Development of Vortex Filament Method for Aerodynamic Loads on Rotor Blades

Wind power is currently one of the most reliable new energy sources serving as an alternative tofossil fuel generated electricity and is known as a widely distributed clean and renewable sourceof energy. It is now the world’s fastest growing energy source and has also become one of themost rapidly expanding industries.The aerodynamics of a wind turbine are governed by the flow around the rotor, where theprediction of air loads on rotor blades in different operational conditions and its relation to rotorstructural dynamics is crucial for design purposes. One of the most important challenges in windturbine aerodynamics is therefore to accurately predict the forces on the blade, where the bladeand wake are modeled by different approaches such as the Blade Element Momentum (BEM)theory, the vortex method and Computational Fluid Dynamics (CFD). Here, the application ofthe vortex filament method for wind turbine aerodynamic performance is used. Different blademodels such as the lifting line and the lifting surface with prescribed and free wake models arestudied. The main purpose is to find the proper combination of blade and wake models for theaerodynamic loads as well as the computational time in order to develop an accurate and efficientaerodynamic tool. The results of the different approaches are compared with the BEM methodand GENUVP code (see the acknowledgments)

Assessment of flow characteristics over complex terrain covered by the heterogeneous forest at slightly varying mean flow directions: (A case study of a Swedish wind farm)

The impact of heterogeneous forest canopies and complex terrain on the horizontal distortion of the inflow is studied. Large-Eddy Simulation (LES) of the neutral Atmospheric Boundary Layer (ABL) flow is performed for a wind farm in Sweden for three cases associated with three different wind directions at the range of the static yaw misalignment (≃\ub16∘) where the yaw control system is not activated. The ground topography and forest properties for the numerical modeling are extracted from the Airborne Laser Scanning (ALS) 3D data. The wind turbines within the wind farm are introduced using the actuator disk model. To focus on the airflow deflection only by the complex terrain and vegetation, the study is limited to upstream wind turbines without any wake interaction. The predicted mean wind speed and turbulence intensity for the upstream wind turbines are compared against the nacelle-mounted anemometers taken from the wind farm\u27s turbine SCADA data. To quantify the additional load and moments induced at the rotor blades by the horizontal misalignment of the incoming flow, aero-structural simulation of the upstream wind turbines in the wind farm for all three cases is performed. The results show that the horizontal distortion of the inflow over the rotor swept area is usually kept below the range of static yaw misalignment (≃6∘) for the majority of the upstream wind turbines for all three cases. However, the impact of a large vertical shear exponent leading to misinterpretation of the results must be taken into consideration. Furthermore, the load imbalance of the rotor due to the vertical wind shear has the least direct contribution to the yaw moment. However, for a mean vertical shear exponent larger than α=0.25, contrary to expectation, a positive mean yaw moment under the positive-yawed inflow may be observed

Assessing the Role of Automation in Managing of Iranian E-banking and its Impact on Social Benefit

Banks in the field of commercial developments have attention to create structural changes in the receiving and payment systems and also have facilities in services process to customers. In fact we can claim one of the reasons of general tendency to electronic business is the banks managers’ attention to the importance and necessity of this phenomenon, thus have led to their trend and serious attention for providing banking structure, based on electronic method. What banking services makes it different in comparing with other conventional methods for using E-Banking systems, is, quantitative and qualitative expansion in customer service. In other words, E-Banking, prepares the situation to customer till have wider and more diverse services. Furthermore, time and spatial dimension will not have effect in reducing or increasing services to customers. Also the customer can control his/her financial activities in every time and everywhere without attending in bank’s branches. The aim of this paper is to illustrate the status of banking automation, its social and organizational consequences in Iranian E-banking system, and providing appropriate recommendations.Bank automation, ATM, E-banking, service quality.

