XCIV.<i>The turbulence in front of a body moving through a viscous fluid</i>

Piercy, N.A.V.; B.A., E.G. Richardson

doi:10.1080/14786443008565073

Cited by 19 publications

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“…Similar phenomena were detected in the next two investigations, one of circular cylinder flow (79) , the other of flow around a streamlined strut (80) . In the case of the cylinder (79) , the hot wire was also used to investigate separation around the cylinder's shoulder, the wire's signal being amplified so that the shed vorticity became audible (Fig.…”

Section: The Aeronautical Departmentsupporting

confidence: 82%

One hundred years of aeronautics in East London

Ackroyd¹,

Bernstein²,

Armstrong³

2008

Aeronaut. j.

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Section: The Aeronautical Departmentsupporting

confidence: 82%

One hundred years of aeronautics in East London

Ackroyd¹,

Bernstein²,

Armstrong³

2008

Aeronaut. j.

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“…The phenomenum of increased turbulence ahead of stagnation was first noted by Piercy & Richardson (1930) in some measurements ahead of an aerofoil in a wind tunnel with a high background turbulence level. Purther mention is made by Keuthe, Willmarth & Crocker (1959), who examined the stagnation region on bodies of revolution.…”

Section: Introductionmentioning

confidence: 84%

Some measurements of the distortion of turbulence approaching a two-dimensional bluff body

Bearman

1972

J. Fluid Mech.

105

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This paper describes an experimental study of the distortion of grid-generated turbulence as it approaches the stagnation region of a two-dimensional bluff body. When Lx/D [Gt ] 1, where Lx, is the scale of turbulence and D is a typical body dimension, along the mean stagnation streamline $(\overline{u^2})^{\frac{1}{2}$ attenuates like the mean flow, whereas if Lx/D [Lt ] 1 the turbulence is distorted by the mean flow field and $(\overline{u^2})^{\frac{1}{2}}$ will amplify because of vortex stretching. When Lx/D = O(1) there is found to be a combination of these effects with attenuation of energy at low wavenumbers and amplification at high wavenumbers. Measurements of the pressure fluctuations at the stagnation point show that at low wavenumbers the level of the pressure fluctuations can be predicted by a direct application of Bernoulli's equation.

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“…A theory of turbulent $ow round two-dimensional bluff bodies 629 There have by now been anumber of experiments to measure mean and fluctuating velocities around a bluff body when the incident stream is turbulent or nonturbulent. The pioneering work of Piercy & Richardson (1930) and all the other relevant experiments have been reviewed by Bearman (1972) and Sadeh et al (1970a). In this paper the only discussion of experiments is left to 87.3, where some experimental results are briefly compared with the theory.…”

Section: Introductionmentioning

confidence: 99%

A theory of turbulent flow round two-dimensional bluff bodies

1973

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By generalizing the theory of ‘rapid distortion’ of turbulence developed by Batchelor & Proudman (1954) it is shown in this paper that the turbulent velocity around a bluff body placed in a turbulent flow can be calculated outside and upstream of the regions of separated flow, if the incident turbulent flow satisfies the following conditions: (i) if a/Lx [Lt ] 1 or = O(1), Re−1$u^{\prime}_{\infty}/\overline{u}_{\infty} $ [Lt ] 1 [Lt ] Re½; (ii) if a/Lx [Gt ] 1, Re−1 [Lt ] $u^{\prime}_{\infty}$ [Lt ] 1/(a/Lx) and Re [Gt ] (a/Lx)2, where $Re = \overline{u}_{\infty} a/ν$, is the mean uniform incident velocity, $u^{\prime}_{\infty}$ is the r.m.s. velocity of the homogeneous incident turbulence, a is a transverse dimension of the body (the radius in the case of a circular cylinder), Lx is the integral scale of the incident turbulence and v is the kinematic viscosity.Detailed calculations are given for the flow around a circular cylinder with particular emphasis on the turbulence very close to the surface. (The results can be generalized to other cylindrical bodies.) Mean-square values and spectra of velocity have been found only in the limiting situations where the turbulence scale is very much larger or smaller than the size of the body, i.e. Lx [Gt ] a or Lx [Lt ] a. But, whatever the value of a/Lx, if the frequency is sufficiently large the results for spectra tend to those of the limiting situation where Lx [Lt ] a. The reason why the turbulence velocities have not been calculated for intermediate values of a/Lx is that closed-form solutions cannot be found and that the computing time then required is quite excessive. However, some computed results are used in the paper to suggest the qualitative behaviour of the turbulence when Lx is of order a. An important result of the theory is that it illuminates and distinguishes between the governing physical processes of distortion of the turbulence by the mean flow, the direct ‘blocking’ of the turbulence by the body, and concentration of vortex lines at the body's surface.The results of the theory have many applications, for example in calculating turbulent dispersion and fluctuating pressures on the body, as shown elsewhere by Hunt & Mulhearn (1973) and Hunt (1973).In conclusion the theoretical results are briefly compared with experimental measurements of turbulent flows round non-circular cylinders. A detailed comparison with measurements round circular cylinders will be published later by Petty (1974).

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XCIV.The turbulence in front of a body moving through a viscous fluid

Cited by 19 publications

References 0 publications

One hundred years of aeronautics in East London

One hundred years of aeronautics in East London

Some measurements of the distortion of turbulence approaching a two-dimensional bluff body

A theory of turbulent flow round two-dimensional bluff bodies

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