The paper presents a computational study of the transonic shock-buffet flow instability phenomenon on threedimensional wings. Reynolds-averaged Navier-Stokes simulations were conducted on three wing configurations, all based on the RA16SC1 airfoil, at shock-buffet flow conditions. Numerical validation is presented for the OAT15A and RA16SC1 swept wings based on wind-tunnel experiments. The simulated configurations include infinite-straight, infinite-swept, and finite-swept three-dimensional wing models of several sweep angles and span lengths. Based on the results, the effects of three-dimensional flow, wing sweep, and span length on the shock-buffet characteristics are identified. For small wing-sweep angles, the fundamental shock-buffet instability mechanism remains similar to the two-dimensional mechanism, which is characterized mainly by chordwise shock oscillations. For moderate sweep angles, a phenomenon of lateral pressure disturbance propagation is observed. This phenomenon is essentially different from the two-dimensional shock-buffet mechanism yet results in oscillations of the sectional aerodynamic coefficients. The paper presents and discusses both phenomena, and it suggests a connection between them. For highwing-sweep angles, the wing is stalled and shock buffet is eliminated. For low-aspect-ratio wings, the flow is dominated by tip vortices, and shock buffet is eliminated. For high-aspect-ratio wings, wingtip effects are minor and limited to the tip region. For intermediate-aspect-ratio cases, tip vortices and shock-buffet interaction results in irregular shock oscillations. Nomenclatureshock-buffet frequency, Hz f 2πfc∕U ∞ = shock-buffet reduced frequency; K = computational domain index in the surface normal direction M ∞ = freestream Mach number R ∞ = freestream Reynolds number, based on chord t = physical time, s t a ∞ t∕c = nondimensional time; U ∞ = freestream velocity, m∕s X = chordwise coordinate normalized to the chord length Y = lateral coordinate normalized to the chord length y = dimensionless wall distance Z = surface-perpendicular coordinate normalized to the chord length α = angle of attack, deg ΔC L = lift coefficient amplitude Δ t = nondimensional computational time step ΔX s = shock-travel distance along the chord, normalized to the chord length τ = mean-flow equations fictitious computational time step τ t = turbulence equations fictitious computational time step

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