scholarly journals Bilateral estimates of the critical Mach number for some classes of carrying wing profiles

2001 ◽  
Vol 42 (4) ◽  
pp. 494-503
Author(s):  
F. G. Avkhadiev ◽  
A. M. Elizarov
Keyword(s):  
Mach Number ◽  
Velocity Field ◽  
Original Problem ◽  
Angle Of Attack ◽  
Minimax Problem ◽  
Chaplygin Gas ◽  
Fixed Interval ◽  
Critical Mach Number ◽  
Extended Class ◽  
Bilateral Estimates

AbstractA problem of estimation of the critical Mach number for a class of carrying wing profiles with a fixed theoretical angle of attack is considered. The Chaplygin gas model is used to calculate the velocity field of the flow. The original problem is reduced to a special minimax problem. A solution is constructed for an extended class of flows including multivalent ones, hence M* is estimated from above. For a fixed interval [0, β0], β0 ≅ 3π/8, an estimate of M* is given from below.

Estimates for critical Mach number under isoperimetric constraints

1995 ◽  
Vol 6 (5) ◽  
pp. 385-398 ◽  
Author(s):  
F. G. Avkhadiev ◽  
A. M. Elizarov ◽  
D. A. Fokin
Keyword(s):  
Mach Number ◽  
Subsonic Flow ◽  
Chaplygin Gas ◽  
Ideal Gas ◽  
Open Problems ◽  
Inverse Boundary ◽  
Critical Mach Number ◽  
Lindelöf Principle ◽  
Isoperimetric Constraints ◽  
Upper Estimate

The problem of maximization of the critical Mach number in a subsonic flow of an ideal gas is considered. The Chaplygin gas approximation and the integral representation of the solution of the inverse boundary-value problem of aerohydrodynamics are used to reduce the problem to a special minimax one. The exact solution of the latter is obtained on the basis of the Lindelöf principle. An upper estimate for the critical Mach number is obtained. The results are generalized for the case of airfoil cascades. Some open problems are described.

Taper stacking for the aerodynamic performance of wings

2020 ◽  
Vol 92 (7) ◽  
pp. 1101-1110
Author(s):  
Mustafa Kaya ◽  
Munir Ali Elfarra
Keyword(s):  
Mach Number ◽  
Drag Force ◽  
Angle Of Attack ◽  
Total Drag ◽  
Content Type ◽  
Critical Mach Number ◽  
Wing Sweep ◽  
Drag Ratio ◽  
First Time ◽  
Lift To Drag Ratio

Purpose The critical Mach number, lift-to-drag ratio and drag force play important role in the performance of the wings. This paper aims to investigate the effect of taper stacking, which has been used to generalize wing sweeping, on those parameters. Design/methodology/approach The results obtained are based on steady-state turbulent flowfields computations. The baseline wing is ONERA M6. Various wing planforms are generated by linearly or parabolically varying the spanwise stacking location. The critical Mach number is determined by changing the freestream Mach number for a fixed angle of attack. On the other hand, the analysis of the drag force is carried out by changing the angle of attack to keep the lift force constant. Findings By changing the stacking location, the critical Mach number and the corresponding lift-to-drag ratio have increased by around 7 and 3%, respectively. A reduction of 12.8% in total drag force has been observed in one of the analyzed cases. Moreover, there exist some cases in which the values of drag reduce significantly while the lift is the same. Practical implications The results of this new stacking approach have implied that the drag force can be decreased without decreasing the lift. This outcome is valuable for increasing the range and endurance of an aircraft. Originality/value This work generalizes wing sweeping by modifying the taper stacking along the span. In literature, wing sweep is enhanced using segmented stacking of taper distribution. The present study is further enhancing this concept by introducing continuous stacking (infinite number of stacking segments) for the first time.

