The stability of two‐dimensional wakes and shear layers at high Mach numbers

1991 ◽  
Vol 3 (5) ◽  
pp. 793-802 ◽  
Author(s):  
Demetrios T. Papageorgiou
Keyword(s):  
Shear Layers ◽  
Two Dimensional ◽  
Mach Numbers ◽  
High Mach ◽  
The Stability

Some Problems of the Stability and Control of Large Aircraft

1948 ◽  
Vol 52 (455) ◽  
pp. 723-734 ◽  
Author(s):  
D. J. Lyons
Keyword(s):  
Slow Speed ◽  
The Troubles ◽  
Stability And Control ◽  
Large Size ◽  
Mach Numbers ◽  
High Mach ◽  
The Stability ◽  
And Control ◽  
Very High ◽  
Large Aircraft

In the Realm of stability and control, we are at present travelling headlong into a region of new problems. Besides tidying up the outstanding items on the types of aircraft we are used to seeing flying about to-day, a not inconsiderable task when one considers the troubles we encounter when we undertake the design of a new so-called “conventional” aeroplane, we have to tackle two major lines of research and development. First, the peculiar problems associated with the stability and control of aircraft of large size, both military and civil, into which difficulties associated with high Mach numbers intrude themselves but little; and secondly, the even more extensive problems associated with the stability and control of aircraft, both large and small, which are to fly at very high Mach numbers, not only at their design cruising and diving speeds, but also in the extremely important slow speed conditions. Mr. M. B. Morgan of the R.A.E. has dealt with some aspects of the second series of problems, so I propose to concentrate on some of the problems involved in the first series, that is those primarily associated with the increase of aircraft size.

Stability Derivatives of Blunt Slender Cones at High Mach Numbers

1979 ◽  
Vol 30 (4) ◽  
pp. 559-589 ◽  
Author(s):  
M. Khalid ◽  
R.A. East
Keyword(s):  
Flow Model ◽  
Finite Thickness ◽  
Theoretical Methods ◽  
Stability Derivatives ◽  
Analytic Expressions ◽  
Mach Numbers ◽  
High Mach ◽  
The Stability ◽  
Semi Empirical ◽  
Derivatives Of

SummaryThis paper presents a semi-empirical theoretical model for calculating the effect of nose bluntness on the stability derivatives of oscillating slender cones at hypersonic Mach numbers. It is based on a hybrid blast wave analogy/shock-expansion flow model and is used to obtain closed form analytic expressions for the derivatives for oscillating slender cones. Two models based on zero thickness and finite thickness entropy layers are proposed which are seen to be appropriate to the cases of very small and large nose bluntnesses, respectively. The results are compared with new and existing experimental data and with the predictions of previous theoretical methods.

An experimental study of turbulent separating and reattaching flows at a high Mach number

1972 ◽  
Vol 52 (3) ◽  
pp. 425-435 ◽  
Author(s):  
J. P. Batham
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Shear Layers ◽  
Two Dimensional ◽  
Pressure Coefficients ◽  
High Mach ◽  
Incipient Separation ◽  
Good Agreement

Separating and reattaching flows in a two-dimensional compression corner were investigated experimentally at a Mach number of 7·0 and Reynolds numbers (based on the distance from the leading edge to the corner) of 4·75 × 106, 9·51 × 106 and 1·55 × 107. Heat-transfer measurements and Pitot traverses in the upstream boundary layer showed that the boundary layer had become fully turbulent at the start of the interactions. Increases in the Reynolds number gave increases in the length of separated shear layers and decreases in the corner angle required for incipient, separation. The reattachment pressure coefficients gave good agreement with the criterion of Batham (1969).

A Note on the Supersonic Panel Flutter of Oblique Clamped Plates

1964 ◽  
Vol 68 (640) ◽  
pp. 270-271 ◽  
Author(s):  
A. Kornecki
Keyword(s):  
Present Note ◽  
Panel Flutter ◽  
Rectangular Plates ◽  
Two Dimensional ◽  
Aerodynamic Loading ◽  
Aspect Ratios ◽  
Flutter Boundary ◽  
Mode Solution ◽  
Mach Numbers ◽  
High Mach

Summary and IntroductionRecently, the effect of sweepback on the boundaries of supersonic panel flutter was studied in Ref. (1), (2) and (3), all of them dealing with rectangular plates.The present note considers the problem of panel flutter boundary of plates in the shape of a parallelogram with all edges clamped.It is assumed that Ackeret's theory of linearised two-dimensional supersonic aerodynamic loading gives an adequate approximation to the air forces for high Mach numbers.The criterion of instability is the coalescence of frequencies.A four-mode solution was obtained by means of Galerkin's method using first two streamwise and spanwise deflection modes. The results are represented in the form of diagrams for different aspect ratios(a/b)and sweep angles(ϕ).

