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1
Miliou, Anthi, Spencer J. Sherwin, and J. Michael R. Graham. "Fluid Dynamic Loading on Curved Riser Pipes." Journal of Offshore Mechanics and Arctic Engineering 125, no. 3 (July 11, 2003): 176–82. http://dx.doi.org/10.1115/1.1576817.
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In order to gain a preliminary understanding of the fluid dynamics developed past a curved riser pipe, a numerical investigation into the flow past curved cylinders at a Reynolds number of 100 has been performed. To approximate the flow conditions on curved riser pipes, different velocity profiles and flow directions were applied and the corresponding results compared. In addition, the fluid dynamic loading and the wake structures for curved cylinder flows were investigated. The fully three-dimensional simulations were computed with a spectral/hp element method. The computational results were compared with experiments undertaken in the towing tank facility of the Department of Aeronautics of Imperial College.
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Rose, J. Bruce Ralphin, P. Saranya, and JV Bibal Benifa. "Investigation of computational flow fields and aeroacoustic characteristics over a re-entry command module." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, no. 3 (December 14, 2016): 532–44. http://dx.doi.org/10.1177/0954410016682272.
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Design and analysis of a wind tunnel model for re-entry vehicle configuration is a prolonged and expensive mission. As the aerothermodynamics loads acting on the vehicle are based on geometry, various wind tunnel models need to be built for aerodynamic characterization by experimental procedure. Alternatively, the intention of this article is to present the influence of aerodynamic and aero acoustic characteristics of a typical re-entry capsule by computational fluid dynamics analysis. A typical re-entry capsule is designed using computational design software and it is imported to a computational fluid dynamics solver and flow simulations are done at various input conditions. Stanford University unstructured computational fluid dynamics solver is used for this purpose to solve complex, multiphysics analysis, and optimization tasks. Computational fluid dynamics results are presented to understand the influence of aerodynamic characteristics of a typical re-entry capsule, by visualizing the flow field around the command module at all the flow regimes like subsonic, supersonic, and hypersonic flows. The flow fields are studied in detail and regions of high flow unsteadiness due to wake separated flow zone are identified. Aeroacoustic loading on the command module at these regions especially at shock wave zone are predicted in the present investigation with high order of accuracy.
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Chatzimarkou, Eirinaios, and Constantine Michailides. "A Comparative Study of Breaking Wave Loads on Cylindrical and Conical Substructures." Water 13, no. 7 (March 28, 2021): 924. http://dx.doi.org/10.3390/w13070924.
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In the present paper, a comparative study of different cylindrical and conical substructures was performed under breaking wave loading with the open-source Computational Fluid Dynamics (CFD) package OpenFoam capable of the development of a numerical wave tank (NWT) with the use of Reynolds-Averaged Navier–Stokes (RANS) equations, the k-ω Shear Stress Transport (k-ω SST) turbulence model, and the volume of fluid (VOF) method. The validity of the NWT was verified with relevant experimental data. Then, through the application of the present numerical model, the distributions of dynamic pressure and velocity in the x-direction around the circumference of different cylindrical and conical substructures were examined. The results showed that the velocity and dynamic pressure distribution did not change significantly with the increase in the substructure’s diameter near the wave breaking height, although the incident wave conditions were similar. Another important aspect of the study was whether the hydrodynamic loading or the dynamic pressure distribution of a conical substructure would improve or deteriorate under the influence of breaking wave loading compared to a cylindrical one. It was concluded that the primary wave load in a conical substructure increased by 62.57% compared to the numerical results of a cylindrical substructure. In addition, the secondary load’s magnitude in the conical substructure was 3.39 times higher and the primary-to-secondary load ratio was double compared to a cylindrical substructure. These findings demonstrate that the conical substructure’s performance will deteriorate under breaking wave loading compared to a cylindrical one, and it is not recommended to use this type of substructure.
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Forouzan, Bahareh, Dilshan SP Amarsinghe Baragamage, Koushyar Shaloudegi, Narutoshi Nakata, and Weiming Wu. "Hybrid simulation of a structure to tsunami loading." Advances in Structural Engineering 23, no. 1 (July 18, 2019): 3–21. http://dx.doi.org/10.1177/1369433219857847.
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A new hybrid simulation technique has been developed to assess the behavior of a structure under hydrodynamic loading. It integrates the computational fluid dynamics and structural hybrid simulation and couples the fluid loading and structural response at each simulation step. The conventional displacement-based and recently developed force-based hybrid simulation approaches are adopted in the structural analysis. The concept, procedure, and required components of the proposed hybrid simulation are introduced in this article. The proposed hybrid simulation has been numerically and physically tested in case of a coastal building impacted by a tsunami wave. It is demonstrated that the force error in the displacement-based approach is significantly larger than that in the force-based approach. The force-based approach allows for a more realistic and reliable structural assessment under tsunami loading.
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Hu, Z. Z., D. M. Causon, C. G. Mingham, and L. Qian. "Numerical simulation of floating bodies in extreme free surface waves." Natural Hazards and Earth System Sciences 11, no. 2 (February 16, 2011): 519–27. http://dx.doi.org/10.5194/nhess-11-519-2011.
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Abstract. In this paper, we use the in-house Computational Fluid Dynamics (CFD) flow code AMAZON-SC as a numerical wave tank (NWT) to study wave loading on a wave energy converter (WEC) device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water). The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.
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Pirrung, Georg Raimund, and Helge Aagaard Madsen. "Dynamic inflow effects in measurements and high-fidelity computations." Wind Energy Science 3, no. 2 (August 22, 2018): 545–51. http://dx.doi.org/10.5194/wes-3-545-2018.
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Abstract. A wind turbine experiences an overshoot in loading after, for example, a collective step change in pitch angle. This overshoot occurs because the wind turbine wake does not immediately reach its new equilibrium, an effect usually referred to as dynamic inflow. Vortex cylinder models and actuator disc simulations predict that the time constants of this dynamic inflow effect should decrease significantly towards the blade tip. As part of the NASA Ames Phase VI experiment, pitch steps have been performed on a turbine in controlled conditions in the wind tunnel. The measured aerodynamic forces from these experiments seemed to show much less radial dependency of the dynamic inflow time constants than expected when pitching towards low loading. Moreover the dynamic inflow effect seemed fundamentally different when pitching from low to high loading, and the reason for this behavior remained unclear in previous analyses of the experiment. High-fidelity computational fluid dynamics and free-wake vortex code computations yielded the same behavior as the experiments. In the present work these observations from the experiments and high-fidelity computations are explained based on a simple vortex cylinder wake model.
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Elsafti, Hisham, Hocine Oumeraci, and Hans Scheel. "HYDRODYNAMIC EFFICIENCY AND LOADING OF A TSUNAMI-FLOODING BARRIER (TFB)." Coastal Engineering Proceedings, no. 35 (June 23, 2017): 23. http://dx.doi.org/10.9753/icce.v35.structures.23.
