Dynamically similar models of bacterial moving near a boundary

Numerical simulations of microorganisms are often not compared to precise measurements because making microscopic measurements of forces and torques in biological experiments is difficult. Instead, we use dynamically similar tabletop experiments to provide precise calibration values as part of our collaborative project (NSF POLS - 2210610). The tabletop experiments use various bacterial models that are about 10 cm in size and match the Reynolds number of swimming microorganisms by using highly viscous silicone oil that is 100,000X more viscous than water so that they are dynamically similar. We can measure the forces and torques with high precision and scale the results to biologically relevant values. We have calibrated the method of timages for regularized Stokeslets and found excellent agreement between our data for both cylinders and helices (Shindell et al. 2021). Our results have also confirmed the theory of Jeffrey and Onishi (1981) for the torque on a cylinder rotating near a plane wall and the theory of O'Neil (1964) for the torque on a sphere near a wall.