The numerical solution of a non-linear boundary integral equation on smooth surfaces

We study a boundary integral equation method for solving Laplace'sequation u=0 with non-linear boundary conditions. This non-linearboundary value problem is reformulated as a non-linear boundaryintegral equation, with u on the boundary as the solution beingsought. The integral equation is solved numerically by usingthe collocation method, with piecewise quadratic functions usedas approximations to u. Convergence results are given for thecases where (1) the original surface is used, and (2) the surfaceis approximated by piecewise quadratic interpolation. In addition,we define and analyze a two-grid iteration method for solvingthe non-linear system that arises from the discretization ofthe boundary integral equation. Numerical examples are given;and the paper concludes with a short discussion of the relativecost of different parts of the method. This work was supported in part by NSF grant DMS-9003287.     

Green's function for Laplace's equation in a circular ring with radiation type boundary conditions

Zusammenfassung Es wird die Greensche Funktion der Laplaceschen Gleichung für einen Kreisring hergeleitet, wobei Randbedingungen vom Strahlungstyp angenommen sind. In demjenigen Spezialfall, in dem die Randbedingungen das Verschwinden der Greenschen Funktion verlangen, wird gezeigt, dass die gefundene Darstellung der Greenschen Funktion übereinstimmt mit der Formel, wie sie im Buch vonHilbert-Courant unter Verwendung von Thetafunktionen hergeleitet ist.     

Diffusive logistic equation with non-linear boundary conditions

We analyze the solutions of a population model with diffusion and logistic growth. In particular, we focus our study on a population living in a patch, Ω⊆Rn with n?1, that satisfies a certain non-linear boundary condition and on its survival when constant yield harvesting is introduced. We establish our existence results by the method of sub-super solutions.     

On the laplace equation with non-linear dynamical boundary conditions

The main part of the paper deals with local existence and globalexistence versus blow-up for solutions of the Laplace equationin bounded domains with a non-linear dynamical boundary condition.More precisely, we study the problem consisting in: (1) theLaplace equation in (0, ) x ; (2) a homogeneous Dirichlet condition(0, ) x ₀; (3) the dynamical boundary condition ; (4) the initial condition u(0, x) = u₀ (x) on . Here is a regular and bounded domain in Rⁿ, with n 1, and₀ and ₁ endow a measurable partition of . Moreover, m>1,2 p < r, where r = 2 (n – 1) / (n – 2) whenn 3, r = when n = 1,2, and u₀ H^1/2 , u₀ = 0 on ₀. The final part of the paper deals with a refinement of a globalnon-existence result by Levine, Park and Serrin, which is appliedto the previous problem. 2000 Mathematics Subject Classification35K55 (primary), 35K90, 35K77 (secondary).     

The heat equation with stochastic non-linear boundary conditions

In this paper we examine the problem of the heat equation with non-linear boundary conditions of stochastic type.     

A fast numerical method for a natural boundary integral equation for the Helmholtz equation

A Neumann boundary value problem of the Helmholtz equation in the exterior circular domain is reduced into an equivalent natural boundary integral equation. Using our trigonometric wavelets and the Galerkin method, the obtained stiffness matrix is symmetrical and circulant, which lead us to a fast numerical method based on fast Fourier transform. Furthermore, we do not need to compute the entries of the stiffness matrix. Especially, our method is also efficient when the wave number k in the Helmholtz equation is very large.     

A boundary function equation and its numerical solution

We consider the asymptotic solution of the plasma-sheath integro-differential equation, which is singularly perturbed due to the presence of a small coefficient multiplying the highest order (second) derivative. The asymptotic solution is obtained by the boundary function method. A second-order differential equation is derived describing the behavior of the zeroth-order boundary functions. A numerical algorithm for this equation is discussed. __________ Translated from Prikladnaya Matematika i Informatika, No. 24, pp. 24–34, 2006.     

A meshfree method for the numerical solution of the RLW equation

In this paper, we present a meshfree technique for the numerical solution of the regularized long wave (RLW) equation. This approach is based on a global collocation method using the radial basis functions (RBFs). Different kinds of RBFs are used for this purpose. Accuracy of the new method is tested in terms of _L2$L_2$ and _L∞$L_{\infty }$ error norms. In case of non-availability of the exact solution, performance of the new method is compared with existing methods. Stability analysis of the method is established. Propagation of single and double solitary waves, wave undulation, and conservation properties of mass, energy and momentum of the RLW equation are discussed.     

