a	Proportion of high water holdup structures	U sg	Gas superficial velocity
b	Proportion of low water holdup structures	U sw	Water superficial velocity
C 0	Distribution parameter	$U_{\infty }$	Terminal rise velocity of a single gas bubble relative to the continuous water phase
C 01	Distribution parameter in annular space	V s	Value of exciting voltage signal
D 1	Diameter of insulated flow deflector 1	V 1	Voltage output 1
d 1	Distance between two ring-shape electrodes	V out	Sensor output
D 4	Diameter of cylindrical insulated plexiglass rod	V A	Voltage output of channel A
E	Relative error	V B	Voltage output of channel B
G	Value of equivalent conductance	V C	Voltage output of channel C
$G_{\mathrm{e}}^{*}$	Normalized conductivity	V D	Voltage output of channel D
H	Axial height of electrodes	V wcs	Output of water conductivity sensor
h	Height of electrode	V up	Output of upstream sensor
H 1	Length of insulated flow deflector 1	V down	Output of downstream sensor
H 4	Distance between insulated flow deflector 1 and insulated flow deflector 2	Y d	Holdup of dispersed phase
I	Value of current	Y g	Gas holdup
I s	Value of exciting current signal	Y g1	Gas holdup in annular space
k	A constant relating to the configuration of electrode	Y w	Water holdup
L	Distance between upstream and downstream sensors	θ	Field angle of electrodes
L 1	Distance between upstream sensor and the head of insulated flow deflector 1	$\delta$	Threshold
N	Amplification factor	$\sigma$	Conductivity
n	Droplet size exponent	${\sigma }_{\mathrm{c}}$	Conductivity of conducting continuous media
R m	Value of equivalent resistance	${\sigma }_{\mathrm{d}}$	Conductivity of dispersed phase
R ref	Value of reference resistance	${\sigma }_{\mathrm{m}}$	Conductivity of mixture
R 1	Resistance 1	${\sigma }_{\mathrm{w}}$	Water conductivity
R 2	Resistance 2	${\sigma }^{\mathrm{A}}$	Conductivity measured by channel A
R 3	Resistance 3	${\sigma }^{\mathrm{B}}$	Conductivity measured by channel B
R 4	Resistance 4	${\sigma }^{\mathrm{C}}$	Conductivity measured by channel C
R 5	Resistance 5	${\sigma }^{\mathrm{D}}$	Conductivity measured by channel D
R 6	Resistance 6	${\sigma }^{\mathrm{up}}$	Conductivity measured by upstream sensor
T	Radial thickness of electrodes	${\sigma }^{\mathrm{down}}$	Conductivity measured by downstream sensor
U cc	Cross-correlation velocity
U m	Mixture velocity
U m1	Mixture velocity in annular space