An inclined jet in crossflow under the effect of streamwise pressure gradients

Coletti, Filippo; Elkins, Christopher J.; Eaton, John K.

doi:10.1007/s00348-013-1589-0

Cited by 27 publications

(8 citation statements)

References 29 publications

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“…Allowing for long acquisition times leads to increase in SNR (Elkins & Alley 2007), which for a desired level of accuracy determines the spatial resolution, leading to high DSR on the mean flow. MRV spatial resolution typically ranges from 0.4 mm to 1 mm, over volumes often exceeding 20 cm of maximum extension (Cherry et al 2008, Grundmann et al 2012, Coletti et al 2013a, Freudenhammer et al 2014, Ryan et al 2016.…”

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confidence: 99%

“…There have been studies focused on accuracy of volumetric velocimetry in specific cases, e.g. turbulent boundary layer measurements by Tomographic PIV (Atkinson et al 2011) and Tomographic PTV (Schneiders et al 2017), and comparisons between MRI and 2D PIV for specific configurations (Elkins et al 2009, Coletti et al 2013a, Töger et al 2016. However, the systematic assessment of uncertainty of volumetric techniques is still in its infancy and will likely be a topic of high significance as the tools gain widespread use.…”

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confidence: 99%

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Volumetric velocimetry for fluid flows

Discetti

Coletti

2018

Meas. Sci. Technol.

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In the last two decades, several techniques have been introduced that are capable to extract three-dimensional three-components velocity fields in fluid flows. Fast-paced developments in both hardware and processing algorithms have generated a diverse collection of methods, with a growing range of application in flow diagnostics. The context has been further enriched by an increasingly marked trend of hybridization, in which the boundaries between different techniques are fading. In this review, we carry out a survey of the prominent methods, including optical techniques and approaches based on medical imaging. Each one is outlined through a sample application from the recent literature, focusing on respective strengths and challenges. A framework for the evaluation of the velocimetry performance in terms of dynamic spatial range is discussed, along with technological trends and emerging strategies to exploit 3D data. While critical challenges still exist, these observations highlight how volumetric techniques are transforming experimental fluid mechanics, and that the possibilities they offer have just begun to be explored.

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confidence: 99%

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confidence: 99%

Volumetric velocimetry for fluid flows

Discetti

Coletti

2018

Meas. Sci. Technol.

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“…Likewise, if the coolant has to undergo the large turning angle on the side of the inlet, due to crossflow, a separation region is created and jetting occurs on the opposite side of the meter [17]. The separation region at the inlet, and the ensuing skewed velocity profile, was also observed experimentally inside a film hole by Coletti et al [18] using magnetic resonance imaging.…”

Section: Review Of Relevant Literaturementioning

confidence: 77%

The Effect of Area Ratio Change Via Increased Hole Length for Shaped Film Cooling Holes With Constant Expansion Angles

Haydt

Lynch

Lewis

2018

Journal of Turbomachinery

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Shaped film cooling holes are used as a cooling technology in gas turbines to reduce metal temperatures and improve durability, and they generally consist of a small metering section connected to a diffuser that expands in one or more directions. The area ratio (AR) of these holes is defined as the area at the exit of the diffuser, divided by the area at the metering section. A larger AR increases the diffusion of the coolant momentum, leading to lower average momentum of the coolant jet at the exit of the hole and generally better cooling performance. Cooling holes with larger ARs are also more tolerant of high blowing ratio conditions, and the increased coolant diffusion typically better prevents jet lift-off from occurring. Higher ARs have traditionally been accomplished by increasing the expansion angle of the diffuser while keeping the overall length of the hole constant. The present study maintains the diffuser expansion angles and instead increases the length of the diffuser, which results in longer holes. Various ARs have been examined for two shaped holes: one with forward and lateral expansion angles of 7 deg (7-7-7 hole) and one with forward and lateral expansion angles of 12 deg (12-12-12 hole). Each hole shape was tested at numerous blowing ratios to capture trends across various flow rates. Adiabatic effectiveness measurements indicate that for the baseline 7-7-7 hole, a larger AR provides higher effectiveness, especially at higher blowing ratios. Measurements also indicate that for the 12-12-12 hole, a larger AR performs better at high blowing ratios but the hole experiences ingestion at low blowing ratios. Steady Reynolds-averaged Navier–Stokes simulations did not accurately predict the levels of adiabatic effectiveness, but did predict the trend of improving effectiveness with increasing AR for both hole shapes. Flowfield measurements with particle image velocimetry (PIV) were also performed at one downstream plane for a low and high AR case, and the results indicate an expected decrease in jet velocity due to a larger diffuser.

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“…where ν is the kinematic viscosity, and U is the freestream velocity distributed along X. K>0 indicates favorable pressure gradient (FPG), and K<0 indicates adverse pressure gradient (APG). In the turbine blade environment, K ranges from -2×10 -6 to 6×10 -6 at the typical position (Filippo et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Large-eddy simulation of shaped hole film cooling with the influence of streamwise pressure gradient

Hu¹,

Wang²,

Chen³

et al. 2022

Proceedings of Global Power &Amp; Propulsion Society

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The complicated streamwise pressure gradient (SPG) environments in gas turbines affect the film cooling performance. In this research, shaped cooling hole with density ratio 1.5, blowing ratio 1.6, and acceleration coefficient, K=1e-6 is studied using Large Eddy Simulation (LES). LES results have been verified by experiment results. The differences between the Reynolds Average Navier – Stokes (RANS) results of zero pressure gradient (ZPG) and favorable pressure gradient (FPG) showed that the FPG keeps the jet closer to the wall surface, and the counter rotating vortex pair (CRVP) is compressed. The time-average and instantaneous flow field obtained from LES were analyzed to get the flow field details. Fast Fourier Transform (FFT) and Lumley triangle were used to analyze the vortices and the turbulence characteristics of the strong shear zone near the hole exit and downstream. The influences of FPG on horseshoe vortex, hairpin vortex and shear layer vortex were analyzed. The results showed that the hairpin vortex enhanced by FPG effect the film cooling performance of the downstream.

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An inclined jet in crossflow under the effect of streamwise pressure gradients

Cited by 27 publications

References 29 publications

Volumetric velocimetry for fluid flows

Volumetric velocimetry for fluid flows

The Effect of Area Ratio Change Via Increased Hole Length for Shaped Film Cooling Holes With Constant Expansion Angles

Large-eddy simulation of shaped hole film cooling with the influence of streamwise pressure gradient

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