Evaluation of Wind Loads on FPSO Topsides Using a Numerical Wind Tunnel

2016 ◽  
Author(s):  
Daniel Barcarolo ◽  
Yann Andrillon ◽  
Erwan Jacquin ◽  
Alain Ledoux
Keyword(s):  
Boundary Layer ◽  
Numerical Model ◽  
Wind Tunnel ◽  
Atmospheric Boundary Layer ◽  
Scale Effects ◽  
Geometric Model ◽  
Wind Tunnel Test ◽  
Offshore Structures ◽  
Wind Loads ◽  
The Impact

The accurate evaluation of wind loads applied on floating offshore structures is extremely important as they are in specific conditions one of the dimensioning criteria for the mooring design. Nowadays these loads are mainly assessed through wind tunnel tests performed at model scale. Estimating realistic wind loads however, remains a big challenge. The complexity and associated simplification level of FPSO topside structures, the scale effects and the establishment of the atmospheric boundary layer imply that many simplifications are to be made. Typically, the FPSO topside is greatly simplified and equivalent blocs of wired frame are used. Today with the evolution of CFD software, and the increase of the meshing capacity, new scopes open to CFD. Aerodynamic simulations on complex FPSO structures are therefore now possible, but need specific developments and validations that are presented in this paper. The main objective of the work presented is to investigate the ability of CFD to evaluate wind loads on complex FPSOs topsides and to provide information on the impact of model simplifications made in wind tunnels. In a first stage, the numerical model was intensively validated by comparing its results to a wind tunnel test case. The numerical model was developed in order to ensure the quality of the results and enable a relevant comparison that was obtained with grids density up to 30 million cells. For this purpose, the geometric model used corresponds to the one used in wind tunnel. The same Atmospheric Boundary Layer was simulated and a thorough effort was performed to ensure the mesh convergence. In a second stage, more physical aspects of the wind tunnel methodology were investigated. Typically the accuracy of the blockage effect correction was evaluated by performing computations with and without blockage, and results were compared with classical corrections applied in wind tunnel. The impacts of the Atmospheric Boundary Layer on wind loads have also been investigated. Finally, the wind load contribution of each component of the FPSO was evaluated.

Numerical Evaluation of Wind Loads on Semi-Submersible Platform by CFD

2010 ◽  
Author(s):  
Shen Zhang ◽  
Lei Wang ◽  
Shi-Zhi Yang ◽  
Huan Yang
Keyword(s):  
Wind Tunnel ◽  
Stokes Equations ◽  
Numerical Study ◽  
Wind Tunnel Test ◽  
Offshore Structures ◽  
Wind Loads ◽  
Navier Stokes ◽  
Offshore Platforms ◽  
Wind Effects ◽  
Eddy Simulation

A numerical study of wind loads on a semisubmersible platform is presented on this paper. The techniques of Computational Fluid Dynamics (CFD), such as Reynolds Averaged Navier-Stokes Equations (RANS) model and Large Eddy Simulation (LES), etc., were adopted in this study to predict wind loads on and wind flows around the platform. The main objective of this study is to explore an effective and reliable approach for evaluation of wind loads on offshore structures by CFD methods. The computed results were compared with experimental data which obtained at wind tunnel test. It was found through the comparison that the LES with a dynamic sub grid-scale (SGS) model can give satisfactory predictions for mean and dynamic wind loads on the tall structures. Therefore, it is necessary to correctly simulate both the incident wind velocity profile and turbulence intensity profile in CFD computations to accurately predict wind effects on huge structures. The recommend CFD techniques and associated numerical treatments provide an effective way for designers to assess wind effects on offshore platforms and the need for a detailed wind tunnel test.

