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We find an explicit form of weak solutions to a Riemann problem for a degenerate semilinear parabolic equation with piecewise constant diffusion coefficient. It is demonstrated that the phase transition lines (free boundaries) correspond to…

Analysis of PDEs · Mathematics 2022-11-01 Evgeny Yu. Panov

We considered classical solutions to the initial boundary value problem for non-isentropic compressible Euler equations with damping in multi-dimensions. We obtained global a priori estimates and global existence results of classical…

Analysis of PDEs · Mathematics 2015-06-19 Fuzhou Wu

In this paper, we consider the 1D wave equation where the spatial domain is a bounded interval. Assuming the initial conditions to be known, we are here interested in identifying an unknown source term, while we take the Neumann derivative…

Optimization and Control · Mathematics 2011-06-30 Marianne Chapouly , Mazyar Mirrahimi

In this paper, we study two systems with a time-variable coefficient and general time-gradually-degenerate damping. More explicitly, we construct the Riemann solutions to the time-variable coefficient Zeldovich approximation and…

Analysis of PDEs · Mathematics 2024-03-28 Richard De la cruz , Wladimir Neves

We solve the continuation problem for the non-isentropic Euler equations following the collapse of an imploding shock wave. More precisely, we prove that the self-similar G\"uderley imploding shock solutions for a perfect gas with adiabatic…

Analysis of PDEs · Mathematics 2024-03-20 Juhi Jang , Jiaqi Liu , Matthew Schrecker

The importance of contact discontinuities in 2D isothermal flows has rarely been discussed, since most Riemann solvers are derived for 1D Euler equations. We present a new contact resolving approximate Riemann solver for the isothermal…

Computational Physics · Physics 2015-07-20 Manuel Jung , Tobias F. Illenseer , Wolfgang J. Duschl

The continuous point symmetry algebra of the hyperbolic Ernst equation is presented. In a second step the corresponding group transformations are considered. Accordingly, the solutions of the hyperbolic Ernst equation that are invariant…

Mathematical Physics · Physics 2013-12-20 Sebastian Moeckel

We study the asymptotic behaviour of solutions to the delayed monostable equation $(*)$: $u_{t}(t,x) = u_{xx}(t,x) - u(t,x) + g(u(t-h,x)),$ $x \in R,\ t >0,$ with monotone reaction term $g: R_+ \to R_+$. Our basic assumption is that this…

Analysis of PDEs · Mathematics 2015-05-22 Abraham Solar , Sergei Trofimchuk

One approach to reduce the cost to simulate transitional compressible boundary layer flow is to adopt a near body reduced domain with boundary conditions enforced to be compatible with a computationally cheaper 3D RANS simulation. In such…

Fluid Dynamics · Physics 2023-02-01 Ganlin Lyu , Chao Chen , Xi Du , Spencer J. Sherwin

We have generalised the exact solution of the Riemann problem in special relativistic hydrodynamics for arbitrary tangential flow velocities. The solution is obtained by solving the jump conditions across shocks plus an ordinary…

Astrophysics · Physics 2007-05-23 J. Pons , J. Ma. Marti , E. Muller

In previous work, we developed a topological framework for solving Riemann initial-value problems for a system of conservation laws. Its core is a differentiable manifold, called the wave manifold, with points representing shock and…

We consider the 2D isentropic compressible Euler equations, with pressure law $p(\rho) = (\sfrac{1}{\gamma}) \rho^\gamma$, with $\gamma >1$. We provide an elementary constructive proof of shock formation from smooth initial datum of finite…

Analysis of PDEs · Mathematics 2019-07-10 Tristan Buckmaster , Steve Shkoller , Vlad Vicol

This article is concerned in establishing the existence and regularity of solution of semi-hyperbolic patch problem for two-dimensional isentropic Euler equations with van der Waals gas. This type of solution appears in the transonic flow…

Analysis of PDEs · Mathematics 2021-10-18 Rahul Barthwal , T. Raja Sekhar

We are concerned with free boundary problems arising from the analysis of multidimensional transonic shock waves for the Euler equations in compressible fluid dynamics. In this expository paper, we survey some recent developments in the…

Analysis of PDEs · Mathematics 2022-03-29 Gui-Qiang G. Chen , Mikhail Feldman

This article addresses the question concerning the existence of global entropy solution for generalized Eulerian droplet models with air velocity depending on both space and time variables. When $f(u)=u,$ $\kappa(t)=const.$ and…

Analysis of PDEs · Mathematics 2023-12-19 Abhrojyoti Sen , Anupam Sen

By adding a particle source term in the Boltzmann equation of kinetic theory, it is possible to represent particles appearing and disappearing throughout the fluid with a specified distribution of particle velocities. By deriving the wave…

Fluid Dynamics · Physics 2013-02-18 Erlend Magnus Viggen

A second-order PDE is derived from Euler's equaitons under certain assumptions. It is shown that this PDE admits shock and rarefaction waves, and that a single point gradient blow-up admits a unique similarity extension after blow-up that…

Analysis of PDEs · Mathematics 2009-02-12 V. A. Galaktionov

After reformulate the incompressible Euler-$\alpha$ equations in 3D smooth domain with Drichlet data, we obtain the unique classical solutions to Euler-$\alpha$ equations exist in uniform time interval independent of $\alpha$. We also show…

Analysis of PDEs · Mathematics 2016-04-19 Aibin Zang

We prove that for the two-dimensional steady complete compressible Euler system, with given uniform upcoming supersonic flows, the following three fundamental flow patterns (special solutions) in gas dynamics involving transonic shocks are…

Analysis of PDEs · Mathematics 2010-04-13 Beixiang Fang , Li Liu , Hairong Yuan

The Riemann problem is one of the basic building blocks for numerical methods in computational fluid mechanics. Nonetheless, there are still open questions and gaps in theory and modelling for situations with complex thermodynamic behavior.…

Computational Physics · Physics 2021-03-17 Timon Hitz , Steven Joens , Matthias Heinen , Jadran Vrabec , Claus-Dieter Munz