Abstract
Oleo-damping performance is a key factor affecting the landing gear buffer performance, while the flow discharge coefficient determines buffer damping force. For improving the calculation precision of discharge coefficient estimation method in aircraft design manual, a model for discharge coefficient is established based on pipeline fluid mechanics and damping orifice structure, and a numerical calculation is performed. Computational fluid dynamics (CFD) analysis is also conducted for damping orifice structure using the commercial software FLUNET. The simulation result of damping orifice discharge coefficient correlates well with the theoretical result. On this basis, landing gear drop dynamic response are calculated with the numerical analysis method using obtained discharge coefficient and compared with experimental results. Furthermore, the influences of current discharge coefficient estimation method and simulation method are analyzed and compared on the hydraulic force and the ground reaction force. The study demonstrates that the poor precision of discharge coefficient estimation method in aircraft design manual leads to more than 30 % differences between the drop dynamic estimation results and the experimental results. The method of CFD simulation or theoretical analysis can improve the calculation precision of discharge coefficient by about 17 %.
Highlights
The shock absorber is an essential component of modern landing gears, as it absorbs most of the impact energy that aircraft suffered during takeoff and landing phase [1]
The initial discharge coefficient estimation result is substituted into the dynamic model to calculate the dynamic response, and it is adjusted according to the comparison with the experimental result
Based on the study of the discharge coefficient calculation methods and their influences on the drop dynamic response of the landing gear, it comes to the conclusions as follows: 1) In this paper, the discharge coefficient theoretical and Computational fluid dynamics (CFD) simulation results are basically identical, and they are in good agreement with the experimental data
Summary
The shock absorber is an essential component of modern landing gears, as it absorbs most of the impact energy that aircraft suffered during takeoff and landing phase [1]. The main focus on the drop dynamic response of landing gear is the structural parameters, air spring force, friction force and structural force, rather than the discharge coefficient [4,5,6,7]. DISCHARGE COEFFICIENT CALCULATION METHOD OF LANDING GEAR SHOCK ABSORBER AND ITS INFLUENCE ON DROP DYNAMICS. In this paper, according to the shortcomings of the current discharge coefficient estimation method, the theoretical calculation and CFD simulation methods are put forward. These methods are adopted to calculate the orifice discharge coefficient, hydraulic force and drop dynamic response of an unmanned aerial vehicle (UAV) nose landing gear respectively. To analyze the influences of calculation methods, comparisons are conducted between obtained results and experimental results
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