Under single-satellite observation,the parameter estimation of the boost phase of high-precision space noncooperative targets requires prior information.To improve the accuracy without prior information,we propose a p...Under single-satellite observation,the parameter estimation of the boost phase of high-precision space noncooperative targets requires prior information.To improve the accuracy without prior information,we propose a parameter estimation model of the boost phase based on trajectory plane parametric cutting.The use of the plane passing through the geo-center and the cutting sequence line of sight(LOS)generates the trajectory-cutting plane.With the coefficient of the trajectory cutting plane directly used as the parameter to be estimated,a motion parameter estimation model in space non-cooperative targets is established,and the Gauss-Newton iteration method is used to solve the flight parameters.The experimental results show that the estimation algorithm proposed in this paper weakly relies on prior information and has higher estimation accuracy,providing a practical new idea and method for the parameter estimation of space non-cooperative targets under single-satellite warning.展开更多
The roughness effect based on the wall function method is introduced into the numerical simulation of the rime ice accretion and the resulting effect on the aerodynamic performance of the airfoil. Incorporating the tw...The roughness effect based on the wall function method is introduced into the numerical simulation of the rime ice accretion and the resulting effect on the aerodynamic performance of the airfoil. Incorporating the two-phase model of air/super-cooled droplets in the Eulerian coordinate system, this paper presents the simulation of the rime ice accretion on the NACA 0012 airfoil. The predicted rime ice shape is compared with those results of measurements and simulations by other icing codes. Also the resulting effects of rime ice on airfoil aerodynamic performance are discussed. Results indicate that the rime ice accretion leads to the loss of the maximum lift coefficient by 26%, the decrease of the stall angle by about 3° and the considerable increase of the drag coefficient.展开更多
Revetments of concrete frame tetrahedrons are being used more and more in river engineering in China. Due to their complex geometry, it is difficult to measure the velocity fields inside them using traditional measure...Revetments of concrete frame tetrahedrons are being used more and more in river engineering in China. Due to their complex geometry, it is difficult to measure the velocity fields inside them using traditional measurement methods. This limits understanding of their mechanics, potentially leading to suboptimal solutions. A 3-D hydrodynamic model based on the commercial computational fluid dynamics (CFD) code, Fluent, was developed to predict velocity fields and drags. The realizable k-e model was adopted for turbulent closure of the Reynolds averaged Navier Stokes (RANS) equations. The study demonstrates that the numerical model can effectively supplement experimental studies in understanding the complex flow fields and mechanics of concrete frame tetrahedron revetments. Graphs showing the drag coefficient CD versus Reynolds number Re and lift coefficient CL versus Reynolds number Re were produced.展开更多
Helicopter mathematical model mainly depends on design helicopter control system, flight simulator, and real time control simulation system. But it is difficult to establish a helicopter flight dynamics mathematical ...Helicopter mathematical model mainly depends on design helicopter control system, flight simulator, and real time control simulation system. But it is difficult to establish a helicopter flight dynamics mathematical model that has features such as rapidness, reliability and precision, because there is no unique and precise expression to some sophisticated phenomenon of helicopter. In this paper a fuzzy helicopter flight model is constructed based on the flight experimental data. The fuzzy model, which is identified by fuzzy inference, has characteristics of computed rapidness and high precision. In order to guarantee the precision of the identified fuzzy model, a new method is adopted to handle the conflict fuzzy rules. Additionally, using fuzzy clustering technology can effectively reduce the number of rules of fuzzy model, namely, the order of the fuzzy model. The simulation results indicate that the method of this paper is effective and feasible.展开更多
Synthetic analysis is conducted to the wind tunnel experiment results of zero lift drag coefficient and lift coefficient for large aspect ratio winged rigid body.By means of wind tunnel experiment data,the dynamics mo...Synthetic analysis is conducted to the wind tunnel experiment results of zero lift drag coefficient and lift coefficient for large aspect ratio winged rigid body.By means of wind tunnel experiment data,the dynamics model of the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body is amended.The research indicates that the change trends of zero lift drag coefficient and lift coefficient to Mach number are similar.The calculation result and wind tunnel experiment data all verify the validity of the amended dynamics model by which to estimate the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body,and thus providing some technical reference to aerodynamics character analysis of the same types of winged rigid body.展开更多
