bluuebunny/crossref_metadata_2025 huggingface dataset:
Velocity Measurements and Visualizations of the Flow Driven by Laser-Induced Cavitation Bubbles in a Blood-Like Liquid
Authors: Molho Joshua I. , Hung Chiao-Chuan , Santiago Juan G. , Levine Marc-Alan , Esch Victor
Published: November 2021

A method for imaging and velocimetry of flows, in small volumes of blood-like liquid is presented. This method allows for imaging of fast moving blood flows (1 to 10 m/s) in volumes on the order of a cubic millimeter. A custom laser light source was developed that provides pulsed illumination at 640 nm. This light source is required by the transmission properties of the blood-like liquid and has other advantages for epi-fluorescence imaging. This custom-built PIV system was used to image the flow caused by a laser induced cavitation bubble. The measurements show the important features of this flow including the high-speed radial collapse of the bubble, the asymmetric collapse of the bubble caused by the presence of the fiber and the presence of a jet that traverses the bubble.
Electroosmotic Flow Field Measurements With Particle Image Velocimetry
Authors: Devasenathipathy Shankar , Molho Joshua I. , Mikkelsen James C. , Santiago Juan G. , Takehara Kohsei
Published: November 2021

A micron-resolution particle image velocimetry (PIV) system has been developed to spatially and temporally resolve electroosmotic flow fields within microfluidic bioanalytical devices. A second diagnostic technique, particle tracking velocimetry (PTV) has been used to determine the distribution of electrophoretic mobilities of seed particles and thereby make the PIV measurements quantitative. This second particle tracking technique has been used to determine probability distribution functions of the seed particles. Results from simulations of electric fields yield local electric field strengths in the geometries of interest. The measured mean mobility of the seed particles (obtained from PTV measurements) is then multiplied by the local electric field vector to obtain the electrophoretic velocity. The variance on the particle mobility measurement influences the errors introduced in the electroosmotic flow measurements. After total particle velocities are measured within a microfluidic system of interest, the seed particle electrophoretic velocities are subtracted from the PIV total velocity data to obtain electroosmotic flow field velocities. Ensemble-averaged velocity field measurements for electroosmotic flow at the intersection of a cross-channel are presented.
Thermal Performance of a Residential Basement
Authors: Emery A. F. , Heerwagen D. R. , Kippenhan C. J. , Steele D. E.
Published: November 2021

This paper describes the measurement of ground and internal wall temperatures, local surface heat fluxes on the basement walls and floor, and overall heat losses for a concrete wall basement. The heat fluxes were measured with heat flux meters and mimic boxes. Daily and seasonal measured performances are displayed. A portion of the walls was covered with additional insulation. This allowed comparison of insulated and non-insulated basements and showed that a modest amount of insulation could reduce the annual heat loss by approximately 50%. The local fluxes are shown to vary significantly with depth and the insulation was most effective when applied to the upper wall surface which communicated with the ambient air through a relatively short path through the earth near grade level. Temperature stratification effects are shown to be important, especially with respect to floor heat fluxes.
Transferred-Substrate InGaAsP-Based Thermionic Emission Coolers
Authors: LaBounty Christopher J. , Robinson Gerry , Abraham Patrick , Shakouri Ali , Bowers John E.
Published: November 2021

Most optoelectronic devices are based on III-V semiconductors such as the InP/InGaAsP material system. Solid state refrigerators based on the same material system can be monolithically integrated with optoelectronics. Thermionic emission cooling in InGaAsP-based heterostructures has been shown experimentally to provide cooling power densities of several 100 W/cm2. Cooling by several degrees across thin films on the order of a micron thick has been demonstrated. Thermionic emission of hot electrons over heterobarriers allows for enhanced cooling power beyond what is possible from the bulk thermoelectric properties. The thermal resistance of the InP substrate between the hot side of the thin film cooler and the heat sink is found to be a limitation in cooler performance. Several possibilities are examined for replacing the InP substrate with a higher thermally conducting one such as silicon, copper, or even diamond, and a process for substrate transfer to a thin copper film has been developed. Three-dimensional simulations predict an order of magnitude improvement in the thermal resistance of the substrate. Experimental results of packaged InGaAsP coolers with copper substrates will be discussed.
Design of Thin-Film Thermoelectric Microcoolers
Authors: Yao D.-J. , Kim C.-J. , Chen G.
Published: November 2021

