Alternative drag coefficient in the wake of an isolated bluff body

Alam, Md. Mahbub; Zhou, Yu

doi:10.1103/physreve.78.036320

Cited by 18 publications

(12 citation statements)

References 33 publications

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“…ζ = C 0.6 D St = 0.2 is the fitting curve based on the least squares technique, with ζ = 0.22 and 0.18 corresponding to the upper and the lower envelopes, respectively. Correlations by Hoerner (1965), Ahlborn et al (2002) and Alam & Zhou (2008) are also included for the purpose of comparison.…”

Section: Relation Between C D and Stmentioning

confidence: 99%

“…Evaluation of various St ∼ CD relations (equation 3.11 to 3.14): (a) St calculated from CD on a circular cylinder summarised in Tropea et al (2007); (b) CD calculated from St on a square cylinder summarised in Blevins (1990). Experimental data from Okajima (1982), White (2001) and Alam & Zhou (2008) are included for the purpose of comparison.…”

Section: Relation Between C D and Stmentioning

confidence: 99%

“…They obtained a relation between St, Re, C D and geometric wake parameters through the definition of a universal St based on the size of an individual shed vortex. Alam & Zhou (2008) conducted a theoretical analysis based on the conservation of the averaged kinetic energy given no energy exchange between the bluff body and its support. They showed on the basis of experimental data reported in the literature as well as theirs that the product C D St is approximately a constant, which is almost independent on the shape of a bluff body, its angle of attack and Re.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study of flow around polygonal cylinders

Zhang²,

Gan

et al. 2016

J. Fluid Mech.

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The wake of polygonal cylinders with side number $N=2\sim \infty$ is systematically studied based on fluid force, hot-wire, particle image velocimetry and flow visualisation measurements. Each cylinder is examined for two orientations, with a flat surface or a corner leading and facing normally to the free stream. The Reynolds number $Re$ is $1.0\times 10^{4}\sim 1.0\times 10^{5}$, based on the longitudinally projected cylinder width. The time-averaged drag coefficient $C_{D}$ and fluctuating lift coefficient on these cylinders are documented, along with the characteristic properties including the Strouhal number $St$, flow separation point and angle $\unicode[STIX]{x1D703}_{s}$, wake width and critical Reynolds number $Re_{c}$ at which the transition from laminar to turbulent flow occurs. It is found that once $N$ exceeds 12, $Re_{c}$ depends on the difference between the inner diameter (tangent to the faces) and the outer diameter (connecting corners) of a polygon, the relationship being approximately given by the dependence of $Re_{c}$ on the height of the roughness elements for a circular cylinder. It is further found that $C_{D}$ versus $\unicode[STIX]{x1D709}$ or $St$ versus $\unicode[STIX]{x1D709}$ for all the tested cases collapse onto a single curve, where the angle $\unicode[STIX]{x1D709}$ is the corrected $\unicode[STIX]{x1D703}_{s}$ associated with the laterally widest point of the polygon and the separation point. Finally, the empirical correlation between $C_{D}$ and $St$ is discussed.

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Section: Relation Between C D and Stmentioning

confidence: 99%

Section: Relation Between C D and Stmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental study of flow around polygonal cylinders

Zhang²,

Gan

et al. 2016

J. Fluid Mech.

Self Cite

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“…The variation of the peak amplitude as a function of the Reynolds number can be estimated using the following assumptions. The mean drag coefficient and the inverse of the Strouhal number for stationary bluff bodies display similar variations as functions of so that the product remains almost constant (Alam & Zhou 2008). For vibrating cylinders, there is also evidence that the corresponding product remains constant (Griffin 1978).…”

Section: Development Of New Linear Theorymentioning

confidence: 98%

Resonance in vortex-induced in-line vibration at low Reynolds numbers

2020

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“…A notable feature was that a compressible and viscous flow near the aircraft can be considered as an incompressible and inviscid in the far wake. Alam and Zhou [18] proposed an alternative drag coefficient for an isolated bluff-body wake. Their drag coefficient formulation could be considered as a drag coefficient with the characteristic length given by U ∞ T s -where U ∞ is the free-stream velocity and T s is the vortex shedding period, instead of the characteristic length of cylinder height.…”

Section: Introductionmentioning

confidence: 99%

Streamlined bodies drag force estimation using wake integration technique

Shirazi

Manshadi

2020

J Braz. Soc. Mech. Sci. Eng.

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In this paper, the drag force calculation around the SUBOFF submarine in axisymmetric configuration was investigated using the "Wake Integration Technique." This method is usually used in wind tunnels as an auxiliary method instead of the common "surface integral technique" for flow around complex geometries or shock wave flows. The results of this method are dependent on data collection vertex space, distance, and section size, where practical suggestions were made for each parameter in this research. Furthermore, the contribution of the pressure, momentum, and fluctuation terms in the total drag force were also evaluated at different cross sections. These findings can be implemented in wind tunnels with small test section length and also to compare the results obtained by the common surface integral method. Simulations were carried out at different aspect ratios at zero angles of attack, and the capabilities of this method at inclined flows were also discussed. The obtained results were also compared against the common method, and the results show only 4% deviation at zero angle. Keywords Wake survey • Wind tunnel • Drag force • Momentum defect principle • Suboff submarine List of symbols L Body length D Maximum body diameter AR Length-to-the-diameter aspect ratio x, y, z Coordinate system Δx, Δy Grid space in x and y-direction d The ratio of grid space to diameter X Longitudinal distance from the body r Measurement radius S Surface area P , u Local pressure and velocity P ∞ , U ∞ Free-stream pressure and velocity C D Drag coefficient C p Pressure coefficient Incidence angle y + Dimensionless wall distance Fluid density xx Normal stress component

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Alternative drag coefficient in the wake of an isolated bluff body

Cited by 18 publications

References 33 publications

Experimental study of flow around polygonal cylinders

Experimental study of flow around polygonal cylinders

Resonance in vortex-induced in-line vibration at low Reynolds numbers

Streamlined bodies drag force estimation using wake integration technique

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