A numerical simulation was performed to investigate the interaction of two bubbles rising side by side in shear-thinning fluid using volume of fluid (VOF) method coupled with continuous surface force (CSF) method....A numerical simulation was performed to investigate the interaction of two bubbles rising side by side in shear-thinning fluid using volume of fluid (VOF) method coupled with continuous surface force (CSF) method. By considering rheological characteristics of fluid, this approach was able to accurately capture the deformation of bubble interface, and validated by comparing with the experimental results. The rising of bubble pairs with different configurations, including horizontal alignment and oblique alignment, was simulated by the method. The influences of the bubble initial distance and the bubble alignment were studied by analyzing the bubble deformation, rising paths and flow fields surrounding bubbles. The results indicate that within certam mltlal bubble spacing of S = 3.3 (S* = SI/D, SI initial distance between bubbles, and D bubble diameter), the dynamic interaction between two bub- bles aligned horizontally shows repulsive effect that decreases with the increase of initial bubble spacing, but weakens to certain degree by the shear-thinning properties of fluid. However, the interaction between two bubbles aligned obliquely presents a repulsive effect for the small angle involved but an attractive impact for the large one, which is vet strengthened by the rheological characteristics of fluid.展开更多
This paper establishes the mathematical model in calculating the effective thermal conductivity and the effective mass diffusivity of dried layer of beef undergoing freeze drying process.First,experimental measurement...This paper establishes the mathematical model in calculating the effective thermal conductivity and the effective mass diffusivity of dried layer of beef undergoing freeze drying process.First,experimental measurements are done on the dehydrated quantity as well as temperature variations at different locations of the beef steak.Then the effective thermal conductivity and the effective mass diffusivity are calculated by applying the above mathematical model on the data of the dehydrated quantity.These two coefficients are further used in the calculation of temperature distribution.The result is in agreement with the measurement,thus confirming the correctness of the model and the values of the coefficients.展开更多
In this paper, we tested the hydrodynamic characteristics of a new, double-winged otter board that consists of a forewing, a leading edge slat and a trailing edge flap. Flume experiments were conducted in a circulatin...In this paper, we tested the hydrodynamic characteristics of a new, double-winged otter board that consists of a forewing, a leading edge slat and a trailing edge flap. Flume experiments were conducted in a circulating flume tank by using a model with an aspect ratio(AR) of 0.85 and a horizontal planform area( S) of 0.09 m^2. The results indicated that the critical angle( α_(cr)) of the model was 44°, whereas the maximum lift coefficient( C_(Lmax)) was up to 1.715, and the door efficiency( K) was 1.122. The attack angle( α) ranged from 30° to 48° and from 10° to 46° when the lift coefficient( C_L) and door efficiency( K) were greater than 1.2 and 1.0, respectively. To compare the difference between double-winged otter board and traditional Morgere Polyvalent Ovale, same model of Morgere Polyvalent Ovale was also tested under the same experimental conditions. The critical angle( α_(cr)) and maximum of lift coefficient( C_(Lmax)) of the doublewinged otter board were 37.5% and 14.6% larger than those of the Morgere Polyvalent Ovale. Therefore, we concluded that the novel, double-winged otter board was more suitable for bottom trawling fisheries in the deep water of the Mauretania Sea due to its better hydrodynamic characteristics and stability.展开更多
Fault detection technique is introduced with similarity measure. The characteristics of conventional similarity measure based on fuzzy number are discussed. With the help of distance measure, similarity measure is con...Fault detection technique is introduced with similarity measure. The characteristics of conventional similarity measure based on fuzzy number are discussed. With the help of distance measure, similarity measure is constructed explicitly. The designed distance-based similarity measure is applicable to general fuzzy membership functions including non-convex fuzzy membership function, whereas fuzzy number-based similarity measure has limitation to calculate the similarity of general fuzzy membership functions. The applicability of the proposed similarity measure to general fuzzy membership structures is proven by identifying the definition. To decide fault detection of flight system, the experimental data (pitching moment coefficients and lift coefficients) are transformed into fuzzy membership functions. Distance-based similarity measure is applied to the obtained fuzzy membership functions, and similarity computation and analysis are obtained with the fault and normal operation coefficients.展开更多
