Unsteady dynamics in a subsonic duct flow with a bluff body

A series of reduced-order numerical simulations on a specific bluff body type (v-gutters) in a subsonic duct flow is done to assess the unsteady wake dynamics. Two of the v-gutter's geometrical parameters are varied: the v-gutter's base angle (θ) and the size of a slit (ξ) at the leading edge of the v-gutter. Five v-gutter angles are considered (θ,{degree sign} = π/6, π/4, π/3, 5π/12, π/2) and three slit sizes (ξ, mm =0,0.25,0.5) are considered only for a particular θ = [π/6]. High fluctuations in velocity and pressure are seen for the bluffest body in consideration (θ = π/2) with higher drag (cd) and total pressure loss (Δp0). On the other hand, the presence of a slit on a streamlined body (θ = π/6) tends to efficiently stabilize the wake and thus, producing almost a periodic shedding structure with lower cd and Δp0. For θ = [π/6], broadened spectra in vortex shedding are seen with a peak at [fL/u∞] ∼ 0.08. For θ {greater than or equal to} [π/4], a dominant discrete shedding frequency is seen with a gradual spectral decay. Similarly, the effects of ξ on the θ = [π/6] case produce a discrete shedding frequency instead of a broadened one, as told before. The shedding frequency increases to a maximum of [fL/u∞] ∼ 0.26 for the maximum slit size of ξ = 0.5. More insights on the shedding vortices, momentum deficit in the wake, varying energy contents in the flow field, and the dominant spatiotemporal structures are also provided.