Determination Of Aerodynamic Forces Research Articles

COMPARISON OF TWO METHODS TO CALCULATE EXTERNAL LOADS AT FLIGHT IN CONTINUOUS TURBULENCE

The external loads from the continuous turbulence on the elastic high aspect ratio wing of the transport category aircraft are calculated by Dynamics of Turbulence Air (DTA) and Interactive Multidisciplinary Aircraft Design (IMAD) methods. The response to continuous turbulence was determined taking into account the requirements of CS-25.341(b). The model of the aircraft structure is directed by symmetrical spatial beam schematization. Determination of aerodynamic forces and moments was performed using the methods of linear computational aerodynamics: the panel method of Doublet-Lattice and Constant Pressures (DLM/CPM) and the method of circulation. Comparison of the results of load determination showed that, in general, the values of the loads calculated using IMAD are lower than the values calculated using DTA. Therefore, when designing an aircraft, it is advisable to combine these methods: calculate the loads using IMAD, as a more functional method, and then the loads obtained in the critical points of the calculated flight area should be confirmed using the DTA method. Thus, this study determined the difference between the results of the calculation of loads from the continuous turbulence on the elastic wing of the transport category aircraft using DTA and IMAD methods.

Determination of Aerodynamic Forces and Control Requirement during Ground Effect

Determination of Aerodynamic Forces and Control Requirement during Ground Effect

The WIG-craft Aerodynamic Model Parameters Calculation

Abstract The problem of determining the aerodynamic parameters of the model of vehicle in the area of the ground-effect, intended for the synthesis of the control system, is considered. The determination of aerodynamic forces and moments for various stationary flight modes is successfully solved by experimental and numerical methods. Each control element is one more additional varied parameter. The volume of calculations is reduced if we consider only the movement in the neighborhood of the balancing modes. We calculate the centering and balancing of the vehicle for a given full model of the dynamics of the object, taking into account the limitations on the control parameters. The vector of control actions in a generalized form is limited to the maximum values of forces and moments. The tasks of centering, balancing and implementing hierarchical control are solved by mathematical programming methods. Synthesis of generalized control is carried out by classical or synergistic methods. Our preliminary calculation of aerodynamic parameters using the COMSOL Multiphysics software package and the CFD module allowed us to solve all these tasks and we will use it to further calculate the aerodynamics of stationary and non-stationary flight modes in the neighborhood of balancing values.

Numerical Simulation of Flow and Determination of Aerodynamic Forces in the Balanced Control Valve

The contribution subscribes a numerical simulation of a steam flow through a balanced control valve. The influence of some parameters in simulations were tested, analyzed and discussed. As a result of the simulations a graph of aerodynamics forces for a specific turbine characteristic was obtained. The results from numerical simulations were compared with results from experiments. The experiment was performed with an air flow, but the final data were converted with a criterion to steam flow.

Mathematical model of aeroelastic vibrations of cascades of axial turbomachine blades, caused by circumferential nonuniformity of the flow

A system of linear differential equations with time-dependent coefficients, which describes aeroelastic vibrations of blade cascades in a nonuniform flow, is derived. With the use of the model of an ideal incompressible fluid and the hypothesis of cylindrical sections, determination of aerodynamic forces acting on the blades is reduced to solving problems by methods fairly well developed in the theory of cascades in unsteady flow. The possibility of the emergence of a parametric resonance is analyzed. It is demonstrated that circumferential nonuniformity of the flow in the turbomachine duct can substantially reduce the critical velocity of the cascade flutter.

Nonlinear Aeroelasticity and Unsteady Aerodynamics

In this von Karman lecture, a subject is addressed whose foundations were significantly influenced by the work of Theodore von Karman. A classic paper by von Karman and Sears first considered the determination of aerodynamic forces on an airfoil undergoing general time-dependent motion. Also, early in his career, von Karman investigated fundamental issues in structural mechanics and derived the celebrated von Karman plate equations for determining the large (nonlinear) deflections of an elastic plate under a distributed force. Finally, he authored a widely cited paper on the importance of nonlinearities for engineers and engineering. In this lecture, these themes are recalled and the current state of the art in nonlinear aeroelasticity and unsteady aerodynamics is discussed. Several of the most significant nonlinearities arising in a structure or in an aerodynamic flow field are identified. Recent and relevant theoretical and experimental studies are reviewed and future developments are projected that are expected to have a significant impact on our ability to understand and beneficially use nonlinear dynamic aeroelastic behavior

Determination of aerodynamic forces on satellites by theory and wind tunnel experiments

Theoretical and experimental aspects of satellite aerodynamics in free molecular flow have been studied. A FORTRAN-program package has been developed to calculate free molecular aerodynamic force and moment coefficients of general and special convex shapes, using an approximation of the surfaces by plane triangular elements. As a special case for concave bodies, the drag of a satellite of TD1A-similar shape has been investigated by an approximate theory and by wind tunnel experiments. Comparisons are made between experimental results, the approximate theory and exact theory.