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The Tsunami-Flooding Barrier (TFB) is an impermeable vertical structure proposed at relatively large water depths, at which it is theorised that a tsunami will reach the structure before turning into a bore. The proposed hypothesis is tested in this study by means of a validated Computational Fluid Dynamics (CFD) model. The hydrodynamic efficiency of the impermeable TFB structure is confirmed and the effect of different aspects on the hydrodynamic efficiency of the structure are studied. These aspects include water depth, free board, surface roughness and the consideration of a deflecting parapet (named here as a surge stopper). Further, a new method is developed for calculating the tsunami-like solitary wave run-up and loads on the structure. The method is then compared to the Goda method for calculating storm wave loads on vertical impermeable structures. It is concluded that using the Goda method will severely underestimate the tsunami-like solitary wave load on the TFB structure.
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Kang, Ki-Yeob, Kwang-Ho Choi, Jae Woong Choi, Yong Hee Ryu, and Jae-Myung Lee. "An Influence of Gas Explosions on Dynamic Responses of a Single Degree of Freedom Model." Shock and Vibration 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/9582702.
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Explosion risk analysis (ERA) is widely used to derive the dimensioning of accidental loads for design purposes. Computational fluid dynamics (CFD) simulations contribute a key part of an ERA and predict possible blast consequences in a hazardous area. Explosion pressures can vary based on the model geometry, the explosion intensity, and explosion scenarios. Dynamic responses of structures under these explosion loads are dependent on a blast wave profile with respect to the magnitude of pressure, duration, and impulse in both positive and negative phases. Understanding the relationship between explosion load profiles and dynamic responses of the target area is important to mitigate the risk of explosion and perform structural design optimization. In the present study, the results of more than 3,000 CFD simulations were considered, and 1.6 million output files were analyzed using a visual basic for applications (VBA) tool developed to characterize representative loading shapes. Dynamic response of a structure was investigated in both time and frequency domains using the Fast Fourier Transform (FFT) algorithm. In addition, the effects of the residual wave and loading velocity were studied in this paper.
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Wu, Yanling. "Numerical tools to predict the environmental loads for offshore structures under extreme weather conditions." Modern Physics Letters B 32, no. 12n13 (May 10, 2018): 1840039. http://dx.doi.org/10.1142/s0217984918400390.
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In this paper, the extreme waves were generated using the open source computational fluid dynamic (CFD) tools — OpenFOAM and Waves2FOAM — using linear and nonlinear NewWave input. They were used to conduct the numerical simulation of the wave impact process. Numerical tools based on first-order (with and without stretching) and second-order NewWave are investigated. The simulation to predict force loading for the offshore platform under the extreme weather condition is implemented and compared.
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Zhou, Xiao, Liu, Incecik, Peyrard, Li, and Pan. "Numerical Modelling of Dynamic Responses of a Floating Offshore Wind Turbine Subject to Focused Waves." Energies 12, no. 18 (September 9, 2019): 3482. http://dx.doi.org/10.3390/en12183482.
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In this paper, we present numerical modelling for the investigation of dynamic responses of a floating offshore wind turbine subject to focused waves. The modelling was carried out using a Computational Fluid Dynamics (CFD) tool. We started with the generation of a focused wave in a numerical wave tank based on a first-order irregular wave theory, then validated the developed numerical method for wave-structure interaction via a study of floating production storage and offloading (FPSO) to focused wave. Subsequently, we investigated the wave-/wind-structure interaction of a fixed semi-submersible platform, a floating semi-submersible platform and a parked National Renewable Energy Laboratory (NREL) 5 MW floating offshore wind turbine. To understand the nonlinear effect, which usually occurs under severe sea states, we carried out a systematic study of the motion responses, hydrodynamic and mooring tension loads of floating offshore wind turbine (FOWT) over a range of wave steepness, and compared the results obtained from two potential flow theory tools with each other, i.e., Électricité de France (EDF) in-house code and NREL Fatigue, Aerodynamics, Structures, and Turbulence (FAST). We found that the nonlinearity of the hydrodynamic loading and motion responses increase with wave steepness, revealed by higher-order frequency response, leading to the appearance of discrepancies among different tools.
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Sepehrirahnama, Shahrokh, Eng Teo Ong, Heow Pueh Lee, and Kian Meng Lim. "Numerical Modeling of Free-Surface Wave Effects on Flexural Vibration of Floating Structures." International Journal of Computational Methods 17, no. 05 (June 20, 2019): 1940016. http://dx.doi.org/10.1142/s0219876219400164.
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To investigate flexural vibration of structures in a fluid, a numerical algorithm was developed to relate the added mass and damping effects of the fluid to each mode of vibration. These are separate from the traditional added mass associated with rigid body motion, such as the translational motion along Cartesian axes. In this formulation, small-amplitude free surface waves were accounted for by using a nonsingular implementation of the free-surface Green’s function for a potential flow solver based on Boundary Element Method. The formulation was applied to the forced vibration of structures, namely, a hemispherical shell and a reinforced half cylinder with typical dimensions of ships and offshore structures, to obtain their dynamic response at various excitation frequencies. It is observed that resonance frequency of the structure, in contact with water, decreases due to the added mass effect. The influence of the free-surface wave on the fluid loading was investigated for large structures. It is simpler to relate the fluid added mass to mode shapes rather than distribution of fluid load over wetted surface of the structure in engineering simulations. Moreover, it is found that the vibration energy radiated away by the fluid surface wave has little influence on the vibration response of the shell structures.
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Wang, Lu, Amy Robertson, Jason Jonkman, and Yi-Hsiang Yu. "Uncertainty Assessment of CFD Investigation of the Nonlinear Difference-Frequency Wave Loads on a Semisubmersible FOWT Platform." Sustainability 13, no. 1 (December 23, 2020): 64. http://dx.doi.org/10.3390/su13010064.
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Current mid-fidelity modeling approaches for floating offshore wind turbines (FOWTs) have been found to underpredict the nonlinear, low-frequency wave excitation and the response of semisubmersible FOWTs. To examine the cause of this underprediction, the OC6 project is using computational fluid dynamics (CFD) tools to investigate the wave loads on the OC5-DeepCwind semisubmersible, with a focus on the nonlinear difference-frequency excitation. This paper focuses on assessing the uncertainty of the CFD predictions from simulations of the semisubmersible in a fixed condition under bichromatic wave loading and on establishing confidence in the results for use in improving mid-fidelity models. The uncertainty for the nonlinear wave excitation is found to be acceptable but larger than that for the wave-frequency excitation, with the spatial discretization error being the dominant contributor. Further, unwanted free waves at the difference frequency have been identified in the CFD solution. A wave-splitting and wave load-correction procedure are presented to remove the contamination from the free waves in the results. A preliminary comparison to second-order potential-flow theory shows that the CFD model predicted significantly higher difference-frequency wave excitations, especially in surge, suggesting that the CFD results can be used to better calibrate the mid-fidelity tools.
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Baldock, Tom E., Hassan Karampour, Rachael Sleep, Anisha Vyltla, Faris Albermani, Aliasghar Golshani, David P. Callaghan, George Roff, and Peter J. Mumby. "Resilience of branching and massive corals to wave loading under sea level rise – A coupled computational fluid dynamics-structural analysis." Marine Pollution Bulletin 86, no. 1-2 (September 2014): 91–101. http://dx.doi.org/10.1016/j.marpolbul.2014.07.038.
