A COMPARISON OF METHODS FOR COMPUTING THE VELOCITY DISTRIBUTION AND THE BOUNDARY LAYER ON BODIES OF REVOLUTION

1963 ◽  
Author(s):  
Hideki Yamaoka
Keyword(s):  
Boundary Layer ◽  
Velocity Distribution ◽  
Comparison Of Methods ◽  
Bodies Of Revolution

Calculation of Subsonic Normal Force and Centre of Pressure Position of Bodies of Revolution Using a Slender Body Theory – Boundary Layer Method

1980 ◽  
Vol 31 (1) ◽  
pp. 1-25
Author(s):  
K.D. Thomson
Keyword(s):  
Boundary Layer ◽  
Velocity Distribution ◽  
Normal Force ◽  
The Body ◽  
Slender Body ◽  
Centre Of Pressure ◽  
Slender Body Theory ◽  
Bodies Of Revolution ◽  
Slender Bodies ◽  
Body Theory

SummaryThe aim of this paper is to present a method for predicting the aerodynamic characteristics of slender bodies of revolution at small incidence, under flow conditions such that the boundary layer is turbulent. Firstly a panel method based on slender body theory is developed and used to calculate the surface velocity distribution on the body at zero incidence. Secondly this velocity distribution is used in conjunction with an existing boundary layer estimation method to calculate the growth of boundary layer displacement thickness which is added to the body to produce the effective aerodynamic profile. Finally, recourse is again made to slender body theory to calculate the normal force curve slope and centre of pressure position of the effective aerodynamic profile. Comparisons made between predictions and experiment for a number of slender bodies extending from highly boattailed configurations to ogive-cylinders, and covering a large range of boundary layer growth rates, indicate that the method is useful for missile design purposes.

Velocity distribution in turbulent oscillatory boundary layer

1992 ◽  
Vol 18 (1-2) ◽  
pp. 21-38 ◽  
Author(s):  
Z.J. You ◽  
D.L. Wilkinson ◽  
P. Nielsen
Keyword(s):  
Boundary Layer ◽  
Velocity Distribution ◽  
Oscillatory Boundary Layer

scholarly journals Instability and Transition of a Boundary Layer over a Backward-Facing Step

Fluids ◽  
2022 ◽  
Vol 7 (1) ◽  
pp. 35
Author(s):  
Ming Teng ◽  
Ugo Piomelli
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Velocity Distribution ◽  
Adverse Pressure Gradient ◽  
Transition Process ◽  
Transition To Turbulence ◽  
Recirculation Region ◽  
Backward Facing Step ◽  
Freestream Velocity ◽  
Displacement Thickness

The development of secondary instabilities in a boundary layer over a backward-facing step is investigated numerically. Two step heights are considered, h/δo*=0.5 and 1.0 (where δo* is the displacement thickness at the step location), in addition to a reference flat-plate case. A case with a realistic freestream-velocity distribution is also examined. A controlled K-type transition is initiated using a narrow ribbon upstream of the step, which generates small and monochromatic perturbations by periodic blowing and suction. A well-resolved direct numerical simulation is performed. The step height and the imposed freestream-velocity distribution exert a significant influence on the transition process. The results for the h/δo*=1.0 case exhibit a rapid transition primarily due to the Kelvin–Helmholtz instability downstream of step; non-linear interactions already occur within the recirculation region, and the initial symmetry and periodicity of the flow are lost by the middle stage of transition. In contrast, case h/δo*=0.5 presents a transition road map in which transition occurs far downstream of the step, and the flow remains spatially symmetric and temporally periodic until the late stage of transition. A realistic freestream-velocity distribution (which induces an adverse pressure gradient) advances the onset of transition to turbulence, but does not fundamentally modify the flow features observed in the zero-pressure gradient case. Considering the budgets of the perturbation kinetic energy, both the step and the induced pressure-gradient increase, rather than modify, the energy transfer.

