Effects of Turbulence Model on Flutter Prediction of a Transonic Fan

Abstract

Four different turbulence models have been employed to investigate the aeroelastic stability of NASA Rotor 67 and a transonic fan by use of the energy method. Firstly, the amplitude and phase of the first harmonic pressure on blade surface have been analyzed. Then the characteristics of flutter at different working points and nodal diameters have been investigated. Finally, the flutter boundary of the fan has been predicted and compared to the measured one. The simulation results for the steady characteristics by use of k-ε model and k-ω model agree better with the test data than those of the SST model and RNG k-ε model. The aerodynamic damping predicted by use of these models are approximately the same at the peak efficiency point. However, compared to the test data, the aerodynamic damping calculated by use of SST model are more conservative than k-ε model at the near-stall point. Therefore, the k-ε model is more suitable to flutter prediction of transonic fans. Nomenclature1B = first bending 1T = first torsion C = damping matrix c = blade chord length, m d k = the k-th vibration displacement vector E = Young's modulus, GPa F a = aerodynamic load matrix K = stiffness matrix M = mass matrix N = number of blade n  = surface unit normal vector p = pressure, Pa PS = pressure surface q cfd = modal amplitude q k = generalized displacement of the k-th modal S = area of blade surface, m 2 Span = height of the blade SS = suction surface T = vibrating period of the blade, s t = time, s v  = vibrating velocity of the blade 2 W aero = aerowork, J x= structural displacement vector y + = dimensionless normal distance from the wall φ k = the k-th modal shape vector λ k = the k-th eigenvalue of system μ = Poisson's ratio ρ = density, kg/m 3 σ = interblade phase angle ω k = the k-th natural angular frequency of the blade, rad/s ζ aero = aerodynamic modal damping ratio