Vibrational characteristics in small horizontal axis wind turbine system are presented in this study with a system concept called tactile response and substructuring.The main focus is on managing the dynamic propertie...Vibrational characteristics in small horizontal axis wind turbine system are presented in this study with a system concept called tactile response and substructuring.The main focus is on managing the dynamic properties like vibration,noise,and harshness that occur during the operational mode.Tactile response is defined as the response of subsystem which is induced when a human body touches a vibrating system.Sub structuring is a computational method used to reduce the dynamic behavior of a large complex system with a smaller number of degrees of freedom without disturbing the mesh size of the model.Sub structuring has the ability to combine numerical results along with the experimental results.Combination of substructuring and tactile response is applied in this study.Mode shapes of the system are analyzed and results obtained are correlated within this study to provide better optimization of the results.Wind turbine excited with wind energy depends on wind speed.Torsional vibration has a significant role in determining dynamic properties.Torsional vibration is caused as a result of the rotation of the turbine blade and depends on wind speed.The study gives importance to investigating the ability to simulate the numerical method and tactile response to predict and improve dynamic properties.展开更多
Rolling bearing and Squeeze Film Damper(SFD)are used in rotor support structures,and most researches on the nonlinear rotor-bearing system are focused on the simple rotor-bearing systems.This work emphasizes the compa...Rolling bearing and Squeeze Film Damper(SFD)are used in rotor support structures,and most researches on the nonlinear rotor-bearing system are focused on the simple rotor-bearing systems.This work emphasizes the comparative analysis of the influence of SFD on the nonlinear dynamic behavior of the dual-rotor system supported by rolling bearings.Firstly,a reduced dynamic model is established by combining the Finite Element(FE)method and the freeinterface method of component mode synthesis.The proposed model is verified by comparing the natural characteristics obtained from an FE model with those from the experiment.Then,the steady-state vibration responses of the system with or without SFD are solved by the numerical integration method.The influences of the ball bearing clearance,unbalance,centralizing spring stiffness and oil film clearance of SFD on the nonlinear steady-state vibration responses of the dual-rotor system are analyzed.Results show that SFD can effectively suppress the amplitude jump of the dual rotor system sustaining two rotors unbalance excitations.As the ball bearing clearance or unbalance increases,the amplitude jump phenomenon becomes more obvious,the resonance hysteresis phenomenon strengthens or weakens,the resonant peaks shift to the left or the right,respectively.SFD with unreasonable parameters will aggravate the system vibration,the smaller the oil film clearance,the better the damping performance of the SFD,the larger the centralizing spring stiffness is,the larger resonance amplitudes are.展开更多
In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the st...In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the strong ground motion is considered as three dimensional stationary white noise process and the pile-soil interaction and water-structure interaction are considered. The stochastic response of a typical platform to earthquake load has been computed with this method and the results compared with those obtained with the response spectrum analysis method. The comparison shows that the stochastic analysis method of the response of piled platforms to earthquake load is suitable for this kind of analysis.展开更多
In this paper, a new method, the step-reduction method, is proposed to investigate the dynamic response of the Bernoulli-Euler beams with arbitrary nonhomogeneity and arbitrary variable cross-section under arbitrary l...In this paper, a new method, the step-reduction method, is proposed to investigate the dynamic response of the Bernoulli-Euler beams with arbitrary nonhomogeneity and arbitrary variable cross-section under arbitrary loads. Both free vibration and forced vibration of such beams are studied. The new method requires to discretize the space domain into a number of elements. Each element can be treated as a homogeneous one with uniform thickness. Therefore, the general analytical solution of homogeneous beams with uniform cross-section can be used in each element. Then, the general analytic solution of the whole beam in terms of initial parameters can be obtained by satisfying the physical and geometric continuity conditions at the adjacent elements. In the case of free vibration, the frequency equation in analytic form can be obtained, and in the case of forced vibration, a final solution in analytical form can also be obtained which is involved in solving a set of simultaneous algebraic equations with only two unknowns which are independent of the numbers of elements divided. The present analysis can also be extended to the study of the vibration of such beams with viscous and hysteretic damping and other kinds of beams and other structural elements with arbitrary nonhomogeneity and arbitrary variable thickness.展开更多
