The technical programme and measurement system of experimental investigation of unsteady dynamic characteristics are introduced. The unsteady lift characteristics of a delta wing with leading edge sweep angle 60°...The technical programme and measurement system of experimental investigation of unsteady dynamic characteristics are introduced. The unsteady lift characteristics of a delta wing with leading edge sweep angle 60°are investigated when the wing is rapidly pitching up at incidence from 0°until 90°.The experimental results are that the maximum lift coefficient and stall incidence are increased with increased pitch-up rate. when the wing is rapidly pitching up. The infuences of reduced frequency. average incidence, the oscillating amplitude and pitch axis location on the unsteady instantaneous force produced by oscillating wings are investigated too.展开更多
Algebraic methods and rapid deforming techniques are used to generate three-dimensional boundary-fitted dynamic grids for assemblies. The conservative full-potential equation is solved by a time-accurate approximate f...Algebraic methods and rapid deforming techniques are used to generate three-dimensional boundary-fitted dynamic grids for assemblies. The conservative full-potential equation is solved by a time-accurate approximate factorization algorithm and internal Newton iterations. An integral boundary layer method based on the dissipation integral is used to account for viscous effects. The computational results about unsteady transonic forces on wings, bodies and control surfaces are in agreement with experimental data.展开更多
As a main tool for the lunar exploration and Mars landing project, the reentry capsule is responsible for the transportation of personnel and supplies, and it is very important to ensure its safety. The complex flow f...As a main tool for the lunar exploration and Mars landing project, the reentry capsule is responsible for the transportation of personnel and supplies, and it is very important to ensure its safety. The complex flow field caused by the shape of the large blunt cone makes it unstable in transonic and supersonic flight, so its dynamic characteristics need to be analyzed. This paper analyzes the dynamic characteristics of the reentry capsule by computational fluid dynamics(CFD) numerical simulation. The pitching combined dynamic derivative was obtained by simulation of forced pitching oscillation of the flight vehicle using the rigid dynamic grid; the time difference derivative was obtained by simulation of plunging of the flight vehicle using the rigid dynamic grid, too. The direct dynamic derivative was gained by negating the plunging derivative from sum. This paper simulates the pitching and plunging motion of NACA0012 air foil and hypersonic ballistic shape(HBS). The results of the simulation are consistent with the references. The Mars exploration rover entry capsule was simulated and analyzed to ensure a basis for the aerodynamic design and control of the reentry capsule.展开更多
Taking a propfan engine as the research object,the CFD method was used for 3D modeling and unsteady slip flow for numerical calculation.The propfan rotation domain and the nacelle outside flow domain were meshed by us...Taking a propfan engine as the research object,the CFD method was used for 3D modeling and unsteady slip flow for numerical calculation.The propfan rotation domain and the nacelle outside flow domain were meshed by using the partition splicing grid technology.Used the Reynolds⁃averaged of N⁃S equation,the Reynolds stress term uses the RNG turbulence model;and based on the slip grid method,numerical calculation of the flow field with different Mach numbers,front and rear blade angles and engine state were carried out;and the change law of propeller fan characteristics and the influence of slip flow on the inlet flow field were analyzed.The blade angle was the key parameter of the propeller fan characteristic conditions.When the blade angle increases from 41°to 50°,the thrust coefficient increases by 31.2%,and the power coefficient increases by 33.4%;in the climbing state of the propeller fan,the maximum total pressure distortion at the inlet port of 6.8%;the cross section is less affected by the slip flow of the propfan;and the pressure distribution is relatively uniform,but the area of the flow channel is small.The research results can provide a solution for the matching of the counter⁃rotating propeller fan and the engine and the arrangement of the air inlet measuring rake.展开更多
This paper numerically studies the aerodynamic performance of a bird-like bionic flapping wing.The geometry and kinematics are designed based on a seagull wing,in which flapping,folding,swaying,and twisting are consid...This paper numerically studies the aerodynamic performance of a bird-like bionic flapping wing.The geometry and kinematics are designed based on a seagull wing,in which flapping,folding,swaying,and twisting are considered.An in-house unsteady flow solver based on hybrid moving grids.is adopted for unsteady flow simulations.We focus on two main issues in this study,i.e.,the influence of the proportion of down-stroke and the effect of span-wise twisting.Numerical results show that the proportion of downstroke is closely related to the efficiency of the flapping process.The preferable proportion is about 0.7 by using the present geometry and kinematic model,which is very close to the observed data.Another finding is that the drag and the power consumption can be greatly reduced by the proper span-wise twisting.Two cases with different reduced frequencies are simulated and compared with each other.The numerical results show that the power consumption reduces by more than 20%,and the drag coefficient reduces by more than 60% through a proper twisting motion for both cases.The flow mechanism is mainly due to controlling of unsteady flow separation by adjusting the local effective angle of attack.These conclusions will be helpful for the high-performance micro air vehicle (MAV) design.展开更多
文摘The technical programme and measurement system of experimental investigation of unsteady dynamic characteristics are introduced. The unsteady lift characteristics of a delta wing with leading edge sweep angle 60°are investigated when the wing is rapidly pitching up at incidence from 0°until 90°.The experimental results are that the maximum lift coefficient and stall incidence are increased with increased pitch-up rate. when the wing is rapidly pitching up. The infuences of reduced frequency. average incidence, the oscillating amplitude and pitch axis location on the unsteady instantaneous force produced by oscillating wings are investigated too.
