Near wake properties of axisymmetric bluff body flows

Humphries, W.

doi:10.1007/bf00384126

Cited by 22 publications

(8 citation statements)

References 12 publications

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“…The recirculation zone length is commonly used to evaluate the influences of inlet flow conditions. This length is sensitive to the incoming turbulence level and decreases towards an asymptote when the inlet turbulence level is increased (Humphries & Vincent 1976 a , b ; Castro & Robins 1977; Durao & Whitelaw 1978). Moreover, an increase in the blockage ratio of the bluff body decreases in unconfined flows (Davies & Beér 1971; Durao & Whitelaw 1978).…”

Section: Introductionmentioning

confidence: 99%

A scaling law for the recirculation zone length behind a bluff body in reacting flows

2019

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The recirculation zone length behind a bluff body is influenced by the turbulence intensity at the base of the body in isothermal flows and also the heat release and its interaction with turbulence in reacting flows. This relationship is observed to be nonlinear and is controlled by the balance of forces acting on the recirculation zone, which arise from the pressure and turbulence fields. The pressure force is directly influenced by the volumetric expansion resulting from the heat release, whereas the change in the turbulent shear force depends on the nonlinear interaction between turbulence and combustion. This behaviour is elucidated through a control volume analysis. A scaling relation for the recirculation zone length is deduced to relate the turbulence intensity and the amount of heat release. This relation is verified using the large eddy simulation data from 20 computations of isothermal flows and premixed flames that are stabilised behind the bluff body. The application of this scaling to flames in an open environment and behind a backward facing step is also explored. The observations and results are explained on a physical basis.

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Section: Introductionmentioning

confidence: 99%

A scaling law for the recirculation zone length behind a bluff body in reacting flows

2019

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“…In this paper, we test an approach for analyzing the transport of aerosols from the wake behind a flat disk (Humphries and Vincent, 1976a,b, hereafter referred to as HV) for studying aerosol transport in a furnished room. That approach is described in detail in the section of this paper.…”

Section: Introductionmentioning

confidence: 99%

Transport of airborne particles within a room

et al. 2006

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The objective of this study is to test a technique used to analyze contaminant transport in the wake of a bluff body under controlled experimental conditions for application to aerosol transport in a complex furnished room. Specifically, the hypothesis tested by our work is that the dispersion of contaminants in a room is related to the turbulence kinetic energy and length scale. This turbulence is, in turn, determined by the size and shape of furnishings within the room and by the ventilation characteristics. This approach was tested for indoor dispersion through computational fluid dynamics simulations and laboratory experiments. In each, 3 mum aerosols were released in a furnished room with varied contaminant release locations (at the inlet vent or under a desk). The realizable k approximately epsilon model was employed in the simulations, followed by a Lagrangian particle trajectory simulation used as input for an in-house FORTRAN code to compute aerosol concentration. For the experiments, concentrations were measured simultaneously at seven locations by laser photometry, and air velocity was measured using laser Doppler velocimetry. The results suggest that turbulent diffusion is a significant factor in contaminant residence time in a furnished room. This procedure was then expanded to develop a simplified correlation between contaminant residence time and the number of enclosing surfaces around a point containing the contaminant. Practical Implications The work presented here provides a methodology for relating local aerosol residence time to properties of room ventilation and furniture arrangement. This technique may be used to assess probable locations of high concentration by knowing only the particle release location, furniture configuration, inlet and outlet locations, and air speeds, which are all observable features. Applications of this method include development of 'rules of thumb' for first responders entering a room where an agent has been released and selection of sampler locations to monitor conditions in sensitive areas.

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“…The usual zeroth law is recovered when n ¼ m ¼ 0, and the new nonequilibrium dissipation law is recovered when n and m are both close to 1. The resulting scaling laws are (in terms of a virtual origin x 0 , which comes out naturally from the analysis) Studies of axisymmetric wakes go back more than 60 years and the bluff bodies which were used as wake generators are mostly spheres and disks placed normal to the incoming stream [14][15][16][17]. The new scaling laws (3) and (4) suggest a significantly higher rate of mixing of momentum than usual and we must therefore chose wake generators accordingly.…”

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confidence: 99%

Axisymmetric Turbulent Wakes with New Nonequilibrium Similarity Scalings

2013

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The recently discovered nonequilibrium turbulence dissipation law implies the existence of axisymmetric turbulent wake regions where the mean flow velocity deficit decays as the inverse of the distance from the wake-generating body and the wake width grows as the square root of that distance. This behavior is different from any documented boundary-free turbulent shear flow to date. Its existence is confirmed in wind tunnel experiments of wakes generated by plates with irregular edges placed normal to an incoming free stream. The wake characteristics of irregular bodies such as buildings, bridges, mountains, trees, coral reefs, and wind turbines are critical in many areas of environmental engineering and fluid mechanics.

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Near wake properties of axisymmetric bluff body flows

Cited by 22 publications

References 12 publications

A scaling law for the recirculation zone length behind a bluff body in reacting flows

A scaling law for the recirculation zone length behind a bluff body in reacting flows

Transport of airborne particles within a room

Axisymmetric Turbulent Wakes with New Nonequilibrium Similarity Scalings

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