The so-called coaxial compound helicopter features two rigid coaxial rotors,and possesses high-speed capabilities.Nevertheless,the small separation of the coaxial rotors causes severe aerodynamic interactions,which re...The so-called coaxial compound helicopter features two rigid coaxial rotors,and possesses high-speed capabilities.Nevertheless,the small separation of the coaxial rotors causes severe aerodynamic interactions,which require careful analysis.In the present work,the aerodynamic interaction between the various helicopter components is investigated by means of a numerical method considering both hover and forward flight conditions.While a sliding mesh method is used to deal with the rotating coaxial rotors,the Reynolds-Averaged Navier-Stokes(RANS)equations are solved for the flow field.The Caradonna&Tung(CT)rotor and Harrington-2 coaxial rotor are considered to validate the numerical method.The results show that the aerodynamic interaction of the two rigid coaxial rotors significantly influences hover’s induced velocity and pressure distribution.In addition,the average thrust of an isolated coaxial rotor is smaller than that of the corresponding isolated single rotor.Compared with the isolated coaxial rotor,the existence of the fuselage results in an increment in the thrust of the rotors.Furthermore,these interactions between the components of the considered coaxial compound helicopter decay with an increase in the advance ratio.展开更多
As a part of the new energy development trend,distributed power generation may fully utilize a variety of decentralized energy sources.Buildings close to the installation location,besides,may have a considerable impac...As a part of the new energy development trend,distributed power generation may fully utilize a variety of decentralized energy sources.Buildings close to the installation location,besides,may have a considerable impact on the wind turbines’operation.Using a combined vertical axis wind turbine with an S-shaped lift outer blade and-shaped drag inner blade,this paper investigates how a novel type of upstream wall interacts with the incident wind at various speeds,the influence region of the turbulent vortex,and performance variation.The results demonstrate that the building’s turbulence affects the wind’s horizontal and vertical direction,as well as its speed,in downstreamplaces.The wall’s effect on wind speed changing in the downstreamarea is thoroughly investigated.It turns out that while choosing an installation location,disturbing flow areas or low disturbing flow zones should be avoided to have the least impact on wind turbine performance.展开更多
In contrast to the concurrent mixer-settler,the interaction between the mixing and settling chambers have to be taken into account in the simulation of the countercurrent mixer-settler,and no work has been reported fo...In contrast to the concurrent mixer-settler,the interaction between the mixing and settling chambers have to be taken into account in the simulation of the countercurrent mixer-settler,and no work has been reported for this equipment.In this work,a three-phase flow model based on the Eulerian multiphase model,coupled with a sliding mesh model is proposed for a countercurrent mixer-settler.Based on this,the dispersed phase distribution,flow pattern,and pressure distribution are investigated,which can help to fill the gap in the operation mechanism.In addition,the velocity vector distribution at the phase port shows an intriguing phenomenon that two types of vectors with opposite directions are distributed on the left and right sides of the same plane,which indicates that the material exchange in the mixing and settling chambers is simultaneous.Analysis of this variation at this location by a fast Fourier transform(FFT)method reveals that it is mainly influenced by the mixing chamber and is consistent with the main period of the outlet flow fluctuations.Therefore,by monitoring the fluctuation of the outlet flow and then analyzing it by the FFT method,the state of the whole tank can be determined,which makes it promising for the design of control systems for countercurrent mixer-settlers.展开更多
The hydraulic robot with large output torque is widely used in industry,however,its precision is not high.In order to solve this problem,this paper presents a new structure of rotary valve with double-rotation valve p...The hydraulic robot with large output torque is widely used in industry,however,its precision is not high.In order to solve this problem,this paper presents a new structure of rotary valve with double-rotation valve port,which can improve the two-step throttle characteristics of the valve port,reduce the cavitation phenomenon of the valve port,and increase the output accuracy of the hydraulic servo joint.Firstly,the internal flow field of the rotary valve is simulated by using the sliding grid technology of FLUENT software,and the changing rule of the throttle position in the working process of the structure is analyzed.Secondly,compared with the simulation results of rotary valve with single-rotation valve port,it is shown that the two-step throttle characteristics of the structure are less affected by the change of the opening of the rotary valve,and the cavitation index of the joint valve port is reduced.Finally,the influence of the rotation speed of the valve core,oil supply pressure and key dimension of valve core on throttle characteristics of rotary valve have been analyzed.展开更多
Rolling characteristics of the canard-controlled rocket with a free-spinning tail are researched based on 3-dimensional Navier–Stokes(N–S)equations.The slide mesh technology of computational fluid dynamics is used ...Rolling characteristics of the canard-controlled rocket with a free-spinning tail are researched based on 3-dimensional Navier–Stokes(N–S)equations.The slide mesh technology of computational fluid dynamics is used to numerically simulate the flow field when tails rotate relative to the rocket body and research the varying pattern of roll moment coefficients of the whole rocket,tail,and canard with Mach number.The comparison between the computation results and a part of experimental data shows that the simulation method is accurate.The convergence criterion during the numerical simulation is put forward;the induced rotation speed of the free-spinning tail and the roll moment coefficient of the rocket under this rotation in actual flight when the canard deflects by 10◦for roll control are obtained and the reason for the free-spinning tail being able to eliminate roll coupling is analyzed.The research provides a reference for the configuration design of canard-controlled rockets with a free-spinning tail and the numerical simulation of their aerodynamic characteristics.展开更多
In this paper we present a generalized lattice Boltzmann based approach for sliding-mesh local reference frame.This scheme exactly conserves hydrodynamic fluxes across local reference frame interface.The accuracy and ...In this paper we present a generalized lattice Boltzmann based approach for sliding-mesh local reference frame.This scheme exactly conserves hydrodynamic fluxes across local reference frame interface.The accuracy and robustness of our scheme are demonstrated by benchmark validations.展开更多
基金supported by Rotor Aerodynamics Key Laboratory[Grant No.RAL202102-4].
