Biomimeticdesignemploystheprinciplesofnaturetosolveengineeringproblems.Suchdesignswhicharehopedtobequick,efficient,robust,andversatile,havetakenadvantageofoptimizationvianaturalselection.Inthepresentresearch,anenvironment-friendlypropulsionsystemmimickingundulatingfinsofstingraywasbuilt.Anon-conventionalmethodwasconsideredtomodeltheflexibilityofthefinsofstingray.Atwo-degree-of-freedommechanismcomprisedofseverallinkageswasdesignedandconstructedtomimictheactualflexiblefin.Thedrivinglinkageswereusedtoformamechanicalfincon-sistingofseveralfinsegments,whichareabletoproduceundulations,similartothoseproducedbytheactualfins.Owingtothemodularityofthedesignofthemechanicalfin,variousundulatingpatternscanberealized.Somequalitativeobservations,obtainedbyexperiments,predictedthatthethrustsproducedbythemechanicalfinaredifferentamongvariousundulatingpatterns.Tofullyunderstandthisexperimentalphenomenonisveryimportantforbetterperformanceandenergysavingforourbioroboticunderwaterpropulsionsystem.Here,fourbasicundulatingpatternsofthemechanicalfinwereperformedusingtwo-dimensionalunsteadycomputationalfluiddynamics(CFD)method.Anunstructured,grid-based,unsteadyNavier-Stokessolverwithautomaticadaptivere-meshingwasusedtocomputetheunsteadyflowaroundthefinthroughtwentycompletecycles.Thepressuredistributiononfinsurfacewascomputedandintegratedtoprovidefinforceswhichweredecomposedintoliftandthrust.Thepressureforceandfrictionforcewerealsocomputedthroughouttheswimmingcycle.Finally,vortexcontourmapsofthesefourbasicfinundulatingpatternsweredisplayedandcompared.