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Dermentzoglou, Dimitrios, Myrta Castellino, Paolo De Girolamo, Maziar Partovi, Gerd-Jan Schreppers, and Alessandro Antonini. "Crownwall Failure Analysis through Finite Element Method." Journal of Marine Science and Engineering 9, no. 1 (December 31, 2020): 35. http://dx.doi.org/10.3390/jmse9010035.
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Several failures of recurved concrete crownwalls have been observed in recent years. This work aims to get a better insight within the processes underlying the loading phase of these structures due to non-breaking wave impulsive loading conditions and to identify the dominant failure modes. The investigation is carried out through an offline one-way coupling of computational fluid dynamics (CFD) generated wave pressure time series and a time-varying structural Finite Element Analysis. The recent failure of the Civitavecchia (Italy) recurved parapet is adopted as an explanatory case study. Modal analysis aimed to identify the main modal parameters such as natural frequencies, modal masses and modal shapes is firstly performed to comprehensively describe the dynamic response of the investigated structure. Following, the CFD generated pressure field time-series is applied to linear and non-linear finite element model, the developed maximum stresses and the development of cracks are properly captured in both models. Three non-linear analyses are performed in order to investigate the performance of the crownwall concrete class. Starting with higher quality concrete class, it is decreased until the formation of cracks is reached under the action of the same regular wave condition. It is indeed shown that the concrete quality plays a dominant role for the survivability of the structure, even allowing the design of a recurved concrete parapet without reinforcing steel bars.
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Sun, Zhenye, Wei Zhu, Wen Shen, Emre Barlas, Jens Sørensen, Jiufa Cao, and Hua Yang. "Development of an Efficient Numerical Method for Wind Turbine Flow, Sound Generation, and Propagation under Multi-Wake Conditions." Applied Sciences 9, no. 1 (December 28, 2018): 100. http://dx.doi.org/10.3390/app9010100.
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The propagation of aerodynamic noise from multi-wind turbines is studied. An efficient hybrid method is developed to jointly predict the aerodynamic and aeroacoustics performances of wind turbines, such as blade loading, rotor power, rotor aerodynamic noise sources, and propagation of noise. This numerical method combined the simulations of wind turbine flow, noise source and its propagation which is solved for long propagation path and under complex flow environment. The results from computational fluid dynamics (CFD) calculations not only provide wind turbine power and thrust information, but also provide detailed wake flow. The wake flow is computed with a 2D actuator disc (AD) method that is based on the axisymmetric flow assumption. The relative inflow velocity and angle of attack (AOA) of each blade element form input data to the noise source model. The noise source is also the initial condition for the wave equation that solves long distance noise propagation in frequency domain. Simulations were conducted under different atmospheric conditions which showed that wake flow is an important part that has to be included in wind turbine noise propagation.
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Kalateh, Farhoud, and Ali Koosheh. "Finite Element Analysis of Flexible Structure and Cavitating Nonlinear Acoustic Fluid Interaction under Shock Wave Loading." International Journal of Nonlinear Sciences and Numerical Simulation 19, no. 5 (July 26, 2018): 459–73. http://dx.doi.org/10.1515/ijnsns-2016-0135.
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AbstractThis paper describes a numerical model and its finite element implementation that used to compute the cavitation effects on nonlinear acoustic fluid and adjacent flexible structure interaction. The system is composed of two sub-systems, namely, the fluid and the flexible flat plate. A fully coupled approach using iterative implicit partitioned scheme was implemented in the present work which can account for the effects associated whit a mutual interaction. This approach included a compressible nonlinear acoustic fluid Eulerian solver and a Lagrangian solver for the flexible structure both in finite element formulation. A novel implementation of acoustic cavitation was made possible with the introduction of a simplified one-fluid cavitation model. The element-by-element PCG (Preconditioned Conjugate Gradient) solver together with diagonal preconditioning is used to solve the large equation system resulting from the finite element discretization of the governing equation of fluid domain. The capability of three different cavitation model, as the cut-off model, Modified Schmidt model and developed model are compared with each other in the evaluation of plate vibration response. Simulation results are presented on a large size shock tube, in which planar shock waves were impacting in “face on” configuration flat plates mounted at tube's end. Results are presented to demonstrate the capability of proposed solver in simulating cavitating nonlinear acoustic fluid. Obtained results show that impact forces caused impinging shock wave and reloading by cavitating region collapse have a considerable effect on the dynamic response of flexible plate.
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Van den Abeele, F., and J. Vande Voorde. "Stability of offshore structures in shallow water depth." International Journal Sustainable Construction & Design 2, no. 2 (November 6, 2011): 320–33. http://dx.doi.org/10.21825/scad.v2i2.20529.
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The worldwide demand for energy, and in particular fossil fuels, keeps pushing the boundaries of offshoreengineering. Oil and gas majors are conducting their exploration and production activities in remotelocations and water depths exceeding 3000 meters. Such challenging conditions call for enhancedengineering techniques to cope with the risks of collapse, fatigue and pressure containment.On the other hand, offshore structures in shallow water depth (up to 100 meter) require a different anddedicated approach. Such structures are less prone to unstable collapse, but are often subjected to higherflow velocities, induced by both tides and waves. In this paper, numerical tools and utilities to study thestability of offshore structures in shallow water depth are reviewed, and three case studies are provided.First, the Coupled Eulerian Lagrangian (CEL) approach is demonstrated to combine the effects of fluid flowon the structural response of offshore structures. This approach is used to predict fluid flow aroundsubmersible platforms and jack-up rigs.Then, a Computational Fluid Dynamics (CFD) analysis is performed to calculate the turbulent Von Karmanstreet in the wake of subsea structures. At higher Reynolds numbers, this turbulent flow can give rise tovortex shedding and hence cyclic loading. Fluid structure interaction is applied to investigate the dynamicsof submarine risers, and evaluate the susceptibility of vortex induced vibrations.As a third case study, a hydrodynamic analysis is conducted to assess the combined effects of steadycurrent and oscillatory wave-induced flow on submerged structures. At the end of this paper, such ananalysis is performed to calculate drag, lift and inertia forces on partially buried subsea pipelines.
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de Montaudouin, J., N. Reveles, and M. J. Smith. "Computational aeroelastic analysis of slowed rotors at high advance ratios." Aeronautical Journal 118, no. 1201 (March 2014): 297–313. http://dx.doi.org/10.1017/s0001924000009131.
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Abstract The aerodynamic and aeroelastic behaviour of a rotor become more complex as advance ratios increase to achieve high-speed forward fight. As the rotor blades encounter large regions of cross and reverse flows during each revolution, strong variations in the local Mach regime are encountered, inducing complex elastic blade deformations. In addition, the wake system may remain in the vicinity of the rotor, adding complexity to the blade loading. The aeroelastic behaviour of a model rotor with advance ratios ranging from 0·5 to 2·0 has been evaluated with aerodynamics provided via a computational fluid dynamics (CFD) method. Significant radial blade-vortex interaction can occur at a high advance ratio; the advance ratio at which this occurs is dependent on the rotor configuration. This condition is accompanied by high vibratory loads, peak negative torsion, and peak torsion and in-plane loads. The high vibratory loading increases the sensitivity of the trim model, so that at some high advance ratios the vibratory loads must be filtered to achieve a trimmed state.
