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Search: MSC category 76 ( Fluid mechanics )

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1. CMB 2011 (vol 55 pp. 176)

Spirn, Daniel; Wright, J. Douglas
Linear Dispersive Decay Estimates for the 3+1 Dimensional Water Wave Equation with Surface Tension
We consider the linearization of the three-dimensional water waves equation with surface tension about a flat interface. Using oscillatory integral methods, we prove that solutions of this equation demonstrate dispersive decay at the somewhat surprising rate of $t^{-5/6}$. This rate is due to competition between surface tension and gravitation at $O(1)$ wave numbers and is connected to the fact that, in the presence of surface tension, there is a so-called "slowest wave". Additionally, we combine our dispersive estimates with $L^2$ type energy bounds to prove a family of Strichartz estimates.

Keywords:oscillatory integrals, water waves, surface tension, Strichartz estimates
Categories:76B07, 76B15, 76B45

2. CMB 2010 (vol 54 pp. 147)

Nelson, Sam
Generalized Quandle Polynomials
We define a family of generalizations of the two-variable quandle polynomial. These polynomial invariants generalize in a natural way to eight-variable polynomial invariants of finite biquandles. We use these polynomials to define a family of link invariants that further generalize the quandle counting invariant.

Keywords:finite quandles, finite biquandles, link invariants
Categories:57M27, 76D99

3. CMB 2008 (vol 51 pp. 386)

Lan, K. Q.; Yang, G. C.
Positive Solutions of the Falkner--Skan Equation Arising in the Boundary Layer Theory
The well-known Falkner--Skan equation is one of the most important equations in laminar boundary layer theory and is used to describe the steady two-dimensional flow of a slightly viscous incompressible fluid past wedge shaped bodies of angles related to $\lambda\pi/2$, where $\lambda\in \mathbb R$ is a parameter involved in the equation. It is known that there exists $\lambda^{*}<0$ such that the equation with suitable boundary conditions has at least one positive solution for each $\lambda\ge \lambda^{*}$ and has no positive solutions for $\lambda<\lambda^{*}$. The known numerical result shows $\lambda^{*}=-0.1988$. In this paper, $\lambda^{*}\in [-0.4,-0.12]$ is proved analytically by establishing a singular integral equation which is equivalent to the Falkner--Skan equation. The equivalence result provides new techniques to study properties and existence of solutions of the Falkner--Skan equation.

Keywords:Falkner-Skan equation, boundary layer problems, singular integral equation, positive solutions
Categories:34B16, 34B18, 34B40, 76D10

4. CMB 2007 (vol 50 pp. 547)

Iakovlev, Serguei
Inverse Laplace Transforms Encountered in Hyperbolic Problems of Non-Stationary Fluid-Structure Interaction
The paper offers a study of the inverse Laplace transforms of the functions $I_n(rs)\{sI_n^{'}(s)\}^{-1}$ where $I_n$ is the modified Bessel function of the first kind and $r$ is a parameter. The present study is a continuation of the author's previous work %[\textit{Canadian Mathematical Bulletin} 45] on the singular behavior of the special case of the functions in question, $r$=1. The general case of $r \in [0,1]$ is addressed, and it is shown that the inverse Laplace transforms for such $r$ exhibit significantly more complex behavior than their predecessors, even though they still only have two different types of points of discontinuity: singularities and finite discontinuities. The functions studied originate from non-stationary fluid-structure interaction, and as such are of interest to researchers working in the area.

Categories:44A10, 44A20, 33C10, 40A30, 74F10, 76Q05

5. CMB 2004 (vol 47 pp. 30)

He, Xinyu
Existence of Leray's Self-Similar Solutions of the Navier-Stokes Equations In $\mathcal{D}\subset\mathbb{R}^3$
Leray's self-similar solution of the Navier-Stokes equations is defined by $$ u(x,t) = U(y)/\sqrt{2\sigma (t^*-t)}, $$ where $y = x/\sqrt{2\sigma (t^*-t)}$, $\sigma>0$. Consider the equation for $U(y)$ in a smooth bounded domain $\mathcal{D}$ of $\mathbb{R}^3$ with non-zero boundary condition: \begin{gather*} -\nu \bigtriangleup U + \sigma U +\sigma y \cdot \nabla U + U\cdot \nabla U + \nabla P = 0,\quad y \in \mathcal{D}, \\ \nabla \cdot U = 0, \quad y \in \mathcal{D}, \\ U = \mathcal{G}(y), \quad y \in \partial \mathcal{D}. \end{gather*} We prove an existence theorem for the Dirichlet problem in Sobolev space $W^{1,2} (\mathcal{D})$. This implies the local existence of a self-similar solution of the Navier-Stokes equations which blows up at $t=t^*$ with $t^* < +\infty$, provided the function $\mathcal{G}(y)$ is permissible.

Categories:76D05, 76B03

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