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When simulating fluid-structure interaction (FSI), it is often essential that the no-slip condition is accurately enforced at the wetted boundary of the structure. This paper aims to evaluate the relative strengths and limitations of the penalty and Lagrange multiplier methods, within the context of modelling FSI, through a comparative analysis.

In the immersed boundary method, the no-slip condition is typically imposed by augmenting the governing equations of the fluid with an artificial body force. The relative accuracy and computational time of the penalty and Lagrange multiplier formulations of this body force are evaluated by using each to solve three test problems, namely, flow through a channel, the harmonic motion of a cylinder through a stationary fluid and the vortex-induced vibration (VIV) of a cylinder.

The Lagrange multiplier formulation provided an accurate solution, especially when enforcing the no-slip condition, and was robust as it did not require “tuning” of problem specific parameters. However, these benefits came at a higher computational cost relative to the penalty formulation. The penalty formulation achieved similar levels of accuracy to the Lagrange multiplier formulation, but only if the appropriate penalty factor was selected, which was difficult to determine a priori.

Both the Lagrange multiplier and penalty formulations of the immersed boundary method are prominent in the literature. A systematic quantitative comparison of these two methods is presented within the same computational environment. A novel application of the Lagrange multiplier method to the modelling of VIV is also provided.

Maintenance planning is a complicated decision-making process that involves the major stakeholders and the main life-cycle phases of an engineering system. The purpose of this paper is to propose an availability-centred maintenance planning approach for offshore wind farms, with special focus on the early system design phase.

The proposed approach is based on a stepwise procedure that integrates logistics consideration into reliability-centred maintenance. For each step, the essential methods for systematic analysis and documentation are introduced.

Practical information from current offshore wind farms and lessons learned from relevant industries are included to exemplify and justify the implementation of the proposed approach. In a general way, the approach shows that valuable input can be provided to decision making about maintainability and maintenance planning. Furthermore, the approach facilitates the initial maintenance plan to be adjusted and improved upon as additional operating experience becomes available.

Offshore wind energy is still an industry in its infancy with an attendant high degree of confidentiality. There is scarcely any detailed practical information available for the production of a case study on this topic. However, the current paper’s theoretical basis may be applied to identify current and future knowledge gaps, for the development of more detailed guidelines as established in the further research.

Maintenance planning of offshore wind farms is an area of current interest, although often the focus is on achieving cost reductions and not on the formal development of such a systematic approach as conceived in this paper.

Since the mid‐1980s the major players in US health care have argued that costs and benefits should underlie the allocation of health care resources. Looks at 30 cost benefit studies taken from the medical literature and examines five of them in depth, using the “depth hermeneutical” approach advocated by Thompson (1990). Concludes that cost benefit studies are about not only the co‐ordination of interests but also the obscuring and exclusion of other interests.