The Impact of Perforation Geometry on Acoustic Damping Attributes of a Perforated Liner With Bias Flow

2012 ◽  
Author(s):  
Alireza Mazdeh ◽  
Reza Kashani
Keyword(s):  
Fluid Dynamic ◽  
Perforated Plate ◽  
Interaction Mechanism ◽  
Industrial Applications ◽  
Radius Ratio ◽  
Damping Properties ◽  
Acoustic Damping ◽  
Spacing Ratio ◽  
Bias Flow ◽  
The Impact

Acoustic damping properties of perforated liners are highly dependent on a number of variables which can be categorized as “flow variables” such as the extent and Mach number of grazing flow as well as bias flow and “geometric variable” such as the shape of the hole which can be rectangular, cylindrical, conical with diverging or converging nozzle, thickness to radius ratio, radius to hole spacing ratio and hole orientation which can be normal to or inclined with respect to the perforated plate. Many of these variables were not incorporated in previous studies. Theoretical and empirical approaches have provided the foundation for understanding the damping properties of liners but they are based on certain simplifying assumptions making them inadequate in addressing the more realistic conditions encountered in industrial applications. These limitations have highlighted the importance of numerical methods for studying damping behavior of liners. Acoustic attributes of perforated plates (mainly in terms of impedance which is a frequency-dependent complex quantity) as a function of non-dimensional variables like Reynolds, Strouhal, Mach, and Helmholtz numbers have been studied by various researchers, including the authors, using a variety of numerical tools starting from the simple 1D network scheme based on linear acoustics and the wall compliance concept introduced by Howe all the way to the computationally intensive Large-Eddy Simulations (LES) and Scaled Adaptive Simulation (SAS) reconstructing the full unsteady turbulent structures. Although the impacts of some geometry variations such as hole inclination angle and diameter, in conjunction with various fluid dynamic parameters, have been investigated using 1D network tools, the focus of LES has been mainly on analysis of a single circular hole with periodic boundary conditions as the representation of multi-perforation (assuming the perforations are spaced far enough from each other so that there is no interaction between neighboring holes). There is certainly a need for thorough investigation of the acoustics impact of these geometric parameters as well as shape of the holes using LES. In an on-going research we are extending the numerical modeling work on characterizing the acoustic damping attributes of a perforation, beyond the current state of the art, by including the geometric variables including hole size, shape, orientation, and radius to thickness ratio, amongst others, in the study. In this paper, following a short review of the research conducted in the recent past for comprehension of the acoustic-vortex interaction mechanism in perforated liners resulting in acoustic absorption, we present the findings on the impact of thickness/radius ratio on the acoustic damping attribute of a perforation. The verification of the CFD results are done by comparing the data with analytical solutions.

Numerical Modeling of the Acoustic Damping of Perforated Liners With Bias Flow

2013 ◽  
Author(s):  
Alireza Mazdeh ◽  
Ahmad Reza Kashani
Keyword(s):  
Numerical Modeling ◽  
Fluid Dynamic ◽  
Perforated Plate ◽  
Industrial Applications ◽  
Radius Ratio ◽  
Damping Properties ◽  
Acoustic Damping ◽  
Spacing Ratio ◽  
Bias Flow ◽  
The Impact

Acoustic damping properties of perforated liners are highly dependent on a number of variables which can be categorized as “flow variables” such as the extent and Mach number of grazing flow as well as bias flow and “geometric variable” such as the shape of the hole which can be rectangular, cylindrical, conical with diverging or converging nozzle, thickness to radius ratio, radius to hole spacing ratio and hole orientation which can be normal to or inclined with respect to the perforated plate. Theoretical and empirical approaches have provided the foundation for understanding the damping properties of liners but they are based on certain simplifying assumptions making them inadequate in addressing the realistic conditions encountered in industrial applications. These limitations have highlighted the importance of numerical methods for studying damping behavior of liners. Acoustic attributes of perforated plates (mainly in terms of impedance as a function of non-dimensional variables like Reynolds, Strouhal, Mach, and Helmholtz numbers have been studied by various researchers, including the authors, using a variety of numerical tools starting from the simple 1D network scheme based on linear acoustics all the way to the computationally intensive Large-Eddy Simulations (LES) and Scaled Adaptive Simulation (SAS) reconstructing the full unsteady turbulent structures. Although the impacts of some geometry variations such as hole inclination angle and diameter, in conjunction with various fluid dynamic parameters, have been investigated using 1D network tools, the focus of LES has been mainly on analysis of a single circular hole with periodic boundary conditions as the representation of multi-perforation (assuming the perforations are spaced far enough from each other so that there is no interaction between neighboring holes). There is certainly a need for thorough investigation of the acoustic impact of these geometric parameters as well as the shape of the holes using LES. In an on-going research we are extending the numerical modeling work on characterizing the acoustic damping attributes of a perforation, beyond the current state of the art, by including the geometric variables including hole size, shape, orientation, and radius to thickness ratio, amongst others, in the study. In this paper, following a short review of the research conducted in the recent past, we present our findings on the impact of the thickness/radius ratio on the acoustic damping attribute of a perforation.