文摘The so-called coaxial compound helicopter features two rigid coaxial rotors,and possesses high-speed capabilities.Nevertheless,the small separation of the coaxial rotors causes severe aerodynamic interactions,which require careful analysis.In the present work,the aerodynamic interaction between the various helicopter components is investigated by means of a numerical method considering both hover and forward flight conditions.While a sliding mesh method is used to deal with the rotating coaxial rotors,the Reynolds-Averaged Navier-Stokes(RANS)equations are solved for the flow field.The Caradonna&Tung(CT)rotor and Harrington-2 coaxial rotor are considered to validate the numerical method.The results show that the aerodynamic interaction of the two rigid coaxial rotors significantly influences hover’s induced velocity and pressure distribution.In addition,the average thrust of an isolated coaxial rotor is smaller than that of the corresponding isolated single rotor.Compared with the isolated coaxial rotor,the existence of the fuselage results in an increment in the thrust of the rotors.Furthermore,these interactions between the components of the considered coaxial compound helicopter decay with an increase in the advance ratio.
基金supported in part by the Provincial,Municipal and Autonomous Region Science and Technology Project Funds of China 2021GG0336 and 2016030331。
文摘As a part of the new energy development trend,distributed power generation may fully utilize a variety of decentralized energy sources.Buildings close to the installation location,besides,may have a considerable impact on the wind turbines’operation.Using a combined vertical axis wind turbine with an S-shaped lift outer blade and-shaped drag inner blade,this paper investigates how a novel type of upstream wall interacts with the incident wind at various speeds,the influence region of the turbulent vortex,and performance variation.The results demonstrate that the building’s turbulence affects the wind’s horizontal and vertical direction,as well as its speed,in downstreamplaces.The wall’s effect on wind speed changing in the downstreamarea is thoroughly investigated.It turns out that while choosing an installation location,disturbing flow areas or low disturbing flow zones should be avoided to have the least impact on wind turbine performance.
基金the National Natural Science Foundation of China(21978198)for financial support。
文摘In contrast to the concurrent mixer-settler,the interaction between the mixing and settling chambers have to be taken into account in the simulation of the countercurrent mixer-settler,and no work has been reported for this equipment.In this work,a three-phase flow model based on the Eulerian multiphase model,coupled with a sliding mesh model is proposed for a countercurrent mixer-settler.Based on this,the dispersed phase distribution,flow pattern,and pressure distribution are investigated,which can help to fill the gap in the operation mechanism.In addition,the velocity vector distribution at the phase port shows an intriguing phenomenon that two types of vectors with opposite directions are distributed on the left and right sides of the same plane,which indicates that the material exchange in the mixing and settling chambers is simultaneous.Analysis of this variation at this location by a fast Fourier transform(FFT)method reveals that it is mainly influenced by the mixing chamber and is consistent with the main period of the outlet flow fluctuations.Therefore,by monitoring the fluctuation of the outlet flow and then analyzing it by the FFT method,the state of the whole tank can be determined,which makes it promising for the design of control systems for countercurrent mixer-settlers.
基金Supported by the National Natural Science Foundation of China(No.61105086)Hubei Province Natural Science Foundation(No.2018CFB626)+1 种基金Wuhan Application Foundation Frontier Project(No.2019010701011404)Institute of Robotics and Intelligent Systems Foundation(No.F201803)。
文摘The hydraulic robot with large output torque is widely used in industry,however,its precision is not high.In order to solve this problem,this paper presents a new structure of rotary valve with double-rotation valve port,which can improve the two-step throttle characteristics of the valve port,reduce the cavitation phenomenon of the valve port,and increase the output accuracy of the hydraulic servo joint.Firstly,the internal flow field of the rotary valve is simulated by using the sliding grid technology of FLUENT software,and the changing rule of the throttle position in the working process of the structure is analyzed.Secondly,compared with the simulation results of rotary valve with single-rotation valve port,it is shown that the two-step throttle characteristics of the structure are less affected by the change of the opening of the rotary valve,and the cavitation index of the joint valve port is reduced.Finally,the influence of the rotation speed of the valve core,oil supply pressure and key dimension of valve core on throttle characteristics of rotary valve have been analyzed.
文摘Rolling characteristics of the canard-controlled rocket with a free-spinning tail are researched based on 3-dimensional Navier–Stokes(N–S)equations.The slide mesh technology of computational fluid dynamics is used to numerically simulate the flow field when tails rotate relative to the rocket body and research the varying pattern of roll moment coefficients of the whole rocket,tail,and canard with Mach number.The comparison between the computation results and a part of experimental data shows that the simulation method is accurate.The convergence criterion during the numerical simulation is put forward;the induced rotation speed of the free-spinning tail and the roll moment coefficient of the rocket under this rotation in actual flight when the canard deflects by 10◦for roll control are obtained and the reason for the free-spinning tail being able to eliminate roll coupling is analyzed.The research provides a reference for the configuration design of canard-controlled rockets with a free-spinning tail and the numerical simulation of their aerodynamic characteristics.
文摘In this paper we present a generalized lattice Boltzmann based approach for sliding-mesh local reference frame.This scheme exactly conserves hydrodynamic fluxes across local reference frame interface.The accuracy and robustness of our scheme are demonstrated by benchmark validations.