Optimization of the Aerodynamic and Aeroacoustic Performance of an Axial-Flow Fan Jin-Hyuk Kim, ∗ Bavuudorj Ovgor, † Kyung-Hun Cha, ‡ Joo-Hyung Kim, ‡ Seungbae Lee, § and Kwang-Yong Kim ¶ Inha University, Incheon 402-751, Republic of Korea DOI: 10.2514/1.J052754 A multidisciplinary optimization to simultaneously enhance the aerodynamic and aeroacoustic performance of an axial-flow fan was performed. Flow analysis through the axial-flow fan was conducted by solving three- dimensional steady and unsteady Reynolds-averaged Navier–Stokes equations with the shear-stress transport turbulence model. Starting with the results for the unsteady flow, aeroacoustic analysis was performed by solving the Ffowcs Williams–Hawkings equations. A single-objective optimization for high-efficiency design was carried out before the multi-objective optimization. The single-objective optimization was conducted using a weighted average surrogate model with five design variables defining the hub-to-tip ratio, hubcap installation distance, hubcap ratio, and angle distributions at the midspan and blade tip. The objective function (i.e., the efficiency) was evaluated at the design points, sampled by Latin hypercube sampling in the design space, to construct the surrogate model. Then, multi-objective optimization on the basis of the single-objective optimization result was performed to simultaneously improve the efficiency and reduce the sound pressure level through a hybrid multi-objective evolutionary algorithm coupled with a response surface approximation surrogate model with two design variables defining the sweep and lean angles at the blade tip. These objective functions were numerically accessed through the aerodynamic and aeroacoustic analyses. Arbitrary selected optimum designs in the Pareto- optimal solutions yielded increases in efficiency and decreases in the sound pressure level compared to the reference design. Nomenclature c 0 = speed of sound in undisturbed medium D = diameter D axial = axial length of the hubcap D hc = hub-cap installation distance D radial = radius of the hubcap D s = DΔP∕ρ 0.25 ∕Q 0.5 , specific fan diameter d h;s;t = hub, shaft, and tip diameters, respectively F opt = objective function value at the optimum point f = function for blade surface description (equal to 0 on blade surface) l i = local force vector l r = root length or l i r i M = Mach number M i = 1∕c 0 · ∂  y i ∕∂t local source Mach number M r =  r i ·  M i , relative Mach number N = rotational speed N s = NQ 0.5 ∕ΔP∕ρ 0.75 , specific fan speed N SM = number of basic surrogate models n = unit normal vector in surface outward direction O = observer position P S;T = static and total pressures, respectively P 1–5 = control-point-generated Bezier curve p t ×   x; t = acoustic pressure by thickness noise Q = local balance value between shear strain rate and vorticity magnitude Q v = volumetric flow rate R 2 = correlation coefficient in least-squares surface fitting R 2 adj = adjusted correlation coefficient R hc = hub-cap ratio R h−t = hub-to-tip ratio r = j  x −  yj, distance from source to observer ^ r = unit vector pointing from source to observer S = surface area t = observer time U t = tip speed v = fluid velocity w = weight coefficient x, y, z = orthogonal coordinate system  x = observer point  y = source point α = angle between the rotational axis and a tangent of the camber line α m;t = α angle distributions at midspan and tip, respectively γ = sweep angle at the blade tip δ = lean angle at the blade tip η = total efficiency ρ = density ρ 0 = undisturbed fluid density σ = torque τ = source time φ = Q∕AU t , flow coefficient ψ = 2ΔP∕ρU 2 t ω = angular velocity Subscripts in = inlet out = outlet Received 7 May 2013; revision received 31 December 2013; accepted for publication 24 January 2014; published online 12 May 2014. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 1533-385X/14 and $10.00 in correspondence with the CCC. *Senior Researcher, Korea Institute of Industrial Technology; jinhyuk@ kitech.re.kr. † Deputy Director, National Renewable Energy Center of Mongolia; bavuudorj@gmail.com. ‡ Graduate Student, Department of Mechanical Engineering, 253 Yonghyun-Dong, Nam-Gu. § Professor, Department of Mechanical Engineering, 253 Yonghyun-Dong, Nam-Gu. ¶ Professor, Department of Mechanical Engineering, 253 Yonghyun-Dong, Nam-Gu; kykim@inha.ac.kr. Associate Fellow AIAA (Corresponding Author). 2032 AIAA JOURNAL Vol. 52, No. 9, September 2014 Downloaded by INHA UNIVERSITY on August 29, 2014 | http://arc.aiaa.org | DOI: 10.2514/1.J052754