The Impacts of Bias Flow and Geometric Variables on Acoustic Damping Attributes of Perforated Liners

2014 ◽  
Author(s):  
Alireza Mazdeh ◽  
Ahmad Reza Kashani
Keyword(s):  
Energy Dissipation ◽  
Square Root ◽  
Simulation Studies ◽  
Acoustic Damping ◽  
Acoustic Liners ◽  
Flow Parameters ◽  
Spacing Ratio ◽  
Bias Flow ◽  
Geometric Variables ◽  
The Impact

The impact of geometric and flow parameters which are practical to modify and have the most influence on the energy dissipation performance of perforated acoustic liners with bias flow are numerically investigated. Such parameters include orifice bias flow velocity, thickness to radius ratio and radius to orifice spacing ratio (square root of porosity). In this paper the results of multiple simulation studies performed on various configurations are presented and used to observe and discuss how these parameters affect the liner acoustic impedance. These results indicate that for different aperture thicknesses and different aperture radii, higher resistive properties are to be expected at lower Strouhal numbers. Also, the increase in liner porosity results in an increase in both inertia and resistive attributes of the impedance.

Parametric Investigation of the Flow-Sound Interaction Mechanism for Single Cylinders in Cross-Flow

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Omar Afifi ◽  
Atef Mohany
Keyword(s):  
Heat Exchangers ◽  
Interaction Mechanism ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Industrial Applications ◽  
Resonance Excitation ◽  
Acoustic Damping ◽  
Radiation Losses ◽  
Cylinder Diameter ◽  
Tube Bundles

Abstract Flow-excited acoustic resonance is a design concern in many industrial applications. If not treated, it may lead to excessive vibrational loads, which could subsequently result in premature structural failure of critical equipment. For the case of tube bundles in heat exchangers, several acoustic damping criteria were proposed in the literature to predict the occurrence of resonance excitation. However, these criteria, in some cases, are not reliable in differentiating between the resonant and nonresonant cases. A primary reason for that is the geometrical differences between reduced scale models and full-scale tube bundles, and their effect on the flow-sound interaction mechanism. Therefore, the effect of two geometrical aspects, namely, the duct height and the cylinder diameter, on the self-excited acoustic resonance for single cylinders in cross-flow is experimentally investigated in this work. Changing the duct height changes the natural frequency of the excited acoustic modes and the duct's acoustic damping and radiation losses. Changing the cylinder diameter changes the flow velocity at frequency coincidence, the pressure drop, and Reynolds number. It is found that increasing the duct height decreases the acoustic impedance, which makes the system more susceptible to resonance excitation. This, in turn, changes the magnitude of the acoustic pressure at resonance, even for cases where the dynamic head of the flow is kept constant. The acoustic attenuation due to visco-thermal losses is quantified theoretically using Kirchhoff's acoustical damping model, which takes into account the geometrical aspects of the different ducts. Results from the experiments are compared with the acoustic damping criteria from the literature for similar cases. It is revealed that the height of the duct is an important parameter that should be included in damping criteria proposed for tube bundles of heat exchangers, as it controls the acoustic damping and radiation losses of the system, which have been over-looked in the past.

