bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Acoustics and Active Constrained Layer Damping of a Full Scale Fuselage Section: An Experimental Approach
Authors: Herdic Peter C. , Baz Amr M. , Houston Brian H. 
Published: January 2022

Abstract
The mechanisms and underlying structural acoustics associated with the response of a full scale aircraft fuselage section are examined in its uncontrolled state and with the application of Active Constrained Layer Damping (ACLD) treatment to the structure. In these experiments, active structural acoustic control is demonstrated, where both the surface vibration and interior acoustic pressure are attenuated. The uncontrolled response is first studied experimentally under three different physical forcing functions by use of high spatially sampled surface velocity and interior pressure measurements over a band from 0–1000 Hz. These results indicate rich modal excitation of the fuselage and interior by a point force applied at a frame/stringer intersection of the structure. Real time active control experiments using simple surface minimization control laws are performed under this excitation, yielding good performance.
The Response of Acoustic Sensor Arrays to Turbulent Boundary Layer Noise by Structural Modification
Authors: Madden Peter E. 
Published: January 2022

Abstract
The performance of high speed, underwater vehicles is limited by flow noise. Turbulent flow over the vehicle shell causes an output from an array which is mounted to it. Arrays which are located under the boundary layer are affected by high wave number components and must be separated from the turbulence by a coating. Arrays which are located in the laminar region are still affected by the turbulent flow but in this case the energy is transported through the structure. The paper discusses the mechanisms involved and shows techniques which can be used to mitigate the problem. Some results are shown indicating the amount of reduction that has been achieved with some of the approaches.
Design and Performance of the Acoustic Wind Tunnel at the Naval Undersea Warfare Center
Authors: Corriveau Pierre , Polhemus Stanley , Tingstad Gordon , Abbot Philip , Gedney Charles 
Published: January 2022

Abstract
The Naval Undersea Warfare Center (NUWC) Division Newport recently designed, built and commissioned a low-noise, low-turbulence acoustic wind tunnel for aerodynamic and aeroacoustic testing. Special features include an upstream centrifugal ventilation fan, integrated sting mounting system, unique downstream flow collector, low-speed return air plenums, an acoustically isolated fan room, and an anechoic test chamber. This paper describes the NUWC wind tunnel facility and its supporting design criteria. The wind tunnel has achieved its design requirements of: 60 m/s maximum flow speed in a 1.2 m diameter open jet with flow uniformity within 0.5% and free stream turbulence level of 0.3%. Background noise levels are below the design goal: at 60 m/s, the 1/3 octave band sound pressure levels, 1 m from the nozzle exit, are less than 60 dB re 20 μPa @ 100 Hz and 33 dB re 20 μPa @ 20 kHz. Examples are given of experiments conducted in the wind tunnel.
Inferring Blade Rate Propeller Forces From Wind Tunnel Sound Power Measurements
Authors: Gedney Charles J. , Abbot Philip A. , Corriveau Pierre J. 
Published: January 2022

Abstract
An extensive series of acoustic tests were conducted on an experimental propeller in the Naval Undersea Warfare Center Acoustic Wind Tunnel. The objective of the tests was to infer the fluctuating forces at blade rate frequency (BR) and its harmonics from sound power measurements, and validate an assumed radiation model. Ten microphones were used to spatially sample the acoustic field. Measurements were made at constant advance ratio for speeds of 6 to 52 m/s, in increments of 3 m/s. As expected, the BR sound power levels scaled as U6 and exhibited cos2θ (θ being the angle to the force) directivity, consistent with compact dipole theory. For (kD)2 &gt; about 6.5 (k is the acoustic wavenumber, D the propeller diameter), the scaling shifted to U8, the mechanism being dominated by lateral quadrupole radiation (two dipoles separated by the diameter). At the second BR harmonic, sound power levels scaled significantly different than at BR. Possible mechanisms for this effect are discussed.
Noise and Flow Measurements in Automotive Blower Scroll
Authors: Humbad Niranjan G. , Foss John F. , Porada Robert A. , Morris Scott C. , Prevost Richard J. , Johnston David G. 
Published: January 2022

