A key consideration in high pressure (HP) turbine designs is the heat load experienced by rotor blades. Impact of turbine inlet nonuniformity of combined temperature and velocity traverses, typical for a lean-burn combustor exit, has rarely been studied. For general turbine aerothermal designs, it is also of interest to understand how the behavior of lean-burn combustor traverses (with both hot-streak and swirl) might contrast with those for a rich-burn combustor (largely hot-streak only). In the present work, a computational study has been carried out on the aerothermal performance of a HP turbine stage under nonuniform temperature and velocity inlet profiles. The analyses are primarily conducted for two combined hot-streak and swirl inlets, with opposite swirl directions. In addition, comparisons are made against a hot-streak only case and a uniform inlet. The effects of three nozzle guide vane (NGV) shape configurations are investigated: straight, compound lean (CL) and reverse CL (RCL). The present results reveal a qualitative change in the roles played by heat transfer coefficient (HTC) and fluid driving (“adiabatic wall”) temperature, Taw. It has been shown that the blade heat load for a uniform inlet is dominated by HTC, whilst a hot-streak only case is largely influenced by Taw. However, in contrast to the hot-streak only case, a combined hot-streak and swirl case shows a role reversal with the HTC being a dominant factor. Additionally, it is seen that the swirling flow redistributes radially the hot fluid within the NGV passage considerably, leading to a much ‘flatter’ rotor inlet temperature profile compared to its hot-streak only counterpart. Furthermore, the rotor heat transfer characteristics for the combined traverses are shown to be strongly dependent on the NGV shaping and the inlet swirl direction, indicating a potential for further design space exploration. The present findings underline the need to clearly define relevant combustor exit temperature and velocity profiles when designing and optimizing NGVs for HP turbine aerothermal performance.

Leachate is a hazardous liquid that poses negative impacts if leaks out into environments such as soil and ground water systems. The impact of leachate on the downgraded quality in terms of chemical characteristic is more concern rather than the physical or mechanical aspect. The effect of leachate on mechanical behaviour of contaminated soil is not well established and should be investigated. This paper presents the preliminary results of the effects of leachate on the Atterberg limit, compaction and shear strength of leachate-contaminated soil. The contaminated soil samples were prepared by mixing the leachate at ratiosbetween 0% and 20% leachate contents with soil samples. Base soil used was residual soil originated from granitic rock and classified as sandy clay soil (CS). Its specific gravity ranged between 2.5 and 2.64 with clay minerals of kaolinite, muscovite and quartz. The field strength of the studied soil ranged between 156 and 207 kN/m 2 . The effects of leachate on the Atterberg limit clearly indicated by the decrease in liquid and plastic limit values with the increase in the leachate content. Compaction tests on leachate-contaminated soil caused the dropped in maximum dry density, dry and increased in optimum moisture content, w opt when the amount of leachate was increased between 0% and 20%. The results suggested that leachate contamination capable to modify some geotechnical properties of the studied residual soils.

The paper discusses expressions such as "characteristic value", "best estimate", "upper bound" and "lower bound" used to describe a design soil profile in practice through the reanalysis of case studies. Characteristic (design) values of undrained shear strength were compared with the results of unbiased statistical analyses. It would seem that when one relies on laboratory test results to establish the characteristic (design) strength, the experienced engineers tend to lie much lower than the average, perhaps one standard deviation below the mean. On the other hand, when one relies on the results of in situ piezocone tests, the characteristic strength can be much closer to the mean of the interpreted measurements in situ. The authors suggest that the profession adopts a univocal definition for the term "Best Estimate" and for parameter variability. This suggestion is proposed as a subject for debate in the coming months so that agreement can be established for use in practice. The authors also suggest that the geotechnical profession should use more extensively than before statistical analysis when establishing design values, look beyond using exclusively statistical analyses and start addressing the variability and uncertainty in soil parameters explicitly by implementing probability theory and reliability analyses. Introduction A detailed geohazards assessment at an offshore site often involves the assessment of the stability of submarine slopes under static and dynamic (ocean wave and seismic) loading. Even the simplest geotechnical calculation models for slope stability and seismic response require mechanical soil properties. These can never be established with complete certainty. Soils are naturally variable because of the way they are formed and the continuous processes of the environment that alter them. The uncertainty in the mechanical properties of offshore soils is due to both the natural variability from point to point within a soil volume, and imperfect interpretation models, measurement errors and other sources. The selection of soil properties for use in geotechnical assessment is often based on subjective judgment and accumulated experience. The uncertainties in the soil properties are only indirectly accounted for when the characteristic (design) value(s) are chosen. Statistics and probability are useful tools for the quantification of the mean (most probable, expected) value and the possible range of values of a parameter. Statistical and probabilistic methods can quantify the uncertainties and make it possible to account for them in a rational and consistent manner. They are however rarely used in practice to establish the design soil parameters. The reason for this is unclear, but perhaps it has become a habit that no one questions, or the restricted use of statistical methods may be a reflection that often there are not enough data available to actually implement statistical methods with confidence. DNV (2006) prepared a guidance note on the statistical representation of soil data. The tools are explained in detail. The profession now needs to make a recommendation of which values to use in design. In this paper, examples of design soil parameters recommended by NGI for offshore sites over the past two decades were reevaluated using statistical methods, and comparisons of characteristic value with best estimates and variance are made.

