Effect of plate thickness on impedance of perforated plates with bias flow

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1573-1578
Author(s):  
Xiaodong Jing ◽  
Xiaofeng Sun
Keyword(s):  
Plate Thickness ◽  
Perforated Plates ◽  
Bias Flow

A Novel Design Method for Robust Acoustic Dampers With Perforated Plates Backed by a Cavity Operating at Low and High Strouhal Numbers

2012 ◽  
Author(s):  
A. Scarpato ◽  
S. Ducruix ◽  
T. Schuller
Keyword(s):  
Flow Velocity ◽  
Design Method ◽  
Resonant Cavity ◽  
Plate Thickness ◽  
Optimization Procedure ◽  
Absorption Frequency ◽  
Perforated Plates ◽  
Peak Absorption ◽  
Bias Flow ◽  
Optimal Bias

It is known that the frequency of thermo-acoustic instabilities may vary according to various parameters during operation. The design of passive acoustic dampers tuned to damp specific unstable frequencies must then include this aspect to offer robust properties. This problem is tackled here for perforated plates backed by a resonant cavity in the absence of grazing flow. Their current design relies on a relatively complex optimization procedure with a large number of parameters to examine. A new methodology is proposed to reduce this number by finding the optimal parameters maximizing absorption in two limit regimes, where the choice of the optimal bias flow velocity and size of the back cavity can be decoupled. The former is only controlled by the plate porosity while the latter fixes the peak absorption frequency. The analysis also includes effects of the plate thickness. In both regimes, the optimal bias flow velocity is analytically determined. A Helmholtz resonance and a narrow absorption peak in the frequency space characterize the first absorption regime reached at high Strouhal numbers. This regime minimizes the size of the resonant back cavity, but the absorption frequency bandwidth narrows with increasing Strouhal numbers. The second absorption regime reached at low Strouhal numbers operates with a quarter-wave resonator. This regime requires larger cavity depths but offers a wider absorption bandwidth around the peak absorption frequency well suited for low frequency dampers when the bias flow velocity or the unstable frequency may vary within the system. Theoretical predictions are validated against experimental data obtained in the two regimes identified. The expressions derived in this study can be used to improve the design of robust acoustic dampers.

Effect of Plate Thickness on Impedance of Perforated Plates with Bias Flow

AIAA Journal ◽  
2000 ◽  
Vol 38 (9) ◽  
pp. 1573-1578 ◽  
Author(s):  
Xiaodong Jing ◽  
Xiaofeng Sun
Keyword(s):  
Plate Thickness ◽  
Perforated Plates ◽  
Bias Flow

EFFECT OF GRAZING–BIAS FLOW INTERACTION ON ACOUSTIC IMPEDANCE OF PERFORATED PLATES

2002 ◽  
Vol 254 (3) ◽  
pp. 557-573 ◽  
Author(s):  
X. SUN ◽  
X. JING ◽  
H. ZHANG ◽  
Y. SHI
Keyword(s):  
Acoustic Impedance ◽  
Perforated Plates ◽  
Flow Interaction ◽  
Bias Flow

Cavitation Inception and Head Loss Due to Liquid Flow Through Perforated Plates of Varying Thickness

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
D. Maynes ◽  
G. J. Holt ◽  
J. Blotter
Keyword(s):  
Plate Thickness ◽  
Area Ratio ◽  
Diameter Ratio ◽  
Hole Diameter ◽  
Loss Coefficient ◽  
Perforated Plates ◽  
Cavitation Inception ◽  
Perforation Hole ◽  
Critical Cavitation ◽  
Free Area

This paper reports results of an experimental investigation of the loss coefficient and onset of cavitation caused by water flow through perforated plates of varying thickness and flow area to pipe area ratio at high speeds. The overall plate loss coefficient, point of cavitation inception, and point where critical cavitation occurs are functions of perforation hole size, number of holes, and plate thickness. Sixteen total plates were considered in the study with the total perforation hole area to pipe area ratio ranging from 0.11 and 0.6, the plate thickness to perforation hole diameter ranging from 0.25 to 3.3, and the number of perforation holes ranging from 4 to 1800. The plates were mounted in the test section of a closed water flow loop. The results reveal a complex dependency between the plate loss coefficient with total free-area ratio and the plate thickness to perforation hole diameter ratio. In general, the loss coefficient decreases with increasing free-area ratio and increasing thickness-to-hole diameter ratio. A model based on the data is presented that predicts the loss coefficient for multiholed perforated plates with nonrounded holes. Furthermore, the data show that the cavitation number at the points of cavitation inception and critical cavitation increases with increasing free-area ratio. However, with regard to the thickness-to-hole diameter ratio, the cavitation number at inception exhibits a local maximum at a ratio between 0.5 and 1.0. Empirical models to allow prediction of the point of cavitation inception and the point where critical cavitation begins are presented and compared to single hole orifice plate behavior.

