scholarly journals Coupled Fluid-Structure Interaction Modelling of Loads Variation and Fatigue Life of a Full-Scale Tidal Turbine under the Effect of Velocity Profile

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2217 ◽  
Author(s):  
Mujahid Badshah ◽  
Saeed Badshah ◽  
James VanZwieten ◽  
Sakhi Jan ◽  
Muhammad Amir ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Velocity Profile ◽  
Fluid Structure Interaction ◽  
Angular Position ◽  
Thrust Coefficient ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Tidal Turbine ◽  
The Mean ◽  
Mean Cycle

Velocity profiles in tidal channels cause cyclic oscillations in hydrodynamic loads due to the dependence of relative velocity on angular position, which can lead to fatigue damage. Therefore, the effect of velocity profile on the load variation and fatigue life of large-scale tidal turbines is quantified here. This is accomplished using Fluid Structure Interaction (FSI) simulations created using the ANSYS Workbench software, which couples the fluid solver ANSYS CFX to the structural solver ANSYS transient structural. While these load oscillations only minimally impact power and thrust fluctuation for rotors, they can significantly impact the load variations on individual rotor blades. To evaluate these loadings, a tidal turbine within a channel with a representative flow that follows a 1/7th power velocity profile and an onset turbulence intensity of 5% is simulated. This velocity profile increases the thrust coefficient variation from mean cycle value of an individual blade from 2.8% to 9% and the variation in flap wise bending moment coefficient is increased from 4.9% to 19%. Similarly, the variation from the mean cycle value for blade deformation and stress of 2.5% and 2.8% increased to 9.8% and 10.3%, respectively. Due to the effect of velocity profile, the mean stress is decreased, whereas, the range and variation of stress are considerably increased.

Fluid Structure Interaction Simulations of the NREL 5 MW Wind Turbine—Part I: Aerodynamics and Blockage Effect

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Ehsan Borouji ◽  
Takafumi Nishino
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Fluid Structure Interaction ◽  
Life Assessment ◽  
Navier Stokes ◽  
Element Analysis ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Reynolds Averaged Navier Stokes ◽  
Blockage Effect

Fluid structure interaction (FSI) simulations of the NREL 5 MW wind turbine are performed using a combination of two separate computational codes: abaqus for the finite element analysis (FEA) of turbine structures and STAR-CCM+ for the unsteady Reynolds-averaged Navier–Stokes analysis of flow around the turbine. The main aim of this study is to demonstrate the feasibility of using two-way coupled FSI simulations to predict the oscillation of the tower, as well as the rotor blades, of a full-scale wind turbine. Although the magnitude of the oscillation of the tower is much smaller than that of the blades, this oscillation is crucial for the assessment of the fatigue life of the tower. In this first part of the paper, the aerodynamic characteristics of the turbine predicted by the two-way coupled FSI simulations are discussed in comparison with those predicted by Reynolds-averaged Navier–Stokes simulations of a rigid turbine. Also, two different computational domains with a cross-sectional size of 2D × 2D and 4D × 4D (where D is the rotor diameter) are employed to investigate the blockage effect. The fatigue life assessment of the turbine is planned to be reported in the second part of the paper in the near future.

scholarly journals Fluid-Structure Interaction Modeling of Abdominal Aortic Aneurysms: The Impact of Patient-Specific Inflow Conditions and Fluid/Solid Coupling

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Santanu Chandra ◽  
Samarth S. Raut ◽  
Anirban Jana ◽  
Robert W. Biederman ◽  
Mark Doyle ◽  
...  
Keyword(s):  
Velocity Profile ◽  
Boundary Conditions ◽  
Fluid Structure Interaction ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Fluid Structure ◽  
Inlet Velocity ◽  
Structure Interaction ◽  
Biomechanical Assessment ◽  
Fully Coupled

Rupture risk assessment of abdominal aortic aneurysms (AAA) by means of biomechanical analysis is a viable alternative to the traditional clinical practice of using a critical diameter for recommending elective repair. However, an accurate prediction of biomechanical parameters, such as mechanical stress, strain, and shear stress, is possible if the AAA models and boundary conditions are truly patient specific. In this work, we present a complete fluid-structure interaction (FSI) framework for patient-specific AAA passive mechanics assessment that utilizes individualized inflow and outflow boundary conditions. The purpose of the study is two-fold: (1) to develop a novel semiautomated methodology that derives velocity components from phase-contrast magnetic resonance images (PC-MRI) in the infrarenal aorta and successfully apply it as an inflow boundary condition for a patient-specific fully coupled FSI analysis and (2) to apply a one-way–coupled FSI analysis and test its efficiency compared to transient computational solid stress and fully coupled FSI analyses for the estimation of AAA biomechanical parameters. For a fully coupled FSI simulation, our results indicate that an inlet velocity profile modeled with three patient-specific velocity components and a velocity profile modeled with only the axial velocity component yield nearly identical maximum principal stress (σ1), maximum principal strain (ε1), and wall shear stress (WSS) distributions. An inlet Womersley velocity profile leads to a 5% difference in peak σ1, 3% in peak ε1, and 14% in peak WSS compared to the three-component inlet velocity profile in the fully coupled FSI analysis. The peak wall stress and strain were found to be in phase with the systolic inlet flow rate, therefore indicating the necessity to capture the patient-specific hemodynamics by means of FSI modeling. The proposed one-way–coupled FSI approach showed potential for reasonably accurate biomechanical assessment with less computational effort, leading to differences in peak σ1, ε1, and WSS of 14%, 4%, and 18%, respectively, compared to the axial component inlet velocity profile in the fully coupled FSI analysis. The transient computational solid stress approach yielded significantly higher differences in these parameters and is not recommended for accurate assessment of AAA wall passive mechanics. This work demonstrates the influence of the flow dynamics resulting from patient-specific inflow boundary conditions on AAA biomechanical assessment and describes methods to evaluate it through fully coupled and one-way–coupled fluid-structure interaction analysis.

