Radiation of waves by a thin cap submerged in ice-covered ocean

Summary The present article is concerned with the radiation of flexural gravity waves due to a thin cap submerged in the ice-covered ocean. The problem is reduced to a system of hypersingular integral equations using the boundary perturbation method. The first-order approximation has only been considered. The effects of the rigidity of the ice sheet and depth of submergence on the added mass and damping coefficient have been analysed. Two types of caps (for example, concave upwards and concave downwards) have been considered for the numerical results. The effect of the concavity on added mass and damping coefficient has also been studied. The present study should be helpful to understand the nature of waves generated by a heaving submerged body in an ice-covered ocean.

Reductional Method in Perturbation Theory of Generalized Spectral E. Schmidt Problem

In this a paper perturbations of multiple eigenvalues of E. Schmidt spectral problems is considered. At the usage of the reductional method suggested in the articles [10, 11] the investigation of the multiple E. Schmidt perturbation eigenvalues is reduced to the investigation of perturbation of simple ones. At the end, as application of the obtained results the problem about the boundary perturbation for the system of two Sturm-Liouville problems with E. Schmidt spectral parameter is considered.

On the approximation error in the problems of conjugate convective heat transfer

Рассмотрено влияние малых возмущений границы области на погрешность аппроксимации модельной краевой задачи. Показано, что игнорирование малых возмущений границы приводит к дополнительной погрешности аппроксимации исходной дифференциальной задачи, не связанной с шагом сетки. Полученные результаты представляют интерес для математического моделирования сопряженного теплообмена, моделирования течений с поверхностными химическими реакциями и других приложений, связанных с течениями рабочих сред вблизи шероховатых поверхностей. The effects of small boundary perturbation on the approximation error for a model boundary value problem are considered. It is shown that the ignorance of small perturbations of the boundary leads to an additional approximation error in the original differential problem. This error is independent of mesh size. The obtained results are of interest for the mathematical modeling of conjugate heat transfer, the modeling of flows with surface chemical reactions and other applications related to fluid flows near rough surfaces.

A non-perturbative method for gravitational potential calculations within heterogeneous and aspherical planets

SUMMARY We present a numerically exact method for calculating the internal and external gravitational potential of aspherical and heterogeneous planets. Our approach is based on the transformation of Poisson’s equation into an equivalent equation posed on a spherical computational domain. This new problem is solved in an efficient iterative manner based on a hybrid pseudospectral/spectral element discretization. The main advantage of our method is that its computational cost reflects the planet’s geometric and structural complexity, being in many situations only marginally more expensive than boundary perturbation theory. Several numerical examples are presented to illustrate the method’s efficacy and potential range of applications.

Optimal Form for Compliance of Membrane Boundary Shift in Nonlinear Case

In this work, we search the existence shifting compliance optimal form of some boundary membrane, which is not elastic and not isotropic, generating nonlinear PDE. An optimal form of the elastic membrane described by the p-Laplacian is investigated. The boundary perturbation method due to Hadamard is applied in Sobolev spaces.