Abstract urinals remain a staple of public spaces yet their designs have stagnated for over a century. Urine splashing upon impact generates droplets that travel back onto the floor and user, creating unhygienic environments, high cleaning costs, and unpleasant workload for custodial staff. Impinging stream angle is one of many factors that affect splashback.

Researchers theoretically predict and experimentally validate that when the impinging angle is below an invariant critical value of approximately 30 degrees, the flow rate of splashback under human urination conditions can be significantly suppressed. A team proposes novel urinal designs generated by solving differential equations derived from the isogonal curve problem to ensure the urine stream impacts at or below this critical angle. Experiments validate that these designs can substantially reduce splashback to only 1.4% of the splash of a common contemporary commercial urinal.

The widespread adoption of these designs would result in considerable conservation of human resources, cost, cleaning chemicals, and water usage, rendering large-scale impacts on modern society by improving sustainability, hygiene, and accessibility. Hygiene infrastructure has transformed human life but is often overlooked due to its ubiquity. The male urinal, for example, its design has remained stagnant for over a century.

Existing designs generate significant splashback, creating hygiene issues and requiring human and material resources to clean. Researchers apply fluid physics to develop and experimentally confirm a theoretical model of splash suppression on contoured surfaces. This model is then applied to create splashless urinals.

Tests show that the designs eliminate splashback, thereby reducing the resources consumed in cleaning while improving hygiene in public spaces. Global adoption renders large-scale improvements to sustainability, sanitation, and accessibility.