scholarly journals Fluid Structure Interaction Modelling of Tidal Turbine Performance and Structural Loads in a Velocity Shear Environment

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1837 ◽  
Author(s):  
Mujahid Badshah ◽  
Saeed Badshah ◽  
Kushsairy Kadir
Keyword(s):  
Fluid Dynamic ◽  
Turbine Blades ◽  
Fluid Structure Interaction ◽  
Angular Position ◽  
Uniform Flow ◽  
Velocity Shear ◽  
Power Coefficient ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Stress And Deformation

Tidal Current Turbine (TCT) blades are highly flexible and undergo considerable deflection due to fluid interactions. Unlike Computational Fluid Dynamic (CFD) models Fluid Structure Interaction (FSI) models are able to model this hydroelastic behavior. In this work a coupled modular FSI approach was adopted to develop an FSI model for the performance evaluation and structural load characterization of a TCT under uniform and profiled flow. Results indicate that for a uniform flow case the FSI model predicted the turbine power coefficient CP with an error of 4.8% when compared with experimental data. For the rigid blade Reynolds Averaged Navier Stokes (RANS) CFD model this error was 9.8%. The turbine blades were subjected to uniform stress and deformation during the rotation of the turbine in a uniform flow. However, for a profiled flow the stress and deformation at the turbine blades varied with the angular position of turbine blade, resulting in a 22.1% variation in stress during a rotation cycle. This variation in stress is quite significant and can have serious implications for the fatigue life of turbine blades.

scholarly journals Stochastic fluid structure interaction of three-dimensional plates facing a uniform flow

2016 ◽  
Vol 794 ◽  
Author(s):  
O. Cadot
Keyword(s):  
Fluid Structure Interaction ◽  
Angular Position ◽  
Three Dimensional ◽  
Uniform Flow ◽  
Steady States ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Fluid Forces ◽  
Long Time ◽  
Order Of Magnitude

An experiment on a flat rectangular plate facing a uniform flow at $Re=264\,000$ shows the importance of the base pressure loading on the asymmetric static modes of the turbulent wake. The plate is free to rotate around its short symmetry axis. For plates with aspect ratio ${\it\kappa}<6$, the angular position exhibits strong random discontinuities between steady states of non-zero angles. The steady states have long time durations, more than one order of magnitude greater than the convective time scale. The discontinuities, comparable to rare and violent events, are due to strong fluid forces associated with a drastic global change of the three-dimensional wake – mainly the switching between the static asymmetric modes. A clear transition occurs at ${\it\kappa}=6$, for which the angular fluctuations are minimum, leading for ${\it\kappa}>6$ to a classical fluid structure interaction with periodic fluctuations. The transition is supported by a recent global stability analysis of rectangular fixed plates in the laminar regime.

scholarly journals Cardiac remodelling following thoracic endovascular aortic repair for descending aortic aneurysms

2018 ◽  
Vol 55 (6) ◽  
pp. 1061-1070 ◽  
Author(s):  
Theodorus M J van Bakel ◽  
Christopher J Arthurs ◽  
Foeke J H Nauta ◽  
Kim A Eagle ◽  
Joost A van Herwaarden ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Blood Pressure ◽  
Computed Tomography Angiography ◽  
Fluid Structure Interaction ◽  
Thoracic Endovascular Aortic Repair ◽  
Endovascular Aortic Repair ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Lv Mass ◽  
The Mean

Abstract OBJECTIVES Current endografts for thoracic endovascular aortic repair (TEVAR) are much stiffer than the aorta and have been shown to induce acute stiffening. In this study, we aimed to estimate the impact of TEVAR on left ventricular (LV) stroke work (SW) and mass using a non-invasive image-based workflow. METHODS The University of Michigan database was searched for patients treated with TEVAR for descending aortic pathologies (2013–2016). Patients with available pre-TEVAR and post-TEVAR computed tomography angiography and echocardiography data were selected. LV SW was estimated via patient-specific fluid–structure interaction analyses. LV remodelling was quantified through morphological measurements using echocardiography and electrocardiographic-gated computed tomography angiography data. RESULTS Eight subjects were included in this study, the mean age of the patients was 68 (73, 25) years, and 6 patients were women. All patients were prescribed antihypertensive drugs following TEVAR. The fluid–structure interaction simulations computed a 26% increase in LV SW post-TEVAR [0.94 (0.89, 0.34) J to 1.18 (1.11, 0.65) J, P = 0.012]. Morphological measurements revealed an increase in the LV mass index post-TEVAR of +26% in echocardiography [72 (73, 17)  g/m2 to 91 (87, 26)  g/m2, P = 0.017] and +15% in computed tomography angiography [52 (46, 29)  g/m2 to 60 (57, 22)  g/m2, P = 0.043]. The post- to pre-TEVAR LV mass index ratio was positively correlated with the post- to pre-TEVAR ratios of SW and the mean blood pressure (ρ = 0.690, P = 0.058 and ρ = 0.786, P = 0.021, respectively). CONCLUSIONS TEVAR was associated with increased LV SW and mass during follow-up. Medical device manufacturers should develop more compliant devices to reduce the stiffness mismatch with the aorta. Additionally, intensive antihypertensive management is needed to control blood pressure post-TEVAR.

Sign in / Sign up

Export Citation Format

Share Document