16,301 research outputs found
Towards High-order Methods for Rotorcraft Applications
This work presents CFD results obtained with an efficient, high-order, finite-volume scheme. The formulation is
based on the variable extrapolation MUSCL-scheme, and high-order spatial accuracy is achieved using correction
terms obtained through successive differentiation. The scheme is modified to cope with physical and multiblock
mesh interfaces, so stability, conservativeness, and high-order accuracy are guaranteed. Results with the proposed
scheme for steady flows, showed better wake and higher resolution of vortical structures compared with
the standard MUSCL, even when coarser meshes were employed. The method was also demonstrated for unsteady
flows using overset and moving grids for the UH-60A rotor in forward flight and the ERICA tiltrotor in aeroplane
mode. The present method adds CPU and memory overheads of 47% and 23%, respectively, in performing
multi-dimensional problems for routine computations
Dynamical analysis for a scalar-tensor model with Gauss-Bonnet and non-minimal couplings
We study the autonomous system for a scalar-tensor model of dark energy with
Gauss-Bonnet and non-minimal couplings. The critical points describe important
stable asymptotic scenarios including quintessence, phantom and de Sitter
attractor solutions. Two functional forms for the coupling functions and the
scalar potential were considered: power-law and exponential functions of the
scalar field. For the exponential functions the existence of stable
quintessence, phantom or de Sitter solutions, allows an asymptotic behavior
where the effective Newtonian coupling becomes constant. The phantom solutions
could be realized without appealing to ghost degrees of freedom. Transient
inflationary and radiation dominated phases can also be described.Comment: 31 pages, 3 figures, to appear in EPJ
Tiltrotor CFD part I: validation
This paper presents performance analyses of the model-scale ERICA and TILTAERO tiltrotors and of the full-scale XV-15 rotor with high-fidelity computational fluids dynamics. For the ERICA tiltrotor, the overall effect of the blades on the fuselage was well captured, as demonstrated by analysing surface pressure measurements. However, there was no available experimental data for the blade aerodynamic loads. A comparison of computed rotor loads with experiments was instead possible for the XV-15 rotor, where CFD results predicted the FoM within 1.05%. The method was also able to capture the differences in performance between hover and propeller modes. Good agreement was also found for the TILTAERO loads. The overall agreement with the experimental data and theory for the considered cases demonstrates the capability of the present CFD method to accurately predict tiltrotor flows. In a second part of this work, the validated method is used for blade shape optimisation
Accurate Predictions of Hovering Rotor Flows Using CFD
With work on the S-76 rotor providing encouraging results regarding the prediction of integral
loads with CFD in hover, the XV-15 rotor is now analysed. Fully turbulent and transitional results
are obtained showing the capability of modern CFD methods. The transition onset and distribution of
skin friction are well predicted and were found to have a mild effect on the overall figure of merit. This
work also shows the potential of transport-based models for transition prediction in complex 3D flows.
Finally, hover simulations for the PSP blade are also shown in terms of surface pressure coefficient and
wake visualisation
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