Does FLUENT use linearized Navier-Stokes equation with all convection terms removed?

Sripadaraja · May 19, 2021, 03:14

It is said that when Reynold's number is much less than 1 (Re << 1), convective terms can be removed/neglected. Does ANSYS Fluent neglect/remove convective terms during computations in such a case?

LuckyTran · May 19, 2021, 16:55

No. It sticks to the same equations.

Furthermore, the general (dimensional) Navier-Stokes equations doesn't have a Reynolds number in it. Without a meaningful velocity scale and length scale, there isn't any notion of Reynolds numbers and no way to know when to remove these terms or not.

Also be careful what you read because more often than not, linearized Navier-Stokes does not refer to eliminating convective terms. Linearized Navier-Stokes is linearizing the non-linear convective term about the perturbation order, neglecting higher order terms, and hence linearizing it. The Stokes equations, although they are deduced from the N-S equations and are linear, are generally not called LNSE.

May 19, 2021, 03:14	Does FLUENT use linearized Navier-Stokes equation with all convection terms removed?	#1
Sripadaraja New Member Sripadaraja Join Date: Sep 2015 Posts: 23 Rep Power: 10	It is said that when Reynold's number is much less than 1 (Re << 1), convective terms can be removed/neglected. Does ANSYS Fluent neglect/remove convective terms during computations in such a case?

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May 19, 2021, 16:55		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 66	No. It sticks to the same equations. Furthermore, the general (dimensional) Navier-Stokes equations doesn't have a Reynolds number in it. Without a meaningful velocity scale and length scale, there isn't any notion of Reynolds numbers and no way to know when to remove these terms or not. Also be careful what you read because more often than not, linearized Navier-Stokes does not refer to eliminating convective terms. Linearized Navier-Stokes is linearizing the non-linear convective term about the perturbation order, neglecting higher order terms, and hence linearizing it. The Stokes equations, although they are deduced from the N-S equations and are linear, are generally not called LNSE.