Traditional passive noise control techniques using Helmholtz resonators have size limitations at ... more Traditional passive noise control techniques using Helmholtz resonators have size limitations at low frequency due to the long wavelengths. Promising noise reductions, with flush mounted Stainless Steel patches with no such constraints can be obtained building on local resonance phenomenon implemented in acoustic metamaterials techniques. The objective of the current paper is to introduce locally resonant thin Steel patches flush mounted to an acoustic duct walls aiming at creating frequency stop bands at the low frequency zone (below 1 KHz). Green’s Function is used under the framework of interface response theory to predict the degree of attenuation of the local resonant patches. The experimental results were compared with Analytical theory and Finite elements and a close agreement was found.
A modelling of low-frequency sound propagation in slowly varying ducts with smoothly varying lini... more A modelling of low-frequency sound propagation in slowly varying ducts with smoothly varying lining is proposed leading to an acoustic mild-slope equation analogue to the with mild-slope equation for water waves. This simple 1D Mild Slope Equation is derived by direct application of the Galerkin method. It is shown that the acoustic mild-slope equation can serve as a good alternative to computationally expensive Helmholtz equations to solve such kind of problem. The results from this equation agrees well with FEM based solutions of Helmholtz equation.
A re ection-less acoustic cloak inside ducts is proposed in the audible range where plane waves a... more A re ection-less acoustic cloak inside ducts is proposed in the audible range where plane waves are bended around the object using boundary impedance. The cloak possesses low-re ection and wave-front bending properties, which could approximate the ideal cloak with inhomogeneous and anisotropic distribution of material parameters. The cloak is e ective in a broadband frequency range, and the cloaking range is a function of the boundary impedance.
Acoustic cloaking for the suppression of backscattering inside ducts is proposed in the audible r... more Acoustic cloaking for the suppression of backscattering inside ducts is proposed in the audible range where plane waves are curved around the object using the surface modes of the liner. It is numerically shown that a slowly varying resonant liner (e. g. based on an array of tubes) creates a zone of silence in which an object of arbitrary shape can be acoustically hidden for a wide range of frequencies. And then, a resonant liner has deflecting properties without reflection of the wavefront, which are close to an ideal invisibility cloak. This kind of cloaking is effective in a wide frequency band and the cloaking band is a function of the impedance and height of the obstacle relative to the conduit. For smooth shaped obstacles, there is an ability of the object to help hide itself, which increases the cloaking frequency band (self-cloaking). Dispersion effects lead to slow sounds and distortion of the wave phase.
The objective of this doctoral thesis is to study three different innovative noise control techni... more The objective of this doctoral thesis is to study three different innovative noise control techniques in ducts namely: acoustic metamaterials, porous absorbers and microperforates. There has been a ...
Acoustic cloaking for the suppression of backscattering inside ducts is proposed in the audible r... more Acoustic cloaking for the suppression of backscattering inside ducts is proposed in the audible range where plane waves are curved around the object using the surface modes of the liner. It is numerically shown that a slowly varying resonant liner (e.g. based on an array of tubes) creates a zone of silence in which an object of arbitrary shape can be acoustically hidden for a wide range of frequencies. And then, a resonant liner has deflecting properties without reflection of the wavefront, which are close to an ideal invisibility cloak. This kind of cloaking is effective in a wide frequency band and the cloaking band is a function of the impedance and height of the obstacle relative to the conduit. For smooth shaped obstacles, there is an ability of the object to help hide itself, which increases the cloaking frequency band (self-cloaking). Dispersion effects lead to slow sounds and distortion of the wave phase.
The Journal of the Acoustical Society of America, 2018
For acoustic waves in lined ducts, at given frequencies, the dispersion relation leads to a trans... more For acoustic waves in lined ducts, at given frequencies, the dispersion relation leads to a transcendental equation for the wavenumber that has to be solved by numerical methods. Based on an Eckart explicit expression initially derived for water waves, accurate explicit approximations are proposed for the wavenumber of the fundamental mode in lined ducts. While the Eckart expression is 5% accurate, some improved approximations can reach maximum relative errors of less than 10 À8. The cases with small dissipation parts in the admittance of the liner and/or axisymmetric ducts are also considered.
