The flight safety is threatened by the special flight conditions and the low speed of carrier-based aircraft ski-jump takeoff. The aircraft carrier motion, aircraft dynamics, landing gears and wind field of sea state ...The flight safety is threatened by the special flight conditions and the low speed of carrier-based aircraft ski-jump takeoff. The aircraft carrier motion, aircraft dynamics, landing gears and wind field of sea state are comprehensively considered to dispose this multidiscipline intersection problem. According to the particular naval operating environment of the carrier-based aircraft ski-jump takeoff, the integrated dynamic simulation models of multi-body system are developed, which involves the movement entities of the carrier, the aircraft and the landing gears, and involves takeoff instruction, control system and the deck wind disturbance. Based on Matlab/Simulink environment, the multi-body system simulation is realized. The validity of the model and the rationality of the result are verified by an example simulation of carrier-based aircraft ski-jump takeoff. The simulation model and the software are suitable for the study of the multidiscipline intersection problems which are involved in the performance, flight quality and safety of carrier-based aircraft takeoff, the effects of landing gear loads, parameters of carrier deck, etc.展开更多
We first analyzed the force and motion of naval aircraft during launching process.Further,we investigated the ship deck with the form of a ramp and established deck motion model and ship airwake model.Finally,we condu...We first analyzed the force and motion of naval aircraft during launching process.Further,we investigated the ship deck with the form of a ramp and established deck motion model and ship airwake model.Finally,we conducted simulations at medium sea.Results showed that the effects of deck motion on takeoff varied with initial phases,and airwake could help reducing aircraft′s sinkage.We also found that the deck motion played a major role in the effects caused by the interaction of deck motion and ship airwake.展开更多
Computational Fluid Dynamics （CFD） methods have opened a new field to perform aerodynamic studies saving money and time. The difficulties presented by this method to calculate complex flow field problems imply that ...Computational Fluid Dynamics （CFD） methods have opened a new field to perform aerodynamic studies saving money and time. The difficulties presented by this method to calculate complex flow field problems imply that CFD validation is needed to provide correct results. Experimental data have recently been used to validate the accuracy of CFD predictions. Particle Image Velocimetry （PIV） has shown to be a powerful tool in the investigation of complex flows. The aim of this paper is to present results from PIV experiments that would be interesting for CFD validation. Regarding aircraft operations, the short runway available implies the necessity of equipment which helps to take-off performances. Ski-jump ramp system improves aircraft performances by an increment of lift resulting in successful take-off operations. The ski-jump ramp presence generates a complex flow bounded by a turbulent shear layer and a low velocity recirculation bubble over the end of the flight deck. The adverse effects on the aircraft aerodynamics affect to pilot safe operations, so this region is an interesting problem to be studied by means of wind tunnel experimental tests.展开更多
Based on the lattice Boltzmann method,a lattice Boltzmann(LB) model of the ski-jump jet two-phase flow is developed first and the corresponding boundary conditions are studied.A simple case study of a droplet horizont...Based on the lattice Boltzmann method,a lattice Boltzmann(LB) model of the ski-jump jet two-phase flow is developed first and the corresponding boundary conditions are studied.A simple case study of a droplet horizontal movement calculation is carried out to test and verify the model,where level set method is used to track and reconstruct the moving droplet free surface. Then,we numerically simulate a two dimensional flow field of the ski-jump jet with the LB model,derive the moving surface and velocity vector field of the jet flow.The simulation results are very consistent with the physical mechanisms.The effectiveness and reliability of the model are demonstrated by the numerical examples.展开更多