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Ong, Muk Chen, Selina C. C. Lee, Arthur T. B. Lim, Edmond Y. M. Lo, and Soon Keat Tan. "Simulating Ship Maneuvers in Deep and Coastal Waters." Journal of Ship Research 51, no. 03 (September 1, 2007): 204–16. http://dx.doi.org/10.5957/jsr.2007.51.3.204.
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An engineering approach for simulating ship maneuvers in both deep and coastal waters taking into account effects of ambient current and wind was developed. The three degree-of-freedom rigid body equations of surge, sway, and yaw were numerically solved. A semiempirical approach was applied to determine the forces and moments arising from the propeller, rudder, current, wind, and wave making. Hydrodynamic calculations coupled with the slender body approximation were used to determine the wave-making resistances for arbitrary water depth. This approach was also adopted for determining the sway and surge added masses and yaw added moment. Computational fluid dynamics calculations were further used to determine the drag forces and the dependence with depth. Predictions of ship trajectories were compared with the field trial data of a full-size containership at design and ballast loading conditions in both deep and coastal waters. The comparison consisted of turning circle motion, zig-zag maneuvers, and actual sea voyage data, and yielded favorable agreement.
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Wheeler, Miles P., Konstantin I. Matveev, and Tao Xing. "Numerical Study of Hydrodynamics of Heavily Loaded Hard-Chine Hulls in Calm Water." Journal of Marine Science and Engineering 9, no. 2 (February 10, 2021): 184. http://dx.doi.org/10.3390/jmse9020184.
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Hard-chine boats are usually intended for high-speed regimes where they operate in the planing mode. These boats are often designed to be relatively light, but there are special applications that may occasionally require fast boats to be heavily loaded. In this study, steady-state hydrodynamic performance of nominal-weight and overloaded hard-chine hulls in calm water is investigated with computational fluid dynamics solver program STAR-CCM+. The resistance and attitude values of a constant-deadrise reference hull and its modifications with more pronounced bows of concave and convex shapes are obtained from numerical simulations. On average, 40% heavier hulls showed about 30% larger drag over the speed range from the displacement to planing modes. Among the studied configurations, the hull with a concave bow is found to have 5–12% lower resistance than the other hulls in the semi-displacement regime and heavy loadings and 2–10% lower drag in the displacement regime and nominal loading, while this hull is also capable of achieving fast planing speeds at the nominal weight with typical available thrust. The near-hull wave patterns and hull pressure distributions for selected conditions are presented and discussed as well.
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Han, Y., Z. Q. Chen, X. G. Hua, Z. Q. Feng, and GJ Xu. "Wind loads and effects on rigid frame bridges with twin-legged high piers at erection stages." Advances in Structural Engineering 20, no. 10 (January 9, 2017): 1586–98. http://dx.doi.org/10.1177/1369433216684350.
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This article presents a procedure for analyzing wind effects on the rigid frame bridges with twin-legged high piers during erection stages, taking into account all wind loading components both on the beam and on the piers. These wind loading components include the mean wind load and the load induced by the three turbulence wind components and by the wake excitation. The buffeting forces induced by turbulence wind are formulated considering the modification due to aerodynamic admittance functions. The buffeting responses are analyzed based on the coherence of buffeting forces and using finite element method in conjunction with random vibration theory in the frequency domain. The peak dynamic response is obtained by combining the various response components through gust response factor approach. The procedure is applied to Xiaoguan Bridge under different erection stages using the analytic aerodynamic parameters fitted from computational fluid dynamics. The numerical results indicate that the obtained peak structural responses are more conservative and accurate when considering the effect of each loading component on the beam and on the piers, and the roles of different loading components are different with regard to bridge configurations. Aerodynamic admittance functions are source of the important part of the error margin of the analytical prediction method for buffeting responses of bridges, and buffeting responses based on wind velocity coherence will underestimate the results.
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Boorsma, Koen, Florian Wenz, Koert Lindenburg, Mansoor Aman, and Menno Kloosterman. "Validation and accommodation of vortex wake codes for wind turbine design load calculations." Wind Energy Science 5, no. 2 (June 11, 2020): 699–719. http://dx.doi.org/10.5194/wes-5-699-2020.
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Abstract. The computational effort for wind turbine design load calculations is more extreme than it is for other applications (e.g., aerospace), which necessitates the use of efficient but low-fidelity models. Traditionally the blade element momentum (BEM) method is used to resolve the rotor aerodynamic loads for this purpose, as this method is fast and robust. With the current trend of increasing rotor size, and consequently large and flexible blades, a need has risen for a more accurate prediction of rotor aerodynamics. Previous work has demonstrated large improvement potential in terms of fatigue load predictions using vortex wake models together with a manageable penalty in computational effort. The present publication has contributed towards making vortex wake models ready for application to certification load calculations. The observed reduction in flapwise blade root moment fatigue loading using vortex wake models instead of the blade element momentum (BEM) method from previous publications has been verified using computational fluid dynamics (CFD) simulations. A validation effort against a long-term field measurement campaign featuring 2.5 MW turbines has also confirmed the improved prediction of unsteady load characteristics by vortex wake models against BEM-based models in terms of fatigue loading. New light has been shed on the cause for the observed differences and several model improvements have been developed, both to reduce the computational effort of vortex wake simulations and to make BEM models more accurate. Scoping analyses for an entire fatigue load set have revealed the overall fatigue reduction may be up to 5 % for the AVATAR 10 MW rotor using a vortex wake rather than a BEM-based code.
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Santo, H., P. H. Taylor, E. Carpintero Moreno, P. Stansby, R. Eatock Taylor, L. Sun, and J. Zang. "Extreme motion and response statistics for survival of the three-float wave energy converter M4 in intermediate water depth." Journal of Fluid Mechanics 813 (January 17, 2017): 175–204. http://dx.doi.org/10.1017/jfm.2016.872.
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This paper presents both linear and nonlinear analyses of extreme responses for a multi-body wave energy converter (WEC) in severe sea states. The WEC known as M4 consists of three cylindrical floats with diameters and draft which increase from bow to stern with the larger mid and stern floats having rounded bases so that the overall system has negligible drag effects. The bow and mid float are rigidly connected by a beam and the stern float is connected by a beam to a hinge above the mid float where the rotational relative motion would be damped to absorb power in operational conditions. A range of focussed wave groups representing extreme waves were tested on a scale model without hinge damping, also representing a more general system of interconnected cylindrical floats with multi-mode forcing. Importantly, the analysis reveals a predominantly linear response structure in hinge angle and weakly nonlinear response for the beam bending moment, while effects due to drift forces, expected to be predominantly second order, are not accounted for. There are also complex and violent free-surface effects on the model during the excitation period driven by the main wave group, which generally reduce the overall motion response. Once the main group has moved away, the decaying response in the free-vibration phase decays at a rate very close to that predicted by simple linear radiation damping. Two types of nonlinear harmonic motion are demonstrated. During the free-vibration phase, there are only double and triple frequency Stokes harmonics of the linear motion, captured using a frequency doubling and tripling model. In contrast, during the excitation phase, these harmonics show much more complex behaviour associated with nonlinear fluid loading. Although bound harmonics are visible in the system response, the overall response is remarkably linear until temporary submergence of the central float (‘dunking’) occurs. This provides a strong stabilising effect for angular amplitudes greater than ${\sim}30^{\circ }$ and can be treated as a temporary loss of part of the driving wave as long as submergence continues. With an experimentally and numerically derived response amplitude operator (RAO), we perform a statistical analysis of extreme response for the hinge angle based on wave data at Orkney, well known for its severe wave climate, using the NORA10 wave hindcast. For storms with spectral peak wave periods longer than the RAO peak period, the response is controlled by the steepness of the sea state rather than the wave height. Thus, the system responds very similarly under the most extreme sea states, providing an upper bound for the most probable maximum response, which is reduced significantly in directionally spread waves. The methodology presented here is relevant to other single and multi-body systems including WECs. We also demonstrate a general and potentially important reciprocity result for linear body motion in random seas: the averaged wave history given an extreme system response and the average response history given an extreme wave match in time, with time reversed for one of the signals. This relationship will provide an efficient and robust way of defining a ‘designer wave’, for both experimental testing and computationally intensive computational fluid dynamics (CFD), for a wide range of wave–structure interaction problems.
