Basically on the multi-body system dynamics,the virtual prototype of the hydraulic shock absorber for the bench test is developed in the ADAMS environment.Dynamic behaviors of the absorber are studied by both computer...Basically on the multi-body system dynamics,the virtual prototype of the hydraulic shock absorber for the bench test is developed in the ADAMS environment.Dynamic behaviors of the absorber are studied by both computer simulation and real test.Numerical predictions of dynamic responses are produced by the established virtual prototype of the absorber and compared with experimental results.It has been shown from the comparison that the vibration behaviors of the prototype with hysteretic damping characteristics are considered to be more identical with the bench test results than those of the same prototype with piecewise linear damping properties are.The current virtual prototype of the shock absorber is correct and can be a developing terrace for the optimizing design of the absorber and matching capability of the whole car.展开更多
A new method, BDA perturbing, is used in ensemble forecasting of typhoon track. This method isbased on the Bogus Data Assimilation scheme. It perturbs the initial position and intensity of typhoons and gets aseries of...A new method, BDA perturbing, is used in ensemble forecasting of typhoon track. This method isbased on the Bogus Data Assimilation scheme. It perturbs the initial position and intensity of typhoons and gets aseries of bogus vortex. Then each bogus vortex is used in data assimilation to obtain initial conditions. Ensembleforecast members are constructed by conducting simulation with these initial conditions. Some cases of typhoonare chosen to test the validity of this new method and the results show that: using the BDA perturbing method toperturb initial position and intensity of typhoon for track forecast can improve accuracy, compared with the directuse of the BDA assimilation scheme. And it is concluded that a perturbing amplitude of intensity of 5 hPa isprobably more appropriate than 10 hPa if the BDA perturbing method is used in combination with initialposition perturbation.展开更多
Based on the real case of a frontal precipitation process affecting South China, 27 controlled numerical experiments was made for the effects of hydrostatic and non-hydrostatic effects, different driving models, combi...Based on the real case of a frontal precipitation process affecting South China, 27 controlled numerical experiments was made for the effects of hydrostatic and non-hydrostatic effects, different driving models, combinations of initial/boundary conditions, updates of lateral values and initial time levels of forecast, on model predictions. Features about the impact of initial/boundary conditions on mesoscale numerical weather prediction (NWP) model are analyzed and discussed in detail. Some theoretically and practically valuable conclusions are drawn. It is found that the overall tendency of mesoscale NWP models is governed by its driving model, with the initial conditions showing remarkable impacts on mesoscale models for the first I0 hours of the predictions while leaving lateral boundary conditions to take care the period beyond; the latter affect the inner area of mesoscale predictions mainly through the propagation and movement of weather signals (waves) of different time scales; initial values of external model parameters such as soil moisture content may affect predictions of more longer time validity, while fast signals may be filtered away and only information with time scale 4 times as large as or more than the updated period of boundary values may be introduced, through lateral boundary, to mesoseale models, etc. Some results may be taken as important guidance on mesoseale model and its data a.ssimilation developments of the future.展开更多
Numerical Forecast of Marine Environment More Reliable For many years the numerical forecast of marine environments around the world has been no more than 60 per-cent accuracte-odds that barely
Li Rongrong:An Argument for Accounting Transparency Li Rongrong,head of the State-owned Assets Supervision and Admin-istration Commission(SASAC)of the State Council,argues that all state-owned enterprises should make ...Li Rongrong:An Argument for Accounting Transparency Li Rongrong,head of the State-owned Assets Supervision and Admin-istration Commission(SASAC)of the State Council,argues that all state-owned enterprises should make their nancial accounts public within three years.Through 2007,the total展开更多
Numerical methods successively became important in the design and optimization of fluid machinery. However, as noise emission is considered, one can hardly find standardized prediction methods combining flow and acous...Numerical methods successively became important in the design and optimization of fluid machinery. However, as noise emission is considered, one can hardly find standardized prediction methods combining flow and acoustical optimization. Several numerical field methods for sound calculations have been developed. Due to the complexity of the considered flow, approaches must be chosen to avoid exhaustive computing. In this contribution the noise of a simple propeller is investigated. The configurations of the calculations comply with an existing experimental setup chosen for evaluation. The used in-house CFD solver SPARC contains an acoustic module based on Ffowcs Williams-Hawkings Acoustic Analogy. From the flow results of the time dependent Large Eddy Simulation the time dependent acoustic sources are extracted and given to the acoustic module where relevant sound pressure levels are calculated. The difficulties, which arise while proceeding from open to closed rotors and from gas to liquid are discussed.展开更多
基金the Shanghai Administration of Education under Shanghai Key Disciplines Development Fund ProjectShanghai Automotive Technology Development Foundation under Contract NO.1 325 A
文摘Basically on the multi-body system dynamics,the virtual prototype of the hydraulic shock absorber for the bench test is developed in the ADAMS environment.Dynamic behaviors of the absorber are studied by both computer simulation and real test.Numerical predictions of dynamic responses are produced by the established virtual prototype of the absorber and compared with experimental results.It has been shown from the comparison that the vibration behaviors of the prototype with hysteretic damping characteristics are considered to be more identical with the bench test results than those of the same prototype with piecewise linear damping properties are.The current virtual prototype of the shock absorber is correct and can be a developing terrace for the optimizing design of the absorber and matching capability of the whole car.