Development of Vortex Filament Method for Wind Power Aerodynamics

Wind power is currently one of the cleanest and widely distributed renewable energy sources serving as an alternative to fossil fuel generated electricity. Exponential growth of wind turbines all around the world makes it apt for different research disciplines. The aerodynamics of a wind turbine is governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is crucial for design, development and optimization purposes. This leads us to focus on high-fidelity modeling of the rotor and wake aerodynamics. There are different methods for modeling the aerodynamics of a wind turbine with different levels of complexity and accuracy, such as the Blade Element Momentum (BEM) theory, Vortex method and Computational Fluid Dynamics (CFD). Historically, the vortex method has been widely used for aerodynamic analysis of airfoils and aircrafts. Generally, it may stand between the CFD and BEM methods in terms of the reliability, accuracy and computational efficiency. In the present work, a free vortex filament method for wind turbine aerodynamics was developed. Among different approaches for modeling the blade (e.g. a lifting line or a lifting surface) and wake (e.g. a prescribed or a free wake model), the Vortex Lattice Free Wake (VLFW) model known as the most accurate and computationally expensive vortex method was implemented. Because of the less restrictive assumptions, it could be used for unsteady load calculations, especially for time-varying flow environment which are classified according to the atmospheric conditions, e.g. wind shear and turbulent inflow together with the turbine structure such as yaw misalignment, rotor tilt and blade elastic deformation. In addition to the standard potential method for aerodynamic load calculation using the VLFW method, two additional methods, namely the 2D static airfoil data model and the dynamic stall model were implemented to increase capability of the free vortex wake method to predict viscous phenomena such as drag and separation using tabulated airfoil data. The implemented VLFW method was validated against the BEM and CFD methods, the GENUVP code by National Technical University of Athens (NTUA), Hönö turbine measurement data and MEXICO wind tunnel measurements. The results showed that the VLFW model might be used as a suitable engineering method for wind turbine’s aerodynamics covering a broad range of operating conditions

Development of Free Vortex Wake Model for Wind Turbine Aerodynamics under Yaw Condition

The aerodynamics of a wind turbine is governed by the flow around the rotor. One of the most severe operating conditions for a wind turbine is the yaw misalignment, when the mean upstream flow is not perpendicular to the rotor plane. This asymmetrical flow changes significantly the velocity field around the rotor blades which in turn reduces power production of the wind turbine. It also makes a periodic load variation along the rotor blade which accordingly increases the fatigue load from the design point of view. In this paper, the effect of the skewed wake, due to the yaw misalignment, on the wake aerodynamics of wind turbine is studied. For this purpose, an in-house Vortex Lattice Free Wake (VLFW) code, based on the potential, inviscid and irrotational flow, is developed. The results are compared with the MEXICO wind tunnel measurements. For the axial traverses, there is a good agreement between the measured axial (w) and tangential (u) velocity components and the simulations. Although the magnitude of the mean radial velocity component (v) is fairly well predicted, its fluctuation is not captured by the simulation. Moreover, for the radial traverses, the simulations are remarkably verified by the measurements

Enhancement of Free Vortex Filament Method for Aerodynamic Loads on Rotor Blades

The aerodynamics of a wind turbine is governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is one of the most important challenges in wind turbine rotor blade design. Because of the unsteady flow field around wind turbine blades, prediction of aerodynamic loads with high level of accuracy is difficult and increases the uncertainty of load calculations. An in-house vortex lattice free wake (VLFW) code, based on the inviscid, incompressible, and irrotational flow (potential flow), was developed to study the aerodynamic loads. Since it is based on the potential flow, it cannot be used to predict viscous phenomena such as drag and boundary layer separation. Therefore, it must be coupled to tabulated airfoil data to take the viscosity effects into account. Additionally, a dynamic approach must be introduced to modify the aerodynamic coefficients for unsteady operating conditions. This approach, which is called dynamic stall, adjusts the lift, the drag, and the moment coefficients for each blade element on the basis of the two dimensional (2D) static airfoil data together with the correction for separated flow. Two different turbines, NREL and MEXICO, are used in the simulations. Predicted normal and tangential forces using the VLFW method are compared with the blade element momentum (BEM) method, the GENUVP code, and the MEXICO wind tunnel measurements. The results show that coupling to the 2D static airfoil data improves the load and power predictions while employing the dynamic stall model to take the time-varying operating conditions into consideration is crucial

Numerical Studies of the Upstream Flow Field around a Horizontal Axis Wind Turbine