The acoustic effects of in-parallel resonators is compared to the behavior of a classical single ... more The acoustic effects of in-parallel resonators is compared to the behavior of a classical single degree of freedom resonator for which the resistance and the mass are in series. In-parallel resonators serve to enhance the acoustic absorption for mid-frequencies thereby extending the active frequency range of perfect acoustic absorbers. Two implementations of these in-parallel absorbers are presented and investigated experimentally as well as numerically. In the first demonstration, the resistance is a perforated plate with a wiremesh and the oscillating mass is the air that fills a tube passing through the plate. The second implementation consists of a thin flexible beam that oscillates and where the resistance is due to the micro-slit resulting from the cutting of the beam.
The Journal of the Acoustical Society of America, 2017
Acoustic impedance for perforates is mainly quantified by semi or totally empirical formulas, whi... more Acoustic impedance for perforates is mainly quantified by semi or totally empirical formulas, which depend on the experimental set-up used and are specific for each type of tested sample. In this work, the acoustic impedance of a micro-perforated plate (MPP) with two-sided low Mach grazing flow is educed by a modified semi-analytical inverse technique. The inputs to this technique are complex acoustic pressure measured at eight positions at the wall of the duct, upstream and downstream of the MPP section. Several measurements on the two sided grazing flow rig are conducted and trends in the impedance shift are observed. These trends serve to quantify the change in the resistance and reactance of a MPP when it is subjected to two sided grazing flow. An empirical formula is also proposed which is based on these trends. This formula helps in approximating the behavior of MPP’s in applications such as perforated cooling fans, perforated guide vanes, and turbine nozzles. It was observed that with increased flo...
The Journal of the Acoustical Society of America, 2016
A thin subwavelength material that can be flush mounted in a duct and that gives an attenuation b... more A thin subwavelength material that can be flush mounted in a duct and that gives an attenuation band at low frequencies in air flow channels is presented. To decrease the material thickness, the sound is slowed in the material using folded side branch tubes. The impedance of the material is compared to the optimal value given by the Cremer condition, which can differ greatly from the air characteristic impedance. Grazing flow on this material increases the losses at the interface between the flow and the material.
The Journal of the Acoustical Society of America, 2016
Since conventional silencers in acoustic ducts have problems of size limitations at low frequenci... more Since conventional silencers in acoustic ducts have problems of size limitations at low frequencies and being prone to high backpressure, locally resonant aluminum patches are introduced in acoustic duct walls aiming at creating frequency stop bands in the low frequency region (below 1 KHz). With these flush mounted patches, promising noise reductions, with no such drawbacks, can be obtained, building on local resonance phenomenon implemented in acoustic metamaterials techniques. The objective of the current paper is to experimentally validate the performance of an array of flexible side-wall-mounted patches inside ducts. The experimental results are compared with Analytical Green's function method as well as Numerical Finite Element Method and a close agreement was found. The results show that the presence of the patches singly or periodically can play a prominent role in designing any acoustic bandgap materials. The effect of the arrays of patches on the effective dynamic density and bulk modulus has also been investigated. V C 2016 Acoustical Society of America.
In this paper, the acoustic impedance of a microperforated plate (MPP) with two-sided grazing flo... more In this paper, the acoustic impedance of a microperforated plate (MPP) with two-sided grazing flow is educed by a modified semi-analytical inverse technique. The MPP sample is placed in the middle ...
SAE International Journal of Materials and Manufacturing, 2015
A novel porous metallic foam has been studied in this work. This composite material is a mixture ... more A novel porous metallic foam has been studied in this work. This composite material is a mixture of resin and hollow spheres. It is lightweight, highly resistive to contamination and heat, and is c ...
