3D flow structures behind a wall-mounted short cylinder

Rinoshika, Hiroka; Rinoshika, Akira; Wang, Jinjun; Zheng, Yan

doi:10.1016/j.oceaneng.2020.108535

Cited by 18 publications

(6 citation statements)

References 39 publications

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“…For both the door mirror and the slotted door mirror, the distributions of the streamwise and lateral components are observed to be symmetric and antisymmetric about the wake centerline, respectively, which are opposite to the distributions of the first two modes, indicating that mode 3 can be linked to the symmetric vortex shedding. 31,32 Additionally, it is worth noting that the spatial patterns of the slotted door mirror are presented in a more symmetric and organized fashion, indicating the enhancement of the symmetric vortex structure. Focusing on mode 4, the spatial patterns of the slotted door mirror still appear as a symmetric vortex structure.…”

Section: Resultsmentioning

confidence: 98%

“…These observations are consistent with the POD analyses of the near-free end surface of a finite-length circular cylinder. 31 In general, the relative energies of the dominant POD modes of the slotted door mirror are reduced for all three measurement planes, which may result in the weakening of the large-scale flow oscillation.…”

Section: Modal Energy and Spatial Patterns Of Pod Modesmentioning

confidence: 95%

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Wake flow modification of vehicle external door mirror with slots

Zheng

Zhang

Rinoshika

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part D:

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A passive flow control method is applied to a vehicle external door mirror by introducing flow from a slot drilling from the front surface to four slots around the rear surface. The wake flow fields behind the door mirror and slotted door mirror are experimentally investigated via particle image velocimetry measurements at a Reynolds number of 12,736. The time-averaged flow fields suggest that the reverse-flow region of the slotted door mirror is reduced and pushed downstream; correspondingly, the turbulent kinetic energy of the slotted door mirror is reduced, implying the suppression of unsteadiness and a reduction in the drag force acting on the door mirror. As a result of the jet flow, the wake flow of the slotted door mirror exhibits a weaker spatial correlation and a smaller length scale, indicating the suppression of large-scale vortex shedding and the enhancement of small-scale flow motion by the slots. The jet flows from the left and right slots of the slotted door mirror prevent the upper and lower shear layers from interacting with each other, which promotes symmetric vortex shedding in the near-wake region. The power spectral density and modal energy distributions suggest that the strength of the primary vortex shedding is reduced by the slotted door mirror. The spatial patterns of the first two proper orthogonal decomposition modes suggest that the jet flow distorts the dominant large-scale structure, reducing the strength of the flow oscillation behind the slotted door mirror. The spatial distributions of modes 3 and 4 suggest that the symmetric vortex shedding is enhanced by the jet flow from the slotted door mirror.

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Section: Resultsmentioning

confidence: 98%

Section: Modal Energy and Spatial Patterns Of Pod Modesmentioning

confidence: 95%

Wake flow modification of vehicle external door mirror with slots

Zheng

Zhang

Rinoshika

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part D:

Self Cite

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show abstract

“…With the multiplicative algebraic reconstruction technique (MART), it realizes the flow measurement with high spatial resolution and accuracy. The TPIV technique has been demonstrated as an effective tool for complex 3-D flow measurements (Gao, Wang & Shen 2013;, such as the cylinder wake (Zhu et al 2017;Rinoshika et al 2021), wakes of stationary and freely moving spheres (van Hout et al 2018(van Hout et al , 2022Eshbal et al 2019), near-wall turbulence (Schröder et al 2008Gao, Ortiz-Dueñas & Longmire 2011;Wang et al 2019) and wakes of aquatic organisms (Adhikari & Longmire 2013;Murphy et al 2016;Mohaghar, Adhikari & Webster 2019;Tu et al 2022). With the access of time-resolved 3-D velocity data, 3-D pressure reconstruction with high spatial and temporal resolution has become achievable.…”

Section: Introductionmentioning

confidence: 99%

“…2017; Rinoshika et al. 2021), wakes of stationary and freely moving spheres (van Hout et al. 2018, 2022; Eshbal et al.…”

Section: Introductionmentioning

confidence: 99%

Tomographic PIV investigation on near-wake structures of a hemisphere immersed in a laminar boundary layer

Tu,

Wang,

Gao

et al. 2023

J. Fluid Mech.

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The near wake of a hemisphere immersed in a laminar boundary layer is studied utilizing time-resolved tomographic particle image velocimetry (TPIV). Focus is placed on the three-dimensional vortical structures and the formation details of hairpin vortices before the onset of transition. The three-dimensional instantaneous pressure field of the hemisphere wake is reconstructed for better understanding the flow mechanism. Experiments are carried out with Reynolds number $Re_{r}=1370$ , based on the hemisphere radius $R$ . Features of periodicity of the near wake are analysed using proper orthogonal decomposition and Fourier transformation. The velocity fluctuation in the wall-normal direction is shown to be crucial to the formation of hairpin vortices in the near wake. By investigating the transport of mass and vorticity, and the correlation between pressure and hairpin vortex strength, the formation mechanism is revealed clearly. Specifically, the main hairpin vortices (MHVs) are formed within the reaction of outer high-speed flow and near-wall flow. The formation of the head portion is followed by the leg portion formation. The shedding of the MHVs is highly correlated with the pressure, as well as the pressure gradient in the wall-normal direction. For the side hairpin vortices (SHVs), the leg portion is formed first, followed by the generation of the head portion thanks to induction of the re-oriented standing vortices. The generation of the SHVs can be regarded as the downstream bridging of the standing vortices, similar to the generation of hairpin vortices due to the connection of streamwise vortices in turbulent boundary layers.

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“…In order to solve this problem, particle image velocimetry (PIV) technology and equipment based on high speed cameras were developed and had successfully been applied in fluid flow. 10 This system only had one more function than the high speed cameras. It could directly extract the velocity of the flow field at any point but it could not extract the pressure.…”

Section: Introductionmentioning

confidence: 99%

Identifying the processes and characterizing the pressure zone of water jet impacting on solid surface

Zhang

Kou

et al. 2022

Advances in Mechanical Engineering

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The difficulty in understanding the flow characteristics of water jets impacting on solid surfaces made the water jet technology requiring further investigations. The Arbitrary Lagrange-Euler (ALE) method is used to develop a numerical model of the water jet impacting on a solid surface. It is also utilized in describing the flow characteristics of water and the pressure evolution in water during the impact process, understanding the formation mechanism of the pressure zone, and clarifying the influence factors of the stagnation pressure zone. The results showed that the pressure zone was characterized by the shock wave produced by the water jet impacting the solid surface. When the shock wave was contained in the water, it was the water hammer pressure stage. However, when the shock wave in water was disappeared, the stage was identified as the stagnation pressure. Besides, the water hammer pressure caused a high speed radial jet, and the stagnation pressure resulted in a low speed and stable radial jet. The stagnation pressure zone was the self-buffer zone of the water jet impacting the object, and the geometric characteristics of this zone were affected by the water jet diameter and the impact angle.

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3D flow structures behind a wall-mounted short cylinder

Cited by 18 publications

References 39 publications

Wake flow modification of vehicle external door mirror with slots

Wake flow modification of vehicle external door mirror with slots

Tomographic PIV investigation on near-wake structures of a hemisphere immersed in a laminar boundary layer

Identifying the processes and characterizing the pressure zone of water jet impacting on solid surface

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