Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

A nonintrusive laser interferometer method for measurement of skin friction

  • 157 Accesses

  • 32 Citations

Abstract

A method is described for monitoring the changing thickness of a thin oil film subject to an aerodynamic shear stress using two focused laser beams. The measurement is then simply analyzed in terms of the surface skin friction of the flow. The analysis includes the effects of arbitrarily large pressure and skinfriction gradients, gravity, and time-varying oil temperature. It may also be applied to three-dimensional flows with unknown direction. Applications are presented for a variety of flows including two-dimensional flows, three-dimensional swirling flows, separated flows, supersonic high-Reynolds-number flows, and delta-wing vortical flows.

This is a preview of subscription content, log in to check access.

Abbreviations

A :

dT/dt [Eq. (9)]

C f :

local skin-friction coefficient, τ/q

dp/dx :

external flow pressure gradient

g :

gravitational acceleration

H :

step height

I :

incidence angle for interferometer flat

i :

laser beam incidence angle measured from the normal to a surface

M :

Mach number

N :

fringe number

n :

coordinate perpendicular to oil-flow direction (Fig. 4)

n g :

interferometer flat index of refraction

n o :

oil index of refraction

q :

free-stream dynamic pressure

R :

Reynolds number; also, refraction angle for interferometer flat

r :

laser beam refraction angle within oil measured from the normal to a surface

S :

oil-viscosity/temperature-slope [Eq. (11)]

s :

coordinate along oil-flow direction (Fig. 4); also, delta wing semispan

T :

temperature; also, interferometer flat thickness

t :

time

V :

tunnel free-stream speed

W s :

transverse speed on surface of rotating cylinder

x :

coordinate parallel to line joining beams (Fig. 4); also, distance downstream from step

Y o :

tunnel height

y :

oil thickness; also, delta wing semispan distance

z :

coordinate perpendicular to line joining beams (Fig. 4) atunnel-wall deflection angle; also, delta-wing angle of attack

y :

local oil-flow angle with respect to the x coordinate (Fig. 4)

ΔN :

incremental change in fringe number

Δt :

incremental change in time

Δx :

beam spacing

Δ:

boundary-layer thickness

σ:

pressure gradient and gravity-correction parameter [Eq. (8)]

θ:

surface inclination from horizontal laser wavelength

λ:

oil kinematic viscosity

ϱ:

oil density

τ:

local skin friction

( )′:

corrected or “effective” value

( ):

average value

L :

model length

x, z :

directions as shown in Fig. 4

1, 2, 3, 4:

refer to positions in Figs. 1 and 4, or to times in Fig. 3

∞:

free-stream conditions

θ:

momentum thickness

References

  1. Higuchi, H.; Peake, D. 1978: Bi-directional, buried-wire skinfriction gauge. NASA TM 78531 Higuchi, H.; Rubesin, M. 1981: An experimental and computational investigation of the transport of Reynold's stress in an axisymmetric swirling boundary layer. AIAA paper 81-0416, 19th Aerosp. Sci. Meet., St. Louis, Miss.

  2. Kline, S.; McClintock, F. 1953: Describing uncertainties in singlesample experiments. Mech. Eng. 75, 3–8

  3. McAllister, J.; Pierce, F.; Tennant, M. 1982: Direct Force wall shear measurements in pressure-driven three-dimensional turbulent boundary layers. J. Fluids Eng. 104, 150–155

  4. Monson, D. 1983: A laser interferometer for measuring skin friction in three-dimensional flows. Paper to be presented at the AIAA 21st Aerosp. Sci. Meet., Reno, Nevada

  5. Monson, D.; Driver, D.; Szodruch, J. 1981: Application of a laser interferometer skin-friction meter in complex flows. ICIASF '81 Rec., IEEE Publ. 81CH1712-9, Dayton, Ohio, pp. 232–243

  6. Monson, D.; Higuchi, H. 1981: Skin friction measurements by a dual-laser-beam interferometer technique. AIAA J. 19, 739–744

  7. Sindir, M. 1982: Numerical study of turbulent flows in backwardfacing step geometries: comparison of four models of turbulence. Ph. D. thesis, Univ. Calif., Davis, Calif.

  8. Tanner, L. 1977: A skin friction meter, using the viscosity balance principle, suitable for use with flat or curved metal surfaces. J. Phys. E 10, 278–284

  9. Tanner, L.; Blows, L. 1976: A study of the motion of oil films on surfaces in air flow, with application to the measurement of skin friction. J. Phys. E 9, 194–202

  10. Winter, K. 1977: An outline of the techniques for the measurement of skin friction in turbulent boundary layers. Aerospace Sci. 18, 1–57

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Monson, D.J. A nonintrusive laser interferometer method for measurement of skin friction. Experiments in Fluids 1, 15–22 (1983). https://doi.org/10.1007/BF00282262

Download citation

Keywords

  • Shear Stress
  • Skin Friction
  • Surface Skin
  • Focus Laser
  • Separate Flow