An Investigation of a Pressure Controlled Fluidic Value Used for Controlling the Volume of the Human Bladder of a Catheterized Patient

The hydraulic behavior of a pressure controlled valve used in conjunction with a catheter was examined to establish functional design criteria. The function of the valve is to allow cycling of the human bladder to minimize the occurrence of bladder infection. The valve consisted of a piston, or poppet, inside a cylinder, which established an annular flow between the poppet and cylinder, while the valve was in the open position. The analysis and experimentation examined two diverse annular flow conditions. First, the case when the poppet positioned itself concentrically with respect to the cylinder was analyzed, in which a Poiseuille flow solution was utilized. Next, the case in which the poppet is in contact with the cylinder (eccentric case) was investigated, which required solving Laplace\u27s equation for velocity over a non-concentric annulus. For both cases fully developed flow was not established throughout the gap, thus the effects of flow in the entrance region on the pressure drop for the gap had to be included in the derived mathematical models. Experiments were performed to test the theoretical models for both the concentric and eccentric cases. Results showed a great dependence of the annular gap size, poppet length and diameter, and valve inlet and outlet diameters. Once the flow behavior was established, then a parametric variation was performed to find a range of parameter dimensions which allowed the valve to function properly