An empirical expression for aerodynamic resistance in the unstable boundary layer

1991 ◽  
Vol 56 (4) ◽  
pp. 381-393 ◽  
Author(s):  
Neil R. Viney
Keyword(s):  
Boundary Layer ◽  
Aerodynamic Resistance ◽  
Empirical Expression ◽  
Unstable Boundary Layer

Estimation of turbulent heat fluxes and exchange coefficients for heat at Dumont d'Urville, East Antarctica

1999 ◽  
Vol 11 (1) ◽  
pp. 93-99 ◽  
Author(s):  
S. Argentini ◽  
G. Mastrantonio ◽  
A. Viola
Keyword(s):  
Boundary Layer ◽  
Heat Fluxes ◽  
East Antarctica ◽  
Turbulent Heat ◽  
Convective Boundary ◽  
Doppler Sodar ◽  
Turbulent Heat Fluxes ◽  
Unstable Boundary Layer ◽  
Sodar Measurements ◽  
The Antarctic

Simultaneous acoustic Doppler sodar and tethersonde measurements were used to study some of the characteristics of the unstable boundary layer at Dumont d'Urville, Adélie Land, East Antarctica during the summer 1993–94. A description of the convective boundary layer and its behaviour in connection with the wind regime is given along with the frequency distribution of free convection episodes. The surface heat flux has been evaluated using the vertical velocity variance derived from sodar measurements. The turbulent exchange coefficients, estimated by coupling sodar and tethered balloon measurements, are in strong agreement with those present in literature for the Antarctic regions.

Secondary flows in an unstable boundary layer

1982 ◽  
Vol 22 (4) ◽  
pp. 476-483 ◽  
Author(s):  
N. A. Zheltukhin ◽  
N. M. Terekhova
Keyword(s):  
Boundary Layer ◽  
Secondary Flows ◽  
Unstable Boundary Layer

scholarly journals КОМПЛЕКСНИЙ МЕТОД РОЗРАХУНКУ ОПОРУ ТЕРТЯ І ТЕПЛООБМІНУ НА ПОВЕРХНІ ЛЬОТНИХ ОСЕСИМЕТРИЧНИХ ОБ’ЄКТІВ ПРИ ПОЛЬОТІ ПО ТРАЄКТОРІЇ З НАЯВНІСТЮ В ПРИСТІННОМУ ПРИКОРДОННОМУ ШАРІ НЕІЗОТЕРМІЧНОСТІ, СТИСЛИВОСТІ, ЛАМІНАРНО-ТУРБУЛЕНТНОГО ПЕРЕХОДУ ТА РЕЛАМІНАРІЗАЦІЇ

2018 ◽  
pp. 4-28
Author(s):  
Анатолій Михайлович Павлюченко ◽  
Олександр Миколайович Шийко
Keyword(s):  
Boundary Layer ◽  
Aerodynamic Resistance ◽  
Aerodynamic Heating ◽  
Calculation Of Parameters ◽  
Theory Of Flow ◽  
Turbulent Transition ◽  
Linearized Theory ◽  
The Moment ◽  
Axisymmetric Bodies ◽  
Laminar Turbulent Transition

The complex method of calculation of aerodynamic resistance of friction and heating on the surface of flight axisymmetric bodies of rotation like a jet uncontrollable shell is developed. The method allows to carry out calculations from the moment of start to landing in limits to-, a trance- and supersonic speeds of flight. Range of speeds corresponds to М∞ ≤ 3,0 Mach numbers. When calculating the phenomena of a non-isothermicity, compressibility, laminar-turbulenttransition and a relaminarization which occur on streamline surfaces when flying on a trajectory are considered. The method is based on use of the asymptotic theory ofa wall turbulent boundary layer ofS.S. Kutateladze and A. І. Leontyeva in combination with results of the linearized theory of flow of bodies of rotation, the theory of turbulent spots of Emmons of a transitionalboundary layer and data on Reynolds numbers of the beginning of laminar-turbulenttransition received by results of flight experiments. On the basis of the carried-out calculations of parameters of a stream on a streamline surface of a shell when flying on a trajectory from the moment of start to landing in limits to-, a trance- and supersonic speeds of flight with use of the boundary numbers of laminar-turbulent transitionreceived in flight experiments it is established that flow of a considerable part of a surface of a shell happens in the conditions of laminar-turbulent transition and a relaminarization which occupy an essential part of the general time of flight. Existence of a reverse of laminar-turbulent transition is established by a settlement way. The analysis of values of temperature on a surface of a head part of a rocket when flying on a settlement trajectory has shown that for rather short period there is an aerodynamic heating of a surface which significantly influences the aerodynamic resistance of friction by a non-isothermicity in a wall boundary layer. The conclusion is drawn that the linearized theory of calculations of flow of rather thin bodies of rotation can be used for calculation of parameters on external border of boundary layer of axisymmetric bodies of rotation like a jet uncontrollable shell in limits to-, a trance- and supersonic speeds of flight for the purpose of account longitudinal to pressure gradient when calculating friction and heating. Use of the linearized theory of flow for calculation of parameters on external border of boundary layer in limits to-, a trance- and supersonic speeds of flight allows to create a "fast" algorithm of calculation of resistance of friction and heating taking into account a longitudinal gradient of pressure existing on the streamline surfaces of axisymmetric bodies of rotation. Numerical results of calculations of parameters of a nonviscous current on external border of boundary layerfor the linearized theory, coefficient of a intermittency, temperature of heating of a surface of a shell and resistance of friction from the start moment before landing are given

Simplified Analysis of Boundary-Layer Oscillations

1960 ◽  
Vol 4 (03) ◽  
pp. 37-54
Author(s):  
Robert Betchov
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Nonlinear Effects ◽  
Adverse Pressure Gradient ◽  
Neutral Curves ◽  
Elastic Wall ◽  
Unstable Boundary Layer ◽  
Incompressible Boundary ◽  
Negative Damping ◽  
The Stability

The stability of an incompressible boundary layer is analyzed in terms of three basic processes. These are (a) the oscillations of a boundary layer when friction is disregarded, (b) the effects of friction at the wall, and (c) the effects of friction at the critical layer. These processes are separately discussed and evaluated. Simple models are presented. A general equation leads to the eigenvalues. The neutral curves corresponding to five typical cases are determined—parabolic and Blasius boundary layers, boundary layers with suction and with adverse pressure gradient, two-dimensional Poiseuille flow. The unstable boundary layer is discussed briefly. The nonlinear effects of the oscillation on the velocity profile are evaluated. Finally, the case of a boundary layer along an elastic wall is considered, and it is found that the wall may have a significant effect on the layer. In particular, a wall with negative damping could completely stabilize the boundary layer.

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