# Manwai Yuen

Are you Manwai Yuen?

## Publications (26)0 Total impact

• ##### Article:Vortical and Self-similar Flows of 2D Compressible Euler Equations
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: This paper presents the vortical and self-similar solutions for 2D compressible Euler equations using the separation method. These solutions complement Makino's solutions in radial symmetry without rotation. The rotational solutions provide new information that furthers our understanding of ocean vortices and reference examples for numerical methods. In addition, the corresponding blowup, time-periodic or global existence conditions are classified through an analysis of the new Emden equation. A conjecture regarding rotational solutions in 3D is also made.
01/2013;
• Source
##### Article:Exact, Rotational, Infinite Energy, Blowup Solutions to the 3-Dimensional Euler Equations
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: In this paper, we construct a new class of blowup solutions with elementary functions to the 3-dimensional compressible or incompressible Euler and Navier-Stokes equations. In detail, we obtain a class of global rotational exact solutions for the compressible fluids with $\gamma>1$:%} [c]{c}% \rho=\max\{\frac{\gamma-1}{K\gamma}[ C^{2}[ x^{2}% +y^{2}+z^{2}-(xy+yz+xz)] -\dot{a}(t)(x+y+z)+b(t)], 0\} ^{\frac{1}{\gamma-1}} u_{1}=a(t)+C(y-z) u_{2}=a(t)+C(-x+z) u_{3}=a(t)+C(x-y). where a(t)=c_{0}+c_{1}t and b(t)=3c_{0}c_{1}t+{3/2}c_{1}^{2}t^{2}+c_{2}% with $C$, $c_{0}$, $c_{1}$ and $c_{2}$ are arbitrary constants; And the corresponding blowup or global solutions for the incompressible Euler equations are also given. Our constructed solutions are similar to the famous Arnold-Beltrami-Childress (ABC) flow. The solutions with infinite energy can exhibit the interesting behaviors locally. Besides, the corresponding global solutions are also given for the compressible Euler equations. Furthermore, due to $\operatorname{div}\vec{u}=0$ for the solutions, the solutions also work for the 3-dimnsional incompressible Euler and Navier-Stokes equations.
05/2011;
• Source
##### Article:Self-Similar Solutions with Elliptic Symmetry for the Density-Dependent Navier-Stokes Equations in R^{N}
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: Based on Yuen's solutions with radially symmetry of the pressureless density-dependent Navier-Stokes in $R^{N}$, the corresponding ones with elliptic symmetry are constructed by the separation method. In detail, we successfully reduce the pressureless Navier-Stokes equations with density-dependent viscosity into $1+N$ differential functional equations. In particular for $\kappa_{1}>0$ and $\kappa_{2}=0$, the velocity is built by the new Emden dynamical system with force-force interaction:%\{{array} [c]{c}% \ddot{a}_{i}(t)=\frac{-\xi(\sum_{k=1}^{N}\frac{\dot{a}_{k}(t)}% {a_{k}(t)})}{a_{i}(t)(\underset{k=1}{\overset{N}{\Pi}}% a_{k}(t)) ^{\theta-1}}\text{for}i=1,2,...,N\ a_{i}(0)=a_{i0}>0,\text{}\dot{a}_{i}(0)=a_{i1}% {array}. with arbitrary constants $\xi$, $a_{i0}$ and $a_{i1}$. We can show some blowup phenomena or global existences for the obtained solutions. Based on the complication of the deduced Emden dynamical systems, the author conjectures there exist limit cycles or chaos for this kind of flows. Numerical simulation or mathematical proofs for the Emden dynamical systems are expected in the future.
05/2011;
• Source
##### Article:Self-Similar Solutions with Elliptic Symmetry for the Compressible Euler and Navier-Stokes Equations in R^{N}
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: Based on Makino's solutions with radially symmetry, we extend the corresponding ones with elliptic symmetry for the compressible Euler and Navier-Stokes equations in R^{N} (N\geq2). By the separation method, we reduce the Euler and Navier-Stokes equations into 1+N differential functional equations. In detail, the velocity is constructed by the novel Emden dynamical system: { | a_{i}(t)=({\xi}/(a_{i}(t)({\Pi}a_{k}(t))^{{\gamma}-1})), for i=1,2,....,N a_{i}(0)=a_{i0}>0, a_{i}(0)=a_{i1} with arbitrary constants {\xi}, a_{i0} and a_{i1}. Some blowup phenomena or global existences of the solutions obtained could be shown.