Researchers in the past had noticed that application of Artificial Neural Networks （ANN） in place of conventional statistics on the basis of data mining techniques predicts more accurate results in hydraulic predict...Researchers in the past had noticed that application of Artificial Neural Networks （ANN） in place of conventional statistics on the basis of data mining techniques predicts more accurate results in hydraulic predictions. Mostly these works pertained to applications of ANN. Recently, another tool of soft computing, namely, Genetic Programming （GP） has caught the attention of researchers in civil engineering computing. This article examines the usefulness of the GP based approach to predict the relative scour depth downstream of a common type of ski-jump bucket spillway. Actual field measurements were used to develop the GP model. The GP based estimations were found to be equally and more accurate than the ANN based ones, especially, when the underlying cause-effect relationship became more uncertain to model.展开更多
The supersaturated total dissolved gas(TDG)generated during high dam spills may cause gas bubble disease for fish and ultimately endanger their existence.As more and more high-dam hydropower projects have been constru...The supersaturated total dissolved gas(TDG)generated during high dam spills may cause gas bubble disease for fish and ultimately endanger their existence.As more and more high-dam hydropower projects have been constructed in China,the environmental assessment of the supersaturated TDG is becoming more and more important.It is of great importance for quantitative impact assessment of the supersaturated TDG of high dams and for the construction of ecological friendly high-dam hydropower projects.Based on the conceptual summarization of the TDG production process,the TDG prediction model for high-dam projects,in which the ski-jump energy dissipation is adopted,is developed in the paper.The model is validated by field data and employed in the TDG prediction of a high-dam hydropower project to be built in southwest China.展开更多
Flip buckets are commonly used to discharge flow away from a hydraulic structure into the downstream to dissipate energy.A new leak-floor flip bucket is presented,making the ski-jump water jet a typical long-narrow na...Flip buckets are commonly used to discharge flow away from a hydraulic structure into the downstream to dissipate energy.A new leak-floor flip bucket is presented,making the ski-jump water jet a typical long-narrow nappe.Based on the model experiments and numerical simulation,the flow pattern,formation process and mechanism of the leak-floor flip bucket are studied.The results show that cross section flow shape develops from the"Y-type"to"|-type",and this is because the natural pressure difference is generated when water flows through the leak-floor area and moves transversely from both sides to the center.Different from the slit-type flip bucket with sidewall contraction,the leak-floor flit bucket makes the water jet narrow and long without high pressure on the side walls of the flip bucket.Under the same jet length condition,the maximum sidewall pressure of the slit-type is 4.67 times that of the leak-floor flip bucket.The effects of flow discharge on the jet length are less significant for the leak-floor bucket than for the slit-type bucket.展开更多
文摘The flight safety is threatened by the special flight conditions and the low speed of carrier-based aircraft ski-jump takeoff. The aircraft carrier motion, aircraft dynamics, landing gears and wind field of sea state are comprehensively considered to dispose this multidiscipline intersection problem. According to the particular naval operating environment of the carrier-based aircraft ski-jump takeoff, the integrated dynamic simulation models of multi-body system are developed, which involves the movement entities of the carrier, the aircraft and the landing gears, and involves takeoff instruction, control system and the deck wind disturbance. Based on Matlab/Simulink environment, the multi-body system simulation is realized. The validity of the model and the rationality of the result are verified by an example simulation of carrier-based aircraft ski-jump takeoff. The simulation model and the software are suitable for the study of the multidiscipline intersection problems which are involved in the performance, flight quality and safety of carrier-based aircraft takeoff, the effects of landing gear loads, parameters of carrier deck, etc.
基金supported by the National Natural Science Foundation of China(No.61304223)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20123218120015)
文摘We first analyzed the force and motion of naval aircraft during launching process.Further,we investigated the ship deck with the form of a ramp and established deck motion model and ship airwake model.Finally,we conducted simulations at medium sea.Results showed that the effects of deck motion on takeoff varied with initial phases,and airwake could help reducing aircraft′s sinkage.We also found that the deck motion played a major role in the effects caused by the interaction of deck motion and ship airwake.