A stratum grouting-soil-structure interaction model which simplified the grouted zone into a series of spherical grout bulbs was established using FLAC3D program. The hypothetical non-uniform expansion process to reac...A stratum grouting-soil-structure interaction model which simplified the grouted zone into a series of spherical grout bulbs was established using FLAC3D program. The hypothetical non-uniform expansion process to reach an assigned volume strain due to soil compression by grouting was achieved by imposing radial velocity on outer mesh nodes of these spheres. This new method avoids the repeated trial calculation needed in the traditional method which applied a fictitious expanding pressure in the grouting element. The deformation and additional internal forces of structure were investigated during each grouting strategy and the influences of various stiffness of grouting proof curtain and bearing capacity of pile tip were discussed simultaneously. The numerical model is proved to be effective to replicate general behavior expected in the field and is capable of modeling the uplifting effect for the surface structure by grouting.展开更多
Thermo-gravimetric-analysis(TGA) was used to analyze the combustion characteristics of an oil shale and semi-cokes prepared from it.The effect of prior pyrolysis and TGA heating rate on the combustion process was stud...Thermo-gravimetric-analysis(TGA) was used to analyze the combustion characteristics of an oil shale and semi-cokes prepared from it.The effect of prior pyrolysis and TGA heating rate on the combustion process was studied.Prior pyrolysis affects the initial temperature of mass loss and the ignition temperature.The ignition temperature increases as the volatile content of the sample decreases.TG/DTG curves obtained at different heating rates show that heating rate has little effect on ignition temperature.But the peak of combustion shifts to higher temperatures as the heating rate is increased.The Coats-Redfern integration method was employed to find the combustion-reaction kinetic parameters for the burning of oil shale and oil shale semi-coke.展开更多
The lattice Boltzmann method (LBM) is employed to simulate the uniform flow past a circular cylinder. The performance of the two-dimensional LBM model on the prediction of force coefficients and vortex shedding freque...The lattice Boltzmann method (LBM) is employed to simulate the uniform flow past a circular cylinder. The performance of the two-dimensional LBM model on the prediction of force coefficients and vortex shedding frequency is investigated. The local grid refinement technique and second-order boundary condition for curved walls are applied in the calculations. It is found that the calculated vortex shedding frequency, drag coefficient and lift coefficient are consistent with experimental results at Reynolds nu...展开更多
To enhance the maneuverability of the selected aircraft model, a standard genetic algorithm (GA) is used as an optimization method for the preliminary design of the leading-edge extension (LEX) layout. The aerodyn...To enhance the maneuverability of the selected aircraft model, a standard genetic algorithm (GA) is used as an optimization method for the preliminary design of the leading-edge extension (LEX) layout. The aerodynamic loads and the maximum lift coefficient of the complete aircraft configuration (fuselage+wing+tail) are computed by using the modified three-dimensional low-order panel method in conjunction with the semi-empirical formulas of DATCOM. Results show that the lift coefficient increases approximately 20.5%- 15.3% for Mach number 0. 4-0.8 and 6.8% for Mach number 1.2, and its maximum value approximately 9.5% -15.0% for Machnumber 0.2-0.95when LEXis installed. A 6.6%-8.0 % gain at altitudes of 1-5 km on the turn rate maneuverability and the corner speed have been achieved in the subsonic regime.展开更多
In this paper, 2-D computational analyses were conducted for unsteady high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. 8.21×104〈Re〈1.54...In this paper, 2-D computational analyses were conducted for unsteady high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. 8.21×104〈Re〈1.54×106. The calculations were performed by means of solving the 2-D Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with a k-ε turbulence model. The calculated results, produced flow structure drag and lift coefficients, as well as Strouhal numbers. The findings were in good agreement with previous published data, which also supplied us with a good understanding of the flow across cylinders of different high Reynolds numbers. Meanwhile, an effective measure was presented to control the lift force on a cylinder, which points the way to decrease the vortex induced vibration of marine structure in future.展开更多
基金supported in part by the National Natural Science Foundation of China(Nos.42271448,41701531)the Key Laboratory of Land Satellite Remote Sensing Application,Ministry of Natural Resources of the People’s Republic of China(No.KLSMNRG202317)。
文摘Under single-satellite observation,the parameter estimation of the boost phase of high-precision space noncooperative targets requires prior information.To improve the accuracy without prior information,we propose a parameter estimation model of the boost phase based on trajectory plane parametric cutting.The use of the plane passing through the geo-center and the cutting sequence line of sight(LOS)generates the trajectory-cutting plane.With the coefficient of the trajectory cutting plane directly used as the parameter to be estimated,a motion parameter estimation model in space non-cooperative targets is established,and the Gauss-Newton iteration method is used to solve the flight parameters.The experimental results show that the estimation algorithm proposed in this paper weakly relies on prior information and has higher estimation accuracy,providing a practical new idea and method for the parameter estimation of space non-cooperative targets under single-satellite warning.
