scholarly journals The Dependence of Flue Pipe Airflow Parameters on the Proximity of an Obstacle to the Pipe’s Mouth

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 10
Author(s):  
Damian Węgrzyn ◽  
Piotr Wrzeciono ◽  
Alicja Wieczorkowska
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Fundamental Frequency ◽  
Coming Out ◽  
Measuring Instruments ◽  
Air Jet ◽  
The Relationship

This paper describes the influence of the presence of an obstacle near the flue pipe’s mouth on the air jet, which directly affects the parameters of the sound generated by the flue pipe. Labial pipes of the most common types of mouth were tested. The method of interval calculus was used instead of invasive measuring instruments. The obtained results prove that the proximity of an obstacle affects the sound’s fundamental frequency, as the airflow speed coming out of the flue pipe’s mouth changes. The relationship between the airflow speed, the value of the Reynolds number, and the Strouhal number was also established. The thesis of the influence of the proximity of an obstacle on the fundamental frequency of the sound of a flue pipe was generalized, and formulas for calculating the untuning of the sound of the pipe were presented for various types of mouth.

Mixing Enhancement by Using Turbulent Jets

2014 ◽  
Author(s):  
Hariyo P. S. Pratomo
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Axial Velocity ◽  
Radial Profile ◽  
Intermittent Flow ◽  
Pulsed Jets ◽  
Pulsed Jet ◽  
Air Jet ◽  
Radial Profiles ◽  
Lower Reynolds Number

Experimental results of a fully pulsed subsonic air jet issuing into the still surrounding air are reported in this paper. The intermittent flow containing a period of no flow between pulses due to the mechanically excitation was gauged by a single wire hot-wire anemometer operated in a constant temperature mode. A range of the Reynolds and Strouhal numbers of 1 × 104 < Re < 4 × 104 and 0.0064 < St < 0.0076 respectively was used to define the jets. Results of the traverse measurement agreed with earlier findings demonstrating strong effects of the excitation on the radial profiles of the mean axial velocity of the jet. Within the parameter ranges investigated, the pulsed jets were found to be significantly more spreading than steady jets. A less dispersive pulsed jet, however, appeared at a higher jet exit velocity. Strikingly, contradictory trends in the jet growth and entrainment at the higher and lower Reynolds number were seen as the lower Reynolds number does not produce a widening radial profile as a result of the increasing Strouhal number. From the axial measurements, the pulsed jets were characterized by the pulsed dominated- and high turbulence steady jet region in which their existences heavily relied on the magnitudes of the controlled parameters. A less fluctuating pulsed jet associated with the reduced magnitudes of aggregate turbulence intensity and relative turbulence energy however, appeared at an increased Strouhal number. Comparative studies with the existing results of non-circular orifice jets i.e cruciform, elliptic, and triangular jets are also reported to display the decay rates of centerline axial velocity and the spreading rates of the jets which benefit for the practical purposes.

Heat transfer of multi-slot nozzle air jet impingement with different Reynolds number

2020 ◽  
pp. 116470
Author(s):  
Jinqi Zhu ◽  
Ruifeng Dou ◽  
Ye Hu ◽  
Shixing Zhang ◽  
Xuyun Wang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Jet Impingement ◽  
Slot Nozzle ◽  
Air Jet

Mixing of an Acoustically Excited Air Jet With a Confined Hot Crossflow

1992 ◽  
Vol 114 (1) ◽  
pp. 46-54 ◽  
Author(s):  
P. J. Vermeulen ◽  
P. Grabinski ◽  
V. Ramesh
Keyword(s):  
Strouhal Number ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Mixing Zone ◽  
Wake Region ◽  
Mixing Processes ◽  
Jet Mixing ◽  
Air Jet ◽  
Percent Increase ◽  
Jet Structure

The mixing of an acoustically pulsed air jet with a confined hot crossflow has been assessed by temperature profile measurements. These novel experiments were designed to examine the effects of acoustic driver power and Strouhal number on jet structure, penetration, and mixing. The results showed that excitation produced strong changes in the measured temperature profiles. This resulted in significant increases in mixing zone size, penetration (at least 100 percent increase), and mixing, and the length to achieve a given mixed state was shortened by at least 70 percent. There was strong modification to the jet-wake region. The increase in jet penetration and mixing was saturating near 90 W, the largest driving power tested. The jet response as determined by penetration and mixing was optimum at a Strouhal number of 0.27. Overall, pulsating the jet flow significantly improved the jet mixing processes in a controllable manner.

