Meeting Abstract
One of the key challenges in studying the biomechanics of organisms moving in fluids is measuring the instantaneous fluid force and moment exerted by the organism on its environment. During the past three decades particle image velocimetry revolutionized our ability to measure the associated flow fields in vivo. These flow field snapshots could then be used to approximate the forces by simplifying the governing control volume equations for fluids in various ways, but this approach is not only cumbersome, it also has limited numerical accuracy. During the past decade we invented and dramatically improved a new method to directly measure fluid forces and moments by using force plates that mechanically integrate the pressure and shear stress distributions on the control surfaces of the fluid volume in which the organism moves. Summing the reaction forces and moments acting on these surfaces precisely matches the resulting instantaneous forces and moments exerted by the organism. During the past decade we refined this method for air, enabling us to record the aerodynamic force generated by freely flying birds directly in vivo. The economic recording method gives instantaneous wingbeat-resolved results, which provided new insights in how birds generate and use lift and drag to fly. Here we summarize the design, manufacturing and testing principles of Fluid Force and Moment Platforms in a simple and ready to use format for anyone studying ‘life in moving fluids’ in the spirit of Steven Vogel. Applications include swimming, running over water, and flight of a wide range of organisms.