Aerodynamic Analysis of a Boundary-Layer-Ingesting Distortion-Tolerant Fan

2013 ◽  
Author(s):  
Razvan V. Florea ◽  
Dmytro Voytovych ◽  
Gregory Tillman ◽  
Mark Stucky ◽  
Aamir Shabbir ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
High Performance ◽  
Risk Mitigation ◽  
Pressure Ratio ◽  
Wind Tunnel Test ◽  
Fuel Burn ◽  
Global And Local ◽  
The Impact ◽  
Stage Efficiency

The paper describes the aerodynamic CFD analysis that was conducted to address the integration of an embedded-engine (EE) inlet with the fan stage. A highly airframe-integrated, distortion-tolerant propulsion preliminary design study was carried out to quantify fuel burn benefits associated with boundary layer ingestion (BLI) for “N+2” blended wing body (BWB) concepts. The study indicated that low-loss inlets and high-performance, distortion-tolerant turbomachines are key technologies required to achieve a 3–5% BLI fuel burn benefit relative to a baseline high-performance, pylon-mounted, propulsion system. A hierarchical, multi-objective, computational fluid dynamics-based aerodynamic design optimization that combined global and local shaping was carried out to design a high-performance embedded-engine inlet and an associated fan stage. The scaled-down design will be manufactured and tested in NASA’s 8′×6′ Transonic Wind Tunnel. Unsteady calculations were performed for the coupled inlet and fan rotor and inlet, fan rotor and exit guide vanes. The calculations show that the BLI distortion propagates through the fan largely un-attenuated. The impact of distortion on the unsteady blade loading, fan rotor and fan stage efficiency and pressure ratio is analyzed. The fan stage pressure ratio is provided as a time-averaged and full-wheel circumferential-averaged value. Computational analyses were performed to validate the system study and design-phase predictions in terms of fan stage performance and operability. For example, fan stage efficiency losses are less than 0.5–1.5% when compared to a fan stage in clean flow. In addition, these calculations will be used to provide pretest predictions and guidance for risk mitigation for the wind tunnel test.

Characteristics of Wind Loads Acting on Complex Long-Span Roof Structure

2013 ◽  
Vol 639-640 ◽  
pp. 523-529
Author(s):  
Fu Bin Chen ◽  
Q.S. Li
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Wind Pressure ◽  
Wind Loads ◽  
Pressure Coefficients ◽  
Long Span ◽  
Roof Structure ◽  
Fluctuating Wind

The Shenzhen New Railway Station (SNRS) has roof dimensions of 450 m long and 408 m wide. This paper presents the results of wind loads acting on the large-span roof structure. In the wind tunnel test, wind-induced pressures including mean and fluctuating components were measured from the roof of a 1:200 scale SNRS model under suburban boundary layer wind flow configuration in a boundary layer wind tunnel of HD-2 at Hunan University. Based on the data obtained simultaneously from the wind tunnel tests, the distributions of the mean and fluctuating wind pressure coefficients and the characteristics of probability density functions of wind pressures of typical pressure taps were analyzed in detailed. The outcomes of the experimental study indicate that: (1) The maximum mean negative wind pressure coefficients on the roof occur at the windward leading edge region, where the maximum fluctuating wind pressure coefficients occur also in this region; (2) There are some differences of the maximum mean negative wind pressure coefficients and RMS wind pressure coefficients under conditions with different number of trains inside the station, but such effects on the overall pressure distributions on the whole roof are negligible; (3) There are clearly negative skewed distributions for some pressure taps at the windward leading roof edge and much longer negative tails are observed, which follow Non-Gaussian distributions. The results presented in this paper are expected to be of considerable interest and of use to researchers and professionals involved in designing complex long-span roof structures.

