1,720,995 research outputs found
Development of CAE tools for fluid-structure interaction and erosion in turbomachinery virtual prototyping
Full text linkThe work presented in this thesis is based on the development of advanced computer aided engineering tools dedicated to multi-physics coupled problems. Starting from the state of the art of numerical tools used in virtual prototyping and testing of turbomachinery systems, we found two interesting and actual possible developments focused on the improved implementation of fluid-structure interaction
and material wearing solvers. For both the topics we will present a brief overview with the contextualization on the industrial and research state of the art, the detailed description of mathematical models (Chapter 2), discretized (FEM) stabilized formulations, time integration schemes and coupling algorithms used in the implementation (Chapter 3). The second part of the thesis (Chapter 4-7) will
report some application of the developed tools on some latest challenges in turbomachinery field as rain erosion and load control in wind turbines and non-linear
aeroelasticity in large axial fans
Investigations on offshore wind turbine inflow modelling using numerical weather prediction coupled with local-scale computational fluid dynamics
Full text linkThe computational power available nowadays to industry and research paves the way to increasingly more accurate systems for the wind resource prediction. A promising approach is to support the mesoscale numerical weather prediction (NWP) with high fidelity computational fluid dynamics (CFD). This approach aims at increasing the spatial resolution of the wind prediction by not only accounting for the complex and multiphysics aspects of the atmosphere over a large geographical region, but also including the effects of the fine scale turbulence and the interaction of the wind flow with the sea surface. In this work, we test a set of model setups for both the mesoscale (NWP) and local scale (CFD) simulations employed in a multi-scale modelling framework. The method comprises a one-way coupling interface to define boundary conditions for the local scale simulation (based on the Reynolds Averaged Navier–Stokes equations) using the mesoscale wind given by the NWP system. The wind prediction in an offshore site is compared with LiDAR measurements, testing a set of mesoscale planetary boundary layer schemes, and different model choices for the local scale simulation, which include steady and unsteady approaches for simulation and boundary conditions, different turbulence closure constants, and the effect of the wave motion of the sea surface. The resulting wind is then used for the simulation of a large wind turbine, showing how a realistic wind profile and an ideal exponential law profile lead to different predictions of wind turbine rotor performance and loads
Increasing spatial resolution of wind resource prediction using NWP and RANS simulation
Full text linkThe detailed prediction of the upcoming wind on wind farms can support optimization of wind energy production and operation and maintenance. Numerical Weather Prediction (NWP) tools allow to simulate the wind over long-term forecasting horizons (up to several days) with a spatial resolution ranging between the continental level down to a few hundred meters. We present a methodology, based upon Computational Fluid Dynamics (CFD) and Reynolds Averaged Navier Stokes (RANS) modelling, that allows to downscale the spatial resolution of the wind prediction supplied by a NWP model down to the typical length-scale of wind energy applications. The proposed approach combines a number of standard tools, including: Geographical Information Systems (GIS), Advanced Research - Weather Research and Forecasting (WRF-ARW) and OpenFOAM, and proposes methods to interface these tools and set-up the local-scale simulation. Models and problem sizes are selected to keep the computational cost of the system sustainable in view of its implementation in operational forecasting. Finally, we present the application of the method on a given onshore site, and for three different meteorological conditions, showing the potential of the approach, but also giving an account of the limitations that it may encounter when dealing with complex planetary boundary layers
Numerical study on the passive control of the aeroelastic response in large axial fans
No full textThe morphing geometry concept finds interesting applications
in load reduction and performance increasing for wings and
rotor blades in off-design conditions. Here we report a numerical
study on the effect that a passive morphing system (made by an
elastic-low stiffness surface) has on the sectional load and flowfield,
when it is applied to the trailing edge of an axial fan. We
obtain the results extracting the section of the fan blade and test it
in the 2D cascade, with and without the elastic device, in different
operating conditions. Keeping in mind the two-dimensional
approximation, it will be possible to observe how the tested device
could reduce the load in off-design and high angle of attack
conditions, while the same solution could introduce vibrations in
design conditions. All the simulations imply the solution of the
fluid-structure interaction between the incompressible, turbulent
flow and the elastic structure. This solution is obtained using a
finite element based, strongly coupled solver, applied to the periodic
2D domain of the section in the cascade
Morphing of reversible axial fan blade: A FSI-FEM study
No full textReversible axial fans are widely used in industrial and tunnel ventilation systems, and a lot of research effort is spent in the design process of the blades shape and blades profile. The target is to achieve reasonable performances in both flow directions, but those are still below the levels of the corresponding nonreversible geometries. In this article, an alternative design solution for reversible axial fan is presented by adopting flexible blades instead of the rigid ones. Such design, inspired by the boat sails, could allow the blade to change its shape by passively adapting to the flow field, from a symmetrical blade profile to a not symmetric one, and thus adapting the curvature to the flow condition. In this article, a series of alternative materials and material distributions are analyzed and compared. The analysis is conducted by performing fluid-structure interaction simulations using stabilized finite elements formulations for both the fluid and the structure dynamics. Simulations are performed using the in-house built software fempar, which implements the Residual Based Variational MultiScale to model the Navier-Stokes equation, the total Lagrangian formulation for the nonlinear elastic solid, and the solid extension moving mesh technique to move the fluid mes
Aerodynamic Characterization of the IEA 15 MW Reference Wind Turbine by Code-to-Code Comparison
