In work on the basis of the deep analysis of approaches to estimation of efficiency of an information exchange of telecommunication systems is offered the method of an estimation on the basis of the generalized indicator – performance coefficient (PC) of transfer of information taking into account losses of information packets. The indicator is specified at network level with use of cybernetic capacity of information losses. The structural scheme of the device with instructions of elements for practical realization of a method is developed. The generalised algorithm providing the analysis and an estimation of information efficiency of telecommunication systems with various structures on the basis of the received method is synthesized. Analytical and imitating modelling of work of algorithm and estimation of information efficiency of telecommunication systems with structures “star” and full connected in the conditions of change of the input traffic taking into account of influence of hindrances is spent. Results of modelling have confirmed working capacity of a method and reliability of estimations received on his basis that can be used at the organisation of complex multi-contour of adaptation.
The model of the landing system for swarms of small unmanned aerial vehicles in fact consists of a queuing system with a space-time holding zone serving as a gathering device for small unmanned aerial vehicles, where the holding elements are represented by the sequentially connected buffer zone for aerial vehicle landing and the landing line itself with a robotic landing platform. The passage of aerial vehicles from the holding area to the landing zone is controlled by the landing line access protocol. Safe movement of small unmanned aerial vehicles in the holding and landing zones is ensured by the information-measurement and management landing system of a universal robotic platform. The article suggests using the “landing system capacity” as one of the indicators of system performance efficiency.
The study considers the operation of an unmanned aerial vehicle in hovering mode over a flat landing platform. As a propulsion system, impellers are used, which are a system of a propeller rotating inside an air ring. The air ring is a body of revolution with an aerodynamic profile in cross section. The paper investigates the effect of unsteady interaction of vortex flows with the design of an aircraft by two alternative numerical methods, one of which is vortex-resolving. Numerical calculations are performed using the traditional turbulence modeling approach based on the averaged Navier-Stokes equations (RANS, Reynolds Averaged Navier-Stokes), where the turbulence is assumed to be isotropic, and the eddy-resolving Large Eddy Simulation method. The main feature of the latter is as follows: a turbulent flow is represented as the superposition of the motion of large-scale and small-scale turbulences. After discretizing the flow using a filtering operation, large-scale turbulence, which depends directly on the boundary conditions, is solved from the full Navier-Stokes equations. Small-scale turbulence has isotropic properties and is modeled similarly to semi-empirical RANS methods. The technique allows one to accurately calculate the vortex structure of any flow directly from the equations of motion using relatively low computing power, in contrast to the RANS models, which simulate the flow using a simplified mathematical model and can provide satisfactory accuracy only for a limited range of problems. The results indicate that eddy-resolving methods for modeling turbulence, in contrast to the methods based on averaged Navier-Stokes equations, make it possible to estimate the effect of aperiodic perturbations on the design of aircraft arising from the interaction of large eddies with each other and with the underlying surface. Such phenomena are accompanied by side impacts of a shock nature on the impeller rings, which can lead to loss of aircraft stability. Under conditions of a small propeller step, the use of an air ring results in a significant increase in the air flow passing through the rotor rotation loop, an increase in thrust due to the creation of flow circulation around the airfoil of the ring, and a decrease in the power on the propeller. Even though the effect of using an air ring disappears with a large incoming flow, this design is considered very promising for use on aircraft with vertical takeoff and landing. This mode of operation is the most energy-consuming and determines the greatest requirements for the lifting force of the power plant. The results of this work have demonstrated that numerical methods based on averaging the Navier-Stokes equations and the use of classical turbulence models of the k-ω or k-ε type, which are widely used in numerical modeling of propellers, in takeoff and landing modes fail to detect aperiodic unsteady phenomena associated with the interaction of large eddies, in contrast to eddy-resolving methods for modeling turbulence.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.