Shape Optimization in Viscous Compressible Fluids

Abstract. We present a method for solving the optimal shape problems for profiles surrounded by viscous compressible fluids. The class of admissible profiles is quite general including the minimal volume condition and a constraint on the thickness of the boundary. The fluid flow is modelled by the Navier—Stokes system for a general viscous barotropic fluid.     

Shape Optimization in Viscous Compressible Fluids

   Abstract. We present a method for solving the optimal shape problems for profiles surrounded by viscous compressible fluids. The class of admissible profiles is quite general including the minimal volume condition and a constraint on the thickness of the boundary. The fluid flow is modelled by the Navier—Stokes system for a general viscous barotropic fluid.     

The Incompressible Limits of Compressible Navier-Stokes Equations in the Whole Space with General Initial Data

It is showed that, as the Mach number goes to zero, the weak solution of the compressible Navier-Stokes equations in the whole space with general initial data converges to the strong solution of the incompressible Navier-Stokes equations as long as the later exists. The proof of the result relies on the new modulated energy functional and the Strichartz＇s estimate of linear wave equation.     

Compressible navier-stokes equations with density-dependent viscosity, vacuum and gravitational force in the case of general pressure

This is a continuation of the article（Comm.Partial Differential Equations 26（2001）965）.In this article,the authors consider the one-dimensional compressible isentropic Navier-Stokes equations with gravitational force,fixed boundary condition,a general pressure and the density-dependent viscosity coefficient when the viscous gas connects to vacuum state with a jump in density.Precisely,the viscosity coefficient μ is proportional to ρ^θ and 0〈θ〈1/2,where ρ is the density,and the pressure P=P（ρ）is a general pressure.The global existence and the uniqueness of weak solution are proved.     

Decay of the 2D Periodic Stationary Viscous Surface Waves

We consider the evolution of viscous fluids in a 2D horizontally periodic slab bounded above by a free top surface and below by a fixed flat bottom. This is a free boundary problem. The dynamics of the fluid are governed by the incompressible stationary Navier–Stokes equations under the influence of gravity and the effect of surface tension. We develop the global theory of solutions in low regularity Sobolev spaces for small data by nonlinear energy estimates.     

The Strong Solution for the Viscous Polytropic Fluids with Non-Newtonian Potential

The authors study an initial boundary value problem for the three-dimensional Navier-Stokes equations of viscous heat-conductive fluids with non-Newtonian potential in a bounded smooth domain. They prove the existence of unique local strong solutions for all initial data satisfying some compatibility conditions. The difficult of this type model is mainly that the equations are coupled with elliptic, parabolic and hyperbolic, and the vacuum of density causes also much trouble, that is, the initial density need not be positive and may vanish in an open set.     

On the Navier-Stokes Equations for Exothermically Reacting Compressible Fluids

Abstract We analyze mathematical models governing planar flow of chemical reaction from unburnt gasesto burnt gases in certain physical regimes in which diffusive effects such as viscosity and heat conduction aresignificant. These models can be then formulated as the Navier-Stokes equations for exothermically reactingcompressible fluids. We first establish the existence and dynamic behavior, including stability, regularity, andlarge-time behavior, of global discontinuous solutions of large oscillation to the Navier-Stokes equations withconstant adiabatic exponent γ and specific heat C_v. Our approach for the existence and regularity is to combinethe difference approximation techniques with the energy methods, total variation estimates, and weak conver-gence argumeots to deal with large jump discontinuities; and for large-time behavior is an a posteriori argumentdirectly from the weak form of the equations. The approach and ideas we develop here can be applied to solvinga more complicated model where γ     

三维可压等熵Euler方程光滑解的整体存在性

研究了三维可压等熵Euler方程Cauchy问题光滑解的整体存在性.如果初值是一个常状态的小扰动并且初速度的旋度等于零,证明了三维可压等熵Euler方程Cauchy问题光滑解的整体存在性.     

Small data solutions of 2-D quasilinear wave equations under null conditions

2 Abstract For the 2-D quasilinear wave equation(?_t~2-?_x)u+2∑ij=0g~(ij)(?u)?_(ij)u = 0 satisfying i,j=0 null condition or both null conditions, a blowup or global existence result has been shown by Alinhac. In this paper, we consider a more general 2-D quasilinear wave equation(?_t~2-?_x)_u+2∑ij=0g~(ij)(?u)?_(ij)u = 0 satisfying null conditions with small initial data and the coefficients i,j=0 depending simultaneously on u and ?u. Through construction of an approximate solution,combined with weighted energy integral method, a quasi-global or global existence solution are established by continuous induction.     

On asynchronous iterations in partially ordered spaces

We extend the idea of asynchronous iterations to self-mappings of product spaces with infinitely many components. In addition to giving a rather general convergence theorem we study in some detail the case of isotone and isotonically decomposable mappings in partially ordered spaces. In particular, we obtain relationships between asynchronous iterations and the total step method and results on enclosures for fixed points. They appear to be new, even for mappings defined on a product space with only finitely many components.     

On global small amplitude solutions to systems of cubic nonlinear Klein-Gordon equations with different mass terms in one space dimension

We consider the Cauchy problem for systems of cubic nonlinear Klein-Gordon equations with different mass terms in one space dimension. We prove some result concerning the global existence of small amplitude solutions and their asymptotic behavior. As a consequence, we see that the condition for small data global existence is actually influenced by the difference of masses in some cases.     

Weak solutions for the Falk model system of shape memory alloys in energy class

We show the unique global existence of energy class solutions for the Falk model system of shape memory alloys under the general non‐linearity as well as considered in Aiki (Math. Meth. Appl. Sci. 2000; 23 : 299). Our main tools of the proofs are the Strichartz type estimate for the Boussinesq type equation and the maximal regularity estimate for the heat equation. Copyright © 2005 John Wiley & Sons, Ltd.     

On the global existence of smooth solutions to the multi-dimensional compressible euler equations with time-depending damping in half space

This paper is a continue work of [4, 5]. In the previous two papers, we studied the Cauchy problem of the multi-dimensional compressible Euler equations with time-depending damping term -μ/((1+t)λ)ρu, where λ≥ 0 and μ 0 are constants. We have showed that, for all λ≥ 0 and μ 0, the smooth solution to the Cauchy problem exists globally or blows up in finite time. In the present paper, instead of the Cauchy problem we consider the initialboundary value problem in the half space R_+~d with space dimension d = 2, 3. With the help of the special structure of the equations and the fluid vorticity, we overcome the difficulty arisen from the boundary effect. We prove that there exists a global smooth solution for 0 ≤λ 1when the initial data is close to its equilibrium state. In addition, exponential decay of the fluid vorticity will also be established.     

The global existence and large time behavior of smooth compressible fluid in an infinitely expanding ball,III: The 3-D Boltzmann equation

This paper is a continuation of the works in [35] and [37], where the authors have established the global existence of smooth compressible flows in infinitely expanding balls for inviscid gases and viscid gases, respectively. In this paper, we are concerned with the global existence and large time behavior of compressible Boltzmann gases in an infinitely expanding ball. Such a problem is one of the interesting models in studying the theory of global smooth solutions to multidimensional compressible gases with time dependent boundaries and vacuum states at infinite time. Due to the conservation of mass, the fluid in the expanding ball becomes rarefied and eventually tends to a vacuum state meanwhile there are no appearances of vacuum domains in any part of the expansive ball, which is easily observed in finite time. In the present paper, we will confirm this physical phenomenon for the Boltzmann equation by obtaining the exact lower and upper bound on the macroscopic density function.