Experimental Characterization of Aqueous and Fiber-laden Foams*

Aqueous and fiber-laden foams have many applications in industrial processes including replacing water with foam to save energy in drying applications of fiber composite products. Aqueous foams exhibit complex flow behavior such as slip layers, shear-thinning, yield stress, and compressibility. The addition of fibers alters the topology and rheological characteristics of foams. This work aims to elucidate the rheological behavior of aqueous and fiber-laden foams experimentally. In this work, an open flow loop is constructed to obtain the flow curves of foams. Compressed air is injected into the pipe flow of water-fiber-surfactant solutions to generate foam at dilute fiber concentrations. Pressure drop along a pipe is measured after a fully developed flow is achieved. Off-line samples are also taken to obtain the bubble size distribution and foam drainage. The method of volume equalization (Valko and Ekonomides, J. Rheol, (1992), 36(6):1033-1055) has been successful in obtaining a master curve for flow curves of aqueous foams, but whether the method is applicable to fiber-laden flows is still unclear. The presentation will show a comparative analysis of aqueous and fiber-laden foam flows and discuss various constitutive relations to explain the behavior of fiber-laden foams.