Meeting Abstract

P3-136  Monday, Jan. 6  The Effect of Shell Shape on Burrowing Dynamics in Granular Media TREERS, LK*; STUART, H; University of California, Berkeley; University of California, Berkeley

The dynamics of burrowing and locomotion within granular media by legged invertebrates is extremely complex. The forces experienced by organisms are governed by substrate properties, the path taken through the substrate, and geometrical properties of the organism’s body. We focus on developing a numerical method for analyzing such forces in three-dimensional space, expanding upon granular resistive force theory (RFT) (previously developed by Chen Li et. al, Science, 2013) to be more easily applied to irregular shapes useful for analyzing biological organisms. This method allows for element-wise integration of forces over a surface, as a function of object insertion angle and direction of insertion. While RFT was developed for dry sand settings, we assume that its key principles apply in some saturated media, and test the limits of this assumption. We explore the effect of “terradynamic streamlining” of shell shape on insertion forces, both through a numerical model and experimental trials. As a biological model, we choose to study the pacific mole crab Emerita analoga, a marine arthropod capable of rapid self-burying in saturated granular media. We compare the resistive forces of the crab carapace shape with more canonical geometric shapes, to analyze the potential streamlining advantage of the crab body profile. Other crustacean shell shapes are also considered via the developed 3D numerical method created for this work. We then consider the effect of body trajectory on total energy consumption to burrow. The energy cost of burrowing is compared for various burrowing paths and oscillations, as predicted by RFT. The burrowing strategy of Emerita analoga (which features oscillation in body pitch throughout a burrowing event) is compared with theoretical results, in order to analyze its effectiveness.