Abstract
The climate control air handling system is one of the major contributors to automobile interior noise. The most annoying features can be characterized as low frequency (20–400 Hz) “rumble”, and “blade passing frequency, BPF tone” noise. Time resolved flow velocity measurements in the blower scroll have been made to identify the noise source locations. The velocity power spectral density (psd) plots show areas within the blower scroll where the turbulence fluctuations are relatively high for the tone and rumble frequencies. The inference of origin of BPF tone near the scroll cut-off is not supported by the present data. The psd magnitudes show that the velocity psd values associated with the rumble noise were highest in the blower scroll expansion near the cut-off. Such findings are expected to be useful in the design development of the scroll geometry to reduce tonal and rumble noise.
Dynamic Performance Characterization of Hockey Sticks Using a Combined Vibrational Energy Level and Modal Analysis Approach
Authors: Barpanda Dev , Mantena P. Raju 
Published: January 2022

Abstract
Composite materials offer significant improvements in fatigue behavior, impact performance and damping coupled with high stiffness and strength. Due to these properties and an increasing demand for high performance cutting-edge sports equipment, more scientific and engineering research is now being focused in the field of recreation. The use of stiff, lightweight composite materials has created many novel features in golf clubs, baseball bats and skis; features generally not possible with conventional materials. The performance, user comfort, and fatigue life of these products are strongly related to their dynamic characteristics. Design decisions relevant to these issues should, therefore, be made based on an understanding of the dynamic characteristics through modal parametric studies.
This paper discusses the vibration response characteristics of some commercially available hockey sticks with wooden, aluminum and graphite shafts, when subjected to short duration impact loads. Using an instrumented impact hammer, a complete modal survey is initially conducted on these hockey sticks to study their dynamic behavior. A comparative study of the modal parameters (natural frequency, damping, and mode shapes) of the different hockey sticks provides valuable information for design optimization and to validate the accuracy of a finite element model. In addition, a refined two-accelerometer technique has been utilized to perform vibrational energy level tests (on the blade portion of the hockey sticks) to obtain the flexural and torsional vibration level distribution and to map out the sweet spot locations. Results indicate that this combined strategy of using both approaches provides a better understanding of the vibration performance characteristics of hockey sticks. Work is currently in progress to extend this technique for characterizing golf clubs.
Reconstruction of Radiated Acoustic Pressure Fields From a Complex Vibrating Structure
Authors: Wu Sean F. , Wu Yuhua 
Published: January 2022

Abstract
The Helmholtz Equation Least Squares (HELS) method previously derived by Wang and Wu (1997) and Wu and Wang (1998) is used to reconstruct the radiated acoustic pressure fields from a complex vibrating structure. The structure under consideration is of the form of a real, full-size four-cylinder engine designed for a passenger vehicle. To simulate sound radiation from a vibrating engine block, harmonic forces are assumed to exert on two arbitrarily selected sides. The resulting vibration responses are solved by using finite element method (FEM) through a commercial software package, I-DEAS Master Series 5®. Once the normal component of surface velocity distribution is determined, the surface acoustic pressures are calculated by the Helmholtz-Kirchhoff integral theory using the standard boundary element method (BEM) codes. The radiated acoustic pressure fields are then calculated by the Helmhollz-Kirchhoff integral formulation. The results thus obtained are taken as the input to the HELS formulation to reconstruct the surface and field acoustic pressures. Numerical results show that good agreement can be obtained with relatively few measurements in the field. Further, sound pressures over the entire surface of a complex structure can be reconstructed This method is shown to be very effective at low to mid frequency ranges. The effectiveness of the HELS method may deteriorate, however, as the frequency increases. This is because the HELS method is based on an expansion of spheroidal functions, which converges slowly at high frequencies. Nonetheless, in engineering practice noise diagnostics are often carried out in the low to mid frequency ranges. Under this circumstance, the present HELS method can become a robust and effective noise diagnostic tool.
Parallel Computation of Harmonic Waves Using Domain Decomposition: Part 1 — General Formulation
Authors: Atassi Hafiz M. , Susan-Resiga Romeo F. 
Published: January 2022

