A computational model for estimating the mechanics of horizontal flapping flight in bats: Model description and validation

We combine three-dimensional descriptions of the movement patterns of the s houlder, elbow, carpus, third metacarpophalangeal joint and wingtip with a constant-circulation estimation of aerodynamic force to model the wing mech anics of the grey-headed flying fox (Pteropus poliocephalus) in level fligh t. Once rigorously validated, this computer model can be used to study dive rse aspects of flight. In the model, we partitioned the wing into a series of chordwise segments and calculated the magnitude of segmental aerodynamic forces assuming an elliptical, spanwise distribution of circulation at the middle of the downstroke. The lift component of the aerodynamic force is t ypically an order of magnitude greater than the thrust component. The large st source of drag is induced drag, which is approximately an order of magni tude greater than body form and skin friction drag. Using this model and st andard engineering beam theory, we calculate internal reaction forces, mome nts and stresses at the humeral and radial midshaft during flight. To asses s the validity of our model, we compare the model-derived stresses with our previous in vivo empirical measurements of bone strain from P. poliocephal us in free flapping flight. Agreement between bone stresses from the simula tion and those calculated from empirical strain measurements is excellent a nd suggests that the computer model captures a significant portion of the m echanics and aerodynamics of flight in this species.