基金"The System of Ensemble Forecasting Models for Tropical Cyclones in the South China Sea",a project of the Scientific and Technological Plans for Guangdong Province(2003C32603)
文摘A new method, BDA perturbing, is used in ensemble forecasting of typhoon track. This method isbased on the Bogus Data Assimilation scheme. It perturbs the initial position and intensity of typhoons and gets aseries of bogus vortex. Then each bogus vortex is used in data assimilation to obtain initial conditions. Ensembleforecast members are constructed by conducting simulation with these initial conditions. Some cases of typhoonare chosen to test the validity of this new method and the results show that: using the BDA perturbing method toperturb initial position and intensity of typhoon for track forecast can improve accuracy, compared with the directuse of the BDA assimilation scheme. And it is concluded that a perturbing amplitude of intensity of 5 hPa isprobably more appropriate than 10 hPa if the BDA perturbing method is used in combination with initialposition perturbation.
基金National Project "973" (Research on Heavy Rain in China) and BMBF of Germany (WTZ- Project CHN01/106)
文摘Based on the real case of a frontal precipitation process affecting South China, 27 controlled numerical experiments was made for the effects of hydrostatic and non-hydrostatic effects, different driving models, combinations of initial/boundary conditions, updates of lateral values and initial time levels of forecast, on model predictions. Features about the impact of initial/boundary conditions on mesoscale numerical weather prediction (NWP) model are analyzed and discussed in detail. Some theoretically and practically valuable conclusions are drawn. It is found that the overall tendency of mesoscale NWP models is governed by its driving model, with the initial conditions showing remarkable impacts on mesoscale models for the first I0 hours of the predictions while leaving lateral boundary conditions to take care the period beyond; the latter affect the inner area of mesoscale predictions mainly through the propagation and movement of weather signals (waves) of different time scales; initial values of external model parameters such as soil moisture content may affect predictions of more longer time validity, while fast signals may be filtered away and only information with time scale 4 times as large as or more than the updated period of boundary values may be introduced, through lateral boundary, to mesoseale models, etc. Some results may be taken as important guidance on mesoseale model and its data a.ssimilation developments of the future.
文摘Numerical Forecast of Marine Environment More Reliable For many years the numerical forecast of marine environments around the world has been no more than 60 per-cent accuracte-odds that barely
文摘Li Rongrong:An Argument for Accounting Transparency Li Rongrong,head of the State-owned Assets Supervision and Admin-istration Commission(SASAC)of the State Council,argues that all state-owned enterprises should make their nancial accounts public within three years.Through 2007,the total
文摘Numerical methods successively became important in the design and optimization of fluid machinery. However, as noise emission is considered, one can hardly find standardized prediction methods combining flow and acoustical optimization. Several numerical field methods for sound calculations have been developed. Due to the complexity of the considered flow, approaches must be chosen to avoid exhaustive computing. In this contribution the noise of a simple propeller is investigated. The configurations of the calculations comply with an existing experimental setup chosen for evaluation. The used in-house CFD solver SPARC contains an acoustic module based on Ffowcs Williams-Hawkings Acoustic Analogy. From the flow results of the time dependent Large Eddy Simulation the time dependent acoustic sources are extracted and given to the acoustic module where relevant sound pressure levels are calculated. The difficulties, which arise while proceeding from open to closed rotors and from gas to liquid are discussed.