基金Aeronautical Science Foundation of China (99A52007)
文摘Algebraic methods and rapid deforming techniques are used to generate three-dimensional boundary-fitted dynamic grids for assemblies. The conservative full-potential equation is solved by a time-accurate approximate factorization algorithm and internal Newton iterations. An integral boundary layer method based on the dissipation integral is used to account for viscous effects. The computational results about unsteady transonic forces on wings, bodies and control surfaces are in agreement with experimental data.
文摘As a main tool for the lunar exploration and Mars landing project, the reentry capsule is responsible for the transportation of personnel and supplies, and it is very important to ensure its safety. The complex flow field caused by the shape of the large blunt cone makes it unstable in transonic and supersonic flight, so its dynamic characteristics need to be analyzed. This paper analyzes the dynamic characteristics of the reentry capsule by computational fluid dynamics(CFD) numerical simulation. The pitching combined dynamic derivative was obtained by simulation of forced pitching oscillation of the flight vehicle using the rigid dynamic grid; the time difference derivative was obtained by simulation of plunging of the flight vehicle using the rigid dynamic grid, too. The direct dynamic derivative was gained by negating the plunging derivative from sum. This paper simulates the pitching and plunging motion of NACA0012 air foil and hypersonic ballistic shape(HBS). The results of the simulation are consistent with the references. The Mars exploration rover entry capsule was simulated and analyzed to ensure a basis for the aerodynamic design and control of the reentry capsule.
文摘Taking a propfan engine as the research object,the CFD method was used for 3D modeling and unsteady slip flow for numerical calculation.The propfan rotation domain and the nacelle outside flow domain were meshed by using the partition splicing grid technology.Used the Reynolds⁃averaged of N⁃S equation,the Reynolds stress term uses the RNG turbulence model;and based on the slip grid method,numerical calculation of the flow field with different Mach numbers,front and rear blade angles and engine state were carried out;and the change law of propeller fan characteristics and the influence of slip flow on the inlet flow field were analyzed.The blade angle was the key parameter of the propeller fan characteristic conditions.When the blade angle increases from 41°to 50°,the thrust coefficient increases by 31.2%,and the power coefficient increases by 33.4%;in the climbing state of the propeller fan,the maximum total pressure distortion at the inlet port of 6.8%;the cross section is less affected by the slip flow of the propfan;and the pressure distribution is relatively uniform,but the area of the flow channel is small.The research results can provide a solution for the matching of the counter⁃rotating propeller fan and the engine and the arrangement of the air inlet measuring rake.
基金Project supported by the National Key Research and Development Program(No.2016YFB0200700)the National Natural Science Foundation of China(Nos.11532016 and 11672324)
文摘This paper numerically studies the aerodynamic performance of a bird-like bionic flapping wing.The geometry and kinematics are designed based on a seagull wing,in which flapping,folding,swaying,and twisting are considered.An in-house unsteady flow solver based on hybrid moving grids.is adopted for unsteady flow simulations.We focus on two main issues in this study,i.e.,the influence of the proportion of down-stroke and the effect of span-wise twisting.Numerical results show that the proportion of downstroke is closely related to the efficiency of the flapping process.The preferable proportion is about 0.7 by using the present geometry and kinematic model,which is very close to the observed data.Another finding is that the drag and the power consumption can be greatly reduced by the proper span-wise twisting.Two cases with different reduced frequencies are simulated and compared with each other.The numerical results show that the power consumption reduces by more than 20%,and the drag coefficient reduces by more than 60% through a proper twisting motion for both cases.The flow mechanism is mainly due to controlling of unsteady flow separation by adjusting the local effective angle of attack.These conclusions will be helpful for the high-performance micro air vehicle (MAV) design.