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Haro, Marco Polo Espinoza, Jong-Chun Park, Dong-Hyun Kim, and Sung-Bum Lee. "CFD Simulation on Workability of a Seaweed Harvesting Boat Due to Wake-Wash." Journal of Marine Science and Engineering 8, no. 8 (July 22, 2020): 544. http://dx.doi.org/10.3390/jmse8080544.
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In the present study, a 2-ton class seaweed harvesting boat was optimized by employing a W-shape hull form to reduce roll motion due to wake-wash from passing boats. A series of numerical simulations were conducted using Star-CCM+, a commercial CFD (computational fluid dynamics) software, to improve workability by optimizing the hull form from the conventional design (original hull form). The 2-dimensional roll decay motion of various hull forms with W-shape midsection were simulated and the hull form with the best performance in free roll decay test was selected. To evaluate stability of each hull in wake-wash, the original or optimized hull was alternately located at the middle of a computational domain as a target ship while an advancing ship (original hull) moved forward generating Kelvin waves which impact the original or optimized boat. Two kinds of working conditions, i.e., ballast and full loading conditions, of the target ship were considered with and without initial roll angle. It was observed through the comparison of motion between the original and optimized hulls a decrement of roll motion for the optimized ship demonstrating the effectiveness of the W-shape hull. Decrement of roll motion was observed for both working conditions. Additionally, the optimized W-shape hull showed an extraordinary performance under the ballast condition without initial roll angle.
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Altomare, Corrado, Angelantonio Tafuni, José M. Domínguez, Alejandro J. C. Crespo, Xavi Gironella, and Joaquim Sospedra. "SPH Simulations of Real Sea Waves Impacting a Large-Scale Structure." Journal of Marine Science and Engineering 8, no. 10 (October 21, 2020): 826. http://dx.doi.org/10.3390/jmse8100826.
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The Pont del Petroli is a dismissed pier in the area of Badalona, Spain, with high historical and social value. This structure was heavily damaged in January 2020 during the storm Gloria that hit southeastern Spain with remarkable strength. The reconstruction of the pier requires the assessment and characterization of the wave loading that determined the structural failure. Therefore, a state-of-the-art Computational Fluid Dynamic (CFD) code was employed herein as an aid for a planned experimental campaign that will be carried out at the Maritime Engineering Laboratory of Universitat Politècnica de Catalunya-BarcelonaTech (LIM/UPC). The numerical model is based on Smoothed Particle Hydrodynamics (SPH) and has been employed to simulate conditions very similar to those that manifested during the storm Gloria. The high computational cost for a full 3-D simulation has been alleviated by means of inlet boundary conditions, allowing wave generation very close to the structure. Numerical results reveal forces higher than the design loads of the pier, including both self-weight and accidental loads. This demonstrates that the main failure mechanism that led to severe structural damage of the pier during the storm is related to the exceeded lateral soil resistance. To the best of the authors’ knowledge, this research represents the first known application of SPH open boundary conditions to model a real-world engineering case.
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Öhrle, Constantin, Felix Frey, Jakob Thiemeier, Manuel Keßler, Ewald Krämer, Martin Embacher, Paul Cranga, and Paul Eglin. "Compound Helicopter X3 in High-Speed Flight: Correlation of Simulation and Flight Test." Journal of the American Helicopter Society 66, no. 1 (January 1, 2021): 1–14. http://dx.doi.org/10.4050/jahs.66.012011.
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This work presents the correlation of simulation results and flight-test data for a high-speed (V = 220 kt), high advance ratio (μ > 0.5) flight of the compound helicopter X3. The simulation tool chain consists of state-of-the-art coupling between the computational fluid dynamics (CFD) code FLOWer and the comprehensive analysis tool HOST. By applying a freeflight trim procedure, the experimental flight state is accurately represented in the simulation. The deviations of most trim controls is below 1°, and the maximum deviation is less than 1.4°. The analysis of the high-fidelity CFD results illustrates key features of the flow physics at this high advance ratio, such as wake interactions, reverse flow, and advancing side loading. The correlation of rotor dynamics data between simulation and flight test is favorable. Good accordance is demonstrated for flap bending moments, torsion moments, and pitch link loads. In contrast, the correlation is weaker for the chord bending moments for which it is shown that the interblade damper and drive train model mostly determine the structural loads.
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Zhang, Di, Daniel R. Cadel, Eric G. Paterson, and K. Todd Lowe. "Hybrid RANS/LES Turbulence Model Applied to a Transitional Unsteady Boundary Layer on Wind Turbine Airfoil." Fluids 4, no. 3 (July 11, 2019): 128. http://dx.doi.org/10.3390/fluids4030128.
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A hybrid Reynolds-averaged Navier Stokes/large-eddy simulation (RANS/LES) turbulence model integrated with a transition formulation is developed and tested on a surrogate model problem through a joint experimental and computational fluid dynamic approach. The model problem consists of a circular cylinder for generating coherent unsteadiness and a downstream airfoil in the cylinder wake. The cylinder flow is subcritical, with a Reynolds number of 64,000 based upon the cylinder diameter. The quantitative dynamics of vortex shedding and Reynolds stresses in the cylinder near wake are well captured, owing to the turbulence-resolving large eddy simulation mode that was activated in the wake. The hybrid model switched between RANS and LES modes outside the boundary layers, as expected. According to the experimental and simulation results, the airfoil encountered local flow angle variations up to ±50°. Further analysis through a phase-averaging technique found phase lags in the airfoil boundary layer along the chordwise locations, and both the phase-averaged and mean velocity profiles collapsed into the Law-of-the-wall in the range of 0 < y + < 50 . The features of high blade-loading fluctuations due to unsteadiness and transitional boundary layers are of interest in the aerodynamic studies of full-scale wind turbine blades, making the current model problem a comprehensive benchmark case for future model development and validation.
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Zhao, Ruiwen, Angus C. W. Creech, Alistair G. L. Borthwick, Vengatesan Venugopal, and Takafumi Nishino. "Aerodynamic Analysis of a Two-Bladed Vertical-Axis Wind Turbine Using a Coupled Unsteady RANS and Actuator Line Model." Energies 13, no. 4 (February 11, 2020): 776. http://dx.doi.org/10.3390/en13040776.
