Vladimir A. Frolov

Development of numerical-analytical method for calculating potential flow around 2D-body

A Numerical-Analytical Method (NAM) and Discrete Vortices Method (DVM) are developed for simulating unsteady separated flow around a two-dimensional body. The solution is determined under the assumption of fluid being ideal and incompressible. The NAM is based on a combination Theory Function of Complex Variable (TFCV) and DVM, which improves the calculation accuracy and reduce the computation time. The paper presents examples of calculations of potential flows around arc-airfoils with spoiler. For flow separated at each sharp edge, such as the spoiler tips and the trailing edge of the airfoil, a vortex sheet is formed with help free discrete vortices which moving at the each time step. Developments of the behavior of the vortex sheet behind the flat plate and the airfoil with the spoiler are considered.

Lift Investigation of Airfoil with Flaps

In the paper a lift calculation of a two-dimensional airfoil with a plain flap and Krueger flap is investigated. Numerical-analytical method (NAM) is used to predict the flow field around this combination. In order to calculate the complex velocity in the flow field, the complex variable function theory is employed. NAM based on the joint application of conformal mapping and the discrete vortex method (DVM). The paper presents a brief description of the NAM and some results of the lift calculations of the airfoil with the plain flap and Kruger flap. Comparison of the calculation results with the theoretical data of other authors showed a good agreement.

Influence of the Curved Ground Surface on the Lift of Flat Plate Airfoil

At present, only the flat ground surface problem is investigated in most studies on ground effect, which is not effective for practical applications due to the universal existence of curved ground surface. In this paper, the lift calculation of a two-dimensional flat plate airfoil placed near a curved ground surface is investigated. In order to calculate the complex velocity in the flow field, the complex variable function theory is employed. The conformal mapping method is applied to transform the flat plate airfoil to a cylinder in the uniform flow. Moreover, the discrete vortices method is modified to convert the curved ground surface to a series of discrete boundary elements. Two kinds of curved ground surfaces are considered: semicylindrical hollows and semicylindrical hills. It is shown that the lift fluctuation of flat plate airfoil located near a hollow or a hill is considerably serious, which should be considered during the design of flight vehicles flying near the ground surface.

Reducing cylinder drag by adding a plate

Reducing the drag of bodies is a central problem of modern aerohydrodynamics. The paper presents theoretical and experimental studies of a new method for reducing the drag of a circular cylinder. To reduce the drag we propose to install a flat plate along the flow in front of the cylinder. The theoretical investigation of the drag was carried out using FlowSimulation software. An experimental study of the body drag was performed in an open wind tunnel. The drag coefficient results of the cylinder depended on the different locations of the flat plate relative to the cylinder. The following geometric characteristics of the cylinder/plate are studied: the width of the gap between the cylinder and the plate and the meridional angle of the plate with respect to the cylinder. On the basis of Numerical and Physical Modeling, the values of the drag coefficient for the cylinder/plate are presented. The results included establishment the locations of the cylinder/plate which give the value of the drag coefficient f...

Ground effect on lift of thick wing airfoil

The paper investigates the influence of the ground on the airfoil lift. The Numerical Analytic Method (NAM) and the Discrete Vortices Method (DVM) are developed for simulating the flow around an airfoil when it is in the close proximity to the ground. The author proposes the NAM for modeling the flow around the airfoil near the ground and analyzes two approaches to solving the problem of Wing-in- Ground (WIG). The first method is based on the simulation of the ground surface, while the second one uses the reflection method. It has been shown that the increasing in the relative airfoil thickness reduces the positive WIG lift effect. It is also established that there is an optimal airfoil angle of attack at which the maximum lift occurs near the ground.

Experimental investigation of lift for a wing-in-ground effect aircraft model

The aim of the investigation is to develop a technique of recalculating the lift as a function of the angle of attack at different reference points of the aircraft model height over the ground surface. A technique for evaluating the lift of the aircraft model close to the ground surface is proposed.

Laminar separation point of flow on surface of symmetrical airfoil

A Numerical-Analytical Method and Shvets’s method for calculating separation point position of the laminar boundary layer on a surface of an airfoil are used. An approximate Shvets’s method allows calculating of the separation point position of the laminar boundary layer if the velocity distribution on the surface of two-dimensional body is known. The velocity distribution on the surface of the airfoil is obtained in the model of an ideal incompressible fluid. It is found that main contribution to the position of the separation point makes through relative airfoil thickness. The thicker the airfoil, the closer to the leading edge of the airfoil is located separation point. The relative coordinate chordwise location of the airfoil maximum thickness affects to position of the separation point only for thick airfoils. The increasing of the relative coordinate of the maximum thickness for thick airfoil leads in displacement of the separation point to trailing edge of the airfoil. With increasing the angle of ...

Critical Mach Number for Flow around Circular-Arc Airfoil

An approximate method for the account of compressibility, which was successfully applied earlier for airfoil with subsonic-type edge, was used for airfoil with supersonic-type edge in the present paper. Calculations of the critical Mach number of free-stream flow around circular-arc airfoil are considered. This method allows defining the parameters of a compressible fluid through the flow characteristics of an incompressible fluid. The method to account of compressibility of a flow does not depend on mathematical model of calculation of incompressible flow. Calculations of the velocity field for incompressible flow on the basis of Theory Function of Complex Variable (TFCV) have been accomplished. It has been shown that the value of critical Mach number decreases with increasing the relative thickness of the circular-arc airfoil.

NAM Application for Simulation of Unsteady Separation Flow around Airfoil with Spoiler

A Numerical-Analytical Method (NAM) and Discrete Vortices Method (DVM) are developed for simulating unsteady separated flow around an airfoil with a spoiler. For flow separated at each sharp edge, such as the spoiler tips and the trailing edge of the airfoil, a vortex sheet is used to feed discrete vortices at each time step. The solution is determined under the assumption of fluid being ideal and incompressible. This paper develops modeling behavior of the vortices around the airfoil with the spoiler. The NAM based into the combination of the DVM and TFCV (Theory Function of Complex Variable) that gives to increase the accuracy of the calculation. In this paper the variation of the separation zones for the unsteady separated flow are shown.