Experiments in Fluids

, Volume 2, Issue 1, pp 47–55

Flying hot-wire anemometry

  • B. E. Thompson
  • J. H. Whitelaw

DOI: 10.1007/BF00266318

Cite this article as:
Thompson, B.E. & Whitelaw, J.H. Experiments in Fluids (1984) 2: 47. doi:10.1007/BF00266318


A flying hot-wire arrangement has been developed for the measurement of the velocity characteristics of the flow around airfoils, and particularly in regions where negative values of instantaneous velocity occur. The mechanism and signal processing system are described and appraised by comparing stationary and flying wire measurements obtained in the trailing edge region of a flap at an angle of attack which leads to upper-surface separation.

List of symbols


time averaged quantity


voltage from hot wire anemometer

Q, φ

magnitude and direction of cooling velocity viewed from a frame of reference on the probe: 〈Q〉=〈U〉+〈Vp

q1, q2, q3

cooling velocity fluctuations oriented with respect to the φ-direction


magnitude of effective cooling velocity measured by the hot wire: Qeff = (QN12 + h2QN22 + k2QT21/2




fluctuations of the effective cooling velocity

QN1, QN2, QT

axial, normal and tangential components of the cooling velocity relative to the hot wire

Qeff (Ψ= 10°)

magnitude of the effective cooling velocity with

Qeff (Ψ = 0°) Qeff (α = 30°)

magnitude of the effective cooling velocity with the wire pitched at 10 ° and 0° to the flow velocity

Qeff (α = 45°) Qeff (α = 30°)

magnitude of the effective colling velocity with the wire yawed at 45° and 30° to the flow velocity

U, θ

magnitude and direction of flow velocity

u, v, w

flow velocity fluctuations (x, y, z)

u1, u2, u3

normalised fluctuations of cooling velocity: ui=qiQ〉 for i=1,2,3

Vp, β

magnitude and direction of probe velocity


probe velocity fluctuations along the β-direction


yaw angle of hot wire relative to the probe axis


angle of mean flow velocity to the probe axis


angle of mean axial cooling component to mean cooling velocity viewed from the wire


pitch angle of probe axis relative to tunnel coordinates (x, y, z)

x, y, z

orthogonal coordinate system with the x-direction aligned with the wall (boundary layer) or tunnel centre-line (wake)

xw, yw, zw

orthogonal coordinate system with the zw-direction aligned with the wire and the probe pintels in the xw- zw plane

Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • B. E. Thompson
    • 1
  • J. H. Whitelaw
    • 1
  1. 1.Department of Mechanical Engineering, Fluids SectionImperial College of Science and TechnologyLondonGreat Britain

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