  Many eukaryotic microorganisms propelled by multiple flagella can swim very
rapidly with distinct gaits. Here, we model a three-dimensional mutiflagellate
swimming strategy, resembling the microalgae, and investigate the effects of
interflagella hydrodynamic interactions (iHIs) on the swimming performance.
When the flagella are actuated synchronously, the swimming efficiency can be
enhanced or reduced by iHIs, determined by the intrinsic tilting angle of the
flagella. The asynchronous gait with a phase difference between neighboring
flagella is found to be important by both utilizing the iHIs and reducing the
oscillatory motion via the basal mechanical coupling. We further demonstrate
that an optimal number of flagella could arise when the microswimmer is loaded
with a swimmer body. Apart from understanding the role of iHIs in the
multiflagellate swimming, this work could also guide laboratory fabrications of
novel microswimmers.