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Close-packed contra-rotating vertical-axis turbines have potential advantages in wind and hydrokinetic power generation. This paper describes the development of a numerical model of a vertical axis turbine with a torque-controlled system using an actuator line model (ALM). The developed model, coupled with the open-source OpenFOAM computational fluid dynamics (CFD) code, is used to examine the characteristics of turbulent flow behind a single two-bladed vertical-axis turbine (VAT). The flow field containing the turbine is simulated by solving the unsteady Reynolds-averaged Navier-Stokes (URANS) equations with a k - ω shear stress transport (SST) turbulence model. The numerical model is validated against experimental measurements from a two-bladed H-type wind turbine. Turbine loading is predicted, and the vorticity distribution is investigated in the vicinity of the turbine. Satisfactory overall agreement is obtained between numerical predictions and measured data on thrust coefficients. The model captures important three-dimensional flow features that contribute to wake recovery behind a vertical-axis turbine, which will be useful for future studies of close-packed rotors with a large number of blades.
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Bennaya, Mohamed, Wen Ping Zhang, and Moutaz M. Hegaze. "Estimation of the Induced Hydrodynamic Periodic Forces of Marine Propeller under Non-Uniform Inflow via CFD." Applied Mechanics and Materials 467 (December 2013): 293–99. http://dx.doi.org/10.4028/www.scientific.net/amm.467.293.
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In this work, both steady and unsteady Reynolds-Averaged Navier Stokes (RANS) simulations have been used via FLUENT software to calculate the induced 3-D hydrodynamic forces and moments of marine propeller. Marine propeller is excited by variation of hydrodynamic loading due to its operation in non-uniform wake field. The induced hydrodynamic forces and moments are calculated for single blade and for all blades at low Reynolds number under two operating conditions. The first one, uniform inflow is considered at the inlet. The second one, non-uniform inflow is considered at the inlet (under the wake effect of the ship) to represent the propeller-ship interaction. Unsteady results show that, due to non-uniform inflow every single blade is suffering from periodic forces and moments with fluctuation amplitude and harmonies higher than that applied on the propeller shaft but with lower frequency. The moments in vertical and transversal directions My and Mz are higher than the axial moment Mx. This study shows that, using Computational Fluid Dynamics (CFD) to solve RANS equation is a reliable tool for calculating the hydrodynamic characteristics and estimating the excited hydrodynamic forces due to propeller-ship interaction.
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Ismail, Ahmed, Mohamed Ezzeldin, Wael El-Dakhakhni, and Michael Tait. "Blast load simulation using conical shock tube systems." International Journal of Protective Structures 11, no. 2 (June 28, 2019): 135–58. http://dx.doi.org/10.1177/2041419619858098.
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With the increased frequency of accidental and deliberate explosions, evaluating the response of civil infrastructure systems to blast loading has been attracting the interests of the research and regulatory communities. However, with the high cost and complex safety and logistical issues associated with field explosives testing, North American blast-resistant construction standards (e.g. ASCE 59-11 and CSA S850-12) recommend the use of shock tubes to simulate blast loads and evaluate relevant structural response. This study first aims at developing a simplified two-dimensional axisymmetric shock tube model, implemented in ANSYS Fluent, a computational fluid dynamics software, and then validating the model using the classical Sod’s shock tube problem solution, as well as available shock tube experimental test results. Subsequently, the developed model is compared to a more complex three-dimensional model and the results show that there is negligible difference between the two models for axisymmetric shock tube performance simulation; however, the three-dimensional model is necessary to simulate non-axisymmetric shock tubes. Following the model validation, extensive analyses are performed to evaluate the influences of shock tube design parameters (e.g. the driver section pressure and length and the expansion section length) on blast wave characteristics to facilitate a shock tube design that would generate shock waves similar to those experienced by civil infrastructure components under blast loads. The results show that the peak reflected pressure increases as the driver pressure increases, while a decrease in the expansion length increases the peak reflected pressure. In addition, the positive phase duration increases as both the driver length and expansion length are increased. Finally, the developed two-dimensional axisymmetric model is used to optimize the dimensions of a physical large-scale conical shock tube system constructed for civil infrastructure component blast response evaluation applications. The capabilities of such shock tube system are further investigated by correlating its design parameters to a range of explosion threats identified by different hemispherical TNT charge weight and distance scenarios.
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Ning, Andrew. "Actuator cylinder theory for multiple vertical axis wind turbines." Wind Energy Science 1, no. 2 (December 16, 2016): 327–40. http://dx.doi.org/10.5194/wes-1-327-2016.
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Abstract. Actuator cylinder theory is an effective approach for analyzing the aerodynamic performance of vertical axis wind turbines at a conceptual design level. Existing actuator cylinder theory can analyze single turbines, but analysis of multiple turbines is often desirable because turbines may operate in near proximity within a wind farm. For vertical axis wind turbines, which tend to operate in closer proximity than do horizontal axis turbines, aerodynamic interactions may not be strictly confined to wake interactions. We modified actuator cylinder theory to permit the simultaneous solution of aerodynamic loading for any number of turbines. We also extended the theory to handle thrust coefficients outside of the momentum region and explicitly defined the additional terms needed for curved or swept blades. While the focus of this paper is a derivation of an extended methodology, an application of this theory was explored involving two turbines operating in close proximity. Comparisons were made against two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulations, across a full 360° of inflow, with excellent agreement. The counter-rotating turbines produced a 5–10 % increase in power across a wide range of inflow conditions. A second comparison was made to a three-dimensional RANS simulation with a different turbine under different conditions. While only one data point was available, the agreement was reasonable, with the computational fluid dynamics (CFD) predicting a 12 % power loss, as compared to a 15 % power loss for the actuator cylinder method. This extended theory appears promising for conceptual design studies of closely spaced vertical axis wind turbines (VAWTs), but further development and validation is needed.
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Payne, Thomas, Andrew Williams, Thomas Worfolk, and Samuel Rigby. "Numerical investigation into the influence of cubicle positioning in large-scale explosive arena trials." International Journal of Protective Structures 7, no. 4 (November 29, 2016): 547–60. http://dx.doi.org/10.1177/2041419616676438.
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In arena blast testing, a common and economical practice employed is to distribute several targets radially around a central charge. However, if these targets are positioned too proximally, reflections and diffractions of blast waves off neighbouring cubicles can affect the nature of expected blast loading. Computational fluid dynamics software has been used through an extensive series of simulations to identify the levels of interference in incident pressure–time histories with and without an obstructing target present. The data were post-processed to identify the Cartesian co-ordinates in which different levels of interference in peak incident overpressure and incident positive phase impulse were achieved. The results indicated that in all cases, there was a greater interference in peak incident overpressure than incident positive phase impulse values directly proximal to the target but, at greater separations, significant differences in incident positive phase impulse existed where peak incident overpressure had returned to free-field equivalent magnitudes. When compared with the established ‘rules of thumb’ for cubicle placement, for targets at different stand-off ranges, an angle of 45° to the rear cubicle still holds some practical relevance, although it is too acute to cover all interference effects. For targets positioned at the same stand-off range, a separation distance of two cubicle widths is generally too conservative and, in many cases, more cubicles can be positioned around the charge. A bespoke recommendation table has been presented for targets at stand-off ranges between 15 and 50 m to allow users to identify the minimum distance from a target at which obstructed-field peak incident overpressure and incident positive phase impulse values differ negligibly from free-field equivalents.
