Vibration characteristics of a rotating sandwich beam with magnetorheological fluid

In order to investigate the vibration characteristics of a rotating sandwich beam with magnetorheological (MR) fluid, the MR fluid can be simplified as linear and viscoelastic material. The finite element theory was applied to establish the finite element model of a two-node element with eight degrees of freedom for the rotating sandwich beam with MR fluid. Then the unit mass matrix and the unit stiffness matrix of the upper and lower surface elastic layers and the MR fluid of the middle layer were formed separately. And then, the equation of motion of the rotating MR fluid sandwich beams can be derived based on the Hamilton’s principle. The simulation provided the vibration characteristics of the sandwich beam under different magnetic field intensity and different rotating speeds. The result showed that the natural frequency and modal loss factor of the rotating MR fluid sandwich beam will increase with the increasing of magnetic field intensity. With the increasing of the rotating speed, the natural frequency of the rotating MR fluid sandwich beam will increase significantly and modal loss factor will reduce to some extent. So under the action of magnetic field, the MR fluid material can significantly influence the vibration characteristics of the rotating flexible beam

Aerodynamic simulation of wind turbine blade airfoil with different turbulence models

The different turbulence models have significant impacts on the aerodynamic performance of wind turbine blade airfoil. A kind of wind turbine blade airfoil was applied as the research object, in order to analyze the impacts of three different turbulence models which are S-A, k-εRNG, k-ωSST on the aerodynamic performance of wind turbine airfoil under different attack angles. By comparing the aerodynamic simulation results with the theoretical values of the lift coefficients, drag coefficients and the ratio of lift coefficient to drag coefficient for the forecast of best angle of attack, the effects of these three turbulence models on the blade airfoil aerodynamic performance were estimated in detail. The simulation of lift coefficient of wind turbine blade airfoil was verified with the flow field simulation of blade airfoil. A combined turbulence model, using different turbulence model for different angle of attack, was put forward. The simulation results demonstrate that, for the selected blade airfoil, using S-A turbulence model before the best attack angle and k-εRNG turbulence model after the best attack angle respectively, can make the simulation of blade airfoil aerodynamic performance much more accurate than the aerodynamic performance simulation using one single turbulence model, with the acceptable iterative time and the acceptable ratio of lift coefficient to drag coefficient. Therefore, the combined turbulence model can overcome the shortcomings when using only a traditional single turbulence model to simulate the aerodynamic performance of wind turbine blade airfoil, which will have a development and application value in the future

The aeroelastic analysis of two different wind turbine blades

The aeroelasticity of the wind turbine blade has been emphasized by the related fields as the size of blade increased dramatically. The eigenvalue approach and the time domain method are applied to analyze the aeroelastic responses of wind turbine blade to determine the flutter region respectively. In order to clarify the difference of the flutter analysis for different blade, two different airfoils are used. The flutter region will be obtained directly by judging the sign of the real part of the eigenvalue of the blade system using the eigenvalue approach. Then the time domain analysis of flutter of wind turbine blade will be carried out through the use of the four-order Runge-Kutta numerical method, so the flutter region will be acquired in another way. The time domain analysis can give the changing tread of the aeroelastic responses in great detail than that of the eigenvalue method. For the two different airfoils, the flutter region given by the eigenvalue approach coincides with that of the time domain analysis method accurately. There are two critical tip speed ratios for the two airfoils, the lower tip speed ratio and the higher tip speed ratio. The flap displacement of these two different airfoils will change from convergence to divergence, and change from divergence to convergence. But the extent of flutter differs with the different blade airfoil. The flutter of airfoil NACA63-418 diverges much more dramatically than that of the airfoil FX77-W-153. So the latter is better for the wind turbine blade. The eigenvalue approach combined with the time domain method can be applied to choose the blade airfoil and to determine the flutter region in order to avoid the flutter of wind turbine blade

Vibration characteristics of a rotating sandwich beam with magnetorheological fluid

In order to investigate the vibration characteristics of a rotating sandwich beam with magnetorheological (MR) fluid, the MR fluid can be simplified as linear and viscoelastic material. The finite element theory was applied to establish the finite element model of a two-node element with eight degrees of freedom for the rotating sandwich beam with MR fluid. Then the unit mass matrix and the unit stiffness matrix of the upper and lower surface elastic layers and the MR fluid of the middle layer were formed separately. And then, the equation of motion of the rotating MR fluid sandwich beams can be derived based on the Hamilton’s principle. The simulation provided the vibration characteristics of the sandwich beam under different magnetic field intensity and different rotating speeds. The result showed that the natural frequency and modal loss factor of the rotating MR fluid sandwich beam will increase with the increasing of magnetic field intensity. With the increasing of the rotating speed, the natural frequency of the rotating MR fluid sandwich beam will increase significantly and modal loss factor will reduce to some extent. So under the action of magnetic field, the MR fluid material can significantly influence the vibration characteristics of the rotating flexible beam

Finite element analysis of smart wind turbine blades sandwiched with magnetorheological fluid

