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

2016 ◽  
Vol 83 (12) ◽  
Author(s):  
Simon Graner ◽  
Denis F. Hinz ◽  
Christian Breitsamter
Keyword(s):  
Cross Sections ◽  
Pipe Flow ◽  
Performance Indicators ◽  
Laser Doppler Velocimetry ◽  
Swirling Flow ◽  
Flow Patterns ◽  
Velocity Profiles ◽  
Doppler Velocimetry ◽  
Characteristic Shape ◽  
And Performance

AbstractWe 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 Voskamp

Experimental Investigation of Confined Swirling Flow and Its Interaction With a Bluff Body

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Zhang Tianxing ◽  
Mohamed Alshehhi ◽  
Lyes Khezzar ◽  
Yakang Xia ◽  
Nabil Kharoua
Keyword(s):  
Flow Structure ◽  
Pipe Flow ◽  
Laser Doppler Velocimetry ◽  
Bluff Body ◽  
Swirling Flow ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Doppler Velocimetry ◽  
Mean Square ◽  
The Mean

Abstract Detailed laser Doppler velocimetry (LDV) measurements of profiles of mean axial and tangential velocities and their corresponding root-mean-square (RMS) components in confined turbulent swirling pipe flow with and without the presence of a conical bluff body have been conducted. The working fluid was water and the Reynolds number based on the bulk velocity inside the pipe was equal to 40,850. The main focus of the study was to document the interaction between turbulent swirling flow inside a pipe and in the presence of a conical bluff body. The flow structure was found in all cases to be composed of a forced-free vortex. The swirl decay was exponential for Reynolds numbers of 40,850 and 14,450. The effect of the presence of the bluff body on the flow is limited to a short region upstream of it; so that the effect on the flow structure and strength of swirl upstream can be considered negligible. The flow around the bluff body adopts a different structure where the mean axial and tangential velocities tend to assume uniform profiles with turbulence activity limited to the region close to the surface of the bluff body.

Experimental Study of Velocity Fields in a Human Nasal Fossa by Laser Anemometry

1983 ◽  
Vol 92 (3) ◽  
pp. 231-236 ◽  
Author(s):  
Marc Girardin ◽  
Ertugrul Bilgen ◽  
Pierre Arbour
Keyword(s):  
Cross Sections ◽  
Laser Doppler Velocimetry ◽  
Velocity Fields ◽  
Nasal Fossa ◽  
Nasal Airway ◽  
Doppler Velocimetry ◽  
Noninvasive Method ◽  
Directional Effect ◽  
Laser Anemometry ◽  
Pathological Conditions

Velocity fields were mapped in a model of a human nasal fossa by laser doppler velocimetry, an innovative, quantitative and noninvasive method of optical anemometry, and by computerization. Other pertinent parameters were also calculated. Studies made at different cross sections of the nasal fossa showed the very definite influence not only of shapes and dimensions but also of direction of flow on velocity fields. The turbinates had a streamlining effect on the velocity fields while the liminal valve had a directional effect. Flow was usually greater in the lower half of the fossa and closer to the septum. The flow was generally turbulent. Velocity fields appear to give more information on intranasal aerodynamics than the calculated flow and Reynolds number for the sections studied, and this allows one to at least theorize that there may be an aerodynamic basis to certain pathological conditions of the nasal airway and its adjoining cavities, the paranasal sinuses, and the eustachian tubes.

Critical Reynolds Number in Constant-Acceleration Pipe Flow From an Initial Steady Laminar State

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Charles W. Knisely ◽  
Kazuyoshi Nishihara ◽  
Manabu Iguchi
Keyword(s):  
Reynolds Number ◽  
Flow Visualization ◽  
Pipe Flow ◽  
Laser Doppler Velocimetry ◽  
Critical Reynolds Number ◽  
Transition To Turbulence ◽  
Doppler Velocimetry ◽  
Constant Acceleration ◽  
Laminar State ◽  
Steady Laminar

The transition to turbulence in a constant-acceleration pipe flow from an initial laminar state was investigated in a custom-made apparatus permitting visual access to the water flow in the pipe. The apparatus allowed both laser Doppler velocimetry measurements and flow visualization using a tracer. The experiment was carried out by accelerating the flow from a steady laminar state to a steady turbulent state. The relation between the critical Reynolds number for transition to turbulence and the acceleration was found to be similar to that in a constant-acceleration pipe flow started from rest. In addition, with increased acceleration, the turbulent transition was found to be delayed to higher Reynolds numbers using flow visualization with simultaneous laser Doppler velocimetry measurements.

Aerodynamics Study of a Linearly-Arranged 5-Swirler Array

2014 ◽  
Author(s):  
Yi-Huan Kao ◽  
Samir B. Tambe ◽  
San-Mou Jeng
Keyword(s):  
Experimental Work ◽  
Laser Doppler Velocimetry ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Doppler Velocimetry ◽  
Wall Distance ◽  
Expansion Angle ◽  
Large Center ◽  
End Wall ◽  
Insight Into

In this experimental work, a series of tests have been conducted to further study the aerodynamics of linearly-arranged 5-swirler arrays, using Laser Doppler Velocimetry (LDV). Two major parameters have been investigated for the 5-swirler arrays in this work, including the inter-swirler spacing, and the end wall distance. An additional effect of dome recession was studied for a single swirler in order to provide some insight into the results for the 5-swirler arrays. The 5-swirler arrays with an inter-swirler spacing of 1.75D, 2D, 2.5D, and 2.75D were studied, where D is the diameter of swirler exit. For the inter-swirler spacing of 1.75D or 2D, the center swirler is shown to have a weak, large center toroidal recirculation zone (CTRZ). The swirlers next to the center swirlers have strong, compact CTRZs whereas the outer swirlers have weak, large CTRZs. Thus, starting from the center swirler, the CTRZs exhibit a large – small – large pattern in either direction. For the swirler spacing of 2.5D or 2.75D, the trend is reversed, with a strong CTRZ for the center swirler and a small – large – small CTRZ pattern. The end wall distances of 0.75D, 1D, 1.25D, and 2D cases were studied. The end wall distances are seen to affect the strength of each CTRZ and the corner swirling flow pattern, though the bulk flow structure did not change significantly. The dome recession shows a clear impact on the expansion of swirling flow generated by a single swirler. As the dome recession distance increases, the expansion angle of the swirling jet reduces significantly for the unconfined cases. A phenomenological description is discussed to understand the reason for the periodically alternating CTRZ pattern observed in the experimental results of the 5-swirler arrays.

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