The growing demands of municipalities, industry, and agriculture for potable water have provoked a water deficit that threatens global energy, food, and economic security. Membrane separation processes offer promising low-energy solutions for desalination and wastewater treatment. However, the retention of solutes on the feed side of the membrane, known as concentration polarization, increases the pressures needed to force the fluid across the membrane surface. With time, the buildup of solutes forms a mineral scale that impedes filtration, damages the membrane, and increases maintenance costs. Many on-going research efforts are exploring both physical and chemical strategies to prevent scaling. One such strategy is to pattern a mesh-like net of physical spacers on the membrane that alters the fluid flow at the surface. This patterning creates complex fluid flow dynamics that are not well understood, particularly with the added complexity of solute filtration and the effect of concentration polarization. This CAREER project will develop a validated computational fluid dynamics model of concentration polarization and mineral scaling with patterned spacers for reverse osmosis and nanofiltration membranes systems. <br/><br/>This project will develop innovative computational fluid dynamics simulations that fully couple interactions between polarization, scaling, and mixing due to feed spacers. The simulations will address complications that arise due to both near-membrane mass transport and three-dimensional mixing due to the feed-spacers. The methods will be experimentally validated, and then used to: (1) develop improved models of polarization and scaling; (2) investigate the roles of spacers and operating conditions on system performance; and (3) explore the design of new spacers that minimize polarization and scaling. The project will directly train both graduate and undergraduates in conducting research, while also integrating the activities into undergraduate engineering design coursework. Outreach activities, in collaboration with a community center and Multicultural Engineering Program, will introduce both under-served middle and high-school students to computer programming, sustainable water issues, and STEM careers. The project is anticipated to accelerate informed design of membranes for extended lifetime and performance.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.