Estimation of three-dimensional aerodynamic damping using CFD

Aeroelastic phenomena of stall flutter are the result of the negative aerodynamic damping associated with separated flow. From this basis, an investigation has been conducted to estimate the aerodynamic damping from a time-marching aeroelastic computation. An initial investigation is conducted on the NACA 0012 aerofoil section, before transition to 3D propellers and full aeroelastic calculations. Estimates of aerodynamic damping are presented, with a comparison made between URANS and SAS. Use of a suitable turbulence closure to allow for shedding of flow structures during stall is seen as critical in predicting negative damping estimations. From this investigation, it has been found that the SAS method is able to capture this for both the aerofoil and 3D test cases

CFD code comparison for 2D airfoil flows

The current paper presents the effort, in the EU AVATAR project, to establish the necessary requirements to obtain consistent lift over drag ratios among seven CFD codes. The flow around a 2D airfoil case is studied, for both transitional and fully turbulent conditions at Reynolds numbers of 3 × 106 and 15 × 106. The necessary grid resolution, domain size, and iterative convergence criteria to have consistent results are discussed, and suggestions are given for best practice. For the fully turbulent results four out of seven codes provide consistent results. For the laminar-turbulent transitional results only three out of seven provided results, and the agreement is generally lower than for the fully turbulent case

Final results from the EU project AVATAR: aerodynamic modelling of 10 MW wind turbines

This paper presents final results from the EU project AVATAR in which aerodynamic models are improved and validated for wind turbines on a scale of 10 MW and more. Special attention is paid to the improvement of low fidelity engineering (BEM based) models with higher fidelity (CFD) models but also with intermediate fidelity free vortex wake (FVW) models. The latter methods were found to be a good basis for improvement of induction modelling in engineering methods amongst others for the prediction of yawed cases, which in AVATAR was found to be one of the most challenging subjects to model. FVW methods also helped to improve the prediction of tip losses. Aero-elastic calculations with BEM based and FVW based models showed that fatigue loads for normal production cases were over predicted with approximately 15% or even more. It should then be realised that the outcome of BEM based models does not only depend on the choice of engineering add-ons (as is often assumed) but it is also heavily dependent on the way the induced velocities are solved. To this end an annulus and element approach are discussed which are assessed with the aid of FVW methods. For the prediction of fatigue loads the so-called element approach is recommended but the derived yaw models rely on an annulus approach which pleads for a generalised solution method for the induced velocities

Study of Blade/Vortex interaction using Computational Fluid Dynamics and Computational Aeroacoustics

Abstract A parametric study of the aerodynamics and the acoustics of parallel BVI has been carried out for different aerofoil shapes and vortex properties. Computing BVI using Computational Fluid Dynamics is challenging since the solution scheme tends to alter the characteristics of the vortex which must be preserved until the interaction. The present work uses the Compressible Vorticity Confinement Method (CVCM) for capturing the vortex characteristics, which is easier to implement and has minimal overhead in the performance of existing CFD solvers either in terms of CPU time or robustness during convergence. Apart from applying the CVCM method with an upwind solver, something not encountered in the literature, the present work couples CFD with Computational Aeroacoustics (CAA) and uses the strengths of both techniques in order to predict the nearfield and farfield noise. Results illustrate the importance of the aerofoil shape at transonic flow and show that the magnitude of the BVI noise depends strongly on the vortex strength and the miss-distance. The effect of the vortex core radius was also found to be important

NUMERICAL SIMULATION OF FILM COOLING IN HYPERSONIC FLOWS

Abstract In this paper, a numerical study of film cooling in both laminar and turbulent hypersonic flows has been performed. The aim of this computational work was to investigate the mechanism and effectiveness of film cooling in hypersonic flows. The coolant fluid was found to affect the primary boundary layer in two ways: 1) a separate boundary layer established by the coolant fluid itself, 2) a mixing layer between the primary and coolant flow streams. According to the analysis of the film cooling effectiveness, it has been revealed that under the same primary flow conditions the flow field of film cooling could be recognized as two separate regions. These two regions are divided by the point of the cooling length x A . For laminar flow, film cooling effectiveness was observed to obey a second-order curve in the log-log coordinates against log 10 η = f (log 10 x hṁ ) 2 . For turbulent flow, a linear relation was found suitable to describe the relation between log 10 η and log 10 x hṁ

Wind-Tunnel Interference Effects on Delta Wing Aerodynamics Computational Fluid Dynamics Investigation

Reynolds averaged Navier-Stokes simulations of a static and pitching delta wing within three wind tunnels have been performed. These simulations have been compared with the case of the wing in free air to ascertain the various influences of the walls on the vortical flow. The presence of tunnel walls has been found to promote vortex breakdown, with side wall proximity being the dominant factor. Roof and floor proximity has been seen to have a negligible effect on vortex breakdown. During pitching motion, side wall proximity delays vortex reformation after breakdown has reached its most upstream location, during cyclic pitching motion. This delay is recovered on the upstroke of the motion. These results confirm previous work with Euler simulations of tunnel interference

