@misc{16869,
  author = {Kei Yamamoto and Kristian Valen-Sendstad},
  title = {Under-resolved DNS of turbulent flow in straight and helically coiled pipes},
  abstract = {Oasis is an open-source Navier-Stokes solver built on FEniCS entirely written in Python. There are other open-source Navier-Stokes solvers available, such as openFOAM, but it is written in low-level programming language C++. One of the advantages of using Oasis over openFOAM is the usage of high-level Python code that enables users to flexibly control the implementation of problems. In addition, Oasis utilizes MPI to ensure high-performance and scalability on parallel clusters. Oasis has been previously verified and validated, but verification and validation is a continuous process that can establish the reliability of the solver when applied to new problems.  Here, we present two turbulent flow problems that can illustrate flexible implementation of Oasis with fast and accurate performance. First, direct numerical simulation (DNS) of turbulent flow in a straight pipe was carried out for numerical validation, and the results were compared against published DNS data-set. Second, we examined turbulent flow in helically coiled pipes using fully developed turbulent flow from straight pipes as an inlet velocity profile. In the straight pipe, our quantitative results showed convergence towards the DNS reference data, as the mesh was refined. In the helically coiled pipe, reported for the first time for a numerical model, stabilization of the turbulent flow was observed towards the outlet. Due to the curved path and the centrifugal force, two counter-rotating vortices referred to as Dean vortices were formed on the cross-section of the pipe. These vortices rapidly intensified the dissipation by creating smaller eddies in the flow and hence contributing to stabilizing the flow.},
  year = {2022},
  journal = {FEniCS 2022, San Diego, USA},
  publisher = {FEniCS2022},
  url = {https://fenicsproject.org/fenics-2022/},
}