文摘Computational Fluid Dynamics （CFD） methods have opened a new field to perform aerodynamic studies saving money and time. The difficulties presented by this method to calculate complex flow field problems imply that CFD validation is needed to provide correct results. Experimental data have recently been used to validate the accuracy of CFD predictions. Particle Image Velocimetry （PIV） has shown to be a powerful tool in the investigation of complex flows. The aim of this paper is to present results from PIV experiments that would be interesting for CFD validation. Regarding aircraft operations, the short runway available implies the necessity of equipment which helps to take-off performances. Ski-jump ramp system improves aircraft performances by an increment of lift resulting in successful take-off operations. The ski-jump ramp presence generates a complex flow bounded by a turbulent shear layer and a low velocity recirculation bubble over the end of the flight deck. The adverse effects on the aircraft aerodynamics affect to pilot safe operations, so this region is an interesting problem to be studied by means of wind tunnel experimental tests.
基金supported by the National Natural Science Foundation of China(Grant No.50579083)
文摘Based on the lattice Boltzmann method,a lattice Boltzmann(LB) model of the ski-jump jet two-phase flow is developed first and the corresponding boundary conditions are studied.A simple case study of a droplet horizontal movement calculation is carried out to test and verify the model,where level set method is used to track and reconstruct the moving droplet free surface. Then,we numerically simulate a two dimensional flow field of the ski-jump jet with the LB model,derive the moving surface and velocity vector field of the jet flow.The simulation results are very consistent with the physical mechanisms.The effectiveness and reliability of the model are demonstrated by the numerical examples.
基金University Sains Malaysia for funding a short term grant (304.PREDAC.6035262) to conduct this on-going research
文摘Researchers in the past had noticed that application of Artificial Neural Networks （ANN） in place of conventional statistics on the basis of data mining techniques predicts more accurate results in hydraulic predictions. Mostly these works pertained to applications of ANN. Recently, another tool of soft computing, namely, Genetic Programming （GP） has caught the attention of researchers in civil engineering computing. This article examines the usefulness of the GP based approach to predict the relative scour depth downstream of a common type of ski-jump bucket spillway. Actual field measurements were used to develop the GP model. The GP based estimations were found to be equally and more accurate than the ANN based ones, especially, when the underlying cause-effect relationship became more uncertain to model.
基金Supported by the National Natural Science Foundation of China(Grant No.50579043)the Open Foundation of the State Key Laboratory of Hydraulics and Mountain River Engineering(Grant No.0604)
文摘The supersaturated total dissolved gas(TDG)generated during high dam spills may cause gas bubble disease for fish and ultimately endanger their existence.As more and more high-dam hydropower projects have been constructed in China,the environmental assessment of the supersaturated TDG is becoming more and more important.It is of great importance for quantitative impact assessment of the supersaturated TDG of high dams and for the construction of ecological friendly high-dam hydropower projects.Based on the conceptual summarization of the TDG production process,the TDG prediction model for high-dam projects,in which the ski-jump energy dissipation is adopted,is developed in the paper.The model is validated by field data and employed in the TDG prediction of a high-dam hydropower project to be built in southwest China.
基金supported by the National Natural Science Foundation of China(Grant Nos.51379138&51179113)Sichuan Province Funds for Distinguished Young Scientists(Grant No.2013JQ0007)
文摘Flip buckets are commonly used to discharge flow away from a hydraulic structure into the downstream to dissipate energy.A new leak-floor flip bucket is presented,making the ski-jump water jet a typical long-narrow nappe.Based on the model experiments and numerical simulation,the flow pattern,formation process and mechanism of the leak-floor flip bucket are studied.The results show that cross section flow shape develops from the"Y-type"to"|-type",and this is because the natural pressure difference is generated when water flows through the leak-floor area and moves transversely from both sides to the center.Different from the slit-type flip bucket with sidewall contraction,the leak-floor flit bucket makes the water jet narrow and long without high pressure on the side walls of the flip bucket.Under the same jet length condition,the maximum sidewall pressure of the slit-type is 4.67 times that of the leak-floor flip bucket.The effects of flow discharge on the jet length are less significant for the leak-floor bucket than for the slit-type bucket.
