On the generation of swirling jets: high-Reynolds-number rotating flow in a pipe with a final contraction

2011 ◽  
Vol 692 ◽  
pp. 78-111 ◽  
Author(s):  
Benjamin Leclaire ◽  
Laurent Jacquin
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
High Reynolds Number ◽  
Global Dynamics ◽  
Wall Region ◽  
Mean Flow ◽  
Subcritical Regime ◽  
Swirling Jet ◽  
Contraction Ratio ◽  
High Reynolds

AbstractWe investigate the generation conditions of a high-Reynolds-number swirling jet experiment, based on a rotating honeycomb device and using a final contraction. Using hot-wire measurements, we first show that for high swirl levels, the flow at the jet exhaust may exhibit fully developed turbulence in the whole plane. By analysing the fluctuation levels obtained for several values of the contraction ratio, ranging from 4 to 18.4, we prove that this turbulence does not result from upstream-propagating disturbances initiated in the jet, but originates in the pipe flow upstream of the exit plane. Using stereo particle image velocimetry, we then measure the flow in the constant-cross-section pipe located between the rotating honeycomb outlet and the contraction. This investigation is supplemented with simplified numerical simulations of the mean flow. The pipe flow dynamics is found to result from the interplay of a rich variety of complex phenomena, which are independent of the contraction ratio in the range considered here. In the near-wall region, centrifugal instability occurs in the form of intermittent azimuthal vortices, starting from moderate swirl levels and persisting for all higher levels. As the flow exiting from the honeycomb has a swirl level high enough to reach the subcritical regime, a complex mean flow organization is observed, dominated by the presence of large-amplitude axisymmetric Kelvin wave trains. Gradients in the resulting flow lead to the appearance of generalized centrifugal instabilities in an annular region in the rotational core, starting in the early subcritical regime. As the swirl level is further increased, large-scale, high-amplitude axisymmetric and simple spiral perturbations add to the global dynamics, leading to an overall very high fluctuation level. Consideration of the turbulent spectra in the jet exit planes suggests that the simple spiral coherent structure could be the resonant response of the flow to the periodic excitation by the rotating honeycomb. Overall, the study illustrates why a swirling jet experiment should exclude the use of a final contraction in order to guarantee smooth flow conditions in the exit at high swirl.

On the theory of unsteady high Reynolds number flow through a circular aperture

1979 ◽  
Vol 366 (1725) ◽  
pp. 205-223 ◽  
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
High Reynolds Number ◽  
Circular Aperture ◽  
Mean Flow ◽  
Reynolds Number Flow ◽  
Contraction Ratio ◽  
Number Flow ◽  
Flow Through ◽  
High Reynolds

This paper examines the theory of the unsteady motion caused by fluctuations in the driving pressure of a high Reynolds number mean flow through a circular aperture in a thin rigid plate. A theoretical model is proposed which is amenable to exact analytical treatment, and involves the shedding of vorticity from the rim of the aperture. The theory determines the dependence of the Rayleigh conductivity of the aperture on the Strouhal number, and provides quantitative estimates for the rate of dissipation of large scale ordered structures as a result of the generation of turbulence at the apertures in a perforated liner. The limit of zero Strouhal number yields a description of steady high Reynolds number flow, the contraction ratio of the emerging jet being predicted to be equal to the minimum theoretical value of ½. Application is made to the problem of sound trans­mission through a uniformly perforated screen in the presence of a low Mach number bias flow.

A Modified Form of the k-ε Model for Predicting Wall Turbulence

1981 ◽  
Vol 103 (3) ◽  
pp. 456-460 ◽  
Author(s):  
C. K. G. Lam ◽  
K. Bremhorst
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
Dissipation Rate ◽  
High Reynolds Number ◽  
Present Form ◽  
Wall Turbulence ◽  
Wall Region ◽  
Wall Function ◽  
High Reynolds ◽  
Number Form

The high Reynolds number form of the k-ε model is extended and tested by application to fully developed pipe flow. It is established that the model is valid throughout the fully turbulent, semilaminar and laminar regions of the flow. Unlike many previously proposed forms of the k-ε model, the present form does not have to be used in conjunction with empirical wall function formulas and does not include additional terms in the k and ε equations. Comparison between predicted and measured dissipation rate in the important wall region is also possible.

scholarly journals A theory for the streamwise turbulent fluctuations in high Reynolds number pipe flow

2012 ◽  
Vol 707 ◽  
pp. 575-584 ◽  
Author(s):  
Marcus Hultmark
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Pipe Flow ◽  
High Reynolds Number ◽  
Mean Flow ◽  
Mean Velocity ◽  
Theoretical Derivation ◽  
Turbulent Fluctuations ◽  
The Mean ◽  
High Reynolds

