Tomographic PIV Characterization of the Near field Topology of the Reacting Jet in Crossflow

Nair, Vedanth; Sirignano, Matthew; Schmidheiser, Sara; Dillon, Lane; Fugger, Christopher A.; Yi, Tongxun; Jiang, Naibo; Hsu, Paul S.; Slipchenko, Mikhail N.; Roy, Sukesh; Emerson, Benjamin; Steinberg, Adam M.; Lieuwen, Tim

doi:10.2514/6.2020-1420

Cited by 4 publications

(5 citation statements)

References 19 publications

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“…First, in Case 1 where J = 9, the vortex rings form almost immediately after the injection, while in Case 2 where J = 0.8, the vortex rings form later; the first ring structure appears after the jet has been largely bent. Second, when J = 9, the vortex rings roll up and distort as they interact with the crossflow; a similar behavior has also been observed in experiments by Nair et al 29 In contrast, for J = 0.8 the vortex rings retain their shape and gradually decay with the flow. In the following analysis, the more interesting Case 1 is retained for a detailed investigation.…”

Section: Mean and Instantaneous Reacting Flow Fieldssupporting

confidence: 77%

“…However, it must be kept in mind that using the Q -criterion to show the vortex structure can be somewhat arbitrary, since the specific value of the Q -criterion changes the perception of the nature and the size of the flow structure . To make a fair comparison, a nondimensionalized Q -criterion is used, with scaling velocity being the jet velocity and scaling length being the jet diameter . The comparison is shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…A maximum spatial resolution of 20 μm is reached to ensure that there are sufficient near-wall grid points to resolve the boundary layer. To estimate the y + distance, the following parameters are used; the freestream velocity v c = 59 m/s, average density ρ ave = 1.88×10 −1 kg/m 3 , dynamic viscosity μ = 5.75 × 10 −5 kg/ms, the boundary layer length scale is set to be the jet diameter 29 which is d j = 1.5 × 10 −3 m. It turns out that the first point of the current mesh locates at y + = 0.5 and there are 20 points below y + = 10. Turbulent fluctuations are superimposed on the mean velocity field of a fully developed channel flow to initialize a turbulent channel flow.…”

Section: Numerical Setupmentioning

confidence: 99%

“…28 To make a fair comparison, a nondimensionalized Q-criterion is used, with scaling velocity being the jet velocity and scaling length being the jet diameter. 29 The comparison is shown in Figure 3. The windward and leeward structures captured in the two cases show distinct behaviors.…”

Section: Mean and Instantaneous Reacting Flow Fieldsmentioning

confidence: 99%

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Combustion Mode and Mixing Characteristics of a Reacting Jet in Crossflow

et al. 2021

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Understanding of flame anchoring in a jet in crossflow (JICF) configuration is vital to the design of fuel injectors in combustion devices. The present study numerically investigates a hydrogen-rich jet injecting perpendicularly into hot vitiated crossflow using direct numerical simulation (DNS). The governing equations of low-Mach-number multicomponent reactive flows are solved, with a chemical mechanism for hydrogen-air flames containing 13 species and 35 reactions. The mixture-averaged multispecies transport model is employed to calculate the diffusion terms. Development of the reacting flow field and flame shape along the jet trajectory is depicted. The flame is found to be anchored around the jet exit and downstream only on the windward side. The heat release rate and chemical explosive mode analysis (CEMA) are used to identify combustion modes. Distinct from flames stabilized in nonvitiated crossflow, diffusion flame is dominant under the current conditions, though some premixed or partially premixed regions are found on the leeward side of the jet due to turbulent mixing. The near-field mixing of the reacting JICF is quantified by spatial unmixedness, in both two-dimensional (2D) and three-dimensional (3D) space.