Abstract
A method is presented for parallel computation of time-harmonic waves using an iterative scheme based on domain decomposition. For exterior radiation and scattering problems, a finite computational domain is obtained by introducing a computational outer boundary on which a modified Dirichlet-to-Neumann map is used as a nonreflecting condition. The computational domain is then decomposed into subdomains and for each a boundary-value problem is defined using impedance-like transmission conditions on the subdomain interfaces. An iterative scheme updates the subdomain boundary conditions so that a global continuous solution is recovered.
Some Recent Advances in the Use of Kirchhoff’s Method in Computational Aeroacoustics
Authors: Lyrintzis Anastasios S. 
Published: January 2022

Abstract
A review of recent advances in the use of Kirchhoff’s method in Computational AeroAcoustics (CAA) is given. Kirchhoff’s integral formulation allows the radiating sound to be evaluated based on quantities on an arbitrary control surface if the wave equation is assumed outside. Thus only surface integrals are needed for the calculation of the far-field sound, instead of the volume integrals required by the traditional acoustic analogy method (i.e. Lighthill, Ffowcs Williams-Hawkings equation). A numerical CFD method is used for the evaluation of the flow-field solution in the near field and thus on the control surface. However, diffusion and dispersion errors associated with wave propagation in the far-field are avoided. The surface integrals and the first derivatives needed can be easily evaluated from the near-field numerical aerodynamic data. The equivalence of Kirchhoff’s method and Acoustic Analogy methods was recently proven rigorously. Kirchhoff’s integral formulation was also extended to include nonlinear source regions as well as refraction effects outside the Kirchhoff control surface. The method has been applied to helicopter noise, jet noise, propeller noise, ducted fan noise, etc. A simple set of portable Kirchhoff/Acoustic Analogy subroutines can be developed to calculate the far-field noise from inputs supplied by any aerodynamic near/mid-field code.
Closed-Form Transient Analysis of Delayed Mechanical Systems
Authors: Yang Bingen , Wu Xuqiang 
Published: January 2022

Abstract
Conventional modal analyses are not applicable to delayed mechanical systems because any possible orthogonality among system eigenvectors would be destroyed by time delays. Presented in this paper is a new approach which relates system eigensolutions to the residues of system transfer function. With this relation, closed-form transient response of mechanical systems can be practically estimated in eigenfunction series through inverse Laplace transform, without the need for orthogonal eigenvectors. The proposed method is illustrated on a delayed gyroscopic dynamic system.
A Study of Damping in a Fluid Loaded Micro-Sensor
Authors: Dohner Jeffrey L. 
Published: January 2022

Abstract
In the macro-domain, the mechanisms of energy loss in a fluid structure system are well understood. Damping can occur in the structure due to relaxation or in the fluid due to relaxation and radiation. For many fluids, such as air or water, fluid relaxation effects are small and are neglected. Moreover, structural relaxation effects are also often negligible. Therefore, for many systems, energy loss is assumed to be dominated by radiation effects alone. This macro-level assumption is a common one; however, as the size of the structure is reduced, the frequencies of excitation are increased, viscous losses are enhanced, and the applicability of this assumption becomes questionable. In this paper the acoustic losses in a micro-scale fluid structure system will be examined and the applicability of this assumption discussed.
A Novel Technique for Measurement of Vibration Using Acousto Optic Modulator (AOM)
Authors: Ngoi B. K. A. , Venkatakrishnan K. 
Published: January 2022

Abstract
A novel method for the measurement of vibration using an acousto optic modulator (AOM) is described. Previous methods generally rely on holographic (off-line measurement) and laser Doppler vibrometers (on line measurement). This method shows a new direction of vibration measurement using AOM rather than relying on laser Doppler vibrometer and laser Doppler displacement meter for on-line vibration measurement. A method of obtaining resolution in the range of sub-nanometer is proposed. The technique proposed not only projects a novel technique but also brings to light the possible application of AOM.
Study of Deformation Processes in Normal Slow Speed Impact
Authors: Lim Chwee Teck , Lim Chee Tiong 
Published: January 2022