Critical Mach Number for Flow around Circular-Arc Airfoil

2015 ◽  
Vol 798 ◽  
pp. 513-517
Author(s):  
Vladimir A. Frolov
Keyword(s):  
Mathematical Model ◽  
Mach Number ◽  
Velocity Field ◽  
Incompressible Flow ◽  
Stream Flow ◽  
Free Stream ◽  
Flow Characteristics ◽  
Relative Thickness ◽  
Circular Arc ◽  
Critical Mach Number

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.

ABOUT CONSTRUCTION OF FLAT BODIES WITH INCREASED CRITICAL MACH NUMBER

2016 ◽  
Vol 47 (6) ◽  
pp. 563-579
Author(s):  
Sergey Alexandrovich Takovitskii
Keyword(s):  
Mach Number ◽  
Critical Mach Number

scholarly journals Critical Mach Numbers of Flow around Two-Dimensional and Axisymmetric Bodies

Aerodynamics ◽  
2021 ◽  
Author(s):  
Vladimir Frolov
Keyword(s):  
Mach Number ◽  
Cross Section ◽  
Flow Simulation ◽  
The Body ◽  
Two Dimensional ◽  
Critical Mach Number ◽  
Method Of Integral Relations ◽  
Viscosity Factor ◽  
Mach Numbers ◽  
Axisymmetric Bodies

The paper presents the calculated results obtained by the author for critical Mach numbers of the flow around two-dimensional and axisymmetric bodies. Although the previously proposed method was applied by the author for two media, air and water, this chapter is devoted only to air. The main goal of the work is to show the high accuracy of the method. For this purpose, the work presents numerous comparisons with the data of other authors. This method showed acceptable accuracy in comparison with the Dorodnitsyn method of integral relations and other methods. In the method under consideration, the parameters of the compressible flow are calculated from the parameters of the flow of an incompressible fluid up to the Mach number of the incoming flow equal to the critical Mach number. This method does not depend on the means determination parameters of the incompressible flow. The calculation in software Flow Simulation was shown that the viscosity factor does not affect the value critical Mach number. It was found that with an increase in the relative thickness of the body, the value of the critical Mach number decreases. It was also found that the value of the critical Mach number for the two-dimensional case is always less than for the axisymmetric case for bodies with the same cross-section.

Wake measurements of oscillating supercritical airfoil in compressible flow

2019 ◽  
Vol 43 (1) ◽  
pp. 112-121
Author(s):  
Behnaz Beheshti Boroumand ◽  
Mahmoud Mani
Keyword(s):  
Mach Number ◽  
Angle Of Attack ◽  
Time History ◽  
Mean Value ◽  
Hot Wire ◽  
Dynamic Tests ◽  
Flow Parameters ◽  
Free Stream Mach Number ◽  
Static And Dynamic Tests ◽  
Wake Characteristics

Boundary layer and wake behaviors are strongly affected by airfoil motion. Moreover, parameters like body oscillation frequency, oscillation type, Mach number, and angle of attack play main roles in wake characteristics. In this research, both static and dynamic tests were carried out in a tri-sonic wind tunnel to study wake profiles experimentally by hot wire anemometry. All data were recorded at a free stream Mach number of 0.4. Quarter-length and half-length of chord were also considered as downstream distances from the trailing edge in pitching motions of mean angle of attack of −0.4°. Frequencies of 3 Hz and 6 Hz with amplitude of 3° were chosen as oscillation parameters. Voltages at hot wire outputs were measured and analyzed qualitatively and statistically with root-mean-square, correlation, mean value distribution, time history, and frequency. Flow parameters were obtained by computational studies under similar experimental test conditions. The wake characteristics obtained from numerical and experimental methods were compared.

scholarly journals Whistler critical Mach number and electron acceleration at the bow shock: Geotail observation

2006 ◽  
Vol 33 (24) ◽  
Author(s):  
M. Oka ◽  
T. Terasawa ◽  
Y. Seki ◽  
M. Fujimoto ◽  
Y. Kasaba ◽  
...  
Keyword(s):  
Mach Number ◽  
Electron Acceleration ◽  
Bow Shock ◽  
Critical Mach Number
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