Based on the stability theory, numerical simulations and theoretical calculations are performed for a projectile with wrap-around fins. Its stability is analyzed and the flow field is simulated with computational flui...Based on the stability theory, numerical simulations and theoretical calculations are performed for a projectile with wrap-around fins. Its stability is analyzed and the flow field is simulated with computational fluid dynamics method. Consequently, the pitching moment coefficient of the projectile is further investigated under the conditions of Mach number ranging from 0.3 to 0.8, attack angle from 0 to 8° and yaw angle from 0 to 4°. A trajectory equation is established and its trajectory characteristics are also explored. All the results of theoretical analysis, numerical simulation and trajectory equation agree well with each other, which indicates the projectile is flying steadily at the given conditions. These results provide an effective way for judging the stability of the projectile with wrap-around fins.展开更多
A model for the vortex distribution in the wake of an aircraft is elaborated to investigate the wake influence on the behaviour of other aircrafts potentially interacting with it.As a realistic case,the interaction of...A model for the vortex distribution in the wake of an aircraft is elaborated to investigate the wake influence on the behaviour of other aircrafts potentially interacting with it.As a realistic case,the interaction of an ARJ21 aircraft with a(leading)A330-200 aircraft is considered.Different distances are considered,namely,6 km,7 km,8 km,9.3 km,and 10 km.Simulations based on the used wake dissipation mechanism are used to investigate different conditions,namely,the ARJ21 in take-off and level flight and the changes induced in the related lift by the front aircraft A330-200 during landing.The induced roll moment is also studied and analyzed by means of a strip method.As a result,the roll moment coefficient is determined to quantify the roll degree of the aircraft when it is influenced by the wake vortex.The results show the overall roll moment coefficient of the considered ARJ21 aircraft is less than 0.05,and the wing roll moment coefficient is less than 0.04.Such results are interpreted and discussed according to existing standards.展开更多
Wind load and response are the major factors that govern the most critical condition for designing tall buildings. This study discusses the variability of wind load and pressure on a Y plan shaped tall building due to...Wind load and response are the major factors that govern the most critical condition for designing tall buildings. This study discusses the variability of wind load and pressure on a Y plan shaped tall building due to the change in the building side ratio. The length to width ratio is changed keeping the total plan area same. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and shear stress transport (SST), are used for doing the numerical simulation and the results are compared with the previous wind tunnel results in a similar flow condition. Sample points were selected based on Audze–Eglais Uniform Latin Hypercube (AELH) method and the analytical expressions of force, moment and torsional coefficients of Y plan shaped tall building are proposed. These expressions are fitted very well and the AELH method has given a great set of sample points that have significantly decreased the total computational time. The graphical representations of these expressions for various coefficients are presented and discussed. Then pressure distributions on three different models are compared and the pros and cons of higher and lower values of side ratios are discussed.展开更多
基金the National Natural Science Foundation of China (10572026)
文摘Based on the stability theory, numerical simulations and theoretical calculations are performed for a projectile with wrap-around fins. Its stability is analyzed and the flow field is simulated with computational fluid dynamics method. Consequently, the pitching moment coefficient of the projectile is further investigated under the conditions of Mach number ranging from 0.3 to 0.8, attack angle from 0 to 8° and yaw angle from 0 to 4°. A trajectory equation is established and its trajectory characteristics are also explored. All the results of theoretical analysis, numerical simulation and trajectory equation agree well with each other, which indicates the projectile is flying steadily at the given conditions. These results provide an effective way for judging the stability of the projectile with wrap-around fins.
基金This work is supported by the[1]National Natural Science Foundation of China,Key Technology of AircraftWake Evolution and Risk Control in the Near-Earth Phase,Approval No.U1733203Civil Aviation Administration Safety Capability Building Project,Research on Technology of Reducing Control Interval Based on Aircraft Wake Prediction,Project No.TM2018-9-1/3+1 种基金Research on the Safety Interval of J21 Aircraft Taking Off and Landing TM2019-16-1/3Sichuan Science and Technology Project(Grant No.2021JDRC0083).
文摘A model for the vortex distribution in the wake of an aircraft is elaborated to investigate the wake influence on the behaviour of other aircrafts potentially interacting with it.As a realistic case,the interaction of an ARJ21 aircraft with a(leading)A330-200 aircraft is considered.Different distances are considered,namely,6 km,7 km,8 km,9.3 km,and 10 km.Simulations based on the used wake dissipation mechanism are used to investigate different conditions,namely,the ARJ21 in take-off and level flight and the changes induced in the related lift by the front aircraft A330-200 during landing.The induced roll moment is also studied and analyzed by means of a strip method.As a result,the roll moment coefficient is determined to quantify the roll degree of the aircraft when it is influenced by the wake vortex.The results show the overall roll moment coefficient of the considered ARJ21 aircraft is less than 0.05,and the wing roll moment coefficient is less than 0.04.Such results are interpreted and discussed according to existing standards.
文摘Wind load and response are the major factors that govern the most critical condition for designing tall buildings. This study discusses the variability of wind load and pressure on a Y plan shaped tall building due to the change in the building side ratio. The length to width ratio is changed keeping the total plan area same. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and shear stress transport (SST), are used for doing the numerical simulation and the results are compared with the previous wind tunnel results in a similar flow condition. Sample points were selected based on Audze–Eglais Uniform Latin Hypercube (AELH) method and the analytical expressions of force, moment and torsional coefficients of Y plan shaped tall building are proposed. These expressions are fitted very well and the AELH method has given a great set of sample points that have significantly decreased the total computational time. The graphical representations of these expressions for various coefficients are presented and discussed. Then pressure distributions on three different models are compared and the pros and cons of higher and lower values of side ratios are discussed.