Quantitative CFD Analyses of Particle Deposition on a Transonic Axial Compressor Blade: Part I — Particle Zones Impact

2014 ◽  
Author(s):  
Alessio Suman ◽  
Rainer Kurz ◽  
Nicola Aldi ◽  
Mirko Morini ◽  
Klaus Brun ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Particle Deposition ◽  
Fluid Dynamic ◽  
Axial Compressor ◽  
Continuous Phase ◽  
Industrial Applications ◽  
Micro Particles ◽  
Compressor Rotor ◽  
Particle Ingestion ◽  
The Impact

Solid particle ingestion is one of the principal degradation mechanisms in the turbine and compressor sections of gas turbines. In particular, in industrial applications, the micro-particles not captured by the air filtration system cause fouling and, consequently, a performance drop of the compressor. This paper presents three-dimensional numerical simulations of the micro-particle ingestion (0–2 μm) on an axial compressor rotor carried out by means of a commercial computational fluid dynamic code. Particles of this size can follow the main air flow with relatively little slip, while being impacted by flow turbulence. It is of great interest to the industry to determine which areas of the compressor airfoils are impacted by these small particles. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separate from the continuous phase. Then, the NASA Rotor 37 is considered as a case study for the numerical investigation. The compressor rotor numerical model and the discrete phase treatment have been validated against the experimental and numerical data available in literature. The number of particles, sizes, and concentrations are specified in order to perform a quantitative analysis of the particle impact on the blade surface. The results show that micro-particles tend to follow the flow by impacting at full span with an higher impact concentration on the pressure side. The suction side is affected only by the impact of the smaller particles (up to 1 μm). Particular fluid-dynamic phenomena such as separation, stagnation point and tip leakage vortex strongly influence the impact location of the particles.

Quantitative Computational Fluid Dynamics Analyses of Particle Deposition in a Heavy-Duty Subsonic Axial Compressor

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Nicola Aldi ◽  
Nicola Casari ◽  
Devid Dainese ◽  
Mirko Morini ◽  
Michele Pinelli ◽  
...  
Keyword(s):  
Particle Deposition ◽  
Fluid Dynamic ◽  
Axial Compressor ◽  
Industrial Applications ◽  
Particle Impact ◽  
Blade Surface ◽  
Heavy Duty ◽  
Compressor Blades ◽  
Kinematic Characteristics ◽  
The Impact

Solid particle ingestion is one of the principal degradation mechanisms in the compressor and turbine sections of gas turbines. In particular, in industrial applications, the microparticles not captured by the air filtration system can cause deposits on blading and, consequently, result in a decrease in compressor performance. In the literature, there are some studies related to the fouling phenomena in transonic compressors, but in industrial applications (heavy-duty compressors, pump stations, etc.), the subsonic compressors are widespread. It is highly important for the manufacturer to gather information about the fouling phenomenon related to this type of compressor. This paper presents three-dimensional (3D) numerical simulations of the microparticle ingestion (0.15–1.50 μm) in a multistage (i.e., eight stage) subsonic axial compressor, carried out by means of a commercial computational fluid dynamic (CFD) code. Particles of this size can follow the main air flow with relatively little slip, while being impacted by flow turbulence. It is of great interest to the industry to determine which zones of the compressor blades are impacted by these small particles. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separately from the continuous phase. The adopted computational strategy allows the evaluation of particle deposition in a multistage axial compressor thanks to the use of a mixing plane approach to model the rotor/stator interaction. The compressor numerical model and the discrete phase model are set up and validated against the experimental and numerical data available in the literature. The number of particles and sizes is specified in order to perform a quantitative analysis of the particle impacts on the blade surface. The blade zones affected by particle impacts and the kinematic characteristics (velocity and angle) of the impact of micrometric and submicrometric particles with the blade surface are shown. Both blade zones affected by particle impact and deposition are analyzed. The particle deposition is established by using the quantity called sticking probability (SP), adopted from the literature. The SP links the kinematic characteristics of particle impact on the blade with the fouling phenomenon. The results show that microparticles tend to follow the flow by impacting on the compressor blades at full span. The suction side (SS) of the blade is only affected by the impacts of the smallest particles. Particular fluid dynamic phenomena, such as corner separations and clearance vortices, strongly influence the impact location of the particles. The impact and deposition trends decrease according to the stages. The front stages appear more affected by particle impact and deposition than the rear ones.

