In two-phase annular flow

interfacial waves play a crucial role in mass

momentum and energy transfers between two phases. It is important to study characteristic parameters of the interfacial waves (wave velocity

wave frequency and amplitude). First

interfacial waves were classified and qualitatively described characteristics of every wave type. Then

interfacial wave velocity prediction model was developed on the basis of interfacial shear stress. With consideration of density increment of gas core caused by entrained droplets and effect of relative velocities between gas core and liquid film surface

a modified disturbance wave velocity prediction model was obtained for vertical two-phase annular flow. Interfacial wave velocity measurement sensor based on near infrared (NIR) absorption attenuation technology and cross-correlation principle was designed for high operating pressure in industrial process. Measurements of 154 different interfacial wave velocities under five system pressures of 0.2-0.9 MPa showed that the modified model had good prediction results with less than ±10% relative standard deviations and some extrapolation capability for different system pressure conditions.