Thin-film thermoelectric devices have potentially higher efficiency than bulk ones due to quantum and classical size effects of electrons and phonons. In this paper, we discuss the design of thin-film thermoelectric microcoolers for achieving high performance. The devices considered are membrane structures based on electron transport along the film plane. A model is developed to include the effects of heat loss and leg shape. Design optimization is performed based on the modeling results.
Interplay Between Thermoelectric and Thermionic Effects in Heterostructures
Authors: Zeng Taofang , Chen Gang
Published: November 2021

When electrons sweep through a double-heterojunction structure, there exist thermionic effects at the junctions and thermoelectric effects in the film. While both thermoelectric and thermionic effects have been studied for refrigeration and power generation applications separately, their interplay in heterostructures is not understood. This paper establishes a unified model including both thermionic and thermoelectric processes based on the Boltzmann transport equation for electrons, and the nonequilibrium interaction between electrons and phonons. Approximate solutions are obtained, leading to the electron temperature and Fermi level distributions inside heterostructures and discontinuities at the interfaces as a consequence of the highly nonequilibrium transport when the film thickness is much smaller than the electron mean free path. It is found that when the film thickness is smaller than the mean free path of electrons, the transport of electrons is controlled by thermionic emission. The coexistence of thermoelectric and thermionic effects may increase the power factor when the electron mean free path is comparable to the film thickness.
Leakage Flow and Heat Transfer Over Shrouded Turbine Blades
Authors: Xiao Yumin , Amano R. S.
Published: November 2021

In this paper a high efficiency labyrinth seal and the staggered labyrinth seal for shrouded blades was presented. The flows in the seal with single, double, and triple tip seals were simulated by solving the two-dimensional Reynolds-averaged Navier-Stokes equations (RANS) and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the presently proposed staggered labyrinth seal is more efficient than the typical one and the leakage flow rate is dominated by the minimum flow area and the pressure difference. Comparing the performance with the typical labyrinth seal, the present staggered labyrinth seal model can average the total pressure drop among the seals, while the typical one induces a sharp drop across the first tooth. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, decreasing the wall temperature will result in an increase of leakage flow.
Thermoelastic Wave Induced by Pulsed Laser Heating
Authors: Wang Xinwei , Xu Xianfan
Published: November 2021

In this work, a generalized solution for the thermoelastic plane wave in a semi-infinite solid induced by pulsed laser heating is formulated in the form of Fourier series. The solution takes into account the non-Fourier effect in heat conduction and the coupling effect between temperature and strain rate, which play significant roles in ultra-short pulsed laser heating. Based on this solution, calculations are conducted to study stress waves induced by different laser parameters. It is found that with the same maximum surface temperature increase, a shorter pulsed laser induces a much stronger stress wave in a solid. The non-Fourier effect causes a higher surface temperature increase, but a weaker stress wave. The surface displacement accompanying thermal expansion shows a time delay to the laser pulse in femtosecond laser heating. On the contrary, surface displacement and heating occur simultaneously in nano- and picosecond laser heating. In femtosecond laser heating, results show that the coupling effect attenuates the stress wave and extends the duration of the stress wave. This may explain the minimal damage in ultra-short laser materials processing.
Thermal Modeling for the Consolidation Process of Thermoplastic Composite Filament Winding
Authors: Loos Alfred C. , Song Xiaolan
Published: November 2021

The quality of thermoplastic composites depends on the thermal history during processing. Therefore it is important to determine the temperature distribution in the composite during the fabrication process. The objective of this investigation was to develop a comprehensive thermal model of the thermoplastic filament winding process. The model was developed in two parts to calculate the temperature profiles in the towpreg and the composite substrate. A finite element heat transfer analysis for the composite-mandrel assembly was formulated in the polar coordinate system, which facilitates the description of the geometry and the boundary conditions. A four-node ‘sector element’ is used to describe the domain of interest. Sector elements were selected to give a better representation of the curved boundary shape which should improve accuracy with fewer elements compared to a finite element solution in the Cartesian-coordinate system. The second thermal analysis was a Cartesian coordinate, finite element model of the towpreg as it enters the nippoint. The results show that the calculated temperature distribution in the composite substrate compared well with temperature data measured during winding and consolidation. The analysis also agreed with the experimental observation that the melt region is formed on the surface of the incoming towpreg in the nippoint and not on the substrate.
Heat Transfer Characteristics of Single Droplet Cooling Using a Microscale Heater Array
Authors: Lee Jungho , Kim Jungho , Kiger Kenneth T. , Horacek Bohumil
Published: November 2021

