Vortex Shedding of Various Bluff Bodies in Cross Flow

Abstract

The generation of noise in combusting jets is of crucial concern in both military and commercial applications. In order to understand the impact of combustion on the noise generation mechanism, one needs to understand the flow structures. Since the flame structures that are observed experimentally are similar to the flow structures behind a cylinder for a non-combusting flow, a detailed comparison of these is warranted. A large eddy simulation (LES) of a cylinder in a cross flow was performed at different Reynolds numbers to compare the relationship between vortex shedding at various Reynolds numbers with the flame structures at different equivalence ratios. This is done to determine if the proposed analogy is valid. Proper orthogonal decomposition (POD) is performed on the non-combusting flow field and the luminosity of the combusting flow to compare how much energy is contained in symmetric, asymmetric, and uncorrelated modes. The initial study suggests an analogy between Reynolds number and equivalence ratio does not exist in terms of symmetric/asymmetric modal energy distribution despite the visual similarities between the two phenomena. Nomenclature Φ = equivalence ratio m f uel = Fuel mass m oxidizer = Oxidizer mass C(t, t ) = Correlation Matrix T = Number of Snapshots u = Velocity a n = Time dependent POD coefficients λ = eigenvalues φ = POD mode r = correlation f = Frequency D = Diameter U = Free stream Velocity St = Strouhal Number