No full textThe consistency of different aerodynamic formulations applied to the analysis of a modern multi-megawatt horizontal axis wind turbine rotor is investigated. The proposed code-to-code comparison involves specific implementations of a hierarchy of solvers based on Blade Element Momentum Theory (AEOLIAN), Actuator Line Modelling (OpenFOAM), free-wake Panel Method (FUNAERO) and blade-resolved Computational Fluid Dynamics (OpenFOAM ). The analysis addresses local and integral aeroloads and flow physical quantities concerning the state-of-the-art IEA 15 MW reference wind turbine in axial uniform flow conditions. The proposed solvers predict consistent rotor performance and blade aeroloads (also in line with data from of IEA Task 47). However, differences emerge close to blade root, where blade-resolved CFD reveals a significant flow separation on the suction side. Furthermore, scattering of induction factors computations is observed, especially in the axial direction. Different methodologies and numerical setup used in blade-resolved simulations allow achieving physically-consistent induction values, especially at blade tip. Finally, flow-field predictions by Computational Fluid Dynamics (CFD) and Panel Method are consistent upstream and close to the disk downstream (except where significant flow separation occurs), whilst a more detailed study on the effect of extending wake refinement zone in CFD simulation is advisable
Generation of Surface Maps of Erosion Resistance for Wind Turbine Blades under Rain Flows
Full text linkRain erosion on wind turbine blades raises considerable interest in wind energy industry and research, and the definition of accurate erosion prediction systems can facilitate a rapid development of solutions for blade protection. We propose here the application of a novel methodology able to integrate a multibody aeroelastic simulation of the whole wind turbine, based on engineering models, with high-fidelity simulations of aerodynamics and particle transport and with semi-empirical models for the prediction of the damage incubation time. This methodology is applied to generate a parametric map of the blade regions potentially affected by erosion in terms of the fatigue life of the coating surface. This map can represent an important reference for the evaluation of the sustainability of maintenance, control and mitigation interventions
Numerical simulation of the blade aging process in an induced draft fan due to long time exposition to fly ash particles
No full textErosion issues usually affect fans used for the extraction of exhaust gas in power plants. Because of the presence of fly ash within the exhaust flow, fan blades are subjected to material wear at the leading edge, trailing edge, and blade surface, and this may cause a modification of the blade aerodynamic profile, a reduction of blade chord and effective camber. All these effects result in a deterioration of the aerodynamic performance of the blade. Prediction of erosion process in industrial applications helps to better schedule the maintenance and predict the blade life. However, since usually numerical simulations of erosion process do not account for the change in target geometry, and then the variation in time of the erosion process itself, they can be only used to study a very short part (namely the beginning) of the whole process. To this aim, we report a numerical simulation of the blade aging process due to particle erosion in an induced draft fan. This is done using in-house numerical tools able to iteratively simulate the flow field, compute the particle tracking/dispersion/erosion, and modify the geometry (and mesh) according to the predicted erosion rate. First, we study the effect of the geometry damage due to erosion, for a generic particle flow and a given expected maximum damage. In the second part of the computation, a scale factor is introduced to align the simulation time and particle concentrations to a real application, comparing the results with the on-field observation
Rain erosion numerical modeling applied to multi-MW Off-shore wind turbine
Full text linkIn this work, the authors present a numerical prediction of erosion on two different blade geometry of a 6 MW HAWT designed for different aerodynamic loading, with the aim of studying their sensitiveness to erosion. First, the fully 3D simulations are performed using an Euler-Lagrangian approach. Flow field simulations are carried out with the open-source code OpenFOAM, based on a finite volume approach, using Multiple Reference Frame methodology. Reynolds Averaged Navier- Stokes equations for incompressible flow were solved with a k-s turbulence model. An in-house code (P-Track) is used to compute the rain drops transport and dispersion, adopting the Particle Cloud Tracking approach (PCT). The PCT was used by some of the authors in previous works (Corsini et al., 2012; Corsini et al., 2014) to predict erosion on both axial and centrifugal fans, obtaining satisfactory results. The PCT allows to simulate a huge number of transported phase tracking just few cloud trajectories, thus resulting in reduction of computational time comparing with single particle tracking approach. Erosion is modelled accounting for the main quantities affecting the phenomenon, which is impact velocity and angle, and material properties of the target surface. Results provide the regions of the two blades more sensitive to erosion, and the effect of the blade geometry on erosion attitude
Impact of meteorological data factors and material characterization method on the predictions of leading edge erosion of wind turbine blades
No full textLeading edge erosion of wind turbine blades is a major contributor to wind farm energy yield losses and maintenance costs. Presented is a multidisciplinary framework for predicting rain erosion lifetimes of wind turbine blades. Key aim is assessing the sensitivity of lifetime predictions to: modeling aspects (material erosion model, blade aerodynamics), input data and/or their preprocessing (joint frequency distribution of wind speed and droplet size based on synchronous site-specific measurements versus frequency distribution generated with partly site-agnostic modeling standards, wind speed records of nacelle anemometer or extrapolated at hub height from met masts), and environmental conditions (UV weathering). The analyses consider a Northwest England onshore site where a utility-scale turbine is operational, focus on a reference 5 MW turbine assumed operational at the site, and use a typical leading edge coating material. It is found that the largest variations in erosion lifetime predictions are due to material erosion model (based on rain erosion test data or fundamental material properties) and wind and rain model (measurement-based joint wind speed and droplet size distribution or standard-based modeled distribution). The use of joint wind and rain distribution also enables identifying wind/rain states with highest erosion potential, knowledge paramount to deploying erosion-safe turbine control
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