The　evaporation　kinetic　mechanisms　of　sessile　droplets　are　investigated　with　numerical　simulations.　A　sessile　droplet　evaporation　model,　combining　flow,　heat　transfer,　and　vapor　transport　equations,　is　developed　based　on　Arbitrary　Lagrange-Euler　(ALE)　method.　The　numerical　results　are　validated　to　be　in　good　accordance　with　the　experimental　results　in　the　literature.　The　results　show　the　formation　and　evolution　mechanisms　of　the　internal　flow　in　an　evaporating　droplet　are　controlled　by　the　thermal　conduction　distance　and　evaporative　cooling　effect.　As　the　contact　angle　decreases,　the　single-vortex　flow　inside　an　evaporating　droplet　transforms　into　a　multi-vortex　flow.　Furthermore,　the　maintenance　of　the　multi-vortex　flow　inside　a　flat　droplet　requires　an　appropriate　volume.　The　results　presented　in　this　work　provide　a　theoretical　basis　and　practical　guidance　for　exploring　more　efficient　heat　transfer　techniques.　©　2022　Elsevier　Ltd