AbstractA new theory for the streamwise turbulent fluctuations in fully developed pipe flow is proposed. The theory extends the similarities between the mean flow and the streamwise turbulence fluctuations, as observed in experimental high Reynolds number data, to also include the theoretical derivation. Connecting the derivation of the fluctuations to that of the mean velocity at finite Reynolds number as introduced by Wosnik, Castillo & George (J. Fluid Mech., vol. 421, 2000, pp. 115–145) can explain the logarithmic behaviour as well as the coefficient of the logarithm. The slope of the logarithm, for the fluctuations, depends on the increase of the fluctuations with Reynolds number, which is shown to agree very well with the experimental data. A mesolayer, similar to that introduced by Wosnik et al., exists for the fluctuations for $300\gt {y}^{+ } \gt 800$, which coincides with the mesolayer for the mean velocities. In the mesolayer, the flow is still affected by viscosity, which shows up as a decrease in the fluctuations.

scholarly journals Video: DNS of turbulent pipe flow at high Reynolds number

2021 ◽  
Author(s):  
Alessandro Ceci ◽  
Sergio Pirozzoli ◽  
Joshua Romero ◽  
Massimiliano Fatica ◽  
Roberto Verzicco ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
High Reynolds Number ◽  
Turbulent Pipe Flow ◽  
High Reynolds

The effect of rigid rotation on the finite-amplitude stability of pipe flow at high Reynolds number

1984 ◽  
Vol 148 ◽  
pp. 193-205 ◽  
Author(s):  
T. R. Akylas ◽  
J.-P. Demurger
Keyword(s):  
Reynolds Number ◽  
Pipe Flow ◽  
High Reynolds Number ◽  
Finite Amplitude ◽  
Linear Instability ◽  
Rigid Rotation ◽  
Transition To Turbulence ◽  
Neutral Stability ◽  
Axisymmetric Mode ◽  
High Reynolds

A theoretical study is made of the stability of pipe flow with superimposed rigid rotation to finite-amplitude disturbances at high Reynolds number. The non-axisymmetric mode that requires the least amount of rotation for linear instability is considered. An amplitude expansion is developed close to the corresponding neutral stability curve; the appropriate Landau constant is calculated. It is demonstrated that the flow exhibits nonlinear subcritical instability, the nonlinear effects being particularly strong owing to the large magnitude of the Landau constant. These findings support the view that a small amount of extraneous rotation could play a significant role in the transition to turbulence of pipe flow.

Experimental study on high Reynolds number pipe flow

2019 ◽  
Vol 2019.68 (0) ◽  
pp. 217
Author(s):  
Kusano Eisuke ◽  
Noriyuki Furuichi ◽  
Wada Yuki ◽  
Yoshiyuki Tsuji
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Pipe Flow ◽  
High Reynolds Number ◽  
High Reynolds

scholarly journals Low-Reynolds-number turbulent boundary layers

1991 ◽  
Vol 230 ◽  
pp. 1-44 ◽  
Author(s):  
Lincoln P. Erm ◽  
Peter N. Joubert
Keyword(s):  
Reynolds Number ◽  
Boundary Layers ◽  
Low Reynolds Number ◽  
Turbulent Boundary Layers ◽  
Stream Velocity ◽  
Wall Region ◽  
Mean Flow ◽  
Low Reynolds ◽  
High Reynolds ◽  
Turbulent Wall

An investigation was undertaken to improve our understanding of low-Reynolds-number turbulent boundary layers flowing over a smooth flat surface in nominally zero pressure gradients. In practice, such flows generally occur in close proximity to a tripping device and, though it was known that the flows are affected by the actual low value of the Reynolds number, it was realized that they may also be affected by the type of tripping device used and variations in free-stream velocity for a given device. Consequently, the experimental programme was devised to investigate systematically the effects of each of these three factors independently. Three different types of device were chosen: a wire, distributed grit and cylindrical pins. Mean-flow, broadband-turbulence and spectral measurements were taken, mostly for values of Rθ varying between about 715 and about 2810. It was found that the mean-flow and broadband-turbulence data showed variations with Rθ, as expected. Spectra were plotted using scaling given by Perry, Henbest & Chong (1986) and were compared with their models which were developed for high-Reynolds-number flows. For the turbulent wall region, spectra showed reasonably good agreement with their model. For the fully turbulent region, spectra did show some appreciable deviations from their model, owing to low-Reynolds-number effects. Mean-flow profiles, broadband-turbulence profiles and spectra were found to be affected very little by the type of device used for Rθ ≈ 1020 and above, indicating an absence of dependence on flow history for this Rθ range. These types of measurements were also compared at both Rθ ≈ 1020 and Rθ ≈ 2175 to see if they were dependent on how Rθ was formed (i.e. the combination of velocity and momentum thickness used to determine Rθ). There were noticeable differences for Rθ ≈ 1020, but these differences were only convincing for the pins, and there was a general overall improvement in agreement for Rθ ≈ 2175.

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