Application of International Standards to Evaluate the Potential of Sustainable Secondary Production of Tin and Tungsten in Portugal

The ambitious movement towards industry 5.0 technologies and the green transition drives the efforts towards securing critical metals’ supply chains globally. In Europe, highly economically important Tin and Tungsten are raising concerns regarding supply security due to geographical reserves’ uniformity and socio-political reluctance to mining. Nevertheless, mines that have seized operations in Portugal due to not being sustainable in the past are attracting renewed attention for further exploitation due to growing market demand and reclamation efforts for environmental concerns. Such abandoned resources need to be reassessed for their feasibility from economic, social, and environmental perspectives to ensure sustainable exploitation. Presenting the production criticality of Tin and Tungsten, this study implements the United Nations Framework Classification for Resources (UNFC) to assess the viability of abandoned mines and tailings dumps in Portugal, considering the indicators of Sustainable Development Goals (SDGs). The work indicates that Portugal’s abandoned Vale das Gatas Tin and Tungsten mine has good potential for further development. Furthermore, social perception towards new and abandoned mining is evaluated by collecting opinions from different parts of the country. It has been identified that sustainable technology and job opportunities are the driving parameters for the social acceptance of mining projects in Portugal

The Influence of Computational Mesh on the Prediction of Vortex Interactions about a Generic Missile Airframe

A research program has been underway for four years to study vortex interaction aerodynamics that are relevant to military air vehicle performance. The program has been conducted under the auspices of the NATO Science and Technology Organization (STO), Applied Vehicle Technology (AVT) panel by a Task Group with the identification of AVT-316. The Missile Facet of this group has concentrated their work on the vortical flow field around a generic missile airframe and its prediction via computational methods. This paper focuses on mesh-related effects and RANS simulations. Simulated vortex characteristics were found to depend strongly on the properties of the employed mesh, in terms of both resolution and topology. Predictions of missile aerodynamic coefficients show a great dependence on mesh properties as they are sensitive to computed vortex dynamics. Key suggestions about the desired mesh characteristics have been made. Based on these, a shared mesh was constructed to perform common analyses between the AVT-316 Missile Facet members. Mesh based uncertainties of the aerodynamic coefficient predictions were estimated via Richardson Extrapolation method

Catalysing sustainable fuel and chemical synthesis

Concerns over the economics of proven fossil fuel reserves, in concert with government and public acceptance of the anthropogenic origin of rising CO2 emissions and associated climate change from such combustible carbon, are driving academic and commercial research into new sustainable routes to fuel and chemicals. The quest for such sustainable resources to meet the demands of a rapidly rising global population represents one of this century’s grand challenges. Here, we discuss catalytic solutions to the clean synthesis of biodiesel, the most readily implemented and low cost, alternative source of transportation fuels, and oxygenated organic molecules for the manufacture of fine and speciality chemicals to meet future societal demands

Non-isothermal viscoelastic simulations of extrusion through dies and prediction of the bending phenomenon

Non-isothermal simulations have been undertaken for the flow of an IUPAC low-density polyethylene melt used previously in an international experimental study. First, extrusion flow from an infinitely long capillary die (LR = ∞) is considered with isothermal walls and different thermal boundary conditions on the extrudate surface. Then the flow through flat dies is studied with the walls kept at different temperatures to create a non-isothermal flow. The viscoelasticity of the polymer melt is described by an integral constitutive equation of the K-BKZ type with a relaxation spectrum, which fits well experimental data for the shear and elongational viscosities and the normal stresses as measured in shear flow. The non-isothermal computations have been based on a pseudo-time method introduced earlier [X.-L. Luo and R. I. Tanner, Rheol. Acta, 26 (1987) 499–507] by applying the Morland-Lee hypothesis. The coupling between the momentum and energy equations is through the time-temperature shift factor by which the pseudo-time is defined. To avoid spurious oscillations in the temperature field due to high convection, a suitable upwind method has been used. The simulations have been performed for the full range of experimental measurements in the system before melt fracture occurs, that is, for apparent shear rates reaching 10 s−1 at 150°C, and showing a very strong viscoelastic character of the melt corresponding to a stress ratio (SR) of about 2 and a Trouton ratio (TR) of about 50. Stable solutions have been obtained for the whole range of experimental values. They show that the capillary die experiments were basically isothermal, due to small Nahme numbers (Na ⪡ 1), but that the Peclet numbers reach up to 44, having an influence on the cooling process occurring in the extrudate. The case of extrusion through flat dies with walls kept at different temperatures shows that the extrudate swell is strongly affected by the asymmetry in the temperature field. More importantly, bending of the extrudate occurs towards the wall with the cooler temperature. The present results aptly manifest the influence that viscoelasticity and thermal boundary conditions have on extrudate swell and are in qualitative agreement with previous experimental studies on the effect of temperature on extrusion flows