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Section: Mean and Instantaneous Reacting Flow Fieldssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Section: Numerical Setupmentioning

confidence: 99%

Section: Mean and Instantaneous Reacting Flow Fieldsmentioning

confidence: 99%

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Combustion Mode and Mixing Characteristics of a Reacting Jet in Crossflow

et al. 2021

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“…This section presents three-component velocity data acquired in the centre plane of a non-reacting JICF, detailed in Nair et al (2020), using the same jet nozzle profile as in Megerian et al (2007). The main flow entering the test section has a velocity of u ∞ = 14.5 m s −1 and a temperature of T ∞ = 1250 K corresponding to a bulk Reynolds number of Re ∞ = 11 000 based on the cross-channel height.…”

Section: Case 3: Velocity Fields From a Non-reacting Jet In Vitiated ...mentioning

confidence: 99%

Permuted proper orthogonal decomposition for analysis of advecting structures

Nair

Douglas

et al. 2021

J. Fluid Mech.

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Flow data are often decomposed using proper orthogonal decomposition (POD) of the space–time separated form, $\boldsymbol {q}'\left (\boldsymbol {x},t\right )=\sum _j a_j\left (t\right )\boldsymbol {\phi }_j\left (\boldsymbol {x}\right )$ , which targets spatially correlated flow structures in an optimal manner. This paper analyses permuted POD (PPOD), which decomposes data as $\boldsymbol {q}'\left (\boldsymbol {x},t\right )=\sum _j a_j\left (\boldsymbol {n}\right )\boldsymbol {\phi }_j\left (s,t\right )$ , where $\boldsymbol {x}=(s,\boldsymbol {n})$ is a general spatial coordinate system, $s$ is the coordinate along the bulk advection direction and $\boldsymbol {n}=(n_1,n_2)$ are along mutually orthogonal directions normal to the advection characteristic. This separation of variables is associated with a fundamentally different inner product space for which PPOD is optimal and targets correlations in $s,t$ space. This paper presents mathematical features of PPOD, followed by analysis of three experimental datasets from high-Reynolds-number, turbulent shear flows: a wake, a swirling annular jet and a jet in cross-flow. In the wake and swirling jet cases, the leading PPOD and space-only POD modes focus on similar features but differ in convergence rates and fidelity in capturing spatial and temporal information. In contrast, the leading PPOD and space-only POD modes for the jet in cross-flow capture completely different features – advecting shear layer structures and flapping of the jet column, respectively. This example demonstrates how the different inner product spaces, which order the PPOD and space-only POD modes according to different measures of variance, provide unique ‘lenses’ into features of advection-dominated flows, allowing complementary insights.

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Combustion and flame position impacts on shear layer dynamics in a reacting jet in cross-flow

et al. 2022

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This study experimentally investigates reacting jets in cross-flow (RJICF), considering flame/shear layer offset, momentum flux ratio ( $J$ ) and density ratio ( $S$ ) effects. These results demonstrate that non-reacting JICF and RJICF can exhibit very similar or completely different dynamics and controlling physics, depending upon streamwise and radial flame location. Consistent with prior measurements of Getsinger et al. (Exp. Fluids, vol. 53 (3), 2012, pp. 783–801), spatial amplification rates of shear layer vortex (SLV) structures increased with decreasing $S$ for non-reacting cases. Similar $S$ dependencies exist for reacting cases in which the flame lay outside the jet shear layer, whose flow topology is also quite similar to non-reacting cases, albeit with reduced SLV growth rates. However, although the reacting cases have lower growth rates, these SLV structures ultimately reach approximately the same peak strength as in the non-reacting cases. Finally, the SLV decay rate in both non-reacting and reacting cases was found to similarly scale inversely with the initial SLV growth rate. As such, primarily inertial mechanisms govern SLV growth and decay for reacting cases where the flame lies outside the shear layer. In contrast, very different behaviour is exhibited by reacting cases where the flame lies inside the shear layer, where the locally increased viscosity exerts significant influences. In these reacting cases, SLV roll-up is completely suppressed and the entire jet column undulates over a long length scale relative to the jet diameter. As such, the relative roles of inertial and viscous mechanisms in controlling combustion influences on the SLV dynamics, changes markedly with shear layer–flame offset.

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Tomographic PIV Characterization of the Near field Topology of the Reacting Jet in Crossflow

Cited by 4 publications

References 19 publications

Combustion Mode and Mixing Characteristics of a Reacting Jet in Crossflow

Combustion Mode and Mixing Characteristics of a Reacting Jet in Crossflow

Permuted proper orthogonal decomposition for analysis of advecting structures

Combustion and flame position impacts on shear layer dynamics in a reacting jet in cross-flow

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