Pavlova K. Modeling of physical processes in control systems of aviation and rocket and space technology

The dissertation is devoted to the study of non-stationary processes of fluid motion in the hydraulic system of aircraft and helicopters, as well as the processes of controlling the release and retraction of the aircraft landing gear and its flaps. Using theoretical physical and mathematical methods, existing models of unsteady fluid flow and aircraft control processes have been further developed, and fundamentally new models of unsteady bubbling fluid flow and the interaction of this flow with the structure have been developed. The first chapter provides a critical review of the literature according to the topic of the work. In the second chapter a mathematical model describing the flap control process of small aircraft is elaborated. An analytical solution corresponding to the nonlinear dynamics of the interconnected motion of the electromechanical actuator rod and the aircraft flap. Comparison with existing data, which indicates the correctness of the obtained results. It is shown that the motion of the hydraulic cylinder rod is described by the (one of) same solution that occurs during hydraulic shock. That results into a logical conclusion about the importance of studying unsteady flows of the hydraulic impulse type in the hydraulic systems of aircrafts and helicopters In the third chapter, first section it is considered the unsteady flow of liquid in pipelines. This work presents achievements both for the inviscid approximation and taking into account internal viscous friction. Internal friction within is insignificant almost everywhere except for thin shock layer. At the same time, the convection of the velocity field significantly affects the distribution of characteristics in the hydraulic shock. In the second section of third chapter the phenomenon of hydraulic shock in a bubble liquid is considered. The model consists of two differential equations regarding the speed of shock wave propagation and pressure disturbances that arise as a result. The shock pulse in a bubbly liquid is not as concentrated in space as in a homogeneous one. In the fourth chapter it is developed a nonlinear model of the interaction of unsteady fluid flow with a structure and analytical solutions of the system of equations that corresponds to the specified model are fond. A generalized model of the interaction of the bubbly flow of liquid with the structure is considered. The obtained results are compared with simpler models