Wave Impact Loads on the Bottom of Flat Decks

2021 ◽  
Author(s):  
Daniel de Oliveira Costa ◽  
Julia Araújo Perim ◽  
Bruno Guedes Camargo ◽  
Joel Sena Sales Junior ◽  
Antonio Carlos Fernandes ◽  
...  
Keyword(s):  
Scale Effects ◽  
Offshore Structures ◽  
Model Tests ◽  
Analytical Models ◽  
Navier Stokes ◽  
Impact Loads ◽  
Wave Impact ◽  
Wave Channel ◽  
Waves And Currents ◽  
The Impact

Abstract Slamming events due to wave impact on the underside of decks might lead to severe and potentially harmful local and/or global loads in offshore structures. The strong nonlinearities during the impact require a robust method for accessing the loads and hinder the use of analytical models. The use of computation fluid dynamics (CFD) is an interesting alternative to estimate the impact loads, but validation through experimental data is still essential. The present work focuses on a flat-bottomed model fixed over the mean free surface level submitted to regular incoming waves. The proposal is to reproduce previous studies through CFD and model tests in a different reduced scale to provide extra validation and to identify possible non-potential scale effects such as air compressibility. Numerical simulations are performed in both experiments’ scales. The numerical analysis is performed with a marine dedicated flow solver, FINE™/Marine from NUMECA, which features an unsteady Reynolds-averaged Navier-Stokes (URANS) solver and a finite volume method to build spatial discretization. The multiphase flow is represented through the Volume of Fluid (VOF) method for incompressible and nonmiscible fluids. The new model tests were performed at the wave channel of the Laboratory of Waves and Currents (LOC/COPPE – UFRJ), at the Federal University of Rio de Janeiro.

A new atmospheric boundary layer wind tunnel simulation methodology for wind effects on large cooling towers considering wind environment variations

2018 ◽  
Vol 22 (5) ◽  
pp. 1194-1210 ◽  
Author(s):  
XX Cheng ◽  
X Chen ◽  
YJ Ge ◽  
H Jiang ◽  
L Zhao
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Atmospheric Boundary Layer ◽  
Model Test ◽  
Test Results ◽  
Wind Effects ◽  
Simulation Methodology ◽  
Codes Of Practice ◽  
Wind Tunnel Simulation ◽  
Tunnel Model

The traditional atmospheric boundary layer wind tunnel model test practice employs wind fields, the flow characteristics of which are in accordance with the empirical formulae of the atmospheric turbulence presented in Codes of Practice and monographs. However, the empirical formulae presented in Codes of Practice and monographs cannot truthfully reflect the high variations of the realistic atmospheric turbulence which sometimes aggravates wind effects on structures. Based on model tests conducted in a multiple-fan actively controlled wind tunnel, it is found that most wind effects on large cooling towers change monotonically with the increase in free-stream turbulence, and the model test results are more unfavorable for a flow field of low turbulence intensity than for a flow field of high turbulence intensity with respect to the measured coherences. Thus, a new atmospheric boundary layer wind tunnel simulation methodology for wind effects on circular cylindrical structures is proposed to overcome the deficiency of the traditional atmospheric boundary layer wind tunnel model tests. The new simulation methodology includes the simulation of two realistic atmospheric boundary layer flow fields with the highest and the lowest turbulence intensities in the wind tunnel and the envelopment of model test results obtained in the two flow fields (e.g. the mean and fluctuating wind pressure distributions, the power spectral density, the coherence function, and the correlation coefficient). The superiority of the new atmospheric boundary layer wind tunnel simulation methodology over the traditional model test practice is demonstrated by comparing the model test results with the full-scale measurement data.

Development of Boundary Layer in CRIACIV in Florence (Prato) and Comparison with CFD

2016 ◽  
Vol 820 ◽  
pp. 359-364
Author(s):  
Marek Magát ◽  
Ivana Olekšáková ◽  
Juraj Žilinský
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Atmospheric Boundary Layer ◽  
Comparison Of The Results

In this article are described the results from testing profile of atmospheric boundary layer in BLWT (Boundary layer wind tunnel) in Florence (Prato), Italy with emphasis on comparison of the results with simulations in CFD (Computational fluid dynamics) software OpenFoam. The values are compared with calculated values from EuroCode.

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