A brand-new smart wind turbine blade with magnetorheological fluid (MRF) sandwiched was proposed in the research. The three-dimension entity model of a 750 KW wind turbine blades was established through the use of UG software, and three kinds of MRF sandwich layouts were considered into the blade model, that is, at the blade tip, at the blade root and at the whole blade from the root till the tip. The MRF was simplified as Kelvin-Voigt model in order to implement the finite element analysis based on ANSYS software, so that the mode shapes of smart wind turbine blade were revealed under various conditions with three different layout forms of MRF sandwich wind turbine blades. Analysis results showed that the magnetic field would influence the mode shapes of the wind turbine blade with MRF sandwiched, especially the torsion vibration. When the MRF was inserted through the blade from the root till the tip, the blade would dramatically influence the torsion vibration, so that the torsion vibration, which originally would have happened at higher orders, would arise in advance. While the MRF was located at the root of wind turbine blade, the torsion vibration would be postponed to arise at the higher orders. Therefore, the MRF should be located at the blade root, instead of the middle and the tip of wind turbine blade. Smart sandwich wind turbine blade will provide a new way to the vibration control of wind turbine blade

The aeroelastic analysis of two different wind turbine blades

The aeroelasticity of the wind turbine blade has been emphasized by the related fields as the size of blade increased dramatically. The eigenvalue approach and the time domain method are applied to analyze the aeroelastic responses of wind turbine blade to determine the flutter region respectively. In order to clarify the difference of the flutter analysis for different blade, two different airfoils are used. The flutter region will be obtained directly by judging the sign of the real part of the eigenvalue of the blade system using the eigenvalue approach. Then the time domain analysis of flutter of wind turbine blade will be carried out through the use of the four-order Runge-Kutta numerical method, so the flutter region will be acquired in another way. The time domain analysis can give the changing tread of the aeroelastic responses in great detail than that of the eigenvalue method. For the two different airfoils, the flutter region given by the eigenvalue approach coincides with that of the time domain analysis method accurately. There are two critical tip speed ratios for the two airfoils, the lower tip speed ratio and the higher tip speed ratio. The flap displacement of these two different airfoils will change from convergence to divergence, and change from divergence to convergence. But the extent of flutter differs with the different blade airfoil. The flutter of airfoil NACA63-418 diverges much more dramatically than that of the airfoil FX77-W-153. So the latter is better for the wind turbine blade. The eigenvalue approach combined with the time domain method can be applied to choose the blade airfoil and to determine the flutter region in order to avoid the flutter of wind turbine blade

Water resource security evaluation and barrier analysis in Henan Province utilizing the DPSIR framework

Water resource health is one of the necessary conditions for society to achieve sustainable development. Due to the predominant focus of most studies on relatively short time spans, with limited attention to long time series and spatial trends, this study, using various regions of Henan Province as a case study, constructs a water resource security assessment framework based on the DPSIR model encompassing Drivers (D), Pressures (P), State (S), Impact (I), and Response (R) dimensions, with a selection of 19 evaluation indicators. Based on this evaluation index system, the CRITIC-TOPSIS evaluation method is formulated by integrating the CRITIC (Criteria Importance Through Intercriteria Correlation) and TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) models. This method is employed to assess the degree of water resource security in Henan Province from 2013 to 2022. And the Obstruction Degree Model is introduced to diagnose the water resource security levels in various regions of Henan Province. The assessment results indicate that over the past decade, the overall level of water resource security in various regions of Henan Province has shown an increasing trend. Irrigated area, per capita water resources, water consumption per unit of industrial value added, per acre water consumption for agricultural irrigation, the ratio of river length meeting water quality standards, groundwater supply proportion, and sewage treatment rate are identified as the primary obstacles influencing the water resource security levels in different regions of Henan Province. The research outcomes of this study can serve as theoretical foundations to enhance urban water resource security globally, ultimately facilitating sustainable development

The Truncated Theta-EM Method for Nonlinear and Nonautonomous Hybrid Stochastic Differential Delay Equations with Poisson Jumps

In this paper, we study a class of nonlinear and nonautonomous hybrid stochastic differential delay equations with Poisson jumps (HSDDEwPJs). The convergence rate of the truncated theta-EM numerical solutions to HSDDEwPJs is investigated under given conditions. An example is shown to support our theory

Assessment of Dairy Product Safety Supervision in Sales Link: A Fuzzy-ANP Comprehensive Evaluation Method

An evaluation index system is developed to assess food safety supervision in the sales links of dairy products. Evaluation research is conducted using the fuzzy-ANP comprehensive evaluation model to assess the product safety supervision of dairy products in the sales link based on 307,705 survey data acquired from 1,501 online and offline dairy businesses in China. Evaluation results show that (1) the overall situation of dairy product safety supervision in the sales link is encumbered by the fact that the online situation of dairy product safety supervision in the sales link is general. It does not achieve a relatively good level; (2) the investment in food safety supervision of dairy products in the sales link is insufficient for the online e-commerce platforms. Especially, the processes of reviewing and approving relevant business sales qualification must be improved; (3) online business types do not directly determine the situation of dairy product safety supervision in the sales link, but the operating environment, sales staff quality, and warehousing management are common regulatory weaknesses; and (4) for offline provinces, the level of economic development can affect the situation of dairy product safety supervision in the sales link. Aside from emphasizing sales qualifications, economically backward provinces should improve the supervision of the operating environment, sales equipment, sanitary status of workers, and other aspects