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Number of results: 4
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Abstract

Using perforated tube in exhaust mufflers is known to improve transmission loss (TL) by improving their sound pressure level (SPL) at the orifice. The perforated tube should affect the muffler performance analogous to a shell-and-tube heat exchanger. To the authors’ knowledge, there are few previous assessments reported in literature of the effects that the perforated tube configuration has on acoustic response and pressure drop predicted. The effects of (i) the perforated tube length, (ii) the diameter of tube holes, and (iii) flow through perforated tube were investigated. To assess the perforated tube effect on flow, the SOLIDWORKS 2017 based on Computational Fluid Dynamics (CFD) tool was utilized using real walls approach model with a surface roughness of 0.5 micrometres (AISI 316 cold rolled stainless steel sheet (ss) Ra = 0:5 μm). Perforated tube was found to cause back pressure which may increase SPL about 10%.
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Bibliography

1. Cui F., Wang Y., Cai R.C. (2014), Improving muffler performance using simulation-based design, [in:] INTER-NOISE and NOISE-CON Congress and Conference Proceedings, 249(7): 1190–1194.
2. Demir A., Çinar Ö.Y. (2009), Propagation of sound in an infinite two-part duct carrying mean flow inserted axially into a larger infinite duct with wall impedance discontinuity, ZAMM – Journal of Applied Mathematics and Mechanics, 89(6): 454–465, doi: 10.1002/zamm.200800145.
3. Elsayed A., Bastien C., Jones S., Christensen J., Medina H., Kassem H. (2017), Investigation of baffle configuration effect on the performance of exhaust mufflers, Case Studies in Thermal Engineering, 10: 86–94, doi: 10.1016/j.csite.2017.03.006.
4. Ferziger J.H., Peric M. (2002), Computational Methods for Fluid Dynamics, 3rd ed., Springer, doi: 10.1007/978-3-642-56026-2.
5. Lee I., Selamet A. (2006), Impact of perforation impedance on the transmission loss of reactive and dissipative silencers, The Journal of the Acoustical Society of America, 120(6): 3706–3713, doi: 10.1121/1.2359703.
6. Mohamad B. (2019), Design and optimization of vehicle muffler using the Ffowcs Williams and Hawkings model, Machine Design, 11(3): 101–106, doi: 10.24867/MD.11.2019.3.101-106.
7. Mohamad B., Karoly J., Zelentsov A., Amroune S. (2020), A hybrid method technique for design and optimization of Formula race car exhaust muffler, International Review of Applied Sciences and Engineering, 11(2): 174–180, doi: 10.1556/1848.2020.20048.
8. Siano D. (2010), Three-dimensional/one-dimensional numerical correlation study of a three-pass perforated tube, Simulation Modelling Practice and Theory, 19(4): 1143–1153, doi: 10.1016/j.simpat.2010.04.005.
9. Sim H.J., Park S.G., Joe Y.G., Oh J.E. (2008), Design of the intake system for reducing the noise in the automobile using support vector regression, Journal of Mechanical Science and Technology, 22(6): 1121–1131, doi: 10.1007/s12206-008-0306-z.
10. Tiryakioglu B. (2020), Radiation of sound waves by a semi-infinite duct with outer lining and perforated end, Archives of Acoustics, 45(1): 77–84, doi: 10.24425/aoa.2020.132483.
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Authors and Affiliations

Barhm Mohamad
1
Jalics Karoly
1
Andrei Zelentsov
2
Salah Amroune
3

  1. Faculty of Mechanical Engineering and Informatics, University of Miskolc, Miskolc, Hungary
  2. Piston Engine Department, Bauman Moscow State Technical University, Moscow, Russia
  3. Université Mohamed Boudiaf, M’sila, Algérie
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Abstract

A pontoon bridge, also known as a floating bridge, can be used as for pedestrian and vehicle traffic. The buoyancy of the floating bridge limits the maximum load it can carry. This research included experimental runs to study variations of open channel flow characteristics upstream and downstream a floating bridge. Eighty one runs have been carried out using a flume in a hydraulic laboratory. The experimental run program is classified into two main categories; the first investigates the velocity ratios (vds/vus) downstream and upstream the floating bridge. The second category is concerned with the energy head losses (hL) due to the presence of a floating bridge. The experimental runs are carried out using three pontoon lengths, three flow depths, six submerged depths, and three discharges. The results are analysed and graphically presented to help predict hydraulic parameters. The outcomes have shown that the floating bridge upstream, Froude number and submergence of the pontoon are the dominant parameters that affect the studied flow characteristics.
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Authors and Affiliations

Mohamed M. Ibrahim
1
ORCID: ORCID
Mahmoud A.R. Eltoukhy
1
ORCID: ORCID
Adnan D. Ghanim
2
ORCID: ORCID

  1. Benha University, Shoubra Faculty of Engineering, PO Box 11629, Shoubra, Egypt
  2. Advisor to the President of the Iraqi Council of Representatives, Iraq
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Abstract

The relationships between the conditions that describe the shape of the flow and power consumption characteristics and the pump design and performance parameters are described. These relations concern: - flow characteristics (throttling curves) described with a fourth-order polynomial, - non-overloading power consumption characteristics of the pump. The pumps that have to exhibit such characteristics are these designed to operate in an arbitrary installation. These pumps must also be characterised by cavitation-free operation in the whole range of discharge variability. In the relations presented, the condition of cavitation-free operation is considered as well.
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Authors and Affiliations

Andrzej Blaszczyk
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Abstract

The flow structure around rising single air bubbles in water and their characteristics, such as equivalent diameter, rising velocity and shape, was investigated using Particle Image Velocimetry (PIV) and Shadowgraphy in a transparent apparatus with a volume of 120 mL. The effect of different volumetric gas flow rates, ranging from 4 μL/min to 2 mL/min on the liquid velocity was studied. Ellipsoidal bubbleswere observedwith a rising velocity of 0.25–0.29m/s. It was found that a Kármán vortex street existed behind the rising bubbles. Furthermore, the wake region expanded with increasing volumetric gas flow rate as well as the number and size of the vortices.

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Authors and Affiliations

Björn Lewandowski
Michał Fertig
Georg Krekel
Mathias Ulbricht

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