The time-dependent liquid film thickness in horizontal and slightly inclined tubes was measured by using parallel-wire conductance probes

and various wave patterns were obtained.The features of probability density function

probability distribution

auto-correlation

cross-correlation and power spectrum density function of waves were studied in amplitude domain

time domain and frequency domain respectively. The parameters of wave

such as wave amplitude

wavelength

wave velocity and wave period were obtained. The variation of wave parameters with gas

liquid superficial velocities and tube inclination angle were presented.