The Relationship Between Frictional Resistance and Roughness for Surfaces Smoothed by Sanding

2002 ◽  
Vol 124 (2) ◽  
pp. 492-499 ◽  
Author(s):  
Michael P. Schultz
Keyword(s):  
Reynolds Number ◽  
Frictional Resistance ◽  
Resistance Coefficient ◽  
Polished Surface ◽  
Average Height ◽  
Freestream Velocity ◽  
Number Range ◽  
Test Fixture ◽  
Plate Length ◽  
The Relationship

An experimental investigation has been carried out to document and relate the frictional resistance and roughness texture of painted surfaces smoothed by sanding. Hydrodynamic tests were carried out in a towing tank using a flat plate test fixture towed at a Reynolds number ReL range of 2.8×106−5.5×106 based on the plate length and freestream velocity. Results indicate an increase in frictional resistance coefficient CF of up to 7.3% for an unsanded, as-sprayed paint surface compared to a sanded, polished surface. Significant increases in CF were also noted on surfaces sanded with sandpaper as fine as 600-grit as compared to the polished surface. The results show that, for the present surfaces, the centerline average height Ra is sufficient to explain a large majority of the variance in the roughness function ΔU+ in this Reynolds number range.

Do We Need Higher Dose Scale Inhibitors to Inhibit Scale under Turbulent Conditions? Insight into Mechanisms and New Test Methodology

2014 ◽  
Author(s):  
Tao Chen ◽  
Ping Chen ◽  
Harry Montgomerie ◽  
Thomas Hagen ◽  
Ronald Benvie ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Growth Inhibitor ◽  
Test Method ◽  
Bulk Precipitation ◽  
Scale Inhibitor ◽  
Surface Deposition ◽  
Test Methodology ◽  
The Relationship ◽  
Scale Deposition

Abstract Turbulent flow, especially around chokes, downhole safety valves and inflow control devices, favors scale deposition potentially leading to severe loss of production. Recently, scale formation under turbulent conditions has been studied and progressed, focused on the bulk precipitation (SPE164070) and a small bore valve loop test (SPE 155428). However, bulk precipitation is not fully representative the surface deposition in the fields and the Reynolds number of modified loop is unknown. The relationship between a measured Reynolds number and surface deposition up until this study has not been addressed. A newly developed test methodology with rotating cylinder has been applied to generate high shear rate and evaluate surface deposition with Reynolds numbers up to ~41000. The relationship between Reynolds number and surface deposition is addressed. Using this highly representable test method for BaSO4 scale deposition, several different generic types of inhibitor chemistries, including polymers and phosphonates, were assessed under different levels of turbulence to evaluate their performance on surface deposition. The results showed it is not always true that higher turbulence results in higher dose of inhibitor being required to control scale. It is inhibitor chemistry and mechanisms dependent. The scale inhibitorscan be classified as three types when evaluating the trend of mass deposition versus Reynolds number and the morphology of the crystals deposited on the metal surface. ➢ Type 1: Crytal growth inhibitors. The mass of surface deposition increases with the increase of turbulence, along with smaller crystals.➢ Type 2: Dispersion and crystal growth inhibitor. The higher the turbulence, the less mass deposition, along with smaller crystals.➢ Type 3: Dispersion scale inhibitors. The higher the turbulence, the less mass deposition. The size of the crystals has no major change. This paper gives a comprehensive study of the effect of flow condition on the scale surface deposition and inhibition mechanisms. In addition, it details how this methodology and new environmentally acceptable inhibitor chemistry can be coupled to develop a chemical technology toolbox that also includes techniques for advanced scale inhibitor analysis and improved scale inhibitor retention, to design optimum scale squeeze packages for the harsh scaling conditions associated with turbulent flow conditions.

