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Experiments in Fluids

, Volume 9, Issue 1–2, pp 43–48 | Cite as

Three-segment electrodiffusion probes for measuring velocity fields close to a wall

  • V. Sobolík
  • O. Wein
  • O. Gil
  • B. Tribollet
Originals

Abstract

Three-segment electrodiffusion probes embedded in a wall allow to determine simultaneously the three kinematic parameters of flow close to the probe surface: the flow directionθ, the wall shear rateq, and the normal velocity coefficientA,v z = −A z2. A well-controlled three-dimensional flow, generated by a rotating disk, was used to demonstrate the capabilities of this new kind of electrodiffusion probes by comparing experimental results with the prediction based on the well-known hydrodynamical theory.

Keywords

Velocity Field Probe Surface Normal Velocity Kinematic Parameter Hydrodynamical Theory 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

A

normal flow coefficient, Eq. (1)

A

axis of the adjustment rod, Fig. 2

c0

concentration of depolarizer (mol/m3)

D

diffusivity of depolarizer (m2/s)

E

correction of total current on normal flow effect

ex

reference direction of the probe, Figs. 1 and 3

F

Faraday constant (F = 96,464 C/mol)

Fs

normalized directional characteristic fors-th segment

fsm,gsm

Fourier coefficients of directional characteristics, Eq. (4) and Table 3

hm

corrections of Fourier coefficients on normal flow effect, Eqs. (4) and (7)

is

limiting diffusion current throughs-th segment (A)

itot(r)

total current through the probe in dependence on its eccentricity (A)

K

transport coefficient, Eqs. (3) and (5)

n

number of electrons involved in redox reaction

O

axis of the rotating disk, Fig. 2

P

centre of the probe, Fig. 2

q

magnitude of vectorial wall shear rate (s-1)

qx,qy

components of vectorial wall shear rate

Q

ratio of the currents in an eccentric and the central position of the probe, Eq. (15)

r

radial coordinate, eccentricity of the probe

rA

eccentricity of the adjustment rod (r A =Ō Ā, Fig. 2)

r, Φ, z

polar coordinates on the rotating disk

R

effective radius of the probe (R = 0.337 mm)

S

macroscopic area of the probe (S = 0.357 mm2)

x, y, z

Cartesian coordinates moving with the probe

α

adjustment angle, Figs. 2 and 3

β

angle included between local radius-vectorō ¯P of the probe and local direction of flow, Fig. 3

θ

angle included between reference directione x of the probe and local direction of flow, Fig. 3

θ0

theoretical prediction ofθ, Eq. (11)

x0

theoretical prediction ofx, Eq. (14)

xexpx

calculated from experimental data using Eq. (4)

v

kinematic viscosity (m2/s)

σ

angle implied between gradient ofq and direction of flow, Eq. (8)

Ω

angular speed of the rotating disk (rad/s)

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References

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Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • V. Sobolík
    • 1
  • O. Wein
    • 1
  • O. Gil
    • 2
  • B. Tribollet
    • 2
  1. 1.Institute of Chemical Process FundamentalsCzechoslovak Academy of Sciences6 SuchdolCzechoslovakia
  2. 2.LP 14 of C.N.R.S.University of P. and M. CurieParis Cedex 05France

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