04/2011;
• Source
##### Article:Blowup for the C^1 Solutions of the Euler-Poisson Equations of Gaseous Stars in R^N
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: The Newtonian Euler-Poisson equations with attractive forces are the classical models for the evolution of gaseous stars and galaxies in astrophysics. In this paper, we use the integration method to study the blowup problem of the $N$-dimensional system with adiabatic exponent $\gamma>1$, in radial symmetry. We could show that the $C^{1}$ non-trivial classical solutions $(\rho,V)$, with compact support in $[0,R]$, where $R>0$ is a positive constant with $\rho(t,r)=0$ and $V(t,r)=0$ for $r\geq R$, under the initial condition $$H_{0}=\int_{0}^{R}r^{n}V_{0}dr>\sqrt{\frac{2R^{2n-N+4}M}{n(n+1)(n-N+2)}}%$$ with an arbitrary constant $n>\max(N-2,0),$\newline blow up before a finite time $T$ for pressureless fluids or $\gamma>1.$ Our results could fill some gaps about the blowup phenomena to the classical $C^{1}$ solutions of that attractive system with pressure under the first boundary condition.\newline In addition, the corresponding result for the repulsive systems is also provided. Here our result fully covers the previous case for $n=1$ in "M.W. Yuen, \textit{Blowup for the Euler and Euler-Poisson Equations with Repulsive Forces}, Nonlinear Analysis Series A: Theory, Methods & Applications 74 (2011), 1465--1470".
12/2010;
• Source
##### Article:Blowup for the Euler and Euler-Poisson Equations with Repulsive Forces II
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: In this paper, we continue to study the blowup problem of the $N$-dimensional compressible Euler or Euler-Poisson equations with repulsive forces, in radial symmetry. In details, we extend the recent result of "M.W. Yuen, \textit{Blowup for the Euler and Euler-Poisson Equations with Repulsive Forces}, Nonlinear Analysis Series A: Theory, Methods & Applications \textbf{74} (2011), 1465--1470.". We could further apply the integration method to obtain the more general results which the non-trivial classical solutions $(\rho,V)$, with compact support in $[0,R]$, where $R>0$ is a positive constant with $\rho(t,r)=0$ and $V(t,r)=0$ for $r\geq R$, under the initial condition% $$H_{0}=\int_{0}^{R}r^{n}V_{0}dr>0$$ where an arbitrary constant $n>0$, blow up on or before the finite time $T=2R^{n+2}/(n(n+1)H_{0})$ for pressureless fluids or $\gamma>1.$ The results obtained here fully cover the previous known case for $n=1$. Comment: 9 pages; Key Words: Euler Equations, Euler-Poisson Equations, Integration Method, Blowup, Repulsive Forces, With Pressure, C? Solutions, No-Slip Condition
12/2010;
• Source
##### Article:Perturbational Blowup Solutions to the 1-dimensional Compressible Euler Equations
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: We study the construction of analytical non-radially solutions for the 1-dimensional compressible adiabatic Euler equations in this article. We could design the perturbational method to construct a new class of analytical solutions. In details, we perturb the linear velocity:% $$u=c(t)x+b(t)$$ and substitute it into the compressible Euler equations. By comparing the coefficients of the polynomial, we could deduce the corresponding functional differential system of $(c(t),b(t),\rho^{\gamma-1}(0,t)).$ Then by skillfully applying the Hubble's transformation: $$c(t)=\frac{\dot{a}(t)}{a(t)},$$ the functional differential equations can be simplified to be the system of $(a(t),b(t),\rho^{\gamma-1}(0,t))$. After proving the existence of the corresponding ordinary differential equations, a new class of blowup or global solutions can be shown. Here, our results fully cover the previous known ones by choosing $b(t)=0$.
12/2010;
• Source
##### Article:Perturbational Blowup Solutions to the 2-Component Camassa-Holm Equations
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: In this article, we study the perturbational method to construct the non-radially symmetric solutions of the compressible 2-component Camassa-Holm equations. In detail, we first combine the substitutional method and the separation method to construct a new class of analytical solutions for that system. In fact, we perturb the linear velocity: u=c(t)x+b(t), and substitute it into the system. Then, by comparing the coefficients of the polynomial, we can deduce the functional differential equations involving $(c(t),b(t),\rho^{2}(0,t)).$ Additionally, we could apply the Hubble's transformation c(t)={\dot{a}(3t)}/{a(3t)}, to simplify the ordinary differential system involving $(a(3t),b(t),\rho ^{2}(0,t))$. After proving the global or local existences of the corresponding dynamical system, a new class of analytical solutions is shown. And the corresponding solutions in radial symmetry are also given. To determine that the solutions exist globally or blow up, we just use the qualitative properties about the well-known Emden equation: {array} [c]{c} {d^{2}/{dt^{2}}}a(3t)= {\xi}{a^{1/3}(3t)}, a(0)=a_{0}>0 ,\dot{a}(0)=a_{1} {array} . Our solutions obtained by the perturbational method, fully cover the previous known results in "M.W. Yuen, \textit{Self-Similar Blowup Solutions to the 2-Component Camassa-Holm Equations,}J. Math. Phys., \textbf{51} (2010) 093524, 14pp." by the separation method.