Quantitative Computational Fluid Dynamics Analyses of Particle Deposition on a Transonic Axial Compressor Blade—Part I: Particle Zones Impact

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Alessio Suman ◽  
Rainer Kurz ◽  
Nicola Aldi ◽  
Mirko Morini ◽  
Klaus Brun ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Particle Deposition ◽  
Fluid Dynamic ◽  
Axial Compressor ◽  
Numerical Data ◽  
Suction Side ◽  
Continuous Phase ◽  
Industrial Applications ◽  
Compressor Rotor ◽  
The Impact

Solid particle ingestion is one of the principal degradation mechanisms in the turbine and compressor sections of gas turbines. In particular, in industrial applications, the microparticles that are not captured by the air filtration system cause fouling and, consequently, a performance drop of the compressor. This paper presents three-dimensional numerical simulations of the microparticle ingestion (0 μm–2 μm) on an axial compressor rotor carried out by means of a commercial computational fluid dynamic (CFD) code. Particles of this size can follow the main air flow with relatively little slip, while being impacted by flow turbulence. It is of great interest to the industry to determine which areas of the compressor airfoils are impacted by these small particles. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separate from the continuous phase. Then, the NASA Rotor 37 is considered as a case study for the numerical investigation. The compressor rotor numerical model and the discrete phase treatment have been validated against the experimental and numerical data available in literature. The number of particles, sizes, and concentrations are specified in order to perform a quantitative analysis of the particle impact on the blade surface. The results show that microparticles tend to follow the flow by impacting at full span with a higher impact concentration on the pressure side (PS). The suction side (SS) is affected only by the impact of the smaller particles (up to 1 μm). Particular fluid dynamic phenomena, such as separation, stagnation point, and tip leakage vortex, strongly influence the impact location of the particles.

Quantitative Computational Fluid Dynamics Analyses of Particle Deposition on a Subsonic Axial Compressor Blade

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Alessio Suman ◽  
Rainer Kurz ◽  
Nicola Aldi ◽  
Mirko Morini ◽  
Klaus Brun ◽  
...  
Keyword(s):  
Particle Deposition ◽  
Fluid Dynamic ◽  
Axial Compressor ◽  
Continuous Phase ◽  
Industrial Applications ◽  
Particle Impact ◽  
High Tendency ◽  
Kinematic Characteristics ◽  
The Impact ◽  
Dynamic Phenomena

In literature, there are some studies related to the fouling phenomena in transonic compressors, but, in industrial applications (heavy-duty compressor, pumping stations, etc.) the subsonic compressors are widespread. It is of great interest to the manufacturer to discover the fouling phenomenon related to this type of compressor. This paper presents three-dimensional numerical simulations of the microparticle ingestion on a subsonic axial compressor rotor carried out by means of a commercial computational fluid dynamic code. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separate from the continuous phase. The number of particles, sizes, and concentrations are specified in order to perform a quantitative analysis of the particle impact on the blade surface. In this paper, the particle impact pattern and the kinematic characteristics (velocity and angle) of the impact are shown. Both of the blade zones affected by particle impact and the blade zones affected by particle deposition are analyzed. The particle deposition is established by using the quantity called sticking probability (SP). The SP links the kinematic characteristics of particle impact on the blade with fouling phenomenon. The results show that microparticles tend to follow the flow by impacting at full span with a higher impact concentration on the leading edge (LE). The suction side (SS) is affected only close to the LE and, at the hub, close to the trailing edge (TE). Particular fluid-dynamic phenomena such as separation, stagnation, and tip leakage vortex strongly influence the impact location of the particles. The kinematic analysis showed a high tendency of particle adhesion on the SS, especially for smaller particles for which the fluid dynamic phenomena play a key role regarding particle impact velocity and angle.