文摘The roughness effect based on the wall function method is introduced into the numerical simulation of the rime ice accretion and the resulting effect on the aerodynamic performance of the airfoil. Incorporating the two-phase model of air/super-cooled droplets in the Eulerian coordinate system, this paper presents the simulation of the rime ice accretion on the NACA 0012 airfoil. The predicted rime ice shape is compared with those results of measurements and simulations by other icing codes. Also the resulting effects of rime ice on airfoil aerodynamic performance are discussed. Results indicate that the rime ice accretion leads to the loss of the maximum lift coefficient by 26%, the decrease of the stall angle by about 3° and the considerable increase of the drag coefficient.
基金Supported by the Science Foundation of China Three Gorges University (No.0620070016)Opening Foundation of the Environmental Engineering Key Discipline from Zhejiang University of Technology (No.20080218)+4 种基金NSFC (No.50779014,No.50879019)Ph.D. Discipline Foundation of the Ministry of Education of China (No.200802940001)Jiangsu "333" Program for High Level Talent"Six Talent Peak" Project Foundation of Jiangsu Province (No.2007006)"11th Five-year Plan" (2008BAB29B09)
文摘Revetments of concrete frame tetrahedrons are being used more and more in river engineering in China. Due to their complex geometry, it is difficult to measure the velocity fields inside them using traditional measurement methods. This limits understanding of their mechanics, potentially leading to suboptimal solutions. A 3-D hydrodynamic model based on the commercial computational fluid dynamics (CFD) code, Fluent, was developed to predict velocity fields and drags. The realizable k-e model was adopted for turbulent closure of the Reynolds averaged Navier Stokes (RANS) equations. The study demonstrates that the numerical model can effectively supplement experimental studies in understanding the complex flow fields and mechanics of concrete frame tetrahedron revetments. Graphs showing the drag coefficient CD versus Reynolds number Re and lift coefficient CL versus Reynolds number Re were produced.
文摘Helicopter mathematical model mainly depends on design helicopter control system, flight simulator, and real time control simulation system. But it is difficult to establish a helicopter flight dynamics mathematical model that has features such as rapidness, reliability and precision, because there is no unique and precise expression to some sophisticated phenomenon of helicopter. In this paper a fuzzy helicopter flight model is constructed based on the flight experimental data. The fuzzy model, which is identified by fuzzy inference, has characteristics of computed rapidness and high precision. In order to guarantee the precision of the identified fuzzy model, a new method is adopted to handle the conflict fuzzy rules. Additionally, using fuzzy clustering technology can effectively reduce the number of rules of fuzzy model, namely, the order of the fuzzy model. The simulation results indicate that the method of this paper is effective and feasible.
