Time-averaged three-dimensional flow topology in the wake of a simplified car model using volumetric PIV

Three dimensional structure of the unsteady wake of an axisymmetric body

“…The level of uncertainty associated with each dataset has been estimated considering a 95% confidence level, as in the work of Perry et al 34 A value of ≈0.3% has been obtained for the free-stream velocity. The level of uncertainty, however, is seen to increase up to more than 5% in the shear layers, in agreement with that found by Sellappan et al 38 A similar error is also observed at the corners of the volumetric field of view, as a consequence of the worsening of the signal-to-noise ratio ( Fig. 3).…”

“…However, they are characterised by a much lower energy content, arguably due to the more limited capability of TPIV to accurately resolve the shear layer bounding the wake. 38 The m = 0 distribution appears to be linked to the unsteady motion of the wake in the axial and radial directions, particularly evident in the…”

Salient three-dimensional features of the turbulent wake of a simplified square-back vehicle

“…The level of uncertainty in the mean velocity associated with each dataset has been estimated considering a 95 % confidence level (Perry et al 2016a). This gives a value of 0.3 % for the free-stream velocity, increasing to over 5 % in proximity to the shear layers (Sellappan, McNally & Alvi 2018) where the fluctuations are greatest. A similar level of uncertainty is also observed at the corners of the volumetric field of view and close to the model base (for x * 0.25), as a consequence of the worsening of the signal-to-noise ratio.…”

Reynolds number and slant angle effects on the flow over a slanted cylinder afterbody

“…Several planes were acquired for the slant angles φ = 32 • and φ = 45 • , with the precise plane locations examined described in the results section. The acquisition of a stack of multiple planes allows for the volumetric reconstruction of the mean flow, which has recently been described in detail for the wake of the Ahmed body by Sellappan, McNally & Alvi (2018), showing the trade-offs involved between performing S-SPIV versus tomographic PIV. The laser pulse energy requirement for tomographic PIV in the large wake volume was the main constraint that guided the choice towards S-SPIV to map this flow topology.…”