Measurement of flow structures and heat transfer behind a wall-proximity square rib using TSP, PIV and split-fiber film

Data assimilation and resolvent analysis of turbulent flow behind a wall-proximity rib

“…As He et al 24 claimed, G/d = 0.25 with suppressed Karman vortex shedding yielded the maximum heat transfer augmentation immediately behind the rib, along with overall improvement in surface heat removal; in contrast, the configuration with G/d = 0.50 resulted in Karman vortex shedding and deteriorated the wall heat transfer. In measurements by He et al, 24 a split-fiber probe accurately captured wall jet and flow reattachment, while the great uncertainty of PIV measurements in the high-shear regions prevented the determination of the exhaustive flow dynamics behind the rib. The same flow configuration is used in the present study, where the Reynolds number based on the free-stream velocity U 0 and rib size d remains Re = 7600.…”

“…For the primary state variables, the inflow boundary condition is obtained by a precursor SA simulation for the flat plate with the boundary layer thickness of 2d at the inflow boundary location, which is consistent with the split fiber measurement. 24 The no-slip condition is imposed on the rib surface and wall, while the free-slip condition is used for the far-field boundary. The zero-gradient condition is applied on the outflow boundary.…”

“…A detailed description of the experiment has been provided in our previous work, 24 and thus only a brief account is given here. A plexiglas square rib with size d = 10 mm was used in the measurement and was placed at the leading edge of the heat area.…”

“…Because PIV aimed to capture the global patterns of the turbulent flow behind the rib, the spatial resolution was limited, giving rise to substantial error in the strong shear layer. 24 In the framework of the present study, only the split fiber results are required as observational data in the data assimilation and in the resolvent analysis for coefficient calibration. The TSP and PIV results, however, are used as complementary data for flow and heat transfer analysis.…”

“…The TSP and PIV results, however, are used as complementary data for flow and heat transfer analysis. and has been discussed in detail by He et al 24 In fact, PIV is still a very good means of flow field measurement in various flow conditions; the present inaccuracy can be solved by zooming in the camera in a small region behind the rib. However, there is a tradeoff between the flow field resolution and the extent of the global flow region.…”