Balmoral HexDefence
Technical development

Preliminary work on Balmoral HexDefence was based on an existing VIV suppression product used widely by the oil and gas sector. Research considered a scaled variant to investigate scour evaluation on downstream flow and the effect of accelerated currents around a monopile . Final prototype testing was completed at a national hydrodynamic laboratory.

Tank testing for Balmoral HexDefence was conducted across a range of velocities, spanning from 0.15 m/s to 0.3 m/s, involving multiple iterations of orientation and geometry parameters. Furthermore, performance validation was carried out through the analysis of simulated marine growth. The subsequent results, categorised according to low to high current conditions, confirm and substantiate the accuracy of the Computational Fluid Dynamics (CFD) models. This validation showcases a significant 40% reduction in shear bed stress, coupled with a decrease in far-field stress originating from the monopile. This tangible reduction is directly observable in the dimensions of the pit, shrinking from +1D to 0.25D, and the scour pit depth, scaling down from 3.6 meters to 1.6 meters. This translates into a substantial 56% improvement in preventing scour pit formation.

Initial analysis

Current = 0.15m/s

Current = 0.3m/s,

Top: Bare monopile
Bottom: Balmoral HexDefence monopile

Development of HexDefence computation model

In the process of developing Balmoral HexDefence, it was imperative to establish a reliable Computational Fluid Dynamics (CFD) model capable of accurately representing the product and its influence on critical performance metrics, including shear bed stress. This capability allowed Balmoral to effectively assess and validate the performance of HexDefence in various real-world field configurations and monopile structures.

The images presented below depict snapshots of the flow field at different time points within a typical wave cycle. The crucial aspect to note here is the disruption of the flow, which effectively disrupts the formation of horseshoe vortices, thereby mitigating the overall shear bed stress. This disruption serves as a key feature of Balmoral HexDefence performance.

The comparison between the image of the plain cylinder (left) and Balmoral HexDefence (right) illustrates the contrasting flow behaviours. The plain cylinder exhibits a concentration of flow around its base, while HexDefence facilitates the dispersion and distribution of the flow. If this unchecked flow pattern persists, it plays a substantial role in the scouring of the seabed around the structure, ultimately resulting in the foreseeable erosion of the surrounding seabed over time. Therefore, by interrupting and altering this flow field, we can provide substantial protection for the seabed.

Balmoral's work has received validation and confirmation from a third-party geotechnical consultancy. The company conducted a comprehensive literature review to authenticate and endorse our findings and results. The utilisation of HexDefence has led to a remarkable reduction in the need for armour layer rocks, replacing them with a filter-grade solution. This transformation results in substantial cost savings during both installation and operation, and eliminates the requirement for additional rock dumping altogether.

Furthermore, in certain extreme operational environments where traditional rock dumping methods were previously considered unfeasible, the incorporation of HexDefence has now made these fields technically and financially viable. This expansion of opportunities for developers around the world is poised to have a significant impact on the industry

The above sequence shows CFD work conducted on jacket foundations, simulating wave and current flows to evaluate shear bed stress and turbulent kinetic energy.

Component design

  • Material selection is based upon field configuration or installation method, where the use of GRP or concrete is preferred.
  • Panel sized to suit monopile or jacket foundation diameters
  • Interlocking geometry for ease of installation
  • Externally profiled flanging to aid rigidity and component connection
  • Integrated lifting and access points
  • Antifouling coatings optional
Typical HexDefence monopile length
Typical HexDefence jacket surround
Get in touch with us today to learn more about Balmoral HexDefence and how it can improve your offshore wind farm's installation, management, and maintenance.

Balmoral Comtec Ltd
Balmoral Park, Loirston, Aberdeen AB12 3GY | +44 (0)1224 859000 |
Registered number SC301819