Abstract
This paper models the normal slow speed impact of a deformable sphere against a rigid surface using elastic-plastic and fully-plastic compliance relationships derived from Johnson’s cavity model (Johnson, 1970) and Chang’s volume conservation model (Chang et al., 1987). These relationships describe the deformation processes occurring at the point of contact of the deformable sphere under slow speed inelastic impact. Comparison with results obtained from finite element program DYNA2D shows that the analytical model can accurately predict the deformation behavior at the point of impact.
Dynamic Numerical Simulation of the Motion of a Clamp Passing Over a Cable Supporting Roller Battery
Authors: Chen Nan , Meyer-Piening H.-R. 
Published: January 2022

Abstract
This paper presents a method to deal with the numerical simulation of a moving clamp that is ranning over a roller battery support of a cable transport system. It is a dynamic procedure involving time and form varying non-holonomic kinematics constraints as well as inter-excitation between parts of the system. The theoretical results are compared with laboratory test results.
Supercritical Speed Stability of an Axially Moving String on an Elastic Foundation
Authors: Parker Robert G. 
Published: January 2022

Abstract
The stability of an axially-moving string supported by a discrete or distributed elastic foundation is examined analytically. Particular attention is directed at the distribution of the critical speeds and identifying divergence instability of the trivial equilibrium. In contrast to the unsupported axially-moving string, the elastically supported string shows considerably different stability behavior. In particular, any elastic foundation (discrete or distributed) leads to multiple critical speeds and a single region of divergence instability above the first critical speed, whereas the unsupported string has one critical speed and is stable at all supercritical speeds. Additionally, the elastically supported string critical speeds are bounded above, and the maximum critical speed is the upper bound of the divergent speed region. The analysis draws on the self-adjoint eigenvalue problem for the critical speeds and a perturbation analysis about the critical speeds. No numerical approximation is required and the identified stability phenomena apply to general elastically supported traveling strings.
Turbulent Heat-Transfer Characteristics in Flow Networks
Authors: Shin Jongmin , Yang Wen-Jei , Wu Chung-Sheng 
Published: January 2022

Abstract
A numerical analysis is performed to investigate turbulent heat-transfer characteristics in flow networks. The Renormalization Group Theory k-ε model is employed to describe turbulent behavior in the flow. A flow network with a higher intersecting angle and a smaller length-to-width ratio yields a higher heat transfer performance, especially in those units with an intersecting angle between 30° and 45°. It is disclosed that the presence of two flow separation zones causes three maxima in the local Nusselt number on the outer walls and a maximum value on the downstream inner wall, resulting in an average heat transfer coefficient much higher than that of a straight channel. A correlation equation similar to the Dittus-Boelter equation is derived to predict the average Nusselt number. This formula can be used in designing a flow network as a heat exchanger.
Heat Transfer in the Confined Impingement of Multiple Air Jets
Authors: Schroeder Vincent P. , Garimella Suresh V. 
Published: January 2022

Abstract
Heat transfer from a discrete heat source to multiple, normally impinging, confined air jets was experimentally investigated. The jets issued from short, square-edged orifices with still-developing velocity profiles on to a foil heat source which produced a constant heat flux. The orifice plate and the surface containing the heat source were mounted opposite each other in a parallel-plates arrangement to effect radial outflow of the spent fluid. The local surface temperature was measured in fine increments over the entire heat source. Experiments were conducted for different jet Reynolds numbers (5000 &lt; Re &lt; 20000), orifice-to-target spacings (0.5 &lt; H/d &lt; 4), and multiple-orifice arrangements. The results are compared to those previously obtained for single air jets. A reduction in orifice-to-target spacing was found to increase the heat transfer coefficient in multiple jets, with this effect being stronger at the higher Reynolds numbers. With a nine-jet arrangement, the heat transfer to the central jet was higher than for a corresponding single jet. For a four-jet arrangement, however, each jet was found to have stagnation-region heat transfer coefficients that were comparable to the single-jet values. The effectiveness of single and multiple jets in removing heat from a given heat source is compared at a fixed total flow rate. Correlations are proposed for single and multiple jet impingement heat transfer.
Heat Transfer by a Two-Dimensional Air Jet Impinging Obliquely on a Flat Surface
Authors: Beitelmal Abdlmonem H. , Saad Michel A. , Patel Chandrakant D. 
Published: January 2022