On Buckling and Ultimate Strength of Perforated Plate Panels under Axial Compression: Experimental and Numerical Investigations with Design Formulations

2008 ◽  
Author(s):  
Ul-Nyeon Kim ◽  
Ick-Heung Choe ◽  
Jeom Kee Paik
Keyword(s):  
Finite Element ◽  
Ultimate Strength ◽  
Steel Plate ◽  
Slenderness Ratio ◽  
Plate Thickness ◽  
Shipbuilding Industry ◽  
Perforated Plates ◽  
Stiffened Panels ◽  
Buckling Strength ◽  
Plate Panels

It has been recognized that the current shipbuilding industry design practice for perforated plates is not relevant with relatively large opening size and/or with large plate thickness, and it is believed that this problem has caused structural damage accidents in actual ship structures with opening. The motive of the present study was initiated to resolve this issue by introducing a new design formulation of the critical buckling strength for perforated plates which is now pertinent to the structural design application at a safety side. For this purpose, a series of experimental and numerical studies are undertaken on buckling and ultimate strength of plates and stiffened panels with an opening and under axial compressive actions. A total of 90 perforated plates and also a total of 9 stiffened panels with an opening are tested until and after the ultimate strength is reached, where important parameters of influence such as the plate aspect ratio, the plate slenderness ratio, the opening size and shape, and the opening location are varied. Elastic-plastic large deflection finite element analyses are performed on the test structures. Existing and newly-derived design formula solutions of buckling and ultimate strength on the test plate panels are compared with experimental results and nonlinear finite element computations, indicating that the critical buckling strength formulation developed in the present study as well as an existing ultimate strength formula is useful for design and strength assessment of steel plate panels with an opening. The experimental database on buckling collapse of steel plate panels with an opening will be very useful for future use. Details of experiments and numerical computations together with insights developed from the present study are documented.

Comparison of Limit Load Solutions with Results of Collapse Tests of Perforated Plates with a Triangular Penetration Pattern

2002 ◽  
Author(s):  
D. P. Jones ◽  
J. L. Gordon
Keyword(s):  
Plate Thickness ◽  
Perforated Plate ◽  
Limit Load ◽  
Small Strain ◽  
Transverse Load ◽  
Strength Parameter ◽  
Plastic Collapse ◽  
Perforated Plates ◽  
Small Deflection ◽  
Deformation Patterns

Limit load solutions obtained by elastic-perfectly plastic finite element analysis (EPP-FEA) are compared to results of tests of low-alloy steel perforated plate geometries loaded to full plastic collapse. Results are given for two plastic-collapse tests of flat circular disks with circular penetrations arranged in a triangular pattern and drilled normal to the surface of the plate. The ligament efficiency (minimum distance between holes divided by the distance between the centers of the holes) of the pattern is 0.32 and the plate thickness is 2.39 inches (60.7 mm). The tests were designed so that a transverse load generated plastic collapse in the outer row of penetrations due to a combination of transverse shear and in-plane bending. Limit-load solutions were obtained using EPP-FEA with small-strain, small-deflection linear geometry assumptions. Two FEA models are used: one where the perforated region is modeled using an equivalent solid plate (EQS) representation and another where each hole is explicitly modeled by FEA. The results presented in this paper demonstrate that the deformation patterns produced by the EPP-FEA solutions match exactly with the deformation patterns produced by the test. The EQS-EPP FEA solution is about 15% lower than the explicit-hole EPP-FEA solution. Using one-third the actual ultimate strength of the material as the strength parameter in the limit load calculation produces a calculated limit load that is greater than a factor of three less than the mean measured plastic-collapse load obtained in the tests. This paper adds to the qualification of the use of limit-load solutions obtained using small-strain, small deflection EPP-FEA programs for the calculation of the limit load for perforated plates.

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