Nicole Sharp<p><strong>Predicting Landslide Speeds</strong></p><p>Knowing what speed a landslide will reach helps us predict how much damage they can cause. That speed depends on many factors: the steepness of the terrain, the sliding distance, the thickness of the flowing layer, and the type of grains making up the flow. <a href="https://doi.org/10.1103/PhysRevLett.134.028201?_gl=1*1cocu0i*_ga*Nzc0NDI4ODAxLjE2NzI4NTgxOTE.*_ga_ZS5V2B2DR1*MTczODAwMDU2My4xLjAuMTczODAwMDU2My4wLjAuMTAzMjUxODgwMA.." rel="nofollow noopener noreferrer" target="_blank">Researchers found</a> that predictions from previous studies often underestimated the speeds reached by thicker flows. Through laboratory experiments with grains of different shapes, a team found that those models mistakenly assumed a fully-developed flow — in other words, one where the grains have reached a constant final speed. While spherical grains reach that state over a short sliding distance, that’s not the case for other grains.</p><p>Instead, the team used their results to build a new predictive model for landslide speeds. This one still depends on incline angle and flow thickness, but it also uses a dynamical friction coefficient to describe the granular material and capture how the flow’s speed varies with distance down the incline. (Image credit: <a href="https://unsplash.com/photos/brown-and-gray-rocky-mountain-fsj6Ly_lqOs" rel="nofollow noopener noreferrer" target="_blank">W. Hasselmann</a>; research credit: <a href="https://doi.org/10.1103/PhysRevLett.134.028201?_gl=1*xhbrcp*_ga*Nzc0NDI4ODAxLjE2NzI4NTgxOTE.*_ga_ZS5V2B2DR1*MTczODAwMDU2My4xLjAuMTczODAwMDU2My4wLjAuMTAzMjUxODgwMA.." rel="nofollow noopener noreferrer" target="_blank">Y. Wu et al.</a>; via <a href="https://physics.aps.org/articles/v18/13?utm_campaign=weekly&utm_medium=email&utm_source=emailalert&__readwiseLocation=" rel="nofollow noopener noreferrer" target="_blank">APS News</a>)</p><p><a rel="nofollow noopener noreferrer" class="hashtag u-tag u-category" href="https://fyfluiddynamics.com/tagged/avalanche/" target="_blank">#avalanche</a> <a rel="nofollow noopener noreferrer" class="hashtag u-tag u-category" href="https://fyfluiddynamics.com/tagged/fluid-dynamics/" target="_blank">#fluidDynamics</a> <a rel="nofollow noopener noreferrer" class="hashtag u-tag u-category" href="https://fyfluiddynamics.com/tagged/geophysics/" target="_blank">#geophysics</a> <a rel="nofollow noopener noreferrer" class="hashtag u-tag u-category" href="https://fyfluiddynamics.com/tagged/granular-flow/" target="_blank">#granularFlow</a> <a rel="nofollow noopener noreferrer" class="hashtag u-tag u-category" href="https://fyfluiddynamics.com/tagged/granular-material/" target="_blank">#granularMaterial</a> <a rel="nofollow noopener noreferrer" class="hashtag u-tag u-category" href="https://fyfluiddynamics.com/tagged/landslide/" target="_blank">#landslide</a> <a rel="nofollow noopener noreferrer" class="hashtag u-tag u-category" href="https://fyfluiddynamics.com/tagged/physics/" target="_blank">#physics</a> <a rel="nofollow noopener noreferrer" class="hashtag u-tag u-category" href="https://fyfluiddynamics.com/tagged/science/" target="_blank">#science</a></p>