1,930 research outputs found
On the Circulation Manifold for Two Adjacent Lifting Sections
No full textThe circulation functional relative to the potential flow past two adjacent lifting sections is studied for two cases. In the first case we consider two adjacent circles. The circulation is computed as a function of the displacement of the secondary circle along the axis joining the two centers and of the angle of attack of the secondary circle. The gradient of such functional is computed by deriving a set of elliptic functions with respect both to their argument and to their period. In the second case studied, we considered a wing-flap configuration. The circulation is computed by some implicit mappings, whose differentials with respect to the variation of the geometrical configuration in the physical space are found by divided differences. Configurations giving rise to local maxima and minima in the circulation manifold are presented
Aerodynamic Constraints for Vortex Trapping Airfoils
No full textInternational audienceNota di BERNARDO GALLETTI, ANGELO IOLLO e del Socio corrispondente LUCA ZANNETTI presentata nell'adunanza del 12 Giugno 2002 Riassunto. Si mostra come è possibile ricavare la geometria del profilo capace di catturare un vortice che realizza una data distribuzione di velocità, essendo tale distribuzione di velocità assegnata in funzione dell'ascissa curvilinea fissata sul contorno del profilo. Vengono altresí espressi i vincoli che detta distribuzione deve soddisfare affinché il problema risulti ben posto
Analysis and low order modeling of the inhomogeneous transitional flow inside a T-mixer
No full textA direct numerical simulation of the transitional flow (Re=300 to Re=700) inside a T-mixer configuration has been carried out. Time records were collected and used to perform a proper orthogonal decomposition (POD) of the flow. Changes of the flow characteristics in the frequency spectra and extracted coherent spatial structures indicate flow transition across the investigated Reynolds numbers. The POD modes were used to derive a low-order model of the flow. An a priori test limits the possibilities of the modeling; for the periodic case it demonstrates that the flow can be reduced to a system of a few degrees of freedom, while for the turbulent ones this results to be extremely difficult because of the large number of degrees of freedom that are necessary to describe the flow
Set of Boundary Conditions for Aerodynamic Design
No full textRobust and flexible numerical methodologies for the imposition of boundary conditions are required to formulate well-posed problems. A boundary condition should be Robust and flexible numerical methodologies for the imposition of boundary conditions are required to formulate well-posed problems. A boundary condition should be nonreflecting, to avoid spurious perturbations that can provocate unsteadiness or instabilities. The reflectiveness of various boundary conditions is analyzed in the context of the Godunov methods. A nonlinear, isentropic wave propagation model is used to investigate the reflection mechanism on the flowfield borders, and a parameter τ is defined to give a measure of the boundary reflectiveness. A new set of boundary conditions, in which τ =0, that is, totally nonreflecting, is then proposed. The approach has been integrated in an aerodynamic design procedure using a distributed boundary control
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