wind Turbines, Buildings and Bridges

Torben Mikkelsen, Mikael Sjöholm, Nikolas Angelou and Jakob Mann  
Dep. of Wind Energy; Technical University of Denmark, DTU Campus Risø, Roskilde, Denmark

 Abstract. WindScanner is a distributed research infrastructure developed at DTU with the participation of a number of European countries. The research infrastructure consists of a mobile technically advanced facility for remote measurement of wind and turbulence in 3D. The WindScanners provide coordinated measurements of the entire wind and turbulence fields, of all three wind components scanned in 3D space. Although primarily developed for research related to on- and offshore wind turbines and wind farms, the facility is also well suited for scanning turbulent wind fields around buildings, bridges, aviation structures and of flow in urban environments. The mobile WindScanner facility enables 3D scanning of wind and turbulence fields in full scale within the atmospheric boundary layer at ranges from 10 meters to 5 (10) kilometers. Measurements of turbulent coherent structures are applied for investigation of flow pattern and dynamical loads from turbines, building structures and bridges and in relation to optimization of the location of, for example, wind farms and suspension bridges. This paper presents our achievements to date and reviews briefly the state-of-the-art of the WindScanner measurement technology with examples of uses for wind engineering applications.

Keywords. 3D Wind field velocity measurements, Atmospheric turbulence, Coherence, dynamic loads application, Suspension bridges, Wind tunnel velocimetry, wind turbines.


COTech107: Aeroelastic Response from Indicial Functions with a Finite Element Model of a Suspension Bridge

Ove Mikkelsen and Jasna B Jakobsen
Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, Norway

Abstract. The present paper describes a comprehensive analysis of the aeroelastic bridge response in time-domain, with a finite element model of the structure. The main focus is on the analysis of flutter instability, accounting for the wind forces generated by the bridge motion, including twisting as well as vertical and horizontal translation, i.e. all three global degrees of freedom. The solution is obtained by direct integration of the equations of motion for the bridge-wind system, with motion-dependent forces approximated from flutter derivatives in terms of rational functions. For the streamlined bridge box-girder investigated, the motion dependent wind forces related to the along-wind response are found to have a limited influence on the flutter velocity. The flutter mode shapes in the time-domain and the frequency domain are consistent, and composed of the three lowest symmetrical vertical modes coupled with the first torsional symmetric mode. The method applied in this study provides detailed response estimates and contributes to an increased understanding of the complex aeroelastic behaviour of long-span bridges.


COTech107: Wind effects on long-span bridges: Probabilistic Wind Data Format for Buffeting and VIV Load Assessments

                   K Hoffmann1,  R Ge Srouji1 and S O Hansen1,2  
               1Svend Ole Hansen ApS, Copenhagen, Denmark ;
               2SOH Wind Engineering LLC, Burlington, Vermont, USA

Abstract. The technology development within the structural design of long-span bridges in Norwegian fjords has created a need for reformulating the calculation format and the physical quantities used to describe the properties of wind and the associated wind-induced effects on bridge decks. Parts of a new probabilistic format describing the incoming, undisturbed wind is presented. It is expected that a fixed probabilistic format will facilitate a more physically consistent and precise description of the wind conditions, which in turn increase the accuracy and considerably reduce uncertainties in wind load assessments. Because the format is probabilistic, a quantification of the level of safety and uncertainty in predicted wind loads is readily accessible. A simple buffeting response calculation demonstrates the use of probabilistic wind data in the assessment of wind loads and responses. Furthermore, vortex-induced fatigue damage is discussed in relation to probabilistic wind turbulence data and response measurements from wind tunnel tests.

Keywords. Buffeting loads, Long-span bridges, Resonant response, Probabilistic wind data, Vortex-induced vibrations, Wind data format.


COTech108: Super-long bridges with floating towers: the role of multi-box decks and Hardware-In-the-Loop technology for wind tunnel tests.

A Zasso, T Argentini, I Bayati, M Belloli, D Rocchi  
Politecnico di Milano: Department of Mechanical Engineering, Milano, Italy

                     Contact author: tommaso.argentini@polimi.it

Abstract. The super long fjord crossings in E39 Norwegian project pose new challenges to long span bridge design and construction technology. Proposed solutions should consider the adoption of bridge deck with super long spans or floating solutions for at least one of the towers, due to the relevant fjord depth. At the same time, the exposed fjord environment, possibly facing the open ocean, calls for higher aerodynamic stability performances. In relation to this scenario, the present paper addresses two topics: 1) the aerodynamic advantages of multi-box deck sections in terms of aeroelastic stability, and 2) an experimental setup in a wind tunnel able to simulate the aeroelastic bridge response including the wave forcing on the floating.


COTech110: Full-Scale Monitoring of Wind and Suspension Bridge Response

Jonas T. Snæbjörnsson, Jasna B. Jakobsen, Etienne Cheynet, Jungao Wang  
Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, 4036 Stavanger
School of Science and Engineering, Reykjav´ık University, Reykjav´ık, Iceland

Abstract. Monitoring of real structures is important for many reasons. For structures susceptible to environmental actions, fullscale observations can provide valuable information about the environmental conditions at the site, as well as the characteristics of the excitation acting on the structure. The recorded data, if properly analyzed, can be used to validate and/or update experiments and models used in the design of new structures, such as the load description and modelling of the structural response. Various aspects of full-scale monitoring are discussed in the paper and the full-scale wind engineering laboratory at the Lysefjord suspension bridge introduced. The natural excitation of the bridge comes from wind and traffic. The surrounding terrain is complex and its effect on the wind flow can only be fully studied on site, in full-scale. The monitoring program and associated data analysis are described. These include various studies of the relevant turbulence characteristics, identification of dynamic properties and estimation of wind- and traffic induced response parameters. The overall monitoring activity also included a novel application of the remote optical sensing in bridge engineering, which is found to have an important potential to complement traditional “single-point” wind observations by sonic anemometers.

Keywords. Suspension bridge, Monitoring, Wind loading, Turbulence, structural response