Considering the aircraft and its external components are subjected to complex and variable aerodynamic loads during the working process,the missile-frame clearance system of the airborne external missile is investigat...Considering the aircraft and its external components are subjected to complex and variable aerodynamic loads during the working process,the missile-frame clearance system of the airborne external missile is investigated.The random vibration characteristics of the airborne external components are analyzed by finite element method.The finite element model is optimized with reference to the test results,and the effects of different clearance on the dynamic response of the missile-frame system are compared.The result shows that the frequency response curves of the same position and the resonant peak frequencies are consistent under different clearances.The acceleration response at both ends of the missile is large and the amplitude near the center of mass is gentle.The results can be used to predict reasonable missile-frame clearance and make guidance to the structural design and reliability analysis of the missile-frame system.展开更多
One of the challenges in predicting the dynamic response of deepwater risers under vortex-induced vibration (VIV) is that it runs short of believable fluid loading model. Moreover, the hydrodynamic loading is also dif...One of the challenges in predicting the dynamic response of deepwater risers under vortex-induced vibration (VIV) is that it runs short of believable fluid loading model. Moreover, the hydrodynamic loading is also difficult to be measured directly in the VIV experiments without disturbing the fluid field. In the present work, by means of a finite element analysis method based on the experimental data of the response displacements, the total instantaneous distributions of hydrodynamic forces together with the hydrodynamic coefficients on the riser model with large aspect ratio (length/diameter) of 1750 are achieved. The steady current speeds considered in the experiments of this work are ranging from 0.15 m/s to 0.60 m/s, giving the Reynolds Number between 2400 and 9600. The hydrodynamic coefficients are evaluated at the fundamental frequency and in the higher order frequency components for both in-line and cross-flow directions. It is found that the Root-Mean Squared hydrodynamic forces of the higher order response frequency are larger than those of the fundamental response frequency. Negative lift or drag coefficients are found in the numerical results which is equivalent to the effect of fluid damping.展开更多
文摘Vibrational characteristics in small horizontal axis wind turbine system are presented in this study with a system concept called tactile response and substructuring.The main focus is on managing the dynamic properties like vibration,noise,and harshness that occur during the operational mode.Tactile response is defined as the response of subsystem which is induced when a human body touches a vibrating system.Sub structuring is a computational method used to reduce the dynamic behavior of a large complex system with a smaller number of degrees of freedom without disturbing the mesh size of the model.Sub structuring has the ability to combine numerical results along with the experimental results.Combination of substructuring and tactile response is applied in this study.Mode shapes of the system are analyzed and results obtained are correlated within this study to provide better optimization of the results.Wind turbine excited with wind energy depends on wind speed.Torsional vibration has a significant role in determining dynamic properties.Torsional vibration is caused as a result of the rotation of the turbine blade and depends on wind speed.The study gives importance to investigating the ability to simulate the numerical method and tactile response to predict and improve dynamic properties.
基金supported by the National Natural Science Foundation of China(Nos.11772089,11972112)the Fundamental Research Funds for the Central Universities,China(Nos.N170308028,N2003014 and N180708009)LiaoNing Revitalization Talents Program,China(Nos.XLYC1807008)。
文摘Rolling bearing and Squeeze Film Damper(SFD)are used in rotor support structures,and most researches on the nonlinear rotor-bearing system are focused on the simple rotor-bearing systems.This work emphasizes the comparative analysis of the influence of SFD on the nonlinear dynamic behavior of the dual-rotor system supported by rolling bearings.Firstly,a reduced dynamic model is established by combining the Finite Element(FE)method and the freeinterface method of component mode synthesis.The proposed model is verified by comparing the natural characteristics obtained from an FE model with those from the experiment.Then,the steady-state vibration responses of the system with or without SFD are solved by the numerical integration method.The influences of the ball bearing clearance,unbalance,centralizing spring stiffness and oil film clearance of SFD on the nonlinear steady-state vibration responses of the dual-rotor system are analyzed.Results show that SFD can effectively suppress the amplitude jump of the dual rotor system sustaining two rotors unbalance excitations.As the ball bearing clearance or unbalance increases,the amplitude jump phenomenon becomes more obvious,the resonance hysteresis phenomenon strengthens or weakens,the resonant peaks shift to the left or the right,respectively.SFD with unreasonable parameters will aggravate the system vibration,the smaller the oil film clearance,the better the damping performance of the SFD,the larger the centralizing spring stiffness is,the larger resonance amplitudes are.
