Gravity-driven azimuthal flow of a layer of thixotropic fluid on the inner surface of a horizontal tube

► We use the lubrication approximation to model the flow of a layer of thixotropic fluid on the inner surface of a horizontal tube. ► Thixotropy effects are obtained through solutions to the Newtonian case, with the aid of a rescaled time variable. ► When capillary forces dominate the motion is very slow. ► When gravity forces dominate, an undulation close to the tube bottom appears at large times.