Praise belongs to Allah, the Lord of all the worlds (2) The All-Merciful, the Very-Merciful. (3) ... more Praise belongs to Allah, the Lord of all the worlds (2) The All-Merciful, the Very-Merciful. (3) The Master of the Day of Requital. (4) You alone do we worship, and from You alone do we seek help. (5) Take us on the straight path (6) The path of those on whom You have bestowed Your Grace, Not of those who have incurred Your wrath, nor of those who have gone astray. (7) Al-Fatiha I begin with the name of Allah, the most beneficent, the most merciful. May Allah bestow peace on our beloved Prophet Mohammed (peace and blessings of Allah be upon him), and his family. I would not have able to complete this work without the help of Allah who endowed me with health, courage, aptitude and patience. During this work my parents were a constant source of motivation and support. Their prayers, love and encouragement helped me to arrive at this milestone. I would like to thank my teacher Dr. Abid Halim. The things I learnt from him are some of the most important lessons of my life. Acknowledgements are due to King Fahd University of Petroleum and Minerals which gave me the opportunity to pursue a graduate degree and also for all the support I received in carrying out this research. I am also grateful to the Dresser Rand at KFUPM (ME project # 002351) and Saudi Aramco for its support during this research. I would like to express my gratitude to my thesis advisor Dr. Samir Mekid for all he taught me, for his patience when I couldn't get things done and for his help when I v needed it. I wouldn't have been what I am today without his supervision I am also very thankful to my thesis committee members Dr. Muhammad A. Hawwa and Dr. Hussain Al Qahtani for their involvement and encouragement. I would also like to thank Dr. Salam A Zummo for giving me an opportunity to carry on such a work under such elites. I would also like to thank Dr. Zheji Liu from Dresser Rand for his helpful comments during this work. Special thanks to my friend Muhammad Usama Siddiqui for all the "technical resources" he provided without which this work would not have been possible. Thanks also to Abdur Rahman Aravind, Syed Abdul Baqi, Ashhad Imam and Amer Bin Ziyad for the moral support and encouragement they have given during the course of this work. It has helped me a lot. Thanks also to all my colleagues in the Mechanical Engineering department for making my course a wonderful experience and believing in me. vi Table of Contents LIST OF TABLES .
ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis, ESDA 2012, 2012
The effect of geometry shape of the Helmholtz resonator on its resonant frequency and noise atten... more The effect of geometry shape of the Helmholtz resonator on its resonant frequency and noise attenuation capability is discussed in this paper. The theory of resonant frequency depending on the shape of the vessel of the resonator is verified analytical and numerically using COMSOL for one degree of freedom resonators. The simulation was validated experimentally and has shown very good agreements. Various shapes of the resonators were compared in arrays. A better understanding of the shape effect is shown through simulations.
ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis, ESDA 2012, 2012
Helmholtz resonators are known to be efficient resonators for ducts if they are properly designed... more Helmholtz resonators are known to be efficient resonators for ducts if they are properly designed. A design procedure is suggested in this paper to identify the size of the resonators in one and two degrees of freedom. The procedure is supported by a through numerical simulation of acoustic wave propagation that is presented and is verified using published experimental results. The overall procedure shows achievable great attenuation of noise in pipeline.
Traditional passive noise control techniques using Helmholtz resonators have size limitations at ... more Traditional passive noise control techniques using Helmholtz resonators have size limitations at low frequency due to the long wavelengths. Promising noise reductions, with flush mounted Stainless Steel patches with no such constraints can be obtained building on local resonance phenomenon implemented in acoustic metamaterials techniques. The objective of the current paper is to introduce locally resonant thin Steel patches flush mounted to an acoustic duct walls aiming at creating frequency stop bands at the low frequency zone (below 1 KHz). Green’s Function is used under the framework of interface response theory to predict the degree of attenuation of the local resonant patches. The experimental results were compared with Analytical theory and Finite elements and a close agreement was found.
A modelling of low-frequency sound propagation in slowly varying ducts with smoothly varying lini... more A modelling of low-frequency sound propagation in slowly varying ducts with smoothly varying lining is proposed leading to an acoustic mild-slope equation analogue to the with mild-slope equation for water waves. This simple 1D Mild Slope Equation is derived by direct application of the Galerkin method. It is shown that the acoustic mild-slope equation can serve as a good alternative to computationally expensive Helmholtz equations to solve such kind of problem. The results from this equation agrees well with FEM based solutions of Helmholtz equation.
A re ection-less acoustic cloak inside ducts is proposed in the audible range where plane waves a... more A re ection-less acoustic cloak inside ducts is proposed in the audible range where plane waves are bended around the object using boundary impedance. The cloak possesses low-re ection and wave-front bending properties, which could approximate the ideal cloak with inhomogeneous and anisotropic distribution of material parameters. The cloak is e ective in a broadband frequency range, and the cloaking range is a function of the boundary impedance.
Acoustic cloaking for the suppression of backscattering inside ducts is proposed in the audible r... more Acoustic cloaking for the suppression of backscattering inside ducts is proposed in the audible range where plane waves are curved around the object using the surface modes of the liner. It is numerically shown that a slowly varying resonant liner (e. g. based on an array of tubes) creates a zone of silence in which an object of arbitrary shape can be acoustically hidden for a wide range of frequencies. And then, a resonant liner has deflecting properties without reflection of the wavefront, which are close to an ideal invisibility cloak. This kind of cloaking is effective in a wide frequency band and the cloaking band is a function of the impedance and height of the obstacle relative to the conduit. For smooth shaped obstacles, there is an ability of the object to help hide itself, which increases the cloaking frequency band (self-cloaking). Dispersion effects lead to slow sounds and distortion of the wave phase.
