Thurairajah Kaveeshan, Song Xianyu Mabel, Zhu J D, Shi Mia, Barlow Ethan A, Hurd Randy C, Pan Zhao
Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada.
Department of Mechanical Engineering, Weber State University, 1465 Edvalson St, Ogden, Utah 84403, USA.
PNAS Nexus. 2025 Apr 8;4(4):pgaf087. doi: 10.1093/pnasnexus/pgaf087. eCollection 2025 Apr.
Urinals are a staple of public spaces yet their designs have remained essentially stagnant for over a century. The use of urinals often results in significant splatter (splashback) as urine splashes upon impact with the urinal generating droplets which travel back onto the floor and user, which generates unhygienic environments, high cleaning costs, and adds unpleasant workload for custodial staff. Impinging stream angle is one of many factors that affect splashback. We theoretically predict and experimentally validate that when the impinging angle is below an invariant critical value of , the flow rate of splashback under human urination conditions can be significantly suppressed. We propose novel urinal designs that were 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 the urinal designs described in this work 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.
小便器是公共场所的常见设施，但其设计在一个多世纪以来基本停滞不前。使用小便器时，尿液撞击小便器会产生大量飞溅（回溅），形成飞沫，这些飞沫会溅回到地面和使用者身上，从而产生不卫生的环境、高昂的清洁成本，并给保洁人员增加不愉快的工作量。撞击流角度是影响回溅的众多因素之一。我们通过理论预测和实验验证，当撞击角度低于一个不变的临界值时，在人类排尿条件下回溅的流速可以得到显著抑制。我们提出了新颖的小便器设计，这些设计是通过求解从等角曲线问题导出的微分方程生成的，以确保尿流以该临界角度或低于该临界角度撞击。实验验证，这些设计可以将回溅大幅降低至普通当代商用小便器飞溅量的仅1.4%。这项工作中描述的小便器设计的广泛采用将在人力资源、成本、清洁化学品和用水方面带来可观的节约，通过提高可持续性、卫生和可达性对现代社会产生重大影响。
