The venous circulation in the lower limb is mainly controlled by the muscular action of the calf. To study the mechanisms governing the venous draining and filling process in such a situation, an experimental setup, composed by a collapsible tube under external pressure, has been built. A valve preventing back flows is inserted at the bottom of the tube and allows to model two different configurations: physiological when the fluid flow is uni-directional and pathological when the fluid flows in both directions. Pressure and flow rate measurements are carried out at the inlet and outlet of the tube and an original optical device with three cameras is proposed to measure the instantaneous cross-sectional area. The experimental results (draining and filling with physiological or pathological valves) are confronted to a simple one-dimensional numerical model which completes the physical interpretation. One major observation is that the muscular contraction induces a fast emptying phase followed by a slow one controlled by viscous effects, and that a defect of the valve decreases, as expected, the ejected volume.

Experimental study of muscular draining. We present an experimental setup representing muscular draining in the lower leg. A collapsible tube is placed vertically in a hermetic chamber connected to a variable pressure tank. With the help of electrovalves we study a draining corresponding to walking. When the external pressure is raised a phenomenon of flow limitation appears and the draining time is very long. We also present numerical simulations showing that a critical passage subcritical supercritical originates the flow limitation.

Venous flow generates a large pressure gradient between lower limbs and the heart. In order to correctly ensure blood circulation, several mechanisms coexist such as the plantar arch pump, the calf pump, breathing, walk accelerations and naturally, the heart action. These added mechanisms provide rapid variations of the wall vessels position and the fluctuations on the venous flow that have global effects on the circulatoiy flow We developed a research program including an experimental set-up that could be numerically validated. Nevertheless, mechanical tube laws evaluation are image reconstruction dependent when tube collapses and it is thus necessary to compute areas precisely for a right validation of the tube dynamics. This communication introduces a new experimental set-up allowing strong vertical accelerations and also presents a new image reconstruction method to compute cross-section areas in collapsible tubes.