12/2010;
• Source
##### Article:Self-Similar Blowup Solutions to the 2-Component Degasperis-Procesi Shallow Water System
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: In this article, we study the self-similar solutions of the 2-component Degasperis-Procesi water system:% [c]{c}% \rho_{t}+k_{2}u\rho_{x}+(k_{1}+k_{2})\rho u_{x}=0 u_{t}-u_{xxt}+4uu_{x}-3u_{x}u_{xx}-uu_{xxx}+k_{3}\rho\rho_{x}=0. By the separation method, we can obtain a class of self-similar solutions,% [c]{c}% \rho(t,x)=\max(\frac{f(\eta)}{a(4t)^{(k_{1}+k_{2})/4}},\text{}0),\text{}u(t,x)=\frac{\overset{\cdot}{a}(4t)}{a(4t)}x \overset{\cdot\cdot}{a}(s)-\frac{\xi}{4a(s)^{\kappa}}=0,\text{}a(0)=a_{0}% \neq0,\text{}\overset{\cdot}{a}(0)=a_{1} f(\eta)=\frac{k_{3}}{\xi}\sqrt{-\frac{\xi}{k_{3}}\eta^{2}+(\frac{\xi}{k_{3}}\alpha) ^{2}}% where $\eta=\frac{x}{a(s)^{1/4}}$ with $s=4t;$ $\kappa=\frac{k_{1}}{2}% +k_{2}-1,$ $\alpha\geq0,$ $\xi<0$, $a_{0}$ and $a_{1}$ are constants. which the local or global behavior can be determined by the corresponding Emden equation. The results are very similar to the one obtained for the 2-component Camassa-Holm equations. Our analytical solutions could provide concrete examples for testing the validation and stabilities of numerical methods for the systems. With the characteristic line method, blowup phenomenon for $k_{3}\geq0$ is also studied.
08/2010;
• Source
##### Article:Self-Similar Blowup Solutions to the 2-Component Camassa-Holm Equations
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: In this article, we study the self-similar solutions of the 2-component Camassa-Holm equations% $$\left\{ \begin{array} [c]{c}% \rho_{t}+u\rho_{x}+\rho u_{x}=0 m_{t}+2u_{x}m+um_{x}+\sigma\rho\rho_{x}=0 \end{array} \right.$$ with $$m=u-\alpha^{2}u_{xx}.$$ By the separation method, we can obtain a class of blowup or global solutions for $\sigma=1$ or $-1$. In particular, for the integrable system with $\sigma=1$, we have the global solutions:% $$\left\{ \begin{array} [c]{c}% \rho(t,x)=\left\{ \begin{array} [c]{c}% \frac{f\left( \eta\right) }{a(3t)^{1/3}},\text{ for }\eta^{2}<\frac {\alpha^{2}}{\xi} 0,\text{ for }\eta^{2}\geq\frac{\alpha^{2}}{\xi}% \end{array} \right. ,u(t,x)=\frac{\overset{\cdot}{a}(3t)}{a(3t)}x \overset{\cdot\cdot}{a}(s)-\frac{\xi}{3a(s)^{1/3}}=0,\text{ }a(0)=a_{0}% >0,\text{ }\overset{\cdot}{a}(0)=a_{1} f(\eta)=\xi\sqrt{-\frac{1}{\xi}\eta^{2}+\left( \frac{\alpha}{\xi}\right) ^{2}}% \end{array} \right.$$ where $\eta=\frac{x}{a(s)^{1/3}}$ with $s=3t;$ $\xi>0$ and $\alpha\geq0$ are arbitrary constants.\newline Our analytical solutions could provide concrete examples for testing the validation and stabilities of numerical methods for the systems. Comment: 5 more figures can be found in the corresponding journal paper (J. Math. Phys. 51, 093524 (2010) ). Key Words: 2-Component Camassa-Holm Equations, Shallow Water System, Analytical Solutions, Blowup, Global, Self-Similar, Separation Method, Construction of Solutions, Moving Boundary
07/2010;
• Source
##### Article:Line Solutions for the Euler and Euler-Poisson Equations with Multiple Gamma Law
Ling Hei Yeung, Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: In this paper, we study the Euler and Euler-Poisson equations in $R^{N}$, with multiple $\gamma$-law for pressure function: $$P(\rho)=e^{s}\sum_{j=1}^{m}\rho^{\gamma_{j}},$$ where all $\gamma_{i+1}>\gamma_{i}\geq1$, is the constants. The analytical line solutions are constructed for the systems. It is novel to discover the analytical solutions to handle the systems with mixed pressure function. And our solutions can be extended to the systems with the generalized multiple damping and pressure function.
