Heat transfer and fluid flow around starfish-inspired cylinder by immersed boundary-simplified thermal lattice Boltzmann method

•IB-STLBM is adopted for solving the governing equations of flow and heat transfer around the cylinder.•There are five different structures are obtained in the present work.•For the unsteady and asymmetrical cases, Cdmean, Cdrms, Clmean, Clrms, Numean and Nurms have a positive function of m.•As increasing θ, Cdmean increases and then decreases at Re = 40. As for Re= 70 or 100, Cdmean decreases and Numean rises.•At Re = 40, there is a critical value of θ for the largest value of Numean. As for Re = 70 or 100, the optimal θ is π/5.