The objective of this doctoral thesis is to study three different innovative noise control techni... more The objective of this doctoral thesis is to study three different innovative noise control techniques in ducts namely: acoustic metamaterials, porous absorbers and microperforates. There has been a ...
Acoustic cloaking for the suppression of backscattering inside ducts is proposed in the audible r... more Acoustic cloaking for the suppression of backscattering inside ducts is proposed in the audible range where plane waves are curved around the object using the surface modes of the liner. It is numerically shown that a slowly varying resonant liner (e.g. based on an array of tubes) creates a zone of silence in which an object of arbitrary shape can be acoustically hidden for a wide range of frequencies. And then, a resonant liner has deflecting properties without reflection of the wavefront, which are close to an ideal invisibility cloak. This kind of cloaking is effective in a wide frequency band and the cloaking band is a function of the impedance and height of the obstacle relative to the conduit. For smooth shaped obstacles, there is an ability of the object to help hide itself, which increases the cloaking frequency band (self-cloaking). Dispersion effects lead to slow sounds and distortion of the wave phase.
The Journal of the Acoustical Society of America, 2018
For acoustic waves in lined ducts, at given frequencies, the dispersion relation leads to a trans... more For acoustic waves in lined ducts, at given frequencies, the dispersion relation leads to a transcendental equation for the wavenumber that has to be solved by numerical methods. Based on an Eckart explicit expression initially derived for water waves, accurate explicit approximations are proposed for the wavenumber of the fundamental mode in lined ducts. While the Eckart expression is 5% accurate, some improved approximations can reach maximum relative errors of less than 10 À8. The cases with small dissipation parts in the admittance of the liner and/or axisymmetric ducts are also considered.
The acoustic effects of in-parallel resonators is compared to the behavior of a classical single ... more The acoustic effects of in-parallel resonators is compared to the behavior of a classical single degree of freedom resonator for which the resistance and the mass are in series. In-parallel resonators serve to enhance the acoustic absorption for mid-frequencies thereby extending the active frequency range of perfect acoustic absorbers. Two implementations of these in-parallel absorbers are presented and investigated experimentally as well as numerically. In the first demonstration, the resistance is a perforated plate with a wiremesh and the oscillating mass is the air that fills a tube passing through the plate. The second implementation consists of a thin flexible beam that oscillates and where the resistance is due to the micro-slit resulting from the cutting of the beam.
The Journal of the Acoustical Society of America, 2017
Acoustic impedance for perforates is mainly quantified by semi or totally empirical formulas, whi... more Acoustic impedance for perforates is mainly quantified by semi or totally empirical formulas, which depend on the experimental set-up used and are specific for each type of tested sample. In this work, the acoustic impedance of a micro-perforated plate (MPP) with two-sided low Mach grazing flow is educed by a modified semi-analytical inverse technique. The inputs to this technique are complex acoustic pressure measured at eight positions at the wall of the duct, upstream and downstream of the MPP section. Several measurements on the two sided grazing flow rig are conducted and trends in the impedance shift are observed. These trends serve to quantify the change in the resistance and reactance of a MPP when it is subjected to two sided grazing flow. An empirical formula is also proposed which is based on these trends. This formula helps in approximating the behavior of MPP’s in applications such as perforated cooling fans, perforated guide vanes, and turbine nozzles. It was observed that with increased flo...
The Journal of the Acoustical Society of America, 2016
A thin subwavelength material that can be flush mounted in a duct and that gives an attenuation b... more A thin subwavelength material that can be flush mounted in a duct and that gives an attenuation band at low frequencies in air flow channels is presented. To decrease the material thickness, the sound is slowed in the material using folded side branch tubes. The impedance of the material is compared to the optimal value given by the Cremer condition, which can differ greatly from the air characteristic impedance. Grazing flow on this material increases the losses at the interface between the flow and the material.
