Non-Newtonian fluid flow in elastic tubes

The knowledge on the non-Newtonian fluid flow behavior in inflatable and collapsible elastic tubes is important to applications such as biofluid mechanics in human body and the transport of food and liquids in pharynx (throat), esophagus and intestines. The ultrasound Doppler based velocity profiles are measured at a fixed position from the outlet of a horizontal collapsible elastic tube immersed in a liquid filled chamber, whose pressure is maintained at a constant value during steady laminar flow of a shear thinning xanthan aqueous solution. For a given volume flow rate and a critical external chamber pressure, the tube is buckled. The shape of the deformed cross section visually observed has two lobes, above and below the horizontal axis through the tube center, with no contact between tube’s two vertical planes. As the external chamber pressure increased, the width at the tube center and area of cross section of the two lobed-shaped deformed tube decreased. Consequently, the measured maximum flow velocity at the center of the tube width increased. The shear rate dependent viscosity of xanthan solution was measured using a rheometer.