Modal Analysis of the Surface Pressure Field Around a Hemispherical Turret using Pressure Sensitive Paint

Lucca, Nicholas G. De; Gordeyev, Stanislav; Morrida, Jacob J.; Jumper, Eric J.; Wittich, Donald J.

doi:10.2514/6.2018-0932

Cited by 8 publications

(5 citation statements)

References 26 publications

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“…The anti-symmetric Modes 1 and 4 have noticeable peaks at St D ≈ 0.18. This is consistent with results obtained in [8,26] and is associated with anti-symmetric vortex shedding. The spectra of modes 2 and 3 for the hemisphere do not have any noticeable peaks.…”

Section: Pod Analysissupporting

confidence: 93%

“…Mode 4 shows a strong anti-correlation in the wake similar to mode 1, which is again related to the alternating vortex shedding off of the turret. This mode was also seen in [26] where the alternating pockets continued downstream, which in this case, if the wake region was extended downstream, we would expect to see another set of correlated regions, but with a blue region on the positive Z side and a yellow region on the negative Z side. This mode also has anti-correlation between the dome and the wake as was seen in mode 2.…”

Section: Pod Analysismentioning

confidence: 57%

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Modal analysis of pressure fields on and around turrets with different protrusions

Bukowski

Kalensky

Gordeyev

et al. 2022

Unconventional Imaging and Adaptive Optics 2022

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Wind tunnel experiments were conducted to measure the unsteady surface pressure field of a hemisphere-oncylinder turret in subsonic flow. These measurements were obtained using pressure transducers coupled with fast response pressure sensitive paint. The surface pressure field data resulting from Mach 0.5 flow (Re D ≈ 2 × 10 6 ) over three different turret protrusion distances were analyzed. Previously, dominant surface pressure modes on the turret were found using proper orthogonal decomposition. The results of which showed that greater turret protrusion into the freestream flow increased the prevalence of spanwise anti-symmetric surface pressure field fluctuations. These anti-symmetric pressure fluctuations are caused by anti-symmetrical vortex shedding. However, when a partially submerged hemispherical turret geometry is used, it was shown that this anti-symmetric mode was of much lower relative energy. This suggests that there is a transition in flow field phenomena as protrusion is changed from partially submerged to a full hemisphere configuration. Further investigation into this so-called "mode switching" is the emphasis of the work presented here. This research heavily relied on modal analysis to identify correlations between turret and wake surface pressure fields. The fluctuations in the surface pressure field around the partial hemisphere were found to be mostly dominated by the wake with little influence from fluidic structures on the turret itself. For the hemisphere and hemisphere-oncylinder configurations, both symmetric and anti-symmetric unsteady separation grew to be the largest influence and was coupled with the wake fluctuations.

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Section: Pod Analysissupporting

confidence: 93%

Section: Pod Analysismentioning

confidence: 57%

Modal analysis of pressure fields on and around turrets with different protrusions

Bukowski

Kalensky

Gordeyev

et al. 2022

Unconventional Imaging and Adaptive Optics 2022

View full text Add to dashboard Cite

show abstract

“…Due to the presence of shock and shock-related separation at the surface of a turret, the flow over it under transonic free stream conditions is quite complex. To study the detailed regime of the transonic flow field over a turret, much experimental and numerical work has been performed (Coirier et al 2014;Vorobiev et al 2014;Beresh et al 2016;De Lucca et al 2018;Kamel et al 2019;Weston and Sherer 2019). Vorobiev et al (2014) studied the relationship between shock and relevant separation in a two-dimensional cylindrical turret in wind tunnel experiments.…”

Section: Introductionmentioning

confidence: 99%

“…The results showed a large distortion of the wavefront as the beam transited through the shock region, and the shock located in front of the top of the turret was different from that observed in the 2D cylindrical turret. De Lucca et al (2018) studied the pressure field of transonic flow over a hemisphere tested with pressure-sensitive paint, and the decomposition methods of proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) were implemented to identify the temporal and spatial characteristics of the flow field. They found that the fluctuation of the wake along the wall-normal direction, which contributed less than the lateral shift of the wake to the flow field, was the second mode feature.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of the Influences of the Features of Transonic Flow over a Hemispherical Turret on Beam Wavefront Distortions

2023

JAFM

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Complex features of transonic flow over a turret make it challenging to use passive flow control to reduce aero-optical effects. In this study, the influence of different flow features on wavefront distortions is numerically investigated through improved delayed detached eddy simulation coupled with a modified sub-grid scale. The proper orthogonal decomposition (POD) method is used to study the spatiotemporal characteristics of the flow features. The flow field changes in the wake along with the motion of the shock. Two features, namely, lateral shift (dominant in modes 1 and 2) and wall-normal fluctuation (dominant in modes 3 and 4) of the wake, are the most dominant in the flow field. All beams share the common feature of transmitting the flow field, in which a large component of optical path difference (OPD) appears at St=0.35, indicating the high impact of wall-normal fluctuation on the distortion of the wavefront. After the different POD modes, which contain 30% of the mode energy, are removed, all beams transmitted through different reconstructed fields show very different features for OPD. The flow features that do not exhibit higher-order modes from modes 21 to 92 affect the OPD slightly, as the OPD components in the low-St region are almost unchanged. With the removal of modes from 3 to 32, wavefront distortions are considerably reduced, particularly at St=0.35. The wavefront distortions are most reduced after the lower order modes from 1 to 20 are removed, as the components of OPD in the low-St region are dramatically reduced. The significant relations between OPD and the flow features reveal that controlling the dominant flow features has significant potential for reducing aero-optical effects.

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“…A companion paper [30] uses the same experimental data to alternatively study the dominant flow features using POD and Dynamic Mode Decomposition (DMD) techniques.…”

Section: Introductionmentioning

confidence: 99%

Conditional Studies of the Wake Dynamics of Hemispherical Turret Using PSP

Gordeyev

Lucca

Morrida

et al. 2018

2018 AIAA Aerospace Sciences Meeting

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Fast-response Pressure-Sensitive Paint (PSP) was used to study the wake response of the hemispherical turret at different subsonic and transonic Mach numbers to different pressure patterns on the hemisphere itself. POD technique was used to extract dominant spatial modes and the corresponding temporal coefficients of the unsteady pressure field on the hemisphere. The unsteady pressure distributions in the wake for different conditional events, such as large positive or negative temporal coefficients for different hemisphere-only POD modes, were computed and analyzed. It was found that the wake has the two main dynamic modes, the "switching" and "breathing" ones. The wake dynamics was found to be coupled with the instantaneous location of the separation line on the hemisphere. In the range of tested Mach numbers, the presence of the unsteady shock on the hemisphere did not have any significant effect of the wake dynamics.

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Modal Analysis of the Surface Pressure Field Around a Hemispherical Turret using Pressure Sensitive Paint

Cited by 8 publications

References 26 publications

Modal analysis of pressure fields on and around turrets with different protrusions

Modal analysis of pressure fields on and around turrets with different protrusions

Numerical Investigation of the Influences of the Features of Transonic Flow over a Hemispherical Turret on Beam Wavefront Distortions

Conditional Studies of the Wake Dynamics of Hemispherical Turret Using PSP

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