Wind tunnel based Virtual Flight Testing (VFT) is a dynamic wind tunnel test for evaluating flight control systems (FCS) proposed in recent decades. It integrates aerodynamics, flight dynamics, and FCS as a whole and is a more realistic and reliable method for FCS evaluation than traditional ground evaluation methods, such as Hardware-in-the-Loop Simulation (HILS). With FCS evaluated by VFT before flight test, the risk of flight test will be further reduced. In this paper, the background, progress, and prospects of VFT are systematically summarized. Specifically, the differences among VFT, traditional dynamic wind tunnel methods, and traditional FCS evaluation methods are introduced in order to address the advantages of evaluating FCS with VFT. Secondly, the progress of VFT is reviewed in detail. Then, the test system and key technologies of VFT for FCS evaluation are analyzed. Lastly, the prospects of VFT for evaluating FCS are described.

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A Review of Wind Tunnel Based Virtual Flight Testing Techniques for Evaluation of Flight Control Systems

Low-speed wind tunnel investigations are performed for the flat spin of slender bodies at high angles of attack at Reynolds numbers of (1.2-4.4) xlO5. Effects of the geometrical configuration of the model, freestream Reynolds number, and angle of attack on the flat spin motion are analyzed using spin rate measurements, in situ surface pressure distribution, and static aerodynamic characteristics. It is verified that the flat spin is caused by differences in flow patterns at the critical Reynolds number. The measured side moment can be used to predict the actual flat spin rate. The flat spin can be alleviated by causing early transition of the boundary layer with artificial surface roughness.

Flat spin of slender bodies at high angles of attack

Heat transfer—A review of 1978 literature

On the number of limit cycles for perturbed pendulum equations

The angular motion of an orbital re-entry experiment (OREX) vehicle model was tested in a transonic wind tunnel using a single-degree-of-freedom test method to investigate the angular motion of the OREX vehicle. The purpose of the OREX is to test heat shield materials and to obtain measurements of an aerodynamically heated flowfield. Approximate static and dynamic derivatives of the model were measured by a local linear curvefitting method. The angular motion of real OREX flight data was compared with the wind-tunnel test results. The maximum amplitude of the OREX vehicle in the transonic region is almost the same as that obtained in the wind-tunnel test.

Orbital re-entry experiment vehicle ground and flight dynamic test results comparison

A method to determine the pitching moment of slender bodies with less support interference was developed by simulating a pitching motion of 1-DOF angular motion in wind tunnels. The pitching moment acting on the bodies was determined to be a one-valued function of the angle of attack a and its time derivative a'. A phase plane concept proved to be useful in the analysis of the pitching motion. It was possible to calculate the pitching motion for an arbitrary initial condition by using the mathematical expression of the moment. The variation of energy in the pitching motion showed the energy exchange between the models and the air flow. The visualization of the wake flowfield revealed the hysteresis of the separated flow about the model which caused the amplification of the pitching motion. The effects of the shapes of models, freestream velocity, and the center of gravity on the pitching moment coefficients were investigated.

Determination of the Pitching Characteristics of Tumbling Bodies by the Free-Rotation Method

Approximate Calculation of Aerodynamic Coefficients for Rotating Slender Bodies at 90 deg Incidence

Nonlinear oscillation described by the equation, \(\ddot{x}+\sin x+(\varepsilon_{1}+\varepsilon_{2}\cos x)\dot{x}{=}0\), is considered. By applying Hori's general perturbation theory for non-canonical system, a necessary condition for the existence of limit cycles is given in terms of e 1 and e 2 , and analytical expressions for limit cycles are obtained up to the first order. The analytical approximate solutions are compared with numerical solutions and satisfactory agreement between them is observed.

Perturbed Motion of a Simple Pendulum

Flat spin of circular cylinders induced by artificial roughness

The method of matched asymptotic expansions is applied to the problem of a parabolic cylinder in a uniform incompressible flow at high Reynolds numbers. The equations and the boundary conditions for the first-order boundary layer, the second-order outer flow and the second-order boundary layer are formulated in terms of the parabolic co-ordinate system. The equations are solved numerically by means of finite-difference approximation. The results for skin friction and surface pressure are compared with the available numerical solutions of the full Navier-Stokes equations. The application of the technique of rational fraction to the two-term asymptotic expansion for skin friction shows that a further approximation will give a better result.

Kenji Inoue

Papers

Determination of the Pitching Characteristics of Tumbling Bodies by the Free-Rotation Method

Approximate Calculation of Aerodynamic Coefficients for Rotating Slender Bodies at 90 deg Incidence

Perturbed Motion of a Simple Pendulum

Flat spin of circular cylinders induced by artificial roughness

Second Approximation to the Laminar Boundary-Layer Flow over a Parabola