Water column impact on a rigid wall with air cavity effects

2019 ◽  
Vol 31 (4) ◽  
pp. 042112 ◽  
Keyword(s):  
Water Column ◽  
Rigid Wall ◽  
Air Cavity ◽  
Cavity Effects

scholarly journals 200. A comparison of air-cavity effects for ^Co and 10MVX ray beams

1990 ◽  
Vol 46 (8) ◽  
pp. 1174
Author(s):  
Hideo Murata ◽  
Mituhiro Chabatake ◽  
Yasuhiro Shimada
Keyword(s):  
Air Cavity ◽  
Cavity Effects

Air cavity effects on the radiation dose to the larynx using Co-60, 6 MV, and 10 MV photon beams

1994 ◽  
Vol 29 (5) ◽  
pp. 1139-1146 ◽  
Author(s):  
Azam Niroomand-Rad ◽  
K. William Harter ◽  
Senti Thobejane ◽  
Kari Bertrand
Keyword(s):  
Radiation Dose ◽  
Photon Beams ◽  
Air Cavity ◽  
Cavity Effects

Absorption of Normal-Incidence Acoustic Waves by Double Perforated Liners of Industrial Gas Turbine Combustors

2012 ◽  
Author(s):  
Charith Jayatunga ◽  
Qin Qin ◽  
Victoria Sanderson ◽  
Phil Rubini ◽  
Danning You ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Parametric Study ◽  
Acoustic Waves ◽  
Rigid Wall ◽  
Gas Turbine Combustor ◽  
Air Cavity ◽  
Impedance Tube ◽  
Impedance Model ◽  
Incident Plane ◽  
Absorption Characteristics

Perforated liners consist of sheet metal perforated with multiple holes with diameters of magnitude in the order of millimeters and regular spacing, backed by an air cavity in front of a rigid wall. This type of liner is very effective at absorbing sound and is used in many applications. At the resonance frequency, the liner shifts the phase of the incident wave by 180° thus providing damping through wave cancellation. The perforations in the liner convert acoustic energy into flow energy through vortex shedding at the rims of the liner apertures. Applied to gas turbine combustors they can attenuate thermoacoustic instabilities and as such significantly improve the reliability of the gas turbine with an additional benefit to the emissions. The Siemens SGT-100 to 400 engines exploit this technology in their DLE combustion system in a configuration of two concentric liners separated by an air cavity with the rear liner acting as the rigid wall in the conventional setting. In this paper the evaluation of double perforated liners in the absorption of normal-incident plane acoustic waves in an impedance tube and in a gas turbine combustor environment is investigated. A one-dimensional impedance model that embodies the electro-acoustic analogy was used to predict the absorption characteristics of the double perforated liner. The model was validated by comparing the predictions with experimental data obtained from the impedance tube, with excellent agreement. With the confidence in the equations of the model in predicting the acoustic behavior, the model was then applied to predict the damping performance under realistic gas turbine combustor operating conditions. The prediction also shows two distinct peaks in the absorption characteristics of a double-liner. Geometric parameters such as hole diameters & thicknesses of the two liners, gap between the liners and the overall pressure drop across the liners have been considered for the predictions. A parametric study of these parameters carried out using the ISIGHT software with design investigation tools identified the order of importance of the parameters considered for sound absorption. The work reported in this paper has successfully validated an impedance model in the prediction of double perforated liners in the absorption of normal-incident plane acoustic waves. Based on the parametric study carried out design guidelines are given for designing a double perforated liner for maximum absorption of normal incident acoustic waves.

Comparison of the performance of oscillating water column devices based on arrangements of water columns

2020 ◽  
Vol 14 (3) ◽  
pp. 7082-7093
Author(s):  
Jahirwan Ut Jasron ◽  
Sudjito Soeparmani ◽  
Lilis Yuliati ◽  
Djarot B. Darmadi
Keyword(s):  
Wave Propagation ◽  
Water Column ◽  
Water Depth ◽  
Graphical Form ◽  
Wave Power ◽  
Oscillating Water Column ◽  
Power Absorption ◽  
Water Columns ◽  
Single Column ◽  
Parallel Arrangement

The hydrodynamic performance of oscillating water column (OWC) depends on the depth of the water, the size of the water column and its arrangement, which affects the oscillation of the water surface in the column. An experimental method was conducted by testing 4 water depths with wave periods of 1-3 s. All data recorded by the sensor is then processed and presented in graphical form. The research focused on analyzing the difference in wave power absorption capabilities of the three geometric types of OWC based on arrangements of water columns. The OWC devices designed as single water column, the double water column in a series arrangement which was perpendicular to the direction of wave propagation, and double water column in which the arrangement of columns was parallel to the direction of wave propagation. This paper discussed several factors affecting the amount of power absorbed by the device. The factors are the ratio of water depth in its relation to wavelength (kh) and the inlet openings ratio (c/h) of the devices. The test results show that if the water depth increases in the range of kh 0.7 to 0.9, then the performance of the double chamber oscillating water column (DCOWC) device is better than the single chamber oscillating water column (SCOWC) device with maximum efficiency for the parallel arrangement 22,4%, series arrangement 20.8% and single column 20.7%. However, when referring to c/h, the maximum energy absorption efficiency for a single column is 27.7%, double column series arrangement is 23.2%, and double column parallel arrangement is 29.5%. Based on the results of the analysis, DCOWC devices in parallel arrangement showed the ability to absorb better wave power in a broader range of wave frequencies. The best wave of power absorption in the three testing models occurred in the wave period T = 1.3 seconds.

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