On the boundary regularity of suitable weak solutions to the Navier-Stokes equations

We consider suitable weak solutions to an incompressible viscous Newtonian fluid governed by the Navier-Stokes equations in the half space \({\mathbb {R}^3_+}\). Our main result is a direct proof of the partial regularity up to the flat boundary based on a new decay estimate, which implies the regularity in the cylinder \({Q_\rho ^+(x_0, t_0)}\) provided

$\limsup_{R\to 0}\frac {1} {R}\int\limits_{Q_R^+(x_0, t_0)} |{\rm rot}\,\mathbf u|^2 dxdt \,\leq\, \varepsilon _0$

with ε ₀ sufficiently small. In addition, we get a new condition for the local regularity beyond Serrin’s class which involves the L ²-norm of ?u and the L ^3/2-norm of the pressure.

     

On the local smoothness of weak solutions to the MHD system

A sufficient condition for local regularity of weak solutions to the system of magnetohydrodynamics is proved. Bibliography: 12 titles.     

On the interior regularity of weak solutions to the non-stationary Stokes system

In this paper, we prove that any weak solution to the non-stationary Stokes system in 3D with right hand side -div f satisfying (1.4) below, belongs to C( ]0, T[; C ^α (Ω)). The proof is based on Campanato-type inequalities and the existence of a local pressure introduced in Wolf [13]. Proc. Conference “Variational analysis and PDE’s”. Intern. Centre “E. Majorana”, Erice, July 5–14, 2006.     

Extension criterion on regularity for weak solutions to the 3D MHD equations

In this paper, we consider the regularity criteria for weak solutions to the 3D incompressible magnetohydrodynamic equations and prove some regularity criteria which are related only with u+B or u?B. This is an improvement of the result given by He and Wang (J. Differential Equations 2007; 238:1–17; Math. Meth. Appl. Sci. 2008; 31:1667–1684) and He and Xin (J. Differential Equations 2005; 213(2):235–254). Copyright © 2010 John Wiley & Sons, Ltd.     

On the regularity of weak solutions to the magnetohydrodynamic equations

In this paper, we study the regularity of weak solution to the incompressible magnetohydrodynamic equations. We obtain some sufficient conditions for regularity of weak solutions to the magnetohydrodynamic equations, which is similar to that of incompressible Navier-Stokes equations. Moreover, our results demonstrate that the velocity field of the fluid plays a more dominant role than the magnetic field does on the regularity of solution to the magneto-hydrodynamic equations.     

On partial regularity for weak solutions to the Navier-Stokes equations

In this paper, we study the partial regularity of the general weak solution u∈L∞(0,T;L2(Ω))∩L2(0,T;H1(Ω)) to the Navier-Stokes equations, which include the well-known Leray-Hopf weak solutions. It is shown that there is a absolute constant ε such that for the weak solution u, if either the scaled local L^q(1?q?2) norm of the gradient of the solution, or the scaled local ) norm of u is less than ε, then u is locally bounded. This implies that the one-dimensional Hausdorff measure is zero for the possible singular point set, which extends the corresponding result due to Caffarelli et al. (Comm. Pure Appl. Math. 35 (1982) 717) to more general weak solution.     

Remarks on the regularity of weak solutions to the Navier-Stokes equations near the boundary

We give a simple proof of the so-called -regularity of suitable weak solutions to the Navier-Stokes equations near the boundary. Bibliography: 7 titles.Dedicated to Olga Aleksandrovna Ladyzhenskaya__________Published in Zapiski Nauchnykh Seminarov POMI, Vol. 295, 2003, pp. 168–179.     

On a partial regularity up to the boundary of weak solutions to quasilinear parabolic systems with quadratic growth

Quasilinear nondiagonal parabolic systems with quadratic growth in the gradient in a parabolic cylinder Q are considered. Under Dirichlet and Neumann boundary conditions, a partial Hölder continuity of solutions u∈W ₂ ^t,1 (Q)～L^∞ (Q) up to the lateral surface of Q is proved.The Hausdorff dimension of a singular set is estimated. In the proof, we get rid of the maximum principle theorem for respective model linear problems. Bibliography: 21 titles.     

On the regularity criteria for weak solutions to the magnetohydrodynamic equations

We study the regularity criteria for weak solutions to the incompressible magnetohydrodynamic equations. Some regularity criteria are obtained for weak solutions to the magnetohydrodynamic equations, which generalize the results in [C. He, Z. Xin, On the regularity of solutions to the magneto-hydrodynamic equations, J. Differential Equations 213 (2) (2005) 235-254]. Our results reveal that the velocity field of the fluid plays a more dominant role than the magnetic field does on the regularity of solutions to the magnetohydrodynamic equations.     

On the regularity of weak solutions of certain elliptic systems

For certain quasilinear elliptic systems with perturbations of natural growth we prove a Caccioppoli-inequality provided the perturbation satisfies an additional “angle condition.” As a consequence weak solutions of these systems have the Hölder-continuity properties established by the so called direct approach to regularity, cf.: [2].     

Partial regularity of weak solutions to a PDE system with cubic nonlinearity

In this paper we investigate regularity properties of weak solutions to a PDE system that arises in the study of biological transport networks. The system consists of a possibly singular elliptic equation for the scalar pressure of the underlying biological network coupled to a diffusion equation for the conductance vector of the network. There are several different types of nonlinearities in the system. Of particular mathematical interest is a term that is a polynomial function of solutions and their partial derivatives and this polynomial function has degree three. That is, the system contains a cubic nonlinearity. Only weak solutions to the system have been shown to exist. The regularity theory for the system remains fundamentally incomplete. In particular, it is not known whether or not weak solutions develop singularities. In this paper we obtain a partial regularity theorem, which gives an estimate for the parabolic Hausdorff dimension of the set of possible singular points.     

Local regularity criteria of a suitable weak solution to MHD equations

We present a regularity condition of a suitable weak solution to the MHD equations in three dimensional space with slip boundary conditions for a velocity and magnetic vector fields. More precisely, we prove a suitable weak solution are H¨older continuous near boundary provided that the scaled mixed L_(x,t)~(p,q) -norm of the velocity vector field with 3/p + 2/q ≤ 2,2 q ∞ is sufficiently small near the boundary. Also, we will investigate that for this solution u ∈ L_(x,t)~(p,q) with 1≤3/p+2/q≤3/2, 3 p ∞, the Hausdorff dimension of its singular set is no greater than max{p, q}(3/p+2/q-1).