Quantitative CFD Analyses of Particle Deposition in a Heavy-Duty Subsonic Axial Compressor

2017 ◽  
Author(s):  
Nicola Aldi ◽  
Nicola Casari ◽  
Devid Dainese ◽  
Mirko Morini ◽  
Michele Pinelli ◽  
...  
Keyword(s):  
Particle Deposition ◽  
Fluid Dynamic ◽  
Axial Compressor ◽  
Industrial Applications ◽  
Particle Impact ◽  
Heavy Duty ◽  
Compressor Blades ◽  
Micro Particles ◽  
Particle Ingestion ◽  
The Impact

Solid particle ingestion is one of the principal degradation mechanisms in the compressor and turbine sections of gas turbines. In particular, in industrial applications, the micro-particles not captured by the air filtration system can cause deposits on blading and, consequently, result in a decrease in compressor performance. In literature there are some studies related to the fouling phenomena in transonic compressors, but in industrial applications (heavy-duty compressors, pump stations, etc.) the subsonic compressors are widespread. It is highly important for the manufacturer to gather information about the fouling phenomenon related to this type of compressor. This paper presents three-dimensional numerical simulations of the micro-particle ingestion (0.15 μm – 1.50 μm) in a multistage (i.e. eight stage) subsonic axial compressor, carried out by means of a commercial computational fluid dynamic code. Particles of this size can follow the main air flow with relatively little slip, while being impacted by flow turbulence. It is of great interest to the industry to determine which zones of the compressor blades are impacted by these small particles. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separately from the continuous phase. The adopted computational strategy allows the evaluation of particle deposition in a multistage axial compressor thanks to the use of a mixing plane approach to model the rotor/stator interaction. The compressor numerical model and the discrete phase model are set up and validated against the experimental and numerical data available in literature. The number of particles and sizes are specified in order to perform a quantitative analysis of the particle impacts on the blade surface. The blade zones affected by particle impacts and the kinematic characteristics (velocity and angle) of the impact of micrometric and sub-micrometric particles with the blade surface are shown. Both blade zones affected by particle impact and deposition are analyzed. The particle deposition is established by using the quantity called sticking probability, adopted from literature. The sticking probability links the kinematic characteristics of particle impact on the blade with the fouling phenomenon. The results show that micro-particles tend to follow the flow by impacting on the compressor blades at full span. The suction side of the blade is only affected by the impacts of the smallest particles. Particular fluid dynamic phenomena, such as corner separations and clearance vortices, strongly influence the impact location of the particles. The impact and deposition trends decrease according to the stages. The front stages appear more affected by particle impact and deposition than the rear ones.

Vortex Shedding and Acoustic Resonance of Single and Tandem Finned Cylinders

2010 ◽  
Author(s):  
Mohammed Eid ◽  
Samir Ziada
Keyword(s):  
Vortex Shedding ◽  
Sound Pressure ◽  
Interaction Mechanism ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Number Range ◽  
Tandem Cylinders ◽  
Spacing Ratio ◽  
High Reynolds ◽  
The Impact

The effect of fins on vortex shedding and acoustic resonance is investigated for isolated and two tandem cylinders exposed to cross-flow in a rectangular duct. Three spacing ratios between the tandem cylinders (S/De = 1.5, 2 and 3) are tested for a Reynolds number range from 1.6×104 to 1.1×105. Measurements of sound pressure and flow velocity are performed for bare and finned cylinders with three different fin densities. The effect of fins on the sound pressure generated before the onset of acoustic resonance as well as during the pre-coincidence and coincidence resonance is found to be rather complex and depends on the spacing ratio between cylinders, the fin density and the nature of the flow-sound interaction mechanism. For isolated cylinders, the fins reduce the strength of vortex shedding only slightly, but strongly attenuate the radiated sound before and during the acoustic resonance. This suggests that the impact of the fins on correlation length is stronger than on velocity fluctuations. In contrast to isolated cylinders, the fins in the tandem cylinder case enhance the vortex shedding process at off-resonant conditions, except for the large spacing case which exhibits a reversed effect at high Reynolds numbers. Regarding the acoustic resonance of the tandem cylinders, the fins promote the onset of the coincidence resonance, but increasing the fin density drastically weakens the intensity of this resonance. The fins are also found to suppress the pre-coincidence resonance for the tandem cylinders with small spacing ratios (S/De = 1.5 and 2), but for the largest spacing case (S/De = 3), they are found to have minor effects on the sound pressure and the lock-in range.

Identification of the Impact of Radius Ratio of Horizontal to Vertical Curves on Highway Safety

CICTP 2020 ◽  
2020 ◽  
Author(s):  
Xiaofei Wang ◽  
Jiangbei Yao ◽  
Zhengkai Li ◽  
Yuntao Liu ◽  
Jin Cai
Keyword(s):  
Highway Safety ◽  
Radius Ratio ◽  
The Impact
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