05/2010;
• Source
##### Article:Stabilities for Euler-Poisson Equations with Repulsive Forces in R^N
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: This article extends the previous paper in "M.W. Yuen, \textit{Stabilities for Euler-Poisson Equations in Some Special Dimensions}, J. Math. Anal. Appl. \textbf{344} (2008), no. 1, 145--156.", from the Euler-Poisson equations for attractive forces to the repulsive ones in $R^{N}$ $(N\geq2)$. The similar stabilities of the system are studied. Additionally, we explain that it is impossible to have the density collapsing solutions with compact support to the system with repulsive forces for $\gamma>1$. Comment: Key Words: Euler-Poisson Equations, Repulsive Forces, Stabilities, Frictional Damping, Second Inertia Function, Non-collapsing Solutions; 6 Pages
01/2010;
• Source
##### Article:Blowup for the Euler and Euler-Poisson Equations with Repulsive Forces
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: In this paper, we study the blowup of the $N$-dim Euler or Euler-Poisson equations with repulsive forces, in radial symmetry. We provide a novel integration method to show that the non-trivial classical solutions $(\rho,V)$, with compact support in $[0,R]$, where $R>0$ is a positive constant and in the sense which $\rho(t,r)=0$ and $V(t,r)=0$ for $r\geq R$, under the initial condition% $H_{0}=\int_{0}^{R}rV_{0}dr>0$ blow up on or before the finite time $T=R^{3}/(2H_{0})$ for pressureless fluids or $\gamma>1.$ The main contribution of this article provides the blowup results of the Euler $(\delta=0)$ or Euler-Poisson $(\delta=1)$ equations with repulsive forces, and with pressure $(\gamma>1)$, as the previous blowup papers (\cite{MUK} \cite{MP}, \cite{P} and \cite{CT}) cannot handle the systems with the pressure term, for $C^{1}$ solutions. Comment: Accepted by Nonlinear Analysis Series A: Theory, Methods & Applications Key Words: Euler Equations, Euler-Poisson Equations, Integration Method, Blowup, Repulsive Forces, With Pressure, $C^{1}$ Solutions, No-Slip Condition
01/2010;
• Source
##### Article:Some Exact Blowup Solutions to the Pressureless Euler Equations in R^N
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: The pressureless Euler equations can be used as simple models of cosmology or plasma physics. In this paper, we construct the exact solutions in non-radial symmetry to the pressureless Euler equations in $R^{N}:$% [c]{c}% \rho(t,\vec{x})=\frac{f(\frac{1}{a(t)^{s}}\underset{i=1}{\overset {N}{\sum}}x_{i}^{s})}{a(t)^{N}}\text{,}\vec{u}(t,\vec{x}% )=\frac{\overset{\cdot}{a}(t)}{a(t)}\vec{x}, a(t)=a_{1}+a_{2}t. \label{eq234}% where the arbitrary function $f\geq0$ and $f\in C^{1};$ $s\geq1$, $a_{1}>0$ and $a_{2}$ are constants$.$\newline In particular, for $a_{2}<0$, the solutions blow up on the finite time $T=-a_{1}/a_{2}$. Moreover, the functions (\ref{eq234}) are also the solutions to the pressureless Navier-Stokes equations.