文摘In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the strong ground motion is considered as three dimensional stationary white noise process and the pile-soil interaction and water-structure interaction are considered. The stochastic response of a typical platform to earthquake load has been computed with this method and the results compared with those obtained with the response spectrum analysis method. The comparison shows that the stochastic analysis method of the response of piled platforms to earthquake load is suitable for this kind of analysis.
文摘In this paper, a new method, the step-reduction method, is proposed to investigate the dynamic response of the Bernoulli-Euler beams with arbitrary nonhomogeneity and arbitrary variable cross-section under arbitrary loads. Both free vibration and forced vibration of such beams are studied. The new method requires to discretize the space domain into a number of elements. Each element can be treated as a homogeneous one with uniform thickness. Therefore, the general analytical solution of homogeneous beams with uniform cross-section can be used in each element. Then, the general analytic solution of the whole beam in terms of initial parameters can be obtained by satisfying the physical and geometric continuity conditions at the adjacent elements. In the case of free vibration, the frequency equation in analytic form can be obtained, and in the case of forced vibration, a final solution in analytical form can also be obtained which is involved in solving a set of simultaneous algebraic equations with only two unknowns which are independent of the numbers of elements divided. The present analysis can also be extended to the study of the vibration of such beams with viscous and hysteretic damping and other kinds of beams and other structural elements with arbitrary nonhomogeneity and arbitrary variable thickness.
基金funded by National Natural Science Foundation of China(No.11972295)the Key Laboratory of Vibration and Control of Aero-Propulsion System Ministry of Education,Northeastern University(No.VCAME201803)+1 种基金Aeronautical Science Foundation of China(Nos.20182953025,2016ZD12032)Graduate Innovation Fund of Northwestern Polytechnical University(No.ZZ2019126)。
文摘Considering the aircraft and its external components are subjected to complex and variable aerodynamic loads during the working process,the missile-frame clearance system of the airborne external missile is investigated.The random vibration characteristics of the airborne external components are analyzed by finite element method.The finite element model is optimized with reference to the test results,and the effects of different clearance on the dynamic response of the missile-frame system are compared.The result shows that the frequency response curves of the same position and the resonant peak frequencies are consistent under different clearances.The acceleration response at both ends of the missile is large and the amplitude near the center of mass is gentle.The results can be used to predict reasonable missile-frame clearance and make guidance to the structural design and reliability analysis of the missile-frame system.
基金supported by the 863 Program of China (Grant No. 2006AA09A103)partially supported by the National Natural Science Foundation of China (Grant No. 50921001)the open fund from the State Key Laboratory of Coastal and Offshore Engineering (Grant No. LP0904)
文摘One of the challenges in predicting the dynamic response of deepwater risers under vortex-induced vibration (VIV) is that it runs short of believable fluid loading model. Moreover, the hydrodynamic loading is also difficult to be measured directly in the VIV experiments without disturbing the fluid field. In the present work, by means of a finite element analysis method based on the experimental data of the response displacements, the total instantaneous distributions of hydrodynamic forces together with the hydrodynamic coefficients on the riser model with large aspect ratio (length/diameter) of 1750 are achieved. The steady current speeds considered in the experiments of this work are ranging from 0.15 m/s to 0.60 m/s, giving the Reynolds Number between 2400 and 9600. The hydrodynamic coefficients are evaluated at the fundamental frequency and in the higher order frequency components for both in-line and cross-flow directions. It is found that the Root-Mean Squared hydrodynamic forces of the higher order response frequency are larger than those of the fundamental response frequency. Negative lift or drag coefficients are found in the numerical results which is equivalent to the effect of fluid damping.