The Navier–Stokes problem modified by an absorption term

Abstract

It is well known that for the classical Navier–Stokes problem the best one can obtain is some decays in time of power type. With this in mind, we consider in this work, the classical Navier–Stokes problem modified by introducing, in the momentum equation, the absorption term |u|^σ−2 u, where σ > 1. For the obtained problem, we prove the existence of weak solutions for any dimension N ≥ 2 and its uniqueness for N = 2. Then we prove that, for zero body forces, the weak solutions extinct in a finite time if 1 < σ < 2 and exponentially decay in time if σ = 2. In the special case of a suitable force field which vanishes at some instant, we prove that the weak solutions extinct at the same instant provided 1 < σ < 2. We also prove that for non-zero body forces decaying at a power-time rate, the solutions decay at analogous power-time rates if σ > 2. Finally, we prove that for a general non-zero body force, the weak solutions exponentially decay in time for any σ > 1.

Keywords:

• modified Navier–Stokes
• absorption
• existence
• uniqueness
• extinction in time
• power decay
• exponential decay

AMS Subject Classifications::

• 35K55
• 35Q30
• 35Q35
• 76D03
• 76D05
• 35B40

Acknowledgements

The work of both authors was partially supported by FEDER and FCT-Plurianual 2009.