Three-dimensional simulations of large eddies in the compressible mixing layer

1991 ◽  
Vol 224 ◽  
pp. 133-158 ◽  
Author(s):  
N. D. Sandham ◽  
W. C. Reynolds
Keyword(s):  
Mach Number ◽  
Large Scale ◽  
Mixing Layer ◽  
Three Dimensional ◽  
Large Scale Structure ◽  
Two Dimensional ◽  
Instability Waves ◽  
Compressible Mixing Layer ◽  
Mach Numbers ◽  
High Mach

The effect of Mach number on the evolution of instabilities in the compressible mixing layer is investigated. The full time-dependent compressible Navier–Stokes equations are solved numerically for a temporally evolving mixing layer using a mixed spectral and high-order finite difference method. The convective Mach number Mc (the ratio of the velocity difference to the sum of the free-stream sound speeds) is used as the compressibility parameter. Simulations with random initial conditions confirm the prediction of linear stability theory that at high Mach numbers (Mc > 0.6) oblique waves grow more rapidly than two-dimensional waves. Simulations are then presented of the nonlinear temporal evolution of the most rapidly amplified linear instability waves. A change in the developed large-scale structure is observed as the Mach number is increased, with vortical regions oriented in a more oblique manner at the higher Mach numbers. At convective Mach numbers above unity the two-dimensional instability is found to have little effect on the flow development, which is dominated by the oblique instability waves. The nonlinear structure which develops from a pair of equal and opposite oblique instability waves is found to resemble a pair of inclined A-vortices which are staggered in the streamwise direction. A fully nonlinear computation with a random initial condition shows the development of large-scale structure similar to the simulations with forcing. It is concluded that there are strong compressibility effects on the structure of the mixing layer and that highly three-dimensional structures develop from the primary inflexional instability of the flow at high Mach numbers.

Effect of Suction on the Stability of Supersonic Boundary Layers. Part II—First-Mode Waves

1991 ◽  
Vol 113 (4) ◽  
pp. 598-601 ◽  
Author(s):  
J. A. Masad ◽  
A. H. Nayfeh ◽  
A. A. Al-Maaitah
Keyword(s):  
Boundary Layers ◽  
Mass Flux ◽  
Growth Rates ◽  
Two Dimensional ◽  
Viscous Instability ◽  
Dimensional Boundary ◽  
Mach Numbers ◽  
The Stability

The effect of suction on the first mode of instability of compressible two-dimensional boundary layers is investigated. Suction is found to be more effective in stabilizing the viscous instability, and hence it is more effective at low Mach numbers. Suction decreases the amplification rates at all frequencies and narrows down the band of unstable frequencies. Moreover, for a given frequency, suction decreases the amplification rates at all streamwise locations. Variations of the growth rates of the most amplified first-mode waves with mass flux are found to be almost linear.

Novel Approach for Loss and Flow-Turning Prediction Using Optimized Surrogate Models in Two-Dimensional Compressor Design

2011 ◽  
Author(s):  
Andreas Schmitz ◽  
Marcel Aulich ◽  
Eberhard Nicke
Keyword(s):  
Neural Networks ◽  
Surrogate Models ◽  
Design Parameters ◽  
Two Dimensional ◽  
Empirical Correlations ◽  
Streamline Curvature ◽  
Flow Parameters ◽  
Compressor Design ◽  
Mach Numbers ◽  
High Mach

Two-dimensional (2D) streamline curvature methods are still an important tool in modern compressor design. In the past most of the streamline curvature methods made use of empirical correlations to approximate the blade row losses and deviation functions on which the accuracy of streamline curvature methods mainly depend. These empirical correlations are just accurate for a small set of geometric airfoil design parameters for which they where obtained and the prediction of airfoil performance at high Mach numbers or at off-design condition is inaccurate. Nowadays, a new approach is needed to consider highly customized, modern airfoil geometries with an increased number of design parameters. A new method with the possibility to predict the performance of these highly customized airfoils also at off-design condition and high Mach numbers is presented in this paper. This method uses a large airfoil database together with optimized surrogate models to accurately predict airfoil performance. The database consists of approximately 106 randomly created airfoils with randomly created inflow conditions and the airfoil performance which results from the 2D Euler-boundary layer code MISES [16]. The airfoil geometry in this database is described by ten geometrical parameters, e.g. stagger angle, chord length etc.. The flow condition is described by four flow parameters such as the relative inflow Mach number, MVDR, relative inflow angle and Reynolds number. Airfoil performance is represented by total pressure loss and flow-turning. This database was used to train neural networks that provides the relationship between the geometrical/flow parameters and the airfoil performance. The topology of the neural networks was optimized to achieve a model which represents this highly nonlinear functionality at best. This model was integrated in the DLR’s in-house streamline curvature tool ACDC which is based on the equations of MO¨NIG et al. [12], GALLIMORE [8]. The code allows viscous throughflow calculations taking into account radial mixing by turbulent diffusion, endwall boundary layers and a model for tip clearance based on the work of DENTON [7], KRO¨GER et al. [9].

scholarly journals The two-dimensional hydrodynamical theory of moving aerofoils. IV

1947 ◽  
Vol 188 (1015) ◽  
pp. 439-463
Keyword(s):  
Stability Problem ◽  
Two Dimensional ◽  
Centre Of Gravity ◽  
First Approximation ◽  
Von Karman ◽  
Moving Cylinder ◽  
Period Equation ◽  
The Stability ◽  
Von Kármán ◽  
Hydrodynamical Theory

In the first part of this paper opportunity has been taken to make some adjustments in certain general formulae of previous papers, the necessity for which appeared in discussions with other workers on this subject. The general results thus amended are then applied to a general discussion of the stability problem including the effect of the trailing wake which was deliberately excluded in the previous paper. The general conclusion is that to a first approximation the wake, as usually assumed, has little or no effect on the reality of the roots of the period equation, but that it may introduce instability of the oscillations, if the centre of gravity of the element is not sufficiently far forward. During the discussion contact is made with certain partial results recently obtained by von Karman and Sears, which are shown to be particular cases of the general formulae. An Appendix is also added containing certain results on the motion of a vortex behind a moving cylinder, which were obtained to justify certain of the assumptions underlying the trail theory.

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