  Research on untethered micro-swimming robots is growing fast owing to their
potential impact on minimally invasive medical procedures. Candidate propulsion
mechanisms of robots are based on flagellar mechanisms of microorganisms such
as rotating rigid helices and traveling plane-waves on flexible rods and
parameterized by wavelength, amplitude, and frequency. For design and control
of swimming robots, accurate real-time models are necessary to compute
trajectories, velocities and hydrodynamic forces acting on robots. Resistive
force theory (RFT) provides an excellent framework for the development of
real-time six degrees-of-freedom surrogate models for design optimization and
control. However, the accuracy of RFT-based models depends strongly on
hydrodynamic interactions. Here, we introduce interaction coefficients that
only multiply body resistance coefficients with no modification to local
resistance coefficients on the tail. Interaction coefficients are obtained for
a single specimen of Vibrio Algino reported in the literature, and used in the
RFT model for comparisons of the forward-swimming component of the resultant
velocities and body rotation rates against other specimens. Furthermore, CFD
simulations are used to obtain forward and lateral velocities and body rotation
rates of bio-inspired swimmers with helical tails and traveling-plane waves for
a range of amplitudes and wavelengths. Interaction coefficients are obtained
from the CFD simulation for the helical tail with the specified amplitude and
wavelength and used in the RFT model for comparisons of velocities and body
rotation rates for other designs. Comparisons indicate that hydrodynamic models
that employ interaction coefficients prove to be viable surrogates for
computationally intensive three-dimensional time-dependent CFD models.
