A 2-D Hybrid Euler-Compressible Vortex Particle Method For Transonic Rotorcraft Flows

Abstract

In the present work, a novel hybrid Euler-compressible vortex particlemethodis developed for 2-D transonic rotorcraft applications. It is identi�edthat the ad-vantages and disadvantages of traditional grid-based Euler/Navier-Stokesmethodsand those of vortex particle methods complement each other. This suggeststhat ahybrid approach, in which a grid-based Euler domain covering the near-�eldaroundthe airfoil, coupled with a compressible vortex particle formulationrepresenting thefar-�eld, would be extremely bene�cial to employ.This work focuses on two areas: �rstly, a compressible vortex particlemethod(CVPM) formulation is developed. Then, the coupling of this methodwith an existingEuler solver (CMB) is completed, using a domain decomposition techniquefeaturingcomplete overlap. This novel hybrid Euler-particle method is thendesignated asHEPM.Validation of HEPM is performed in three phases. First, the convergenceof themethod is examined for steady �ows at low and high Mach numbers andalso for arapidly sinusoidally pitching airfoil. Then, validation against experimentalresults isperformed by comparisons to the AGARD CT6 and CT5 cases for ramped-upandsinusoidally pitching airfoils, respectively. Finally, airfoil-vortexinteraction (AVI)studies are performed for an impinging vortex, with various vortexmiss distancesconsidered at both low and high Mach numbers. All of the above casesrepresenttypical problems in rotorcraft aerodynamics.iii