eprintid: 10066586 rev_number: 19 eprint_status: archive userid: 608 dir: disk0/10/06/65/86 datestamp: 2019-02-04 12:30:01 lastmod: 2021-10-15 22:57:47 status_changed: 2019-02-04 12:30:01 type: article metadata_visibility: show creators_name: Chen, LF creators_name: Stagonas, D creators_name: Santo, H creators_name: Buldakov, EV creators_name: Simons, RR creators_name: Taylor, PH creators_name: Zang, J title: Numerical modelling of interactions of waves and sheared currents with a surface piercing vertical cylinder ispublished: pub divisions: UCL divisions: B04 divisions: C05 divisions: F44 keywords: Focussed wave groups, Sheared currents, Wave-on-current focussing methodology, Lagrangian wave-current flume, Harmonic reconstruction, OpenFOAM note: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. abstract: Vertical surface piercing cylinders, such as typical coastal wind turbine foundations and basic elements of many coastal structures, are often exposed to combined loading from waves and currents. Accurate prediction of hydrodynamic loads on a vertical cylinder in a combined wave-current flow is a challenging task. This work describes and compares two different approaches for numerical modelling of the interaction between focussed wave groups and a sheared current, and then their interactions with a vertical piercing cylinder. Both approaches employ an empirical methodology to generate a wave focussed at the location of the structure in the presence of sheared currents and use OpenFOAM, an open source Computational Fluid Dynamics (CFD) package. In the first approach, the empirical wave-on-current focussing methodology is applied directly in the OpenFOAM domain, replicating the physical wave-current flume. This approach is referred to as the Direct Method. In the second approach, a novel Lagrangian model is used to calculate the free surface elevation and flow kinematics, which are then used as boundary conditions for a smaller 3-D OpenFOAM domain with shorter simulation time. This approach is referred to as the Coupling Method. The capabilities of the two numerical methods have been validated by comparing with the experimental measurements collected in a wave-current flume at UCL. The performance of both approaches is evaluated in terms of accuracy and computational effort required. It is shown that both approaches provide satisfactory predictions in terms of local free surface elevation and nonlinear wave loading on the vertical cylinders with an acceptable level of computational cost. The Coupling Method is more efficient because of the use of a smaller computational domain and the application of the iterative wave-current generation in the faster Lagrangian model. Additionally, it is shown that a Stokes-type perturbation expansion can be generalized to approximate cylinder loads arising from wave groups on following and adverse sheared currents, allowing estimation of the higher-order harmonic shapes and time histories from knowledge of the linear components alone. date: 2019-03 date_type: published official_url: https://doi.org/10.1016/j.coastaleng.2019.01.001 oa_status: green full_text_type: other language: eng primo: open primo_central: open_green article_type_text: Article verified: verified_manual elements_id: 1622063 doi: 10.1016/j.coastaleng.2019.01.001 lyricists_name: Buldakov, Eugeny lyricists_name: Simons, Richard lyricists_id: EBULD04 lyricists_id: RRSIM33 actors_name: Buldakov, Eugeny actors_id: EBULD04 actors_role: owner full_text_status: public publication: Coastal Engineering volume: 145 pagerange: 65-83 issn: 0378-3839 citation: Chen, LF; Stagonas, D; Santo, H; Buldakov, EV; Simons, RR; Taylor, PH; Zang, J; (2019) Numerical modelling of interactions of waves and sheared currents with a surface piercing vertical cylinder. Coastal Engineering , 145 pp. 65-83. 10.1016/j.coastaleng.2019.01.001 <https://doi.org/10.1016/j.coastaleng.2019.01.001>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10066586/1/wave-sheared%20current_revision_final.pdf