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Drikakis, Dimitris, Michael Frank, and Gavin Tabor. "Multiscale Computational Fluid Dynamics." Energies 12, no. 17 (August 25, 2019): 3272. http://dx.doi.org/10.3390/en12173272.
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Computational Fluid Dynamics (CFD) has numerous applications in the field of energy research, in modelling the basic physics of combustion, multiphase flow and heat transfer; and in the simulation of mechanical devices such as turbines, wind wave and tidal devices, and other devices for energy generation. With the constant increase in available computing power, the fidelity and accuracy of CFD simulations have constantly improved, and the technique is now an integral part of research and development. In the past few years, the development of multiscale methods has emerged as a topic of intensive research. The variable scales may be associated with scales of turbulence, or other physical processes which operate across a range of different scales, and often lead to spatial and temporal scales crossing the boundaries of continuum and molecular mechanics. In this paper, we present a short review of multiscale CFD frameworks with potential applications to energy problems.
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Hansen, Olav R., Peter Hinze, Derek Engel, and Scott Davis. "Using computational fluid dynamics (CFD) for blast wave predictions." Journal of Loss Prevention in the Process Industries 23, no. 6 (November 2010): 885–906. http://dx.doi.org/10.1016/j.jlp.2010.07.005.
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Chen, P. Y. P., and E. J. Hahn. "Use of computational fluid dynamics in hydrodynamic lubrication." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 212, no. 6 (June 1, 1998): 427–36. http://dx.doi.org/10.1243/1350650981542236.
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This paper demonstrates the suitability of using computational fluid dynamics software for solving steady state hydrodynamic lubrication problems pertaining to slider bearings, step bearings, journal bearings and squeeze-film dampers under conditions of constant unidirectional or rotating loading. The relevance of the inertia and viscous terms which are neglected in the derivation of the Reynolds equation are briefly investigated for the above bearing and damper configurations and it is shown that the neglected viscous terms have negligible effect whereas the inertia effect predictions agree reasonably well with those reported in the literature.
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Finnegan, William, Edward Fagan, Tomas Flanagan, Adrian Doyle, and Jamie Goggins. "Operational fatigue loading on tidal turbine blades using computational fluid dynamics." Renewable Energy 152 (June 2020): 430–40. http://dx.doi.org/10.1016/j.renene.2019.12.154.
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Erdelyiová, Romana, Lucia Figuli, and Matúš Ivančo. "Prediction of fire loading on the structures using computational fluid dynamics." MATEC Web of Conferences 313 (2020): 00033. http://dx.doi.org/10.1051/matecconf/202031300033.
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The development of a fire in a large-space fire section differs significantly from the development in a small fire section. In large-space objects, to design structures under the fire load often proceeds through a performance-based approach. Advanced methods can be used in all parts of the design in predicting of the scatter of temperature field, in calculating of the heat transfer to the structure and in assessing of the mechanical behaviour of the structure or its part under the fire load. The prediction of the gas temperature in the fire compartment is crucial for the structure design. The paper is focused on selection of different fire scenarios in the large-space building. The aim is to provide background for structural design in a fire using a performance-based design. The problem is solved by using FDS (Fire Dynamics Simulator) software based on the CFD (Computational Fluid Dynamics) method.
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Tipton, D. Gregory, Mark A. Christon, and Marc S. Ingber. "Coupled fluid-solid interaction under shock wave loading." International Journal for Numerical Methods in Fluids 67, no. 7 (August 25, 2010): 848–84. http://dx.doi.org/10.1002/fld.2390.
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COSTA NETO, M. L., and G. N. DOZ. "Study of blast wave overpressures using the computational fluid dynamics." Revista IBRACON de Estruturas e Materiais 10, no. 3 (June 2017): 669–77. http://dx.doi.org/10.1590/s1983-41952017000300007.
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ABSTRACT The threats of bomb attacks by criminal organizations and accidental events involving chemical explosives are a danger to the people and buildings. Due the severity of these issues and the need of data required for a safety design, more research is required about explosions and shock waves. This paper presents an assessment of blast wave overpressures using a computational fluid dynamics software. Analyses of phenomena as reflection of shock waves and channeling effects were done and a comparison between numerical results and analytical predictions has been executed, based on the simulation on several models. The results suggest that the common analytical predictions aren’t accurate enough for an overpressure analysis in small stand-off distances and that poorly designed buildings may increase the shock wave overpressures due multiple blast wave reflections, increasing the destructive potential of the explosions.
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Abdul Aziz, M. S., M. Z. Abdullah, C. Y. Khor, M. Mazlan, A. M. Iqbal, and Z. M. Fairuz. "A computational fluid dynamics analysis of the wave soldering process." International Journal of Numerical Methods for Heat & Fluid Flow 25, no. 5 (June 1, 2015): 1231–47. http://dx.doi.org/10.1108/hff-02-2014-0053.
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Purpose – The purpose of this paper is to present a three-dimensional finite volume-based analysis on the effects of propeller blades on fountain flow in a wave soldering process and performs an experimental validation. Design/methodology/approach – Solder pot models with various numbers of propeller blades were developed and meshed by using hybrid elements and simulated by using the FLUENT fluid flow solver. The characteristics of the fountain, such as flow profile, velocity vector, filling time, and fountain advancement, were investigated. Molten solder (Sn63Pb37) material, a temperature of 250°C, and a propeller speed of 830 rpm were applied in the simulation. The predicted results were validated by the experimental fountain profile. Findings – The use of a six-blade propeller in a solder pot increased the fountain thickness profile and reduced the filling time. Moreover, a six-blade propeller design resulted in a stable fountain profile and was considered the best choice for current wave soldering processes. Practical implications – This study provides a better understanding of the effects of propeller blades on the fountain flow in the wave soldering process. Originality/value – The study explores the fountain flow behavior and provides a reference to the engineers and designers in order to improve the fountain flow of the wave soldering.
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Tahara, Y., F. Stern, and Y. Himeno. "Computational Fluid Dynamics–Based Optimization of a Surface Combatant." Journal of Ship Research 48, no. 04 (December 1, 2004): 273–87. http://dx.doi.org/10.5957/jsr.2004.48.4.273.
