Temporal decays and asymptotic behaviors for a Vlasov equation with a flocking term coupled to incompressible fluid flow

TL;DR

This paper analyzes the long-term behavior of solutions to coupled Vlasov-Navier-Stokes and Vlasov-Stokes systems, demonstrating exponential decay of fluid velocity and particle distribution, including effects of velocity alignment and misalignment.

Contribution

It refines decay estimates for these systems, accounting for misalignment interactions, and proves exponential convergence of particle distributions and fluid velocities to equilibrium.

Findings

Fluid velocity decays exponentially to its average.

Particle distribution's support in velocity shrinks exponentially.

Wasserstein distance between distribution and equilibrium converges exponentially.

Abstract

We are concerned with large-time behaviors of solutions for Vlasov--Navier--Stokes equations in two dimensions and Vlasov-Stokes system in three dimensions including the effect of velocity alignment/misalignment. We first revisit the large-time behavior estimate for our main system and refine assumptions on the dimensions and a communication weight function. In particular, this allows us to take into account the effect of the misalignment interactions between particles. We then use a sharp heat kernel estimate to obtain the exponential time decay of fluid velocity to its average in $L^\infty$-norm. For the kinetic part, by employing a certain type of Sobolev norm weighted by modulations of averaged particle velocity, we prove the exponential time decay of the particle distribution, provided that local particle distribution function is uniformly bounded. Moreover, we show that the support of particle distribution function in velocity shrinks to a point, which is the mean of averaged initial particle and fluid velocities, exponentially fast as time goes to infinity. This also provides that for any $p \in [1,\infty]$, the $p$-Wasserstein distance between the particle distribution function and the tensor product of the local particle distributions and Dirac measure at that point in velocity converges exponentially fast to zero as time goes to infinity.