文摘Synthetic analysis is conducted to the wind tunnel experiment results of zero lift drag coefficient and lift coefficient for large aspect ratio winged rigid body.By means of wind tunnel experiment data,the dynamics model of the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body is amended.The research indicates that the change trends of zero lift drag coefficient and lift coefficient to Mach number are similar.The calculation result and wind tunnel experiment data all verify the validity of the amended dynamics model by which to estimate the zero lift drag coefficient and lift coefficient for the large aspect ratio winged rigid body,and thus providing some technical reference to aerodynamics character analysis of the same types of winged rigid body.
基金Supported by the National Natural Science Foundation of China (21076139, 21106106), Tianjin Natural Science Foundation of China (12JcQNJC3700), and Foundation of Tianjin Educational Committee of China (20100508).
文摘A numerical simulation was performed to investigate the interaction of two bubbles rising side by side in shear-thinning fluid using volume of fluid (VOF) method coupled with continuous surface force (CSF) method. By considering rheological characteristics of fluid, this approach was able to accurately capture the deformation of bubble interface, and validated by comparing with the experimental results. The rising of bubble pairs with different configurations, including horizontal alignment and oblique alignment, was simulated by the method. The influences of the bubble initial distance and the bubble alignment were studied by analyzing the bubble deformation, rising paths and flow fields surrounding bubbles. The results indicate that within certam mltlal bubble spacing of S = 3.3 (S* = SI/D, SI initial distance between bubbles, and D bubble diameter), the dynamic interaction between two bub- bles aligned horizontally shows repulsive effect that decreases with the increase of initial bubble spacing, but weakens to certain degree by the shear-thinning properties of fluid. However, the interaction between two bubbles aligned obliquely presents a repulsive effect for the small angle involved but an attractive impact for the large one, which is vet strengthened by the rheological characteristics of fluid.
基金the National Natural Science Foundation of China!(No.597760 14 )
文摘This paper establishes the mathematical model in calculating the effective thermal conductivity and the effective mass diffusivity of dried layer of beef undergoing freeze drying process.First,experimental measurements are done on the dehydrated quantity as well as temperature variations at different locations of the beef steak.Then the effective thermal conductivity and the effective mass diffusivity are calculated by applying the above mathematical model on the data of the dehydrated quantity.These two coefficients are further used in the calculation of temperature distribution.The result is in agreement with the measurement,thus confirming the correctness of the model and the values of the coefficients.
基金Supported by the Technological Research on Reforming Otter Boards of Bottom Trawl in Mauretania and Guinea(China National Fisheries Corporation,CNFC)Technological Research on Transformation and Upgrading of Shrimp Trawl in Sierra Leone(CNFC)Far Sea Fisheries Resources Monitoring and Assessment of South China Sea(No.2013050212)
文摘In this paper, we tested the hydrodynamic characteristics of a new, double-winged otter board that consists of a forewing, a leading edge slat and a trailing edge flap. Flume experiments were conducted in a circulating flume tank by using a model with an aspect ratio(AR) of 0.85 and a horizontal planform area( S) of 0.09 m^2. The results indicated that the critical angle( α_(cr)) of the model was 44°, whereas the maximum lift coefficient( C_(Lmax)) was up to 1.715, and the door efficiency( K) was 1.122. The attack angle( α) ranged from 30° to 48° and from 10° to 46° when the lift coefficient( C_L) and door efficiency( K) were greater than 1.2 and 1.0, respectively. To compare the difference between double-winged otter board and traditional Morgere Polyvalent Ovale, same model of Morgere Polyvalent Ovale was also tested under the same experimental conditions. The critical angle( α_(cr)) and maximum of lift coefficient( C_(Lmax)) of the doublewinged otter board were 37.5% and 14.6% larger than those of the Morgere Polyvalent Ovale. Therefore, we concluded that the novel, double-winged otter board was more suitable for bottom trawling fisheries in the deep water of the Mauretania Sea due to its better hydrodynamic characteristics and stability.