The Journal of the Acoustical Society of America, 2016
Since conventional silencers in acoustic ducts have problems of size limitations at low frequenci... more Since conventional silencers in acoustic ducts have problems of size limitations at low frequencies and being prone to high backpressure, locally resonant aluminum patches are introduced in acoustic duct walls aiming at creating frequency stop bands in the low frequency region (below 1 KHz). With these flush mounted patches, promising noise reductions, with no such drawbacks, can be obtained, building on local resonance phenomenon implemented in acoustic metamaterials techniques. The objective of the current paper is to experimentally validate the performance of an array of flexible side-wall-mounted patches inside ducts. The experimental results are compared with Analytical Green's function method as well as Numerical Finite Element Method and a close agreement was found. The results show that the presence of the patches singly or periodically can play a prominent role in designing any acoustic bandgap materials. The effect of the arrays of patches on the effective dynamic density and bulk modulus has also been investigated. V C 2016 Acoustical Society of America.
In this paper, the acoustic impedance of a microperforated plate (MPP) with two-sided grazing flo... more In this paper, the acoustic impedance of a microperforated plate (MPP) with two-sided grazing flow is educed by a modified semi-analytical inverse technique. The MPP sample is placed in the middle ...
SAE International Journal of Materials and Manufacturing, 2015
A novel porous metallic foam has been studied in this work. This composite material is a mixture ... more A novel porous metallic foam has been studied in this work. This composite material is a mixture of resin and hollow spheres. It is lightweight, highly resistive to contamination and heat, and is c ...
Praise belongs to Allah, the Lord of all the worlds (2) The All-Merciful, the Very-Merciful. (3) ... more Praise belongs to Allah, the Lord of all the worlds (2) The All-Merciful, the Very-Merciful. (3) The Master of the Day of Requital. (4) You alone do we worship, and from You alone do we seek help. (5) Take us on the straight path (6) The path of those on whom You have bestowed Your Grace, Not of those who have incurred Your wrath, nor of those who have gone astray. (7) Al-Fatiha I begin with the name of Allah, the most beneficent, the most merciful. May Allah bestow peace on our beloved Prophet Mohammed (peace and blessings of Allah be upon him), and his family. I would not have able to complete this work without the help of Allah who endowed me with health, courage, aptitude and patience. During this work my parents were a constant source of motivation and support. Their prayers, love and encouragement helped me to arrive at this milestone. I would like to thank my teacher Dr. Abid Halim. The things I learnt from him are some of the most important lessons of my life. Acknowledgements are due to King Fahd University of Petroleum and Minerals which gave me the opportunity to pursue a graduate degree and also for all the support I received in carrying out this research. I am also grateful to the Dresser Rand at KFUPM (ME project # 002351) and Saudi Aramco for its support during this research. I would like to express my gratitude to my thesis advisor Dr. Samir Mekid for all he taught me, for his patience when I couldn't get things done and for his help when I v needed it. I wouldn't have been what I am today without his supervision I am also very thankful to my thesis committee members Dr. Muhammad A. Hawwa and Dr. Hussain Al Qahtani for their involvement and encouragement. I would also like to thank Dr. Salam A Zummo for giving me an opportunity to carry on such a work under such elites. I would also like to thank Dr. Zheji Liu from Dresser Rand for his helpful comments during this work. Special thanks to my friend Muhammad Usama Siddiqui for all the "technical resources" he provided without which this work would not have been possible. Thanks also to Abdur Rahman Aravind, Syed Abdul Baqi, Ashhad Imam and Amer Bin Ziyad for the moral support and encouragement they have given during the course of this work. It has helped me a lot. Thanks also to all my colleagues in the Mechanical Engineering department for making my course a wonderful experience and believing in me. vi Table of Contents LIST OF TABLES .
ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis, ESDA 2012, 2012
The effect of geometry shape of the Helmholtz resonator on its resonant frequency and noise atten... more The effect of geometry shape of the Helmholtz resonator on its resonant frequency and noise attenuation capability is discussed in this paper. The theory of resonant frequency depending on the shape of the vessel of the resonator is verified analytical and numerically using COMSOL for one degree of freedom resonators. The simulation was validated experimentally and has shown very good agreements. Various shapes of the resonators were compared in arrays. A better understanding of the shape effect is shown through simulations.
ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis, ESDA 2012, 2012
Helmholtz resonators are known to be efficient resonators for ducts if they are properly designed... more Helmholtz resonators are known to be efficient resonators for ducts if they are properly designed. A design procedure is suggested in this paper to identify the size of the resonators in one and two degrees of freedom. The procedure is supported by a through numerical simulation of acoustic wave propagation that is presented and is verified using published experimental results. The overall procedure shows achievable great attenuation of noise in pipeline.
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Papers by Maaz Farooqui