Numerical characterization of three-dimensional bluff body shear layer behaviour

Prosser, Daniel; Smith, Marilyn J.

doi:10.1017/jfm.2016.344

Cited by 21 publications

(20 citation statements)

References 22 publications

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“…When normalized by the initial values, x R 0 , the trend is apparently a weak function of Reynolds number with the reattachment lengths changing only a few per cent. It is noteworthy that this lack of dependency on Reynolds number has been recently confirmed in a three dimensional numerical simulation of a 3-D rectangular prism conducted by Prosser & Smith (2016) indicating that the two-dimensional nature of the current PIV data is still sufficient to capture most of the important physical phenomena associated with the shear layer.…”

Section: Reynolds Number Dependencymentioning

confidence: 89%

Energetic scales in a bluff body shear layer

Moore

Letchford²,

Amitay

2019

J. Fluid Mech.

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A detailed experimental campaign into separated shear layers stemming from rectangular sections (having aspect ratios of 5 : 1, 3 : 1 and 1 : 1) was carried out at Reynolds numbers range between $1.34\times 10^{4}$ and $1.18\times 10^{5}$ based on the body thickness. Particle image velocimetry was used to locate the highest concentration of fluctuations in the velocity field and subsequent hot-wire measurements at those locations provided adequate spectral resolution to follow the evolution of various instabilities that are active within the separated shear layer. Similar to recent findings by this same group, the shear layer behaviour is observed to contain a combination of Reynolds invariant characteristics, including its time-averaged position, while other properties demonstrate clear Reynolds number dependency, including the spatial amplification of turbulent kinetic energy. Additional results here show that the ratio of side lengths of the body is a key parameter in revealing these effects. One reason for this is the level of coupling between modes of instability, which is evaluated using two-point correlation methods. These findings indicate that the separated shear layer on a bluff body is highly nonlinear. A specific set of scales responsible for these unique behaviours is identified and discussed, along with their relationship to other scales in the flow.

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Section: Reynolds Number Dependencymentioning

confidence: 89%

Energetic scales in a bluff body shear layer

Moore

Letchford²,

Amitay

2019

J. Fluid Mech.

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“…Their results showed that the AR and Re have a great influence on the vortex shedding pattern, and five types of vortex shedding patterns were identified as: (I) periodic oblique vortex shedding (large AR, Re > Re c ); (II) quasi-periodic oblique vortex shedding (large AR, Re < Re c ); (III) hairpin vortex that periodically falls off (moderate AR); (IV) two stable counter-rotating vortex pairs (small AR and Re); (V) the counter-rotating vortex pairs alternately shed from the free ends (small AR, high Re). Prosser & Smith (2016) conducted large-eddy simulations coupled with the unsteady Reynolds-averaged Navier-Stokes (NS) equations using a finite-volume method to study the flow around bluff bodies (finite cylinder or prism) with much higher Re in the range of [10 5 , 10 6 ] and AR = 1 and 2. The influences of the geometric features and attitude of the bluff body on the reattachment distance, pressure coefficient and stagnation point position were investigated and modelled empirically.…”

Section: Flows Past a Finite Cylinder With Two Free Endsmentioning

confidence: 99%

“…and the cylinder with two free ends, e.g. submarine-like shape (Tezuka & Suzuki 2006;Sheard, Thompson & Hourigan 2008), torpedoes-like shape (Schouveiler & Provansal 2001), wheels (Zdravkovich et al 1989) and the short cylindrical bluff bodies (Prosser & Smith 2016;Yang et al 2021) etc. However, compared with the extensively studied flow past an infinite cylinder, there are relatively fewer works on the flow past a finite-length cylinder with two free ends and, thus, the current understanding of the flow dynamics past a finite-length cylinder is insufficient.…”

Section: Introductionmentioning

confidence: 99%

Onset of vortex shedding around a short cylinder

2021

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This paper presents results of three-dimensional direct numerical simulations (DNS) and global linear stability analyses of a viscous incompressible flow past a finite-length cylinder with two free flat ends. The cylindrical axis is normal to the streamwise direction. The work focuses on the effects of aspect ratios (in the range of $0.5\leq {\small \text{AR}} \leq 2$ , cylinder length over diameter) and Reynolds numbers ( $Re\leq 1000$ based on cylinder diameter and uniform incoming velocity) on the onset of vortex shedding in this flow. All important flow patterns have been identified and studied, especially as ${\small \text{AR}}$ changes. The appearance of a steady wake pattern when ${\small \text{AR}} \leq 1.75$ has not been discussed earlier in the literature for this flow. Linear stability analyses based on the time-mean flow has been applied to understand the Hopf bifurcation past which vortex shedding happens. The nonlinear DNS results indicate that there are two vortex shedding patterns at different $Re$ , one is transient and the other is nonlinearly saturated. The vortex-shedding frequencies of these two flow patterns correspond to the eigenfrequencies of the two global modes in the stability analysis of the time-mean flow. Wherever possible, we compare the results of our analyses to those of the flows past other short- ${\small \text{AR}}$ bluff bodies in order that our discussions bear more general meanings.

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“…Prosser Daniel T. and Smith Marilyn J. [10,11] used LES model and full-scale model flight tests to study the flow around the bluff body ( ⁄ = 1, 2) at 1×10 5 ≤ ≤ 1×10 6 . For the first time, the influence of angle of attack (0-90°) on the aerodynamic parameters of a short cylindrical bluff body is considered.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis on aerodynamic characteristics of short cylindrical terminal-sensitive bullet

Yang¹,

Guo²,

Rongzhong³

et al. 2018

Vib. proced.

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Abstract. The flow-induced lateral vibration phenomenon of the terminal sensitive bullets (TSB) when it is dispersed by the airborne distributor is taken as the research background. Based on the Fluent, the flow around a rotating short cylindrical TSB ( ⁄ < 1) is simulated and analyzed varying with relative rotation velocity at high Re number (1×10 5 ≤ ≤ 3×10 6 ). The simulation results show that the flow field structure of the short cylinder with two free ends is different from the symmetry of the short cylindrical flow field with one free end, and there is no horseshoe vortex. Compared to the long cylinder with double free ends, the of the short cylinder is more sensitive to the change of Re. With the increase of , the of the short cylinder decreases, and the value is between the infinite cylinder and the sphere in the non-critical region. When the short cylinder rotates at the angular velocity , the top vortex bends and deforms to a 'C' shape on the leeward side where the fluid is accelerated. Due to the periodic disturbance of the detector, the aerodynamic coefficient of the rotating TSB is periodically vibrated. In a single cycle, the waveform of the shows a 'W' shape, and the waveform of the is 'M'.

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Numerical characterization of three-dimensional bluff body shear layer behaviour

Cited by 21 publications

References 22 publications

Energetic scales in a bluff body shear layer

Energetic scales in a bluff body shear layer

Onset of vortex shedding around a short cylinder

Numerical analysis on aerodynamic characteristics of short cylindrical terminal-sensitive bullet

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