10/2009;
• Source
##### Article:Stabilities for Euler-Poisson Equations in Some Special Dimensions
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: We study the stabilities and classical solutions of Euler-Poisson equations of describing the evolution of the gaseous star in astrophysics. In fact, we extend the study the stabilities of Euler-Poisson equations with or without frictional damping term to some special dimensional spaces. Besides, by using the second inertia function in 2 dimension of Euler-Poisson equations, we prove the non-global existence of classical solutions with $2\int_{\Omega}(\rho| u| ^{2}+2P)dx<gM^{2}-\epsilon$, for any $\gamma$. Comment: 15 pages
07/2009;
• Source
##### Article:Blowup of C^2 Solutions for the Euler Equations and Euler-Poisson Equations in R^N
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: In this paper, we use integration method to show that there is no existence of global $C^{2}$ solution with compact support, to the pressureless Euler-Poisson equations with attractive forces in $R^{N}$. And the similar result can be shown, provided that the uniformly bounded functional:% \int_{\Omega(t)}K\gamma(\gamma-1)\rho^{\gamma-2}(\nabla\rho)^{2}% dx+\int_{\Omega(t)}K\gamma\rho^{\gamma-1}\Delta\rho dx+\epsilon\geq -\delta\alpha(N)M, where $M$ is the mass of the solutions and $| \Omega|$ is the fixed volume of $\Omega(t)$. On the other hand, our differentiation method provides a simpler proof to show the blowup result in "D. H. Chae and E. Tadmor, \textit{On the Finite Time Blow-up of the Euler-Poisson Equations in}$R^{N}$, Commun. Math. Sci. \textbf{6} (2008), no. 3, 785--789.". Key Words: Euler Equations, Euler-Poisson Equations, Blowup, Repulsive Forces, Attractive Forces, $C^{2}$ Solutions Comment: 7 pages
07/2009;
• Source
##### Article:Analytical Blowup Solutions to the Isothermal Euler-Poisson Equations of Gaseous Stars in R^N
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: This article is the continued version of the analytical blowup solutions for 2-dimensional Euler-Poisson equations in "M.W. Yuen, Analytical Blowup Solutions to the 2-dimensional Isothermal Euler-Poisson Equations of Gaseous Stars, J. Math. Anal. Appl. 341 (1)(2008), 445-456." and "M.W. Yuen, Analytical Blowup Solutions to the 2-dimensional Isothermal Euler-Poisson Equations of Gaseous Stars II. arXiv:0906.0176v1". With the extension of the blowup solutions with radial symmetry for the isothermal Euler-Poisson equations in R^2, other special blowup solutions in R^N with non-radial symmetry are constructed by the separation method. Key words: Analytical Solutions, Euler-Poisson Equations, Isothermal, Blowup, Special Solutions, Non-radial Symmetry Comment: 13 pages
05/2009;
• Source
##### Article:Analytical Blowup Solutions to the 2-dimensional Isothermal Euler-Poisson Equations of Gaseous Stars II
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: This article is the continued version of the analytical blowup solutions for 2-dimensional Euler-Poisson equations \cite{Y1}. With extension of the blowup solutions with radial symmetry for the isothermal Euler-Poisson equations in $R^{2}$, other special blowup solutions in $R^{2}$ with non-radial symmetry are constructed by the separation method. We notice that the results are the first evolutionary solutions with non-radial symmetry for the system. Key words: Analytical Solutions, Euler-Poisson Equations, Isothermal, Blowup, Non-radial Symmetry, Line Source or Sink
05/2009;
• Source
##### Article:Analytical Solutions to the Navier-Stokes Equations with Density-dependent Viscosity and with Pressure
Ling Hei Yeung, Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: This article is the continued version of the analytical solutions for the pressureless Navier-Stokes equations with density-dependent viscosity in "M.W. Yuen, Analyitcal Solutions to the Navier-Stokes Equations, J. Math. Phys., 49 (2008) No. 11, 113102, 10pp". We are able to extend the similar solutions structure to the case with pressure under some restriction for $\gamma$ and $\theta$. Comment: 7 pages, Typos are corrected
02/2009;
• Source
##### Article:Analytically Periodic Solutions to the 3-dimensional Euler-Poisson Equations of Gaseous Stars with Negative Cosmological Constant
Manwai Yuen
[show abstract] [hide abstract]
ABSTRACT: By the extension of the 3-dimensional analytical solutions of Goldreich and Weber "P. Goldreich and S. Weber, Homologously Collapsing Stellar Cores, Astrophys, J. 238, 991 (1980)" with adiabatic exponent gamma=4/3, to the (classical) Euler-Poisson equations without cosmological constant, the self-similar (almost re-collapsing) time-periodic solutions with negative cosmological constant (lambda<0) are constructed. The solutions with time-periodicity are novel. On basing these solutions, the time-periodic and almost re-collapsing model is conjectured, for some gaseous stars. Key Words: Analytically Periodic Solutions, Re-collapsing, Cosmological Constant, Euler-Poisson Equations, Collapsing Comment: 9 pages
01/2009;