The large eddy simulation(LES)method combined with the global dynamic grid strategy is used to numerically study the influence of pitch angles on cavitation and ventilation phenomena in the rear of fuselage during dit...The large eddy simulation(LES)method combined with the global dynamic grid strategy is used to numerically study the influence of pitch angles on cavitation and ventilation phenomena in the rear of fuselage during ditching.The volume of fluid(VOF)method is used to capture the interface.By analyzing the normal force,moment,pressure distribution and nephograms,we find that the pitch angle has a great influence on the total load,the cavitation occurrence time and its transition to ventilation,thus affects the longitudinal load distribution and the controlling of aircraft dynamics.展开更多
The violent water entry of flat plates is investigated using a Riemann-arbitrary Eulerian-Lagrangian（ALE） smoothed particle hydrodynamics（SPH） model. The test conditions are of interest for problems related to air...The violent water entry of flat plates is investigated using a Riemann-arbitrary Eulerian-Lagrangian（ALE） smoothed particle hydrodynamics（SPH） model. The test conditions are of interest for problems related to aircraft and helicopter emergency landing in water. Three main parameters are considered： the horizontal velocity, the approach angle（i.e., vertical to horizontal velocity ratio） and the pitch angle, a. Regarding the latter, small angles are considered in this study. As described in the theoretical work by Zhao and Faltinsen（1993）, for small a a very thin, high-speed jet of water is formed, and the time-spatial gradients of the pressure field are extremely high. These test conditions are very challenging for numerical solvers. In the present study an enhanced SPH model is firstly tested on a purely vertical impact with deadrise angle α=4°. An in-depth validation against analytical solutions and experimental results is carried out, highlighting the several critical aspects of the numerical modelling of this kind of flow, especially when pressure peaks are to be captured. A discussion on the main difficulties when comparing to model scale experiments is also provided. Then, the more realistic case of a plate with both horizontal and vertical velocity components is discussed and compared to ditching experiments recently carried out at CNR-INSEAN. In the latter case both 2-D and 3-D simulations are considered and the importance of 3-D effects on the pressure peak is discussed for α=4° and α=10°.展开更多
文摘The large eddy simulation(LES)method combined with the global dynamic grid strategy is used to numerically study the influence of pitch angles on cavitation and ventilation phenomena in the rear of fuselage during ditching.The volume of fluid(VOF)method is used to capture the interface.By analyzing the normal force,moment,pressure distribution and nephograms,we find that the pitch angle has a great influence on the total load,the cavitation occurrence time and its transition to ventilation,thus affects the longitudinal load distribution and the controlling of aircraft dynamics.
基金partially received funding from the European Union's Horizon 2020 Research and Innovation Programme (Grant No. 724139)
文摘The violent water entry of flat plates is investigated using a Riemann-arbitrary Eulerian-Lagrangian（ALE） smoothed particle hydrodynamics（SPH） model. The test conditions are of interest for problems related to aircraft and helicopter emergency landing in water. Three main parameters are considered： the horizontal velocity, the approach angle（i.e., vertical to horizontal velocity ratio） and the pitch angle, a. Regarding the latter, small angles are considered in this study. As described in the theoretical work by Zhao and Faltinsen（1993）, for small a a very thin, high-speed jet of water is formed, and the time-spatial gradients of the pressure field are extremely high. These test conditions are very challenging for numerical solvers. In the present study an enhanced SPH model is firstly tested on a purely vertical impact with deadrise angle α=4°. An in-depth validation against analytical solutions and experimental results is carried out, highlighting the several critical aspects of the numerical modelling of this kind of flow, especially when pressure peaks are to be captured. A discussion on the main difficulties when comparing to model scale experiments is also provided. Then, the more realistic case of a plate with both horizontal and vertical velocity components is discussed and compared to ditching experiments recently carried out at CNR-INSEAN. In the latter case both 2-D and 3-D simulations are considered and the importance of 3-D effects on the pressure peak is discussed for α=4° and α=10°.
