A note on the Prodi-Serrin conditions for the regularity of a weak solution to the Navier-Stokes equations

The paper is concerned with the regularity of weak solutions to the Navier-Stokes equations. The aim is to investigate on a relaxed Prodi-Serrin condition in order to obtain regularity for t > 0. The most interesting aspect of the result is that no compatibility condition is required to the initial data v_0\in J^2(\OO) J2({\Omega})

Higher regularity of solutions to the singular p-Laplacean parabolic system

We study existence and regularity properties of solutions to the singular $p$-Laplacean parabolic system in a bounded domain $\Omega$. The main purpose is to prove global $L^r(\varepsilon,T;L^q(\Omega))$, $\varepsilon\geq0$, integrability properties of the second spatial derivatives and of the time derivative of the solutions. Hence, for suitable $p$ and exponents $r,\,q$, by Sobolev embedding theorems, we deduce global regularity of $u$ and $\nabla u$ in H\"older spaces. Finally we prove a global pointwise bound for the solution under the assumption $p>\frac{2n}{n+2}$

On the spatial asymptotic decay of a suitable weak solution to the Navier-Stokes Cauchy problem

We prove space-time decay estimates of suitable weak solutions to the Navier-Stokes Cauchy problem, corresponding to a given asymptotic behavior of the initial data of the same order of decay. We use two main tools. The first is a result obtained by the authors in the paper "A remark on the partial regularity of a suitable weak solution to the Navier-Stokes Cauchy problem" (submitted), on the behavior of the solution in a neighborhood of $t=0$ in the $L^\infty_{loc}$-norm, which enables us to furnish a representation formula for a suitable weak solution. The second is the asymptotic behavior of the $L^2(\R^3\setminus B_R)$ norm of $u(t)$ for $R\to\infty$. Following a Leray's point of view, roughly speaking our result proves that a possible space-time turbulence does not perturb the asymptotic spatial behavior of the initial data of a suitable weak solution

Existence of regular time-periodic solution to shear-thinning fluids

In this note we investigate the existence of time-periodic solutions to the $p$-Navier-Stokes system in the singular case of $p\in (1, 2)$, that describes the flows of an incompressible shear-thinning fluid. In the $3D$ space-periodic setting and for $p \in [ \frac{5}{3} , 2)$ we prove the existence of a regular time-periodic solution corresponding to a time periodic force data which is assumed small in a suitable sense. As a particular case we obtain `regular' steady solutions

Navier-Stokes flow past a rigid body: attainability of steady solutions as limits of unsteady weak solutions, starting and landing cases

Consider the Navier-Stokes flow in 3-dimensional exterior domains, where a rigid body is translating with prescribed translational velocity $-h(t)u_\infty$ with constant vector $u_\infty\in \mathbb R^3\setminus\{0\}$. Finn raised the question whether his steady slutions are attainable as limits for $t\to\infty$ of unsteady solutions starting from motionless state when $h(t)=1$ after some finite time and $h(0)=0$ (starting problem). This was affirmatively solved by Galdi, Heywood and Shibata for small $u_\infty$. We study some generalized situation in which unsteady solutions start from large motions being in $L^3$. We then conclude that the steady solutions for small $u_\infty$ are still attainable as limits of evolution of those fluid motions which are found as a sort of weak solutions. The opposite situation, in which $h(t)=0$ after some finite time and $h(0)=1$ (landing problem), is also discussed. In this latter case, the rest state is attainable no matter how large $u_\infty$ is

On the LpL^p-LqL^q estimates of the gradient of solutions to the Stokes problem

The paper is concerned with estimates of the gradient of the solutions to the Stokes IBVP both in a bounded and in an exterior domain. More precisely, we look for estimates of the kind $\|\nabla v(t)\|_q\leq g(t)\|\nabla v_0\|_p, q\geq p>1$, for all $t>0$, where function $g$ is independent of $v_0$.Comment: There is an improvement of Proposition

Global L^r-estimates and regularizing effect for solutions to the p(t, x) -Laplacian systems

We consider the initial boundary value problem for the p(t, x)-Laplacian system in a bounded domain \Omega. If the initial data belongs to L^{r_0}, r_0 \geq 2, we give a global L^{r_0}({\Omega})-regularity result uniformly in t>0 that, in the particular case r_0 =\infty, implies a maximum modulus theorem. Under the assumption p- = \inf p(t, x) > 2n/(n+r_0), we also state L^{r_0}- L^r estimates for the solution, for r \geq r_0. Complete proofs of the results presented here are given in the paper [F. Crispo, P. Maremonti, M. Ruzicka, Global L^r-estimates and regularizing effect for solutions to the p(t, x) -Laplacian systems, accepted for publication on Advances in Differential Equations, 2017]

Singular p-Laplacian parabolic system in exterior domains: higher regularity of solutions and related properties of extinction and asymptotic behavior in time

We consider the IBVP in exterior domains for the p-Laplacian parabolic system. We prove regularity up to the boundary, extinction properties for p \in ( 2n/(n+2) , 2n/(n+1) ) and exponential decay for p= 2n/(n+1)

On the high regularity of solutions to the p-Laplacian boundary value problem in exterior domains

In this note, we consider the boundary value problem in exterior domains for the p-Laplacian system, p ∈ (1, 2). For suitable p and Lr -spaces, r > n, we furnish existence of a high-regular solution that is a solution whose second derivatives belong to L r (Ω ). Hence, in particular we get λ-Hölder continuity of the gradient of the solution, with λ = 1 − n/r Further, we improve previous results on W2,2-regularity in a bounded domain