Currently, a novel coronavirus named “SARS-CoV-2” is spreading rapidly across the world, causing a public health crisis, economic losses, and panic. Fecal–oral transmission is a common transmission route for many viruses, including SARS-CoV-2. Blocking the path of fecal–oral transmission, which occurs commonly in toilet usage, is of fundamental importance in suppressing the spread of viruses. However, to date, efforts at improving sanitary safety in toilet use have been insufficient. It is clear from daily experience that flushing a toilet generates strong turbulence within the bowl. Will this flushing-induced turbulent flow expel aerosol particles containing viruses out of the bowl? This paper adopts computational fluid dynamics to explore and visualize the characteristics of fluid flow during toilet flushing and the influence of flushing on the spread of virus aerosol particles. The volume-of-fluid (VOF) model is used to simulate two common flushing processes (single-inlet flushing and annular flushing), and the VOF–discrete phase model (DPM) method is used to model the trajectories of aerosol particles during flushing. The simulation results are alarming in that massive upward transport of virus particles is observed, with 40%–60% of particles reaching above the toilet seat, leading to large-scale virus spread. Suggestions concerning safer toilet use and recommendations for a better toilet design are also provided.

Heat barrier, the unrestricted increase in airplane or rocket speeds caused by aerodynamic heating, which—without adequate provisions for cooling the exposed surfaces—can lead to the loss of a hypersonic vehicle’s reusability, maneuverability, and cost-effectiveness. To date, indirect thermal protection methods, such as regenerative cooling, film cooling, and transpiration cooling, have proven to be complex and inefficient. Here, we propose a direct liquid cooling system to mitigate the heat barrier, utilizing a blunt-sharp structured thermal armor (STA)—a recently proposed material [36] to elevate the Leidenfrost point. The fiber-metal nano-/micro-STA withstands rigorous simulated hypersonic aerodynamic heating using butane and acetylene flames, ensuring effective temperature management in scenarios where flame temperatures reach up to 3000 °C—far exceeding the melting point of the STA substrate. Systematic cycling and durability tests further confirm the STA’s exceptional tolerance and robustness under extreme conditions. This work offers an efficient thermal protection method for hypersonic vehicles.