CFD simulations of flow around the tandem cylinders close to the seabed

Abstract

CFD is a useful tool for understanding continuum mechanics and analyzing flows, both disturbed and undisturbed. When we analyze flow around cylinders with CFD, we can get numerical results. We have the opportunity to see how the flow actually will distribute around cylinders. Pressure and Velocity can be obtained and measured in all points of the simulation field and the valid forces imposed on the cylinder can be obtained too. Computational Fluid Dynamics is cheaper and accessible to get results than doing experiments CFD simulation is also cheaper than making tests, and at present, CFD can substitute or enhance many experiments. On streamlined over sea or river underwater pipeline affect the horizontal force of viscous resistance, which is proportional to the square of the flow rate. Of course, this configuration and analysis of a cylinder with a subsequent analysis of the two, taken with an ulterior motive. Most probably a good example of a joint international project "North Stream" and "Nord Stream-2". The first project is a branch of gas pipeline laid on the bottom of the Baltic Sea. The second, in turn, will be the second branch of the main gas pipeline, which will run in tandem with the first. In other words, the relevance of this issue is in demand, especially when it comes to a marine pipeline, with energy consumption increasing, and therefore requires payment and the amount of product are being pumped. Just offshore field development infrastructure is not in place and is developing dynamically. Due to the daily production of gas, there is growing demand for the expansion of the oil and gas transportation. Subsea pipelines, get the constant influence of regular and irregular waves due to the influence of underwater currents in certain areas. Depending on the nature of the flow, it can influence the vortex formation, which can erode the soil directly beneath the pipe and because of this certain parts of the pipeline can be formed free-spans. They can occur during the vortex formation and as a consequence of vortex induced vibrations. To prevent such situations and the effects of the design of pipelines, it is necessary to simulate the flow around the planned pipeline. In this paper, calculated the flow impact on a subsea pipeline, which is associated with the formation of internal waves in a stratified flow based on the results of simulation models, which made in OpenFOAM software. The present study has been done for both the single cylinder and the tandem cylinder arrangements scenarios. All simulation model is evaluated for a steady flow with the parameters such as Reynolds number Re = 3.6x106, a roughness of the plane bottom and cylinder`s surface zw = 1x10-6 and boundary layer thickness δ/D = 0.5. The pre-processing software as GMESH was used to perform all grids for the CFD simulation model. Also, a size of the computational domains arrangements of the single case cylinder and the tandem cylinders case has been accomplished in this software. Teckplot360 was chosen in the post-processing step to get visualization for all cases, and to plot graphs, two programs were used such as Wolfram Matematica 10.0 and Matlab. By using the supercomputers Gorina1 and Gorina 2 at UIS, It is possible to get a model of the flow around the tandem cylinder, which would be impossible with a personal computer.