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e., the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under nonuniform temperature conditions (commonly referred to as a “hot-streak”) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the nozzle guide vane (NGV) blades are shaped. In the present work, a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier–Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analyzed. After confirming the typical NGV loading and aeroloss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. While the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favorable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed. The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e. the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under non-uniform temperature conditions (commonly referred to as a ‘hot-streak’) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the NGV blades are shaped. In the present work a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier-Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analysed. After confirming the typical NGV loading and aero-loss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. Whilst the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favourable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed. The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.

The Geotechnics Sub-Committee of the American Society of Civil Engineers (ASCE) Coasts, Oceans, Ports, and Rivers Institute (COPRI) Marine Renewable Energy (MRE) Committee is preparing a guide document for marine renewable energy foundations. That guide would use standard design codes for fixed foundations and mooring anchors in API RP 2GEO and DNV.The static method of computing axial pile capacity described in API RP 2GEO (2011) is generally used to compute ultimate compressive and tensile capacities of pipe piles driven to a given penetration. Lateral soil resistance -pile deflection (p-y) data for clays and sands are usually developed using procedures proposed by Matlock (1970) andMurchison (1983), respectively, and outlined in API RP 2GEO (2011). Marine energy foundations are unique in several ways. Axial pile capacity computations are usually based on a reasonable lower bound, in contrast to the soil resistance to driving, which is based on a reasonable upper bound. For structures supporting wind turbines, however, underestimating (or overestimating) the soil stiffness could require a change in turbine operation and a loss of power production. Although the classical API method is recognized as an appropriately conservative design method for offshore pile foundations, a prediction method is more well suited for structures supporting wind turbines, such as the CPT-based methods for predicting pile capacity in granular soils presented in API RP 2GEO (2011). If a prediction method is used to compute the soil resistance to driving, the evaluation of pile drivability may be overly conservative. Ageing in both clay and sand should also be taken into account. Wind turbines are often supported on large diameter monopiles. The applicability of the p-y data for such large diameter piles needs to be verified. Finally, marine renewable energy generated by in-stream hydrokinetics, ocean thermal energy conversion, and wave energy converters may be floating devices usually anchored to the seafloor. There are uncertainties in the design and installation of these anchors, which become critical for large sustained tensile loads that may degrade due to creep and cyclic loading.

Structural Health Monitoring (SHM) of wind turbines can be used for verification and investigation of uncertainties in design, as well as provide input for possible future design optimization. It may also provide early warning of degradation. This allows for condition-based maintenance and status evaluation for possible lifetime extension or changed operational conditions (for example turbine modifications). SHM monitoring applications include environmental loads, corrosion, natural frequencies and damping characteristics of foundations, stress concentrations, deformation, fatigue cycles, foundation scour, seabed stiffness, pore pressure and settlement. Benefits of SHM are described with examples of case studies where monitoring made an important contribution to design improvements. Advantages of integrated monitoring solutions are outlined where an intelligent combination of sensors can provide information of linked parameters and overall assessment of the structural health Recommendations and examples of monitoring systems are described. These cover different foundation types with emphasis on the most significant monitoring aspects for the design of each foundation type. This paper and the detailed report to BSEE provide useful guidelines on structural health monitoring of offshore wind turbine foundations where relevant industry standards presently are missing.

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