Resolving combined wave-current fields from measurements using interior point optimization

• Published in: Coastal engineering (Amsterdam) 2019-07, Vol.149, p.4-14
• Main Authors: Draycott, S., Pillai, A.C., Ingram, D.M., Johanning, L.
• Format: Article
• Language: English
• Subjects: Interior-point optimization; Non-linear programming; Tank testing; Wave reflection analysis; Wave-current interactions
• ISSN: 0378-3839; 1872-7379
• DOI: 10.1016/j.coastaleng.2019.03.008

Complex wave and wave-current conditions exist in the natural world, and are increasingly emulated in advanced experimental facilities to de-risk the deployment, operation and maintenance of offshore structures and renewable energy devices. This can include combinations of ocean swell, multi-directional wind-driven seas, and reflected wave conditions interacting with a current field. It is vital to understand the full nature of these potentially hazardous conditions so they can be properly simulated in numerical models, to contextualize measurements made in field, and experimental programmes. Here, a numerical framework is presented for isolating both the wave systems and the mean current velocities from measured data using an interior point optimizer. A developed frequency domain solver is used to resolve, from experimentally obtained wave gauge measurements, two opposing wave systems on a collinear current, and used to effectively isolate the wave systems and predict the current velocity using only wave gauge measurements. Thirty five test cases are considered; consisting of five wave spectra interacting with seven different current velocities ranging from −0.3m s-10.3m s-1. Comparisons between the theoretical and derived wave numbers and current velocities show good agreement and the performance of the method is similar to that of existing methodologies while requiring no a priori knowledge of the current velocity impacting the wave field required. Although results are presented for the collinear problem, the presented method can be applied to a wide range of wave and current combinations, and provides a useful tool for increasing understanding of both ocean and experimental conditions. •Frequency domain solver developed for resolving combined wave-current fields.•Wave gauge measurements from a circular combined wave-current tank utilized.•Method enables the isolation of wave systems and prediction of current velocity.•Low errors observed in estimates of incident and reflected spectra and wavenumbers.•Applicability to a wide range of complex wave and wave-current fields.