Potential Probe (Conductance Anemometer)
The principle of the conductance anemometry is based on the deducibility
of the velocity from the measurements of an electrical field
induced by the motion of an electrically conducting fluid in
the presence of an external magnetic field
.
The function of the potential-difference probe is governed by the Ohm´s law in moving fluids.
In general, the measured electric field
cannot be considered as
. However, in special cases such as
for MHD channel flows at high Hartmann numbers and a small wall conductance ratio
cw (1/Ha << cw << 1) the total current density
can be neglected compared to the induced one:
Let us assume the magnetic field as uniform and directed transverse to the velocity component which should be measured. Consequenty, the measured electric potential drop between the electrodes, separated by the distance l, has the following simple dependance on the fluid velocity
Due to the following factors this measuring technique appears as very attractive:
Measuring principle of the potential-difference probe
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