Whispering gallery mode resonators (WGMR), as silica microspheres, have been recently proposed as an efficient tool for the realisation of optical biosensors. In this work we present a functionalization procedure based on the DNA-aptamer sequence immobilization on WGMR, able to recognize specifically thrombin or VEGF protein, preserving a high Q factor. The protein binding was optically characterized in terms of specificity in buffer solution or in 10% diluted human serum. Simulation of the protein flow was found in good agreement with experimental data. The aptasensor was also chemically regenerated and tested again, demonstrating the reusability of our system.

The adoption of lean-burn technology in modern aero-engines influences the already critical aerothermal conditions at turbine entry, where the absence of dilution holes preserves the swirl component generated by burners and prevents any control on pattern factor. The associated uncertainty and lack of confidence entail the application of wide safety margins in turbine cooling design, with a detrimental effect on engine efficiency. Computational fluid dynamics (CFD) can provide a deeper understanding of the physical phenomena involved in combustor–turbine interaction, especially with hybrid Reynolds-averaged Navier–Stokes (RANS) large eddy simulation (LES) models, such as scale adaptive simulation (SAS), which are proving to overcome the well-known limitations of the RANS approach and be a viable approach to capture the complex flow physics. This paper describes the numerical investigation on a test rig representative of a lean-burn, effusion cooled, annular combustor developed in the EU Project Full Aerothermal Combustor-Turbine interactiOns Research (FACTOR) with the aim of studying combustor–turbine interaction. Results obtained with RANS and SAS were critically compared to experimental data and analyzed to better understand the flow physics, as well as to assess the improvements related to the use of hybrid RANS-LES models. Significant discrepancies are highlighted for RANS in predicting the recirculating region, which has slight influence on the velocity field at the combustor outlet, but affects dramatically mixing and the resulting temperature distribution. The accuracy of the results achieved suggests the exploitation of SAS model with a view to the future inclusion of the nozzle guide vanes in the test rig.

A high-pressure vane (HPV) equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side, while the leading edge (LE) is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-averaged Navier–Stokes simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and HPVs are then investigated, considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first in which hot spot and swirl core are aligned with passage; and the second in which they are aligned with the LE. Comparisons between metal temperature distributions obtained from conjugate heat transfer (CHT) simulations are performed, evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The LE aligned configuration is determined to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage-aligned case. A strong sensitivity to both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.

Numerical techniques are commonly used during both design and analysis processes, mainly considering single components. Technological progress asks for advanced approaches that include real-machine conditions and analyze components interaction, especially considering the combustor/turbine coupling. Modern combustors operate with strong swirl motions in order to obtain an adequate flame stabilization, generating a very complex flow field characterized by high turbulence level. These aspects affect performance of downstream components which are subjected to very aggressive inlet flow conditions: non-uniform total temperature, non-uniform total pressure, swirl and high turbulence intensity. For these reasons coupled analysis of combustor and turbine is necessary to accurately predict aero-thermal aspects that influence performance and reliability of these two components. From a numerical point of view the simulation of a single domain characterized by a reactive flow with very different Mach number regimes (from low-Mach flow in combustion chamber to transonic flow in turbine) is problematic due to the different numerical requirements needed, especially concerning stability and accuracy. These problems could be overcome using coupled methods to simultaneously simulate combustor and turbine in separated domains which are managed by different solvers that communicate with each other. A coupling method for the study of combustor/turbine interaction using the RANS methodology is proposed. In the first part of the paper the method is described and validated. The second part is dedicated to the application of the proposed coupling methodology to a realistic test case consisting of a model annular combustor and the Nozzle Guide Vane (NGV) of the MT1 high-pressure turbine stage. A commercial solver and an in-house code are respectively used for the simulation of combustor and NGV. Results are presented and analyzed highlighting the importance of such type of simulations in understanding aero-thermal phenomena that characterize combustor/vane interaction.

Nanoprobe tips are key components in many applications such as scanning probe microscopes, nanoscale imaging, nanofabrication and sensing. This paper describes a dynamic chemical etching method for the fabrication of optical nanoprobes. The tips are produced by mechanically rotating and dipping a silica optical fibre in a chemical etching solution (aqueous hydrofluoric acid) covered with a protection layer. Using different dynamic regimes of the mechanical movements during the chemical etching process, it is possible to vary the cone angle, the shape, and the roughness of the nanoprobes. It is found that the tip profiles are determined by the nonlinear dynamic evolution of the meniscus of the etchant near the fibre. Computational fluid dynamic simulations have been performed, showing that different flow regimes correspond to different shear forces acting on the forming nanotip, in agreement with experimental results. With this method, a high yield of reproducible nanotips can be obtained, thus overcoming the drawbacks of conventional etching techniques. Typical tip features are short taper length (∼200 μm), large cone angle (up to 40°), and small probe tip dimension (less than 30 nm).