The oscillatory longwave Marangoni convection in a thin film heated from below

A novel type of Marangoni convection was predicted theoretically a decade ago. The thin liquid film atop a substrate of low thermal conductivity was considered. In the case of heating from below, the Marangoni convection emerges not only in a conventional stationary regime, but also as oscillatory flows. Specifically, the oscillatory Marangoni convection emerges if (1) the heat flux from the free surface is small, and (2) the large-scale deformation of the free surface is allowed. During the past decade, this novel Marangoni convection was detected and investigated in several other theoretical works. The review discusses the recent achievements in studying the oscillatory Marangoni convection in a thin film heated from below. The guiding data for observation of the oscillatory regime are also provided.

Numerical Simulations of Flows Around Subsea Cover

Glass reinforced plastic (GRP) subsea protection covers are often used to protect offshore pipelines, umbilicals and other important subsea structures from dropped objects released from offshore oil and gas and fishing activities. These covers are often subjected to waves. In the present study, flows around an oscillating GRP subsea cover and oscillatory flows around a stationary subsea cover are investigated using numerical simulations at three different KC numbers of 5, 11 and 20, which are representative for low, medium and large KC number regions. The simulations of flows around an oscillating subsea cover are used to compare with the experiments done by SINTEF Ocean (formerly MARINTEK) and validate the present numerical model. Two-dimensional (2D) simulations are carried out by solving the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations combined with the k-ω Shear Stress Transport (SST) turbulence model. It is found that the hydrodynamic forces for the two cases (flows around the oscillating cover and oscillatory flows around the stationary cover) are almost the same, which verifies that the experimental tests of subsea covers with forced motions can be used to study hydrodynamic forces on the stationary cover subjected to waves. The horizontal and vertical force coefficients and the surrounding flow fields around the covers are discussed.