Experimental study of wave propagation on liquid/air surfaces under perpendicular electric field

In this paper the behaviour of the waves generated on insulating liquid-air interfaces and subjected to an electric field is experimentally studied. The experimental device is mainly composed of a tank filled with diesel oil and two parallel metallic electrodes; one of them immersed in the liquid and brought to a high potential and the other one placed above the liquid. The waves are created by a vibrator the frequency and amplitude of which are controlled. The electric charges present at the liquid/air interface come from injection and/or dissociation and/or conduction phenomena. A high speed camera records the shape of the waves and an associated image analysis system extracts from them all the information needed (frequency, amplitude, wavelength). This information is used to investigate the influence of the electric field and liquid conductivity on the wavelengths at different amplitudes and frequencies and to calculate the surface tension. The propagation of waves on electrically charged liquid/air interfaces is also studied. The measurements are carried out for different frequencies and amplitudes of the vibrator at various applied voltages with different electrical conductivities of the diesel oil. We found that the wavelength and the apparent surface tension decreased with the applied voltage. The amplitude of the vibrator practically has no influence on the wavelength and the surface tension.