Strouhal Number for VIV Excitation of Long Slender Structures

2018 ◽  
Author(s):  
Andrew E. Potts ◽  
Douglas A. Potts ◽  
Hayden Marcollo ◽  
Kanishka Jayasinghe
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Degrees Of Freedom ◽  
Measurement Techniques ◽  
Cross Flow ◽  
Degree Of Freedom ◽  
Circular Cylinders ◽  
Two Degrees Of Freedom ◽  
Shedding Frequency ◽  
Eddy Shedding

The prediction of Vortex-Induced Vibration (VIV) of cylinders under fluid flow conditions depends upon the eddy shedding frequency, conventionally described by the Strouhal Number. The most commonly cited relationship between Strouhal Number and Reynolds Number for circular cylinders was developed by Lienhard [1], whereby the Strouhal Number exhibits a consistent narrow band of about 0.2 (conventional across the sub-critical Re range), with a pronounced hump peaking at about 0.5 within the critical flow regime. The source data underlying this relationship is re-examined, wherein it was found to be predominantly associated with eddy shedding frequency about fixed or stationary cylinders. The pronounced hump appears to be an artefact of the measurement techniques employed by various investigators to detect eddy-shedding frequency in the wake of the cylinder. A variety of contemporary test data for elastically mounted cylinders, with freedom to oscillate under one degree of freedom (i.e. cross flow) and two degrees of freedom (i.e. cross flow and in-line) were evaluated and compared against the conventional Strouhal Number relationship. It is well established for VIV that the eddy shedding frequency will synchronise with the near resonant motions of a dynamically oscillating cylinder, such that the resultant bandwidth of lock-in exhibits a wider range of effective Strouhal Numbers than that reflected in the narrow-banded relationship about a mean of 0.2. However, whilst cylinders oscillating under one degree of freedom exhibit a mean Strouhal Number of 0.2 consistent with fixed/stationary cylinders, cylinders with two degrees of freedom exhibit a much lower mean Strouhal Number of around 0.14–0.15. Data supports the relationship that Strouhal Number does slightly diminish with increasing Reynolds Number. For oscillating cylinders, the bandwidth about the mean Strouhal Number value appears to remain largely consistent. For many practical structures in the marine environment subject to VIV excitation, such as long span, slender risers, mooring lines, pipeline spans, towed array sonar strings, and alike, the long flexible cylinders will respond in two degrees of freedom, where the identified difference in Strouhal Number is a significant aspect to be accounted for in the modelling of its dynamic behaviour.

Strouhal number of flat and flapped plates at moderate Reynolds number and different angles of attack: experimental data

2018 ◽  
Vol 230 (1) ◽  
pp. 333-349 ◽  
Author(s):  
Ali Bakhshandeh Rostami ◽  
Mohammad Mobasheramini ◽  
Antonio Carlos Fernandes
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Strouhal Number ◽  
Moderate Reynolds Number

Vocal Tract Steadiness

1992 ◽  
Vol 35 (4) ◽  
pp. 761-768 ◽  
Author(s):  
Petra Zwirner ◽  
Gary J. Barnes
Keyword(s):  
Motor Control ◽  
Fundamental Frequency ◽  
Vocal Tract ◽  
Upper Airway ◽  
Normal Subjects ◽  
Subject Group ◽  
Formant Frequency ◽  
Control Subjects ◽  
Acoustic Analyses ◽  
The Relationship

Acoustic analyses of upper airway and phonatory stability were conducted on samples of sustained phonation to evaluate the relation between laryngeal and articulomotor stability for 31 patients with dysarthria and 12 non-dysarthric control subjects. Significantly higher values were found for the variability in fundamental frequency and formant frequency of patients who have Huntington’s disease compared with normal subjects and patients with Parkinson’s disease. No significant correlations were found between formant frequency variability and the variability of the fundamental frequency for any subject group. These findings are discussed as they pertain to the relationship between phonatory and upper airway subsystems and the evaluation of vocal tract motor control impairments in dysarthria.

Sign in / Sign up

Export Citation Format

Share Document