An Analytical Model for Flow in Banded-Screen Liquid Acquisition Devices With Variable Permeability

This paper presents an extension of the analytical model for steady, incompressible, laminar flow through a finite-length channel with one porous wall to account for spatially banded screen configurations. Traditional Liquid Acquisition Devices (LADs) designs assume uniform porous media along the channel length; however, emerging fabrication techniques now enable the integration of multiple screen types with distinct flow-through-screen (FTS) characteristics within a single channel. To capture the effects of such banded configurations, the original model is reformulated to incorporate continuous or piecewise-continuous FTS resistance terms, allowing the laminar and inertial pressure drop coefficients to vary with longitudinal position. A modified momentum-integral approach is employed to derive a coupled set of nonlinear ordinary differential equations governing the longitudinal velocity and pressure fields. The model is used to explore how screen banding influences the distribution of injection velocity, pressure drop, and flow acceleration along the channel. Results indicate that the hydrodynamic behavior is highly dependent on the permeability gradient between screen bands. While fine-to-coarse configurations can reduce the localized pressure spike at the outlet, this benefit must be weighed against the lower bubble-point pressure associated with coarser screens. This work provides a theoretical foundation for the design and optimization of banded-screen LADs, offering insights into how spatial tailoring of porous media can enhance fluid acquisition in microgravity environments.