A Note on the Resistance of Bodies of Revolution and Ship Forms

1974 ◽  
Vol 18 (03) ◽  
pp. 153-168
Author(s):  
N. Matheson ◽  
P. N. Joubert
Keyword(s):  
Boundary Layer ◽  
Reasonable Agreement ◽  
The Body ◽  
Experimental Results ◽  
Body Of Revolution ◽  
Bodies Of Revolution ◽  
Boundary Layer Development ◽  
Layer Development

A simple so-called 'equivalent' body of revolution is proposed for reflex ship forms in an attempt to simplify calculation of the boundary layer over a ship's hull when there is no wavemaking. How­ever, exhaustive testing of one body of revolution did not produce a favorable comparison with re­sults for the corresponding reflex model. Gadd's recently proposed theory was used to calculate the boundary-layer development over the body of revolution. Reasonable agreement was obtained between the calculated and experimental results.

scholarly journals Effects of Free-Stream Turbulence Intensity on a Boundary Layer Recovering From Concave Curvature Effects

1993 ◽  
Author(s):  
Michael D. Kestoras ◽  
Terrence W. Simon
Keyword(s):  
Boundary Layer ◽  
Velocity Distribution ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Outer Region ◽  
Free Stream Turbulence ◽  
Flat Wall ◽  
Curvature Effects ◽  
Turbulent Eddies ◽  
Concave Wall

Experiments are conducted on a flat recovery wall downstream of sustained concave curvature in the presence of high free-stream turbulence (TI∼8%). This flow simulates some of the features of the flow on the latter parts of the pressure surface of a gas turbine airfoil. The combined effects of concave curvature and TI, both present in the flow over a turbine airfoil, have so far little been studied. Computation of such flows with standard turbulence closure models has not been particularly successful. This experiment attempts to characterize the turbulence characteristics of this flow. In the present study, a turbulent boundary layer grows from the leading edge of a concave wall then passes onto a downstream flat wall. Results show that turbulence intensities increase profoundly in the outer region of the boundary layer over the recovery wall. Near-wall turbulent eddies appear to lift off the recovery wall and a “stabilized” region forms near the wall. In contrast to a low-free-stream turbulence intensity flow, turbulent eddies penetrate the outer parts of the “stabilized” region where sharp velocity and temperature gradients exist. These eddies can more readily transfer momentum and heat. As a result, skin friction coefficients and Stanton numbers on the recovery wall are 20% and 10%, respectively, above their values in the low-free-stream turbulence intensity case. Stanton numbers do not undershoot flat-wall expectations at the same ReΔ2 values as seen in the low-TI case. Remarkably, the velocity distribution in the core of the flow over the recovery wall exhibits a negative gradient normal to the wall under high free-stream turbulence intensity conditions. This velocity distribution appears to be the result of two effects: 1) cross transport of kinetic energy by boundary work in the upstream curved flow and 2) readjustment of static pressure profiles in response to the removal of concave curvature.

Boundary-Layer Control as a Means of Reducing Drag on Fully Submerged Bodies of Revolution

1985 ◽  
Vol 107 (3) ◽  
pp. 342-347 ◽  
Author(s):  
B. Bar-Haim ◽  
D. Weihs
Keyword(s):  
Boundary Layer ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Boundary Layer Control ◽  
Layer Transition ◽  
Bodies Of Revolution ◽  
Boundary Layer Suction ◽  
Technique Optimization ◽  
Axisymmetric Bodies ◽  
Layer Control

The drag of axisymmetric bodies can be reduced by boundary-layer suction, which delays transition and can control separation. In this study, boundary-layer transition is delayed by applying a distributed suction technique. Optimization calculations were performed to define the minimal drag bodies at Reynolds numbers of 107 and 108. The saving in drag relative to optimal bodies with non-controlled boundary layers is shown to be 18 and 78 percent, at Reynolds numbers of 107 and 108, respectively.

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