Abstract
An experimental study was performed to determine the effect of the inclination of an impinging two-dimensional air jet on the heat transfer from a uniformly heated flat plate. The impingement surface was a stainless steel plate of the same width as the jet nozzle. Local Nusselt numbers were determined as a function of three parameters: a) inclination angle of the air jet relative to the plate in the range of 90° to 40°, b) nozzle exit-to-plate spacing, z/Dh, in the range of 4 to 12 and c) Reynolds number based on the hydraulic diameter of the slot nozzle in the range of 4049 to 12020. The results are presented in the form of graphs showing the variation of the local Nusselt number as a function of these parameters. The point of maximum heat transfer shifts towards the uphill side of the plate and the maximum Nusselt number decreases from its value at θ = 90° as the inclination angle decreases. The location of the maximum heat transfer region lies between 0 and 3Dh away from the geometrical impinging point and appears to be insensitive to the Reynolds number in the range used in this study. For lower values of inclination angle, the local Nusselt number downstream from the maximum heat transfer point was insensitive to jet exit-to-plate spacing.
Representation of Local Heat Transfer Coefficient for Slot and Radial Jet Reattachment Nozzles
Authors: Narayanan Vinod , Seyed-Yagoobi Jamal , Page Robert H. 
Published: January 2022

Abstract
A scheme to represent local heat transfer data in submerged two-dimensional (slot) and axisymmetric (radial) reattachment jet flows is presented. A characteristic length that relates to the jet path length facilitates the representation of heat transfer results in a proper form. A detailed parametric study of the 0° Slot Jet Reattachment (SJR) nozzle is initially presented. The parameters varied are nozzle to surface spacing, exit opening, and the flow exit Reynolds number. Correlations for the location of peak Nusselt number, and local Nusselt number distribution along the minor axis of the 0° SJR nozzles are provided. The dimensionless scheme is then extended to incorporate the effects of different exit angles. A modified correlation to represent the location of peak local Nusselt number to account for changes due to exit angle is determined. The same length scale is also shown to adequately represent the heat transfer data for a Radial Jet Reattachment (RJR) nozzle.
Modeling of Solid Particle Flows, Heat Transfer, and Mass Transfer in Rotary Kilns
Authors: Yang Lei , Farouk Bakhtier , Boateng Akwasi A. 
Published: January 2022

Abstract
Results from a computational model are presented in this paper for material flow, and heat and mass transfer in a rotary kiln. A kinetic theory based granular flow model has been employed to establish the particle flow field in a two-dimensional plane to predict the rotation induced flow of the solid particles. A pseudo three-dimensional model for heat and mass transfer and kinetics was developed as an extension to one-dimensional models which are usually used to predict thermal or concentration gradients in the bulk bed. To validate the model, limestone calcination is predicted and compared with available experimental data from a pilot kiln.
Kinetic Theory Analysis of Thermal Conductivity in Granular Material Flows
Authors: Hsiau Shu-San 
Published: January 2022

Abstract
The effective thermal conductivity is developed by employing the dense-gas kinetic theory. The free path used in the theory varies with the particle velocity. The analytical results can be used for the whole range of the product of Biot number and Fourier number provided that the Biot number is less than 0.1. For the very small Biot-Fourier numbers, the conductivities are found to increase with the particle diameters and the square root of granular temperatures. For the limit of very large Biot-Fourier numbers, the two effective thermal conductivities are found to be linearly proportional to the granular temperature.
The Concentration of a Spent Liquor in an Experimental Falling Film Evaporator With Plastic Heat Transfer Surfaces
Authors: Hughes D. T. , Bott T. R. , Pratt D. C. F. 
Published: January 2022

Abstract
A low pH spent sulphite liquor with a dissolved solids content of 16% has been experimentally evaporated in a single tube falling film evaporator with a small temperature driving force of 1.4°C. Nylon and polyethylene tubes 4m in length with an internal diameter of 6mm were used in the study.
The measured heat transfer coefficients at the initial concentration of 16wt% solids were in the range 900–1000 W/m2K. At the final concentration at 45 wt% solids the heat transfer coefficients were approximately 250–300 W/m2K.