基金Project supported by the Second Stage of Brain Korea and Korea Research Foundation
文摘Fault detection technique is introduced with similarity measure. The characteristics of conventional similarity measure based on fuzzy number are discussed. With the help of distance measure, similarity measure is constructed explicitly. The designed distance-based similarity measure is applicable to general fuzzy membership functions including non-convex fuzzy membership function, whereas fuzzy number-based similarity measure has limitation to calculate the similarity of general fuzzy membership functions. The applicability of the proposed similarity measure to general fuzzy membership structures is proven by identifying the definition. To decide fault detection of flight system, the experimental data (pitching moment coefficients and lift coefficients) are transformed into fuzzy membership functions. Distance-based similarity measure is applied to the obtained fuzzy membership functions, and similarity computation and analysis are obtained with the fault and normal operation coefficients.
基金Project(2007AA11Z134)supported by the National High Technology Research and Development Program of ChinaProject(10JJ4035)supported by the Natural Science Foundation of Hunan Province,ChinaProject(2010ybfz046)supported by the Fund of Excellent Doctoral Dissertation of Central South University,China
文摘A stratum grouting-soil-structure interaction model which simplified the grouted zone into a series of spherical grout bulbs was established using FLAC3D program. The hypothetical non-uniform expansion process to reach an assigned volume strain due to soil compression by grouting was achieved by imposing radial velocity on outer mesh nodes of these spheres. This new method avoids the repeated trial calculation needed in the traditional method which applied a fictitious expanding pressure in the grouting element. The deformation and additional internal forces of structure were investigated during each grouting strategy and the influences of various stiffness of grouting proof curtain and bearing capacity of pile tip were discussed simultaneously. The numerical model is proved to be effective to replicate general behavior expected in the field and is capable of modeling the uplifting effect for the surface structure by grouting.
基金Project CPEUKF08-04 support by the Key Laboratory of Coal Processing and Efficient Utilization, Ministry of Education of China
文摘Thermo-gravimetric-analysis(TGA) was used to analyze the combustion characteristics of an oil shale and semi-cokes prepared from it.The effect of prior pyrolysis and TGA heating rate on the combustion process was studied.Prior pyrolysis affects the initial temperature of mass loss and the ignition temperature.The ignition temperature increases as the volatile content of the sample decreases.TG/DTG curves obtained at different heating rates show that heating rate has little effect on ignition temperature.But the peak of combustion shifts to higher temperatures as the heating rate is increased.The Coats-Redfern integration method was employed to find the combustion-reaction kinetic parameters for the burning of oil shale and oil shale semi-coke.
基金Supported by the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20060056036)
文摘The lattice Boltzmann method (LBM) is employed to simulate the uniform flow past a circular cylinder. The performance of the two-dimensional LBM model on the prediction of force coefficients and vortex shedding frequency is investigated. The local grid refinement technique and second-order boundary condition for curved walls are applied in the calculations. It is found that the calculated vortex shedding frequency, drag coefficient and lift coefficient are consistent with experimental results at Reynolds nu...
文摘To enhance the maneuverability of the selected aircraft model, a standard genetic algorithm (GA) is used as an optimization method for the preliminary design of the leading-edge extension (LEX) layout. The aerodynamic loads and the maximum lift coefficient of the complete aircraft configuration (fuselage+wing+tail) are computed by using the modified three-dimensional low-order panel method in conjunction with the semi-empirical formulas of DATCOM. Results show that the lift coefficient increases approximately 20.5%- 15.3% for Mach number 0. 4-0.8 and 6.8% for Mach number 1.2, and its maximum value approximately 9.5% -15.0% for Machnumber 0.2-0.95when LEXis installed. A 6.6%-8.0 % gain at altitudes of 1-5 km on the turn rate maneuverability and the corner speed have been achieved in the subsonic regime.
基金Foundation item: Supported by Supported by the National Natural Science Foundation of China (Grant No. 51009070).
文摘In this paper, 2-D computational analyses were conducted for unsteady high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. 8.21×104〈Re〈1.54×106. The calculations were performed by means of solving the 2-D Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with a k-ε turbulence model. The calculated results, produced flow structure drag and lift coefficients, as well as Strouhal numbers. The findings were in good agreement with previous published data, which also supplied us with a good understanding of the flow across cylinders of different high Reynolds numbers. Meanwhile, an effective measure was presented to control the lift force on a cylinder, which points the way to decrease the vortex induced vibration of marine structure in future.