A new approach to the study on the transient properties of the levitated object in near-field acoustic levitation （NFAL） is presented. In this article, the transient response characteristics, including the levitated...A new approach to the study on the transient properties of the levitated object in near-field acoustic levitation （NFAL） is presented. In this article, the transient response characteristics, including the levitated height of an object with radius of 24 mm and thickness of 5 mm, the radial velocity and pressure difference of gas at the boundary of clearance between the levitated object and radiating surface （squeeze film）, is calculated according to severa/velocity amplitudes of radiating surface. First, the basic equations in fluid areas on Arbitrary Lagrange--Euler （ALE） form are numericaJly solved by using streamline upwind petrov gaJerkin （SUPG） finite elements method. Second, the formed a/gebraic equations and solid control equations are solved by using synchronous alternating method to gain the transient messages of the levitated object and gas in the squeeze film. Through theoretical and numerical analyses, it is found that there is a oscillation time in the transient process and that the response time does not simply increase with the increasing of velocity amplitudes of radiating surface. More investigations in this paper are helpful for the understanding of the transient properties of levitated object in NFAL, which are in favor of enhancing stabilities and responsiveness of levitated object.展开更多
An optimal design configuration of leading edge extensions （LEXs） is presented based on the standard genetic algorithms （GAs）. Aircraft longitudinal dynamic response of the system with and without LEX is analyzed ...An optimal design configuration of leading edge extensions （LEXs） is presented based on the standard genetic algorithms （GAs）. Aircraft longitudinal dynamic response of the system with and without LEX is analyzed by solving the state equation of aircraft longitudinal motion. Aerodynamic force, moments, and longitudinal stability derivatives are estimated by three-dimensional low-order panel method. A novel aircraft model with LEX is optimized and its lift curve slope is increased by 13%-17% for Ma=0. 4-0. 9 and 12% for Ma=1. 5. Numerical results show that because the frequency and damping ratio in a short period are improved, the aircraft rapidly responds to a specified deflection control input in the battle area when LEX is installed. Finally, compared the results from the panel method with those from the Cy-20 aircraft flight test data,aerodynamic characteristics are verified.展开更多
基金Supported by the National Basic Research Program of China(973 Program)(2011CB707602)the China Natural Science Fond under Grant No.11174149the Funding of Jiangsu Innovation Program for Graduate Education under Grant No.CXl0B_092Z
文摘A new approach to the study on the transient properties of the levitated object in near-field acoustic levitation （NFAL） is presented. In this article, the transient response characteristics, including the levitated height of an object with radius of 24 mm and thickness of 5 mm, the radial velocity and pressure difference of gas at the boundary of clearance between the levitated object and radiating surface （squeeze film）, is calculated according to severa/velocity amplitudes of radiating surface. First, the basic equations in fluid areas on Arbitrary Lagrange--Euler （ALE） form are numericaJly solved by using streamline upwind petrov gaJerkin （SUPG） finite elements method. Second, the formed a/gebraic equations and solid control equations are solved by using synchronous alternating method to gain the transient messages of the levitated object and gas in the squeeze film. Through theoretical and numerical analyses, it is found that there is a oscillation time in the transient process and that the response time does not simply increase with the increasing of velocity amplitudes of radiating surface. More investigations in this paper are helpful for the understanding of the transient properties of levitated object in NFAL, which are in favor of enhancing stabilities and responsiveness of levitated object.
文摘An optimal design configuration of leading edge extensions （LEXs） is presented based on the standard genetic algorithms （GAs）. Aircraft longitudinal dynamic response of the system with and without LEX is analyzed by solving the state equation of aircraft longitudinal motion. Aerodynamic force, moments, and longitudinal stability derivatives are estimated by three-dimensional low-order panel method. A novel aircraft model with LEX is optimized and its lift curve slope is increased by 13%-17% for Ma=0. 4-0. 9 and 12% for Ma=1. 5. Numerical results show that because the frequency and damping ratio in a short period are improved, the aircraft rapidly responds to a specified deflection control input in the battle area when LEX is installed. Finally, compared the results from the panel method with those from the Cy-20 aircraft flight test data,aerodynamic characteristics are verified.
