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International audience; The application of riblets on a typical regional turboprop configuration is discussed in this paper. The effect of the riblets is modeled as a singular roughness problem by a proper boundary condition at the wall. The model, already proposed in a previous paper, is briefly described. The drag prediction capabilities are verified by showing some airfoil flow applications. Then a typical wing-body of a regional aircraft is considered. The configuration has been designed to have extended natural laminar flow in cruise conditions. Riblets are applied at flow specifications representative of cruise in combination with the natural laminar flow technology and in climb/descent conditions. A comparison of the two technologies in terms of drag reduction is presented. Their combined application can result in a cruise drag reduction of more than 20%. The resulting fuel savings during a typical operational day are evaluated.

A numerical methodology for the prediction of aerodynamics of VAWT is proposed, coupling the Beddoes-Leishman (BL) model for the airfoil’s unsteady aerodynamic coefficients prediction with the Paraschivoiu Double Streamtube (DS) aerodynamic model for VAWT. The model couples the rotational dynamics of the wind turbine modeled by DS with the aerodynamic coefficients degradation due to the local flow unsteadiness on the blade modeled by BL. The results achieved were compared with a set of experimental data available in literature and with CFD simulation, showing the importance of the non-stationary BL model for the blade’s aerodynamic coefficients prediction. Furthermore the coupled DSBL model is able to provide key information about the non-stationary aerodynamic conditions experienced on the blade for design and optimization purposes.

An assessment of the impact of cruise ship emissions while hotelling in the port of Naples has been studied by means of wind tunnel and computational fluid dynamics (CFD) models. An area of about 1.2 km2 was reproduced at a scale of 1:500 for the wind tunnel experiments. The worst but most emission scenario with three cruise ships emitting at the same time was studied. Wind blows from the south-east with a speed of 3 m/s at funnel height in neutral stability conditions of the atmospheric boundary layer. Two different values of the velocity ratio UR = 1 and UR = 4 (funnel gas velocity/wind speed) were considered. In the experiments, Ethane was used as the tracer gas and the concentration was measured at 35 receptor points inside the urban structure and at different heights. Experimental data show good agreement with those estimated by numerically solving steady Reynolds-Averaged Navier-Stokes (RANS) with the k-ω shear-stress transport (SST) turbulence model. The results were used to analyse the accuracy of the predictions of the model CALifornia Puff (CALPUFF), testing two model options: the building downwash module and the parameterisation of the dispersion coefficients. The CALPUFF results are less accurate than the CFD simulations and show a general tendency to underestimate the experimental data. The optimization process improves the performance of CALPUFF. Finally, a more comprehensive analysis of the effect of a varying UR in the range 0.25–16 was undertaken using numerical models. The research provides useful insights to improve the assessment of the impact of ship emissions in port cities.

The breakdown of the aerodynamic force is an important topic for the aerodynamic designer. The information provided by straightforward surface stress integration near field method are not sufficient, therefore, the interest in the development of far field methods arised. In this article a review of the activities carried out at the University of Naples is provided, in particular showing the potentiality and the limitations of two classes of algorithms: the thermodynamic and the vortex-force methods. Some applications and comparisons on a non-conventional wing configuration (box wing) and on an advanced turbo-prop wing-body configuration are presented.

The characterization and reproduction of tyre behaviour for vehicle modelling is a topic of particular interest both for real-time driver in the loop simulations and for offline performance optimization algorithms. Since the accuracy of the tyre forces and moments can be achieved by the accurate physical modelling of all the phenomena concerning the tyre-road interaction, the link between the tyre thermal state and the tyre frictional performance turns into a crucial factor. An integrated numerical methodology, allowing to couple the full 3D CFD (Computational Fluid Dynamics) flux within the internal chamber of the tyre with an equivalent discrete 3D structure model, is proposed with the aim to completely represent the tyre thermodynamic convective behaviour in the steady-state operating conditions. 3D CFD model enables the evaluation of the internal distribution of the gas temperature and of the thermal powers exchanged at each sub-wall in detail. This allows to increase the reliability of the tyre thermodynamic modelling with a particular reference to the proper managing of the aero-thermal flow of the brake disc impact on the rim temperature and therefore on the internal gas dynamics in terms of temperature and pressure, being able to optimize the tyre overall dynamic performance in both warm-up and stabilized thermal conditions. The steady RANS (Reynolds Averaged Navier–Stokes) simulations have been performed employing the 3D CFD model in a wide range of angular velocities with the aim to calculate the convective thermal flux distributions upon rim and inner liner surfaces. The simulation results have been then exploited to derive the convective heat transfer coefficients per each sub domain to be employed within the real-time tyre physical thermal model, with the peculiar advantage of an enhanced model reliability for thermal characteristics. To validate the proposed methodology, the tyre thermal model outputs, in terms of temperatures of internal and external layers, have been validated towards the acquired ones within the specific routine performed on tyre force and moment test bench, confirming an excellent agreement with the experimental data in the entire range of operating conditions explored.

The effectiveness of riblets in reducing friction drag has been well assessed by many experi- ments in flat plate and channel flow in the end of the last century. Both theory and experiments showed that the effect of riblets only depends on the local Reynolds number, however some experiments in pressure gradient flow showed increased effectiveness of riblets. This effects are still debated because a physical motivation on the effect of riblets on form drag was not provided. Recently a model based on slip length concept for riblets simulation at high Reynolds numbers has been proposed in RANS solver, providing a contribution to understanding the origin of the increased effectiveness of riblets in pressure gradient flow. In the present paper the model is extended to Large Eddy Simulation methods and applied to the analysis of airfoil flows. The analysis provides a reliable analysis of the effect of pressure gradient on riblet performance.

In the frame of aerodynamic drag reduction for low-emission target, Natural Laminar Flow (NLF) control and riblets are the most interesting passive techniques. The drag breakdown in the case of riblets installed is a topical matter for understanding on which form of drag riblets act. Indeed, linear theories and flat-plate experiments show that riblets act on friction drag whereas other experiments in pressure-gradient flow revealed an increased performance of riblets that was not interpreted. A contribution to clarify this effect has been recently provided analyzing the effect of riblets on form drag in two-dimensional pressure-gradient flows. In the present paper the effect of riblets on pressure drag is discussed also in three-dimensional flows analyzing CFD solutions of the flow around an innovative regional turbo-prop aircraft (wing-body configuration) with NLF and riblets installed. For the first time, the contribution of each of two drag reduction systems is identified and a deep analysis on which form of drag riblets act in three-dimensional flow is proposed thanks to a far-field aerodynamic drag breakdown.

An exact Lamb vector-based theory for the computation and decomposition of the aerodynamic force in unsteady viscous flows is presented and analyzed. This decomposition allows for a correct and straightforward computation of the dynamic force derivatives even in strongly nonlinear flows. Theory has been applied to numerical solutions around a pitching and plunging plate at low (300) and high (106 ) Reynolds numbers. A breakdown between thrust and drag contributions is also obtained, evidencing the flow regions where the thrust force is generated. The obtained decomposition is compared with the classical analytical linear inviscid theories. In addition, a new mixed inertial–non- inertial formula is proposed for the computation of the aerodynamic force, which is more accurate when dealing with high Reynolds numbers flows.