The decay of a turbulent swirl in a pipe

Kreith, Frank; Sønju, O. K.

doi:10.1017/s0022112065000733

Cited by 152 publications

(59 citation statements)

References 7 publications

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“…the standard deviation) of this histogram quantifies the turbulence intensity (18). As discussed by Durst et al [5] and generalized by Pashtrapanska [25], the turbulence intensity (18) …”

Section: Turbulence Factormentioning

confidence: 97%

“…Formed on early experimental observations, Kreith and Sonju [18] develop a theory that yields an exponential decay for turbulent swirling flow, granted the assumption of an axial mean velocity profile with a small perturbation and an eddy-viscosity for the tangential direction. Senoo and Nagata [29] derive an exponential law for the decay of through differentiating (1) with respect to the pipe length and making additional assumptions on the decay of the axial momentum flux.…”

Section: Decay Of Swirlmentioning

confidence: 99%

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Downstream relaxation of velocity profiles in pipe-flow with swirl disturbances

Graner¹,

Hinz²,

Breitsamter

2016

Tm - Technisches Messen

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Abstract:We study characteristic flow patterns downstream of a standardized swirl disturbance generator using laser-Doppler velocimetry (LDV). To investigate the spatial development of flow patterns, we conduct LDV measurements in cross-sections located at various distances downstream from the swirl disturbance generator. Focusing on velocity profiles, decay of swirl, and performance indicators used to describe the characteristic shape of the velocity profiles, we systematically compare the experimental results with available references and various theories for decay of swirl disturbances. We find that the standardized swirl disturbance generator provides exponentially decaying swirling flow that is best captured by the theory of Steenbergen and Voskamp¹. In addition, deviations from the axial reference profile caused by the swirl disturber persist for long downstream distances. In particular, our results suggest that the peakness factor relaxes linearly towards the fully-developed state.Keywords: Laser-Doppler velocimetry, swirl disturbance generator, swirling pipe-flow, performance indicators, downstream relaxation.

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“…the standard deviation) of this histogram quantifies the turbulence intensity (18). As discussed by Durst et al [5] and generalized by Pashtrapanska [25], the turbulence intensity (18) …”

Section: Turbulence Factormentioning

confidence: 97%

Section: Decay Of Swirlmentioning

confidence: 99%

Downstream relaxation of velocity profiles in pipe-flow with swirl disturbances

Graner¹,

Hinz²,

Breitsamter

2016

Tm - Technisches Messen

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“…where u,:' is the friction velocity and S is the particle stop distance given in dimensionless form, S+, by (50) This stop distance is calculated on a basis of a single constant value for the velocity of approaching the wall. The velocity is BNWL-578…”

Section: Model Of Friedlander and Johnstonementioning

confidence: 99%

Aerosol Deposition From Turbulent Airstreams in Vertical Conduits.

Sehmel¹

1968

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BNWL-578The general equations of continuity are set up to describe deposition of particles in which the eddy diffusi vity is related to the Reynolds stress. Simplifying assumptions in the general equations as well as simplifying assumptions to obtain a workable model are discussed. The general equations are used as a basis from which to discuss existing models of turbulent deposition. A model is being developed for the case of deposition in tubes. Deposition velocities are shown using the initial assumptions for solving the model.

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“…The influence of these parameters is related to the similar influence of heat flow density and pressure over the bubble boiling in the substantial volume. Performed numerical estimation of parts of pulsation duration Δτ 0 from the expression (38) shows the following. Processes of hermetic insertion in the calorimeter, gluing the wires on the case cover, insertion and sealing of cover openings and welding the wires to the mixer board are identical with the previously mentioned procedure for high-frequency generators.…”

Section: Analytical Evaluationmentioning

confidence: 99%

The Study of Condensation Processes in the Low-Temperature Short Heat Pipes with a Nozzle-Shaped Vapour Channel

Seryakov¹

2017

ENG

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The results of researches of condensation processes in the vapour channel similar to the Laval nozzle of short linear heat pipes are presented. Capacitive sensors are additionally installed in cooled top covers of the heat pipes, and electromagnetic pulses were supplied to them from the external generator. At heating the heat pipe evaporator, starting from a certain thermal power threshold value, electromagnetic pulses became modulated. It is related with the formations of the boiling process in the capillary-porous evaporator and large amount of vapour over it. Boiling process results in rapid increase of the pressure under which the average temperature of the evaporator occurs to be less than the boiling temperature of the working fluid under increased pressure. Considering condensation of excess vapour, this leads to repeated initiation and extinction of the boiling process in the evaporator, which reflects in pressure pulsations in the vapour channel. Pressure pulsations cause modulating effect on electromagnetic impulses. Pulsations frequencies are measured as well as their dependence from overheating of the evaporator. Using the capacitive sensors and a special electronic equipment we measured the local thickness of the working fluid at the condensing surface inside the heat pipes. Time-averaged values of the condensate film thickness are measured, depending on the heat load on the capillary-porous evaporator. The measurement error does not exceed 2 × 10 −3 mm. It is demonstrated that the condensate film thickness lessens sharply with the increase of the heat load on the evaporator of a Laval-like low-temperature heat pipe, while the heat resistance of the film on the condensing surface reaches 60% of the total heat resistance of heat pipe with the capillary-porous evaporator.

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The decay of a turbulent swirl in a pipe

Cited by 152 publications

References 7 publications

Downstream relaxation of velocity profiles in pipe-flow with swirl disturbances

Downstream relaxation of velocity profiles in pipe-flow with swirl disturbances

Aerosol Deposition From Turbulent Airstreams in Vertical Conduits.

The Study of Condensation Processes in the Low-Temperature Short Heat Pipes with a Nozzle-Shaped Vapour Channel

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