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Computational fluid dynamics (CFD)-based optimization of a surface combatant is presented with the following main objectives:development of a high-performance optimization module for a Reynolds averaged Navier-Stokes (RANS) solver for with-free-surface condition; anddemonstration of the capability of the optimization method for flow- and wave-field optimization of the Model 5415 hull form. The optimization module is based on extension of successive quadratic programming (SQP) for higher-performance optimization method by introduction of parallel computing architecture, that is, message passing interface (MPI) protocol. It is shown that the present parallel SQP module is nearly m(= 2k+ 1; k is number of design parameters) times faster than conventional SQP, and the computational speed does not depend on the number of design parameters. The RANS solver is CFDSHIP-IOWA, a general-purpose parallel multiblock RANS code based on higher-order upwind finite difference and a projection method for velocity-pressure coupling; it offers the capability of free-surface flow calculation. The focus of the present study is on code development and demonstration of capability, which justifies use of a relatively simple turbulence model, a free-surface model without breaking model, static sinkage and trim, and simplified design constraints and geometry modeling. An overview is given of the high-performance optimization method and CFDSHIP-IOWA, and results are presented for stern optimization for minimization of transom wave field disturbance; sonar dome optimization for minimization of sonar-dome vortices; and bow optimization for minimization of bow wave. In conclusion, the present work has successfully demonstrated the capability of the CFD-based optimization method for flow- and wave-field optimization of the Model 5415 hull form. The present method is very promising and warrants further investigations for computer-aided design (CAD)-based hull form modification methods and more appropriate design constraints.
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Sohaimi, Arif S. M., M. S. Risby, Saiddi A. F. M. Ishak, S. Khalis, M. N. Norazman, I. Ariffin, and M. A. Yusof. "Using Computational Fluid Dynamics (CFD) for Blast Wave Propagation under Structure." Procedia Computer Science 80 (2016): 1202–11. http://dx.doi.org/10.1016/j.procs.2016.05.463.
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Lycklama à Nijeholt, J. A., M. E. H. Tijani, and S. Spoelstra. "Simulation of a traveling-wave thermoacoustic engine using computational fluid dynamics." Journal of the Acoustical Society of America 118, no. 4 (October 2005): 2265–70. http://dx.doi.org/10.1121/1.2035567.
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Su, Ke Qin, Ya Wei Wang, and Jian Ping Wang. "The Research and Application on Computational Methods in Fluid Dynamics." Advanced Materials Research 317-319 (August 2011): 807–10. http://dx.doi.org/10.4028/www.scientific.net/amr.317-319.807.
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The NND scheme based on Van Leer flux vector splitting is presented. The flow field of shock wave tube is calculated by the difference method presented in this paper, which shows that the presented finite difference method has fine calculation precision and efficiency, and could capture shock automatically.
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McGuill, Christopher, and Jennifer Keenahan. "A Parametric Study of Wind Pressure Distribution on Façades Using Computational Fluid Dynamics." Applied Sciences 10, no. 23 (December 2, 2020): 8627. http://dx.doi.org/10.3390/app10238627.
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This paper uses Computational Fluid Dynamics (CFD) to determine wind pressures on façades for the purpose of efficient design of these elements. An outstand fin arrangement was modeled where local brackets are used to protrude the fins from the building. A parametric study, for both changes in the length of the bracket and the fin, was derived from CFD simulations with 1-in-50-year storm conditions adopted throughout. Further simulations are performed for revised wind directions that ensure all fins are equally exposed to oncoming winds. In total, 15 models are created to act as a representative sample of the total number of possible configurations. Peak values for pressure are used to calculate forces and moments on the fins. These wind loading results were then used to interpolate the values for the remaining façade geometries. From interpreting the trends that are apparent in the relationship of fin size and bracket length to efficient loading, a set of design criteria is established. The optimal façade design is defined, based on placing equal importance onto minimizing the force along the fin’s length and the moment acting at the fin-bracket connection. The performance of some façade elements is shown to worsen the effects of the wind, relative to other designs, with the potential for very negative consequences. Wind direction is shown to have a significant effect on loading, with the magnitude of wind pressures reduced considerably for the worst affected fin, if the sheltering effect is absent between the fins.
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Tiaple, Yodchai. "Hydrodynamic Simulation of Wave Energy Converter Using Particle-Based Computational Fluid Dynamics." Journal of Marine Science and Application 18, no. 1 (February 8, 2019): 48–53. http://dx.doi.org/10.1007/s11804-019-00070-0.
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Silva, Kevin M., and Kevin J. Maki. "Towards a Computational Fluid Dynamics implementation of the critical wave groups method." Ocean Engineering 235 (September 2021): 109451. http://dx.doi.org/10.1016/j.oceaneng.2021.109451.
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TAMURA, Tetsuro. "Applied Computational Fluid Dynamics to the prediction of Wind Loading on Buildings and Structures." Wind Engineers, JAWE 1994, no. 60 (1994): 7–16. http://dx.doi.org/10.5359/jawe.1994.60_7.
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AVRAHAMI, IDIT, and MORTEZA GHARIB. "Computational studies of resonance wave pumping in compliant tubes." Journal of Fluid Mechanics 608 (July 11, 2008): 139–60. http://dx.doi.org/10.1017/s0022112008002012.
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The valveless impedance pump is a simple design that allows the producion or amplification of a flow without the requirement for valves or impellers. It is based on fluid-filled flexible tubing, connected to tubing of different impedances. Pumping is achieved by a periodic excitation at an off-centre position relative to the tube ends. This paper presents a comprehensive study of the fluid and structural dynamics in an impedance pump model using numerical simulations. An axisymmetric finite-element model of both the fluid and solid domains is used with direct coupling at the interface. By examining a wide range of parameters, the pump's resonance nature is described and the concept of resonance wave pumping is discussed. The main driving mechanism of the flow in the tube is the reflection of waves at the tube boundary and the wave dynamics in the passive tube. This concept is supported by three different analyses: (i) time-dependent pressure and flow wave dynamics along the tube, (ii) calculations of pressure–flow loop areas along the passive tube for a description of energy conversion, and (iii) an integral description of total work done by the pump on the fluid. It is shown that at some frequencies, the energy given to the system by the excitation is converted by the elastic tube to kinetic energy at the tube outlet, resulting in an efficient pumping mechanism and thus significantly higher flow rate. It is also shown that pumping can be achieved with any impedance mismatch at one boundary and that the outlet configuration does not necessarily need to be a tube.
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Chahine, Georges L., and Chao-Tsung Hsiao. "Modelling cavitation erosion using fluid–material interaction simulations." Interface Focus 5, no. 5 (October 6, 2015): 20150016. http://dx.doi.org/10.1098/rsfs.2015.0016.
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Material deformation and pitting from cavitation bubble collapse is investigated using fluid and material dynamics and their interaction. In the fluid, a novel hybrid approach, which links a boundary element method and a compressible finite difference method, is used to capture non-spherical bubble dynamics and resulting liquid pressures efficiently and accurately. The bubble dynamics is intimately coupled with a finite-element structure model to enable fluid/structure interaction simulations. Bubble collapse loads the material with high impulsive pressures, which result from shock waves and bubble re-entrant jet direct impact on the material surface. The shock wave loading can be from the re-entrant jet impact on the opposite side of the bubble, the fast primary collapse of the bubble, and/or the collapse of the remaining bubble ring. This produces high stress waves, which propagate inside the material, cause deformation, and eventually failure. A permanent deformation or pit is formed when the local equivalent stresses exceed the material yield stress. The pressure loading depends on bubble dynamics parameters such as the size of the bubble at its maximum volume, the bubble standoff distance from the material wall and the pressure driving the bubble collapse. The effects of standoff and material type on the pressure loading and resulting pit formation are highlighted and the effects of bubble interaction on pressure loading and material deformation are preliminarily discussed.