The aerodynamics of a wind turbine is governed by the flow around the rotor. Prediction of the velocity field, both upstream and downstream, is one of the challenges for wind turbine performance in terms of the aerodynamic loads and the generated power at different operational conditions. For simplicity, the wind velocity at the rotor plane is assumed to be equal to far upstream flow where the interaction of the rotor blades with upstream flow, close to the rotor plane, is not taken into account. This paper aims to study the effect of the rotor blade azimuthal position and the trailing wake, on upstream and downstream flow near to the rotor plane. For this purpose, an in-house Vortex Lattice Free Wake (VLFW) code, based on the potential, inviscid and irrotational flow, is developed. The results are compared with the MEXICO wind tunnel measurements. They show that the wind speed decreases in the axial direction upstream the rotor plane because of the induced velocity field by the rotor blades and the trailing wake vortices. This leads to a power reduction of the wind turbine. Furthermore, contrary to the traditional actuator disk model, the VLFW simulations predicts a tangential velocity component upstream the rotor due to the blade rotation which is in agreement with the measurement data. Finally, it is found that the flow field downstream and upstream the rotor blades depends on the blade azimuthal direction

Site-specific analysis of on wind turbines in complex terrain: A case study

This study aims to analyse and understand how the structural and drivetrain loads on the turbines can vary within a wind farm situated in a complex terrain. To this end, the flow field is studied using computational fluid and aero-elastic simulations and\ua0 \ua0a modified version of the FAST software is used to determine the turbine response Verification of the numerical results is performed by using data from turbine SCADA system for a case study of R\uf6bergsfj\ue4llet wind farm with 8 turbines located in the mid-western part of Sweden

Development of fuel and heat management systems for liquid hydrogen powered aircraft

The presentation describes the recent developments in the design of the fuel and heat management systems for liquid hydrogen powered aircraft within the H2020 project ENABLEH2. The fuel distribution system main task is to deliver the right amount of hydrogen to the combustion chamber at an adequate pressure. This requires the usage of fuel pumps, valves, insulated piping, and a fuel control system to adjust the fuel flow for a given engine rating. Moreover, since liquid hydrogen is stored at cryogenic temperatures (-253C), it also requires the integration of heat exchanger technology to increase the fuel temperature up to a state where it can be efficiently mixed with air and combusted. The combination of hydrogen high specific heat with cryogenic temperatures results in formidable cooling capacity that can be explored by compact heat-exchanger solutions. Concepts that use existing engine aero-surfaces located after rotating turbomachinery are currently being investigated a Chalmers University of Technology.\ua0 A recently commissioned facility to investigate the potential benefits of a compressor flow cooling heat rejection system will also be discussed.\ua0 The test facility comprises a vertically mounted low-speed 2.5 stage compressor designed to operate continuously at rotor mid-span chord Reynold number up to 600,000, which is representative of a large-size future geared turbofan engine. Detailed aerothermal studies at TRL4 will be conducted to calibrate in-house design methods for radical core integrated heat exchangers. The facility is driven by a 147kW electric drive at a nominal speed of 1920 RPM. Traverse access is included in two 18-degree sectors for all the rotor-stator interfaces. At the upstream plane of the compressor outlet-guide-vane, four independent access traverse systems are included for a 360-degree access. Downstream, an ABB robot arm with a U-shaped probe mount provides full volume probing access in the exit compressor duct

HRCTCov19 -- A High-Resolution Chest CT Scan Image Dataset for COVID-19 Diagnosis and Differentiation

Introduction: During the COVID-19 pandemic, computed tomography (CT) was a popular method for diagnosing COVID-19 patients. HRCT (High-Resolution Computed Tomography) is a form of computed tomography that uses advanced methods to improve image resolution. Publicly accessible COVID-19 CT image datasets are very difficult to come by due to privacy concerns, which impedes the study and development of AI-powered COVID-19 diagnostic algorithms based on CT images. Data description: To address this problem, we have introduced HRCTCov19, a new COVID-19 high-resolution chest CT scan image dataset that includes not only COVID-19 cases of Ground Glass Opacity (GGO), Crazy Paving, and Air Space Consolidation but also CT images of cases with negative COVID-19. The HRCTCov19 dataset, which includes slice-level, and patient-level labels, has the potential to aid COVID-19 research, especially for diagnosis and differentiation using artificial intelligence algorithms, machine learning, and deep learning methods. This dataset is accessible through the web at: http://databiox.com and includes 181,106 chest HRCT images from 395 patients with four labels: GGO, Crazy Paving, Air Space Consolidation, and Negative. Keywords: COVID-19, CT scan, Computed Tomography, Chest Image, Dataset, Medical ImagingComment: 5 pages, 2 figures and 1 tabl