Marine Scour At Large Foundations

This paper presents the results from a study into the scour development around a monopile and three different large (20m diameter) marine foundations in currents and waves. The relevant hydraulic processes are discussed and the results from a mobile bed physical model investigating the scour process presented

Assessment of Scour Development at a Deep-Water Marine Jetty Using 3d Computational Fluid Dynamics

To assess the interaction of the tidal flow with a deep-water marine jetty, Computational Fluid Dynamics (CFD) was used to predict flow patterns for fast flood and ebb tide conditions both without and with the jetty in place. The modelled area covered three square kilometres of coastal bathymetry around the jetty head, with pile diameters of the order of one metre and water depths ranging from 3 m to 45 m. The predicted changes in velocity and bed shear stress distribution were used to explain the observed local bed level changes at this site over a period of three years

Evaluation of seabed stability and scour control around subsea gravity protection structures

Results from an advanced 3-dimensional Computational Fluid Dynamics (CFD) model have proven to form an effective basis on which to design stable and scour resistant subsea structures in areas of seabed which are prone to scouring. A case study application from the UK sector of the southern North Sea is presented to demonstrate the benefits of the CFD analysis.</jats:p

Laboratory Tests of Scour at a Seawall

A set of medium-scale laboratory tests of wave-induced scour at seawalls has been performed in a flume at HR Wallingford. The methodology is presented along with test conditions and summarized results. The scour depth at the toe of the seawall is highly dependent on the form of wave breaking onto the structure. Sea states where waves plunge directly onto the wall generate jets of water that may penetrate to the seabed and cause a local scour hole immediately adjacent to the seawall. This is a different scouring mechanism to that observed in deeper water and is also absent when the seawall is well within the surf zone and most of the large waves have broken before they reach the seawall. Theoretical limitations are discussed

Influence of blade aerodynamic model on the prediction of helicopter high-frequency airloads

Brown’s vorticity transport model has been used to investigate the influence of the blade aerodynamic model on the accuracy with which the high-frequency airloads associated with helicopter blade–vortex interactions can be predicted. The model yields an accurate representation of the wake structure yet allows significant flexibility in the way that the blade loading can be represented. A simple lifting-line model and a somewhat more sophisticated liftingchord model, based on unsteady thin aerofoil theory, are compared. A marked improvement in the accuracy of the predicted high-frequency airloads of the higher harmonic control aeroacoustic rotor is obtained when the liftingchord model is used instead of the lifting-line approach, and the quality of the prediction is affected less by the computational resolution of the wake. The lifting-line model overpredicts the amplitude of the lift response to blade–vortex interactions as the computational grid is refined, exposing the fundamental deficiencies in this approach when modeling the aerodynamic response of the blade to interactions with vortices that are much smaller than its chord. The airloads that are predicted using the lifting-chord model are relatively insensitive to the resolution of the computation, and there are fundamental reasons to believe that properly converged numerical solutions may be attainable using this approach