Publication

Abstract : 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 (\theta) and the size of a slit (\xi) at the leading-edge of the v-gutter. Turbulent flow kinematics and pressure field are analyzed to evaluate the unsteadiness at a freestream Mach number of M_\infty = 0.25 and a freestream Reynolds number based on bluff body's transverse length (L) of Re_L=0.1 \times 10^6. Five v-gutter angles are considered (\theta, ^\circ = \pi/6, \pi/4, \pi/3, 5\pi/12, \pi/2) and three slit sizes (\xi, mm =0,0.25,0.5) are considered only for a particular \theta = [\pi/6]. In general, high fluctuations in velocity and pressure are seen for the bluffest body in consideration (\theta = \pi/2) with higher drag (c_d) and total pressure loss (\Delta p_0). On the other hand, the presence of a slit on a streamlined body (\theta = \pi/6) tends to efficiently stabilize the wake and thus, producing almost a periodic shedding structure with lower c_d and \Delta p_0. For \theta = [\pi/6], broadened spectra in vortex shedding is seen with a peak at [fL/u_\infty] \sim 0.08. For \theta \geq [\pi/4], a dominant discrete shedding frequency is seen with a gradual spectral decay. Similarly, the effects of \xi on the \theta = [\pi/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_\infty] \sim 0.26 for the maximum slit size of \xi = 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.