A dynamic contact angle can be defined as the angle formed by the approaching liquid gas interface as it moves relative to a surface at constant velocity. The surface may be dry or wet with a liquid layer. The dynamic contact angle varies as a function of the interface velocity. In general contact angle is the angle that a solid surface makes with a liquid when they come in contact with each other.
A dynamic contact angle is measured when the three phase boundary is moving. The angle is determined by the properties of the solid material and the liquid it carries. The inter-molecular forces of cohesion and adhesion determine the contact angle created. Contact angle can be measured using optical and force tensiometry, Sessile drop method, Wilhelmy plate method and capillary rise method. Contact angle also determines the wettability of a solid and is very important in sewer and water pipe manufacturing.
Pipes that do not have the appropriate contact angle with the liquid they carry can be rehabilitated using trenchless methods such as cured-in-place pipe (CIPP), sliplining and pipe bursting.