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Turbulence Models

In the case of flows at high Reynolds num­ber, the choice of the tur­bu­lence mod­el is cru­cial in or­der to cor­rect­ly re­pro­duce vor­tex­es, bound­ary lay­er lam­i­nar to tur­bu­lent tran­si­tions and oth­er tur­bu­lent three di­men­sion­al be­hav­iors. Sev­er­al tur­bu­lence mod­els are al­ready avail­able :

  • The RANS mod­els. The RANS equa­tions de­ter­mine mean flow quan­ti­ties but they re­quire tur­bu­lence mod­els to close them. These equa­tions are pro­vid­ed by the dif­fer­ent RANS mod­els as­sum­ing dif­fer­ent hy­poth­e­sis on the flow. The in­com­press­ible solver pro­vides a k −ε  mod­el which is one of the most wide­ly used tur­bu­lence mod­els in CFD.
  • The LES mod­els. As the pow­er of com­put­er in­creas­es LES mod­els have be­come a pop­u­lar tech­nique in or­der to sim­u­late tur­bu­lence. Those mod­els are based on the as­sump­tion that large ed­dies con­tain most of the ki­net­ic en­er­gy of the flow and de­pen­don the geom­e­try while the small­er ones are con­sid­ered more uni­ver­sal and in­de­pen­dent of the flow’s geom­e­try. There­fore LES mod­els will ap­ply a fil­ter on the flow di­rect­ly solv­ing large ed­dies while sim­u­lat­ing small­er ones.