The non stationary flow induced by a cylinder with a square cross-section was studied on the cylinder's surface and in the wake with two different electrochemical probes. On the cylinder was mounted split rectangular electrodes with high enough aspect ratio so as to measure the chordwise component of the wall shear stress with its sign. The non-linear response of this transducer was studied. In the wake, the longitudinal component of the velocity was obtained with conical electroactive elementswhich are mainly sensitive to this component.
The fluctuating coherent components are separated from the aleatory part of the signal and then decomposited by a Fourier analysis into parts corresponding to the fundamental frequency and its higher order harmonics. The phase of the fundamental frequency is measured with reference to the coherent motion of the cylinder, so that the coherent motion can be reconstituted simultaneously anywhere. Thus the phase of the viscous torque and periodic lift is easily obtained.The reconstitution of the fundamental movement makes apparent the particular locations of the geometric stagnation and separation points in the generation of vortices. With the second harmonic, a secondary flow appears and the wake oscillates.
Py, B. and Tournier, C., "Two-Dimensional Analysis of the Coherent Instationary Motion Induced by an Obstacle, Using Electrochemical Methods" (1975). Symposia on Turbulence in Liquids. 28.
4th Biennial Symposium on Turbulence in Liquids (1975: Sep., Rolla, MO)
Chemical and Biochemical Engineering
Article - Conference proceedings
Electrochemical Methods of Turbulence Measurement
© 1975 University of Missouri--Rolla, All rights reserved.