Benedetto Mele

Aerodynamic force by Lamb vector integrals in compressible flow

A new exact expression of the aerodynamic force acting on a body in steady high Reynolds number (laminar and turbulent) compressible flow is proposed. The aerodynamic force is obtained by integration of the Lamb vector field given by the cross product of vorticity times velocity. The result is obtained extending a theory developed for the incompressible case. A decomposition in lift and drag contribution is obtained in the two-dimensional case. The theory links the force generation to local flow properties, in particular to the Lamb vector field and to the kinetic energy. The theoretical results are confirmed analyzing numerical solutions obtained by a standard Reynolds Averaged Navier-Stokes solver. Results are discussed for the case of a two-dimensional airfoil in subsonic, transonic, and supersonic free stream conditions.

Osteogenic differentiation and mineralization in fibre-reinforced tubular scaffolds: theoretical study and experimental evidences

The development of composite scaffolds with well-organized architecture and multi-scale properties (i.e. porosity, degradation) represents a valid approach for achieving a tissue-engineered construct capable of reproducing the medium- and long-term in vitro behaviour of hierarchically complex tissues such as spongy bone. To date, the implementation of scaffold design strategies able to summarize optimal scaffold architecture as well as intrinsic mechanical, chemical and fluid transport properties still remains a challenging issue. In this study, poly ɛ-caprolactone/polylactid acid (PCL/PLA) tubular devices (fibres of PLA in a PCL matrix) obtained by phase inversion/salt leaching and filament winding techniques were proposed as cell instructive scaffold for bone osteogenesis. Continuous fibres embedded in the polymeric matrix drastically improved the mechanical response as confirmed by compression elastic moduli, which vary from 0.214 ± 0.065 to 1.174 ± 0.143 MPa depending on the relative fibre/matrix and polymer/solvent ratios. Moreover, computational fluid dynamic simulations demonstrated the ability of composite structure to transfer hydrodynamic forces during in vitro culture, thus indicating the optimal flow rate conditions that, case by case, enables specific cellular events—i.e. osteoblast differentiation from human mesenchymal stem cells (hMSCs), mineralization, etc. Hence, we demonstrate that the hMSC differentiation preferentially occurs in the case of higher perfusion rates—over 0.05 ml min–1—as confirmed by the expression of alkaline phosphate and osteocalcin markers. In particular, the highest osteopontin values and a massive mineral phase precipitation of bone-like phases detected in the case of intermediate flow rates (i.e. 0.05 ml min–1) allows us to identify the best condition to stimulate the bone extracellular matrix in-growth, in agreement with the hydrodynamic model prediction. All these results concur to prove the succesful use of tubular composite as temporary device for long bone treatment.

Vorticity Based Breakdown of the Aerodynamic Force in Three-Dimensional Compressible Flows

Recently, a definition of the lift-induced drag in terms of a field integral of the Lamb vector has been proposed in case of incompressible high-Reynolds-number flow and verified by postprocessing computational-fluid-dynamics solutions around wings. The possibility to extend this definition also to the case of compressible flows is investigated in this paper. An exact expression of the aerodynamic force in three-dimensional flows is discussed; it allows for a breakdown of the aerodynamic force (both drag and lift) in its physical contributions. Its applicability is analyzed in case of Reynolds-averaged Navier–Stokes numerical solutions around an elliptic wing in subsonic and transonic conditions. A rigorous and unambiguous definition of lift-induced drag is obtained. It still depends on the vortex force of the flow (the volume integral of the Lamb vector field), but a compressibility correction term is also to be taken into account. Both viscous and wave drag components can be computed by a surface integr...

Aircraft Lift and Drag Decomposition in Transonic Flows

A vorticity-based exact theory for the analysis of the aerodynamic force is here applied to three-dimensional aircraft configurations in steady transonic flow by postprocessing numerical solutions....

Advances in Aerodynamic Drag Extraction by Far-Field Methods

Far-field methods for aerodynamic drag calculation and breakdown around aircraft configurations by Computational Fluid Dynamics are widely adopted. Recent improvements and advances of one of these algorithms are discussed. Because these methods rely for breakdown purposes on the detection of the boundary-layer region around the body, an analysis of possible alternatives to the currently adopted boundary-layer sensor is proposed. Furthermore, a recently published study in the case of inviscid flow on the influence of the accuracy of the numerical solution at far field has been repeated in viscous flow. It shows how a far-field solution influences the computation of near-field drag, in particular, in high-lift conditions. Finally, an application to a complex high-lift three-dimensional configuration of an alternative method for the computation of the lift-induced drag is discussed. The method is based on the integration of the Lamb-vector field.

Performance Assessment of a Transonic Wing–Body Configuration with Riblets Installed

The effectiveness of the riblets, one of the most interesting drag-reduction device, is discussed in this paper. Numerical simulations by the Reynolds-averaged Navier–Stokes equations with the riblets properly taken into account are presented. Riblets are modeled as a singular roughness problem by modifying the classical Wilcox boundary condition for rough walls. The boundary condition is able to predict the flow features in the low roughness range (transitional roughness) where riblets operate. A brief discussion of the simulations performed to validate the model is first presented. Then, a complex wing–body configuration is analyzed, and the overall effect of riblets on the aerodynamic coefficients is evaluated. Calculations of a complete aircraft configuration at transonic conditions show how a proper optimized choice of the riblet height can significantly improve the drag reduction.

Linear and Nonlinear Decomposition of Aerodynamic Force Acting on an Oscillating Plate

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 str...

Airfoil Drag Calculations in Stall and Post-stall Conditions

Numerical solutions of the Reynolds Averaged Navier-Stokes equations around airfoils in stall and post-stall conditions are proposed and post-processed by a drag analysis method, developed for applications in cruise and near-cruise conditions. The possibility to neglect Reynolds stresses in the wake when massive separations are present is discussed. Present method makes it possible to identify a considerable part of the spurious unphysical drag which is generated by the numerical scheme. Respect to cruise conditions, a much larger spurious drag contribution is detected, which makes, for high-lift flows, present far-field drag analysis even more useful in order to correct drag predictions obtained by the classical near-field integration. The capability to obtain a breakdown into viscous and wave drag evidenced the presence of a significant wave contribution in stall and post-stall conditions even for moderately low freestream Mach numbers.

Effects of riblets on the performances of a regional aircraft configuration in NLF conditions

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Effects of riblets on the performances of a regional aircraft configuration in NLF conditions Pietro Catalano, Donato de Rosa, Benedetto Mele, Renato Tognaccini, Frédéric Moens

Vortex force and lift induced drag in compressible flows

Recently a definition of the lift induced drag in terms of a field integral of the Lamb vector has been proposed in case of incompressible high Reynolds number flow and verified by post processing CFD solutions around wings. The possibility to extend this definition also to the case of compressible flows is investigated in this paper. In particular an exact expression of the aerodynamic force is discussed and its applicability is analyzed in case of RANS numerical solutions around an elliptic wing in subsonic and transonic conditions. A rigorous and unambiguous definition of lift induced drag is obtained. The lift induced drag still depends on the vortex force of the flow (the volume integral of the Lamb vector field), but a compressibility correction term (providing a thrust contribution) is also to be taken into account for.