The equimaterial approach for the numerical solution of the one dimensional transient diffusion equation with zero flux boundary conditions

A new approach is proposed for the grid motion for the numerical solution of a general transient diffusion equation in one spatial dimension with zero flux boundary conditions. The new criterion for grid motion is that the solute amount contained in each discretization section should be a pre-described fraction of the total solute amount at each time step. This requirement is not explicitly enforced to the solution technique but it is implicitly included in the equation through the appropriate variable transformation. The results showed that although the technique leads to the required grid motion the numerical results are of pure quality due to the appearance of singularities during the variable transformation procedure. Nevertheless, it is shown that by appropriate numerical handling of the solution at the singularity region the technique can lead to accurate results and potentially can replace the existing moving grid algorithms at least for the particular problem at hand.     

Recovering unknown terms in a nonlinear boundary condition for Laplace's equation

^** Email: gabriele{at}fi.iac.cnr.it We consider a thin metallic plate whose top side is inaccessibleand in contact with a corroding fluid. Heat exchange betweenmetal and fluid follows linear Newton's cooling law as longas the inaccessible side is not damaged. We assume that theeffects of corrosion are modelled by means of a nonlinear perturbationin the exchange law. On the other hand, we are able to heatthe conductor and take temperature maps of the accessible side.Our goal is to recover the nonlinear perturbation of the exchangelaw on the top side from thermal data collected on the oppositeone (thermal imaging). In this paper, we use a stationary model,i.e. the temperature inside the plate is assumed to fulfil Laplace'sequation. Hence, our problem is stated as an inverse ill-posedproblem for Laplace's equation with nonlinear boundary conditions.We study identifiability and local Lipschitz stability. In particular,we prove that the nonlinear term is identified by one Cauchydata set. Moreover, we produce approximated solutions by meansof an optimizational method.     

A numerical verification method for a periodic solution of a delay differential equation

We describe a numerical method with guaranteed accuracy to enclose a periodic solution for a system of delay differential equations. Using a certain system of equations corresponding to the original system, we derive sufficient conditions for the existence of the solution, the satisfaction of which can be verified computationally. We describe the verification procedure in detail and give a numerical example.     

Analysis and numerical solution of Benjamin-Bona-Mahony equation with moving boundary

In this work we present the existence, the uniqueness and numerical solutions for a mathematical model associated with equations of Benjamin-Bona-Mahony type in a domain with moving boundary. We apply the Galerkin method, multiplier techniques, energy estimates and compactness results to obtain the existence and uniqueness. For numerical solutions, we shall employ the finite element method together with the Crank-Nicolson method. Some numerical experiments are presented to show the moving boundary for the problem.     

Spectral method for Zakharov equation with periodic boundary conditions

This paper describes the spectral method for numerically solving Zakharov equation with periodic boundary conditions. This method is spectral method for spatial variable and difference method for time variable. We make error estimation of approximate solution and prove the convergence of spectral method. We had given the convergence rate. Also, we prove the stability of approximate method for initial values.Project supported by the Science Foundation of the Chinese Academy of Sciences.     

A fast numerical method for harmonic equation based on natural boundary integral

Based on the coupling of the natural boundary integral method and the finite elements method, we mainly investigate the numerical solution of Neumann problem of harmonic equation in an exterior elliptic. Using our trigonometric wavelets and Galerkin method, there obtained stiffness matrix is symmetrical and circulant, which lead us to a fast numerical method based on fast Fourier transform. Furthermore, we do not need to compute the entries of the stiffness matrix. On the other hand, we prove that the numerical solution possesses exponential convergence rate. Especially, examples state that our method still has good accuracy for small j when the solution u ₀(θ) is almost singular.     

On the numerical solution of a boundary integral equation for the exterior Neumann problem on domains with corners

The authors propose a “modified” Nyström method to approximate the solution of a boundary integral equation connected with the exterior Neumann problem for Laplace's equation on planar domains with corners. They prove the convergence and the stability of the method and show some numerical tests.     

Uniform decay of the solution to a wave equation with memory conditions on the boundary

A wave equation with variable coefficients in principal part and memory conditions on the boundary is considered. The Riemannian geometry method is applied to prove the exponential decay of the energy provided the relaxation function also decays exponentially.