Heat transfer by phase change is an attractive method of cooling since large amounts of heat can be removed with relatively small temperature differences. Droplet cooling is one method whereby very high heat transfer rates coupled with good temperature uniformity across surfaces can be provided, which is important in microelectronics where even small temperature gradients across the chip can cause component failure. In this study, time and space resolved heat transfer characteristics for a single droplet striking a heated surface were experimentally investigated. The local wall heat flux and temperature measurements were provided by a novel experimental technique in which 96 individually controlled heaters were used to map the heat transfer coefficient contour on the surface. Significant time and space resolved variations in wall heat fluxes were exhibited during boiling and evaporation. The droplet behavior with wall interaction was simultaneously viewed using a high-speed digital video camera. Local heat transfer measurements can provide much needed information regarding the relevant wall heat transfer mechanisms by pinpointing when and where large amounts of heat are removed. This study should result in benchmark data against which numerical calculations can be compared.
Simulation of Thermal Plasma Spraying of Partially Molten Ceramics: Effect of Carrier Gas on Particle Deposition and Phase Change Phenomena
Authors: Ahmed I. , Bergman T. L.
Published: November 2021

A 3D simulation of the thermal plasma spraying process is reported. In particular, the effect of the radial injection of a carrier gas is taken into account for a dilute spray. The thermal history of powder particles of different sizes is predicted. It is shown that introduction of a carrier gas can lead to a significant modification of the plasma jet, and can have an effect on the thermal histories of the injected particles. The study is motivated by the processing of non-traditional materials, specifically nanostructured ceramics.
A Heat Flux Correlation for Spray Cooling in the Nucleate Boiling Regime
Authors: Cabrera E. , Gonzalez J. E.
Published: November 2021

In this work an experimental study of spray cooling using monodispersed droplet sprays impinging on a flat and heated surface is reported. The aim of the work was to formulate an empirical model describing the heat flux (HF) for the nucleate boiling regime. Monodispersed water droplets with a known diameter and velocity, produced by a droplet generator, were directed toward a heated surface and the heat transfer was registered using a data acquisition system. The resulting high heat flux was investigated as function of the droplets’ diameter and velocity, mass flow rate, ambient pressure, subcooling degree and surface roughness. The resulting matrix of variables investigated in the experiments included; mass flux rate (340 < ṁ″ < 750 kg/m2s), subcooling degree (25 < Tsub < 78 °C), ambient pressure (1 < P < 1.8 bar), and surface roughness (79 < Rt < 5 μm). A generalized correlation was developed for the dimensionless HF as function of the dimensionless mass flow rate, temperature, surface roughness and pressure, along with the Jacob number. The form of the correlation is q ˙ ″ ρ V h f g = 0.245 ( Ja ) 1.038 ( Δ T sub Δ T sat ) 0.491 ( ρ σ m ˙ μ 3 ) 0.133 ( R t D ) 0.0213 ( P P 0 ) 0.291 having a confidence level greater than 95%, the differences between predicted and experimental HF were less than ±19%.
A Fully Eulerian Approach to Particle-Laden Compressible Flows
Authors: Dolatabadi Ali , Mostaghimi Javad , Ivanovic Mihajlo
Published: November 2021

Dense particles in highly compressible gas flows are analyzed using the Eulerian-Eulerian approach. Simulations are applied to a High Velocity Oxy-Fuel (HVOF) thermal spray torch. In this analysis, by using a fully Eulerian approach, the dispersed flow like the continuous flow is considered in the Eulerian frame whereby most of the physical aspects of the gas-particle flow in the HVOF process can be incorporated. These two phases are coupled through momentum and energy exchanges that are expressed in the form of source terms appearing in the governing equations. The numerical simulations show large variations in gas velocity and temperature both inside and outside the torch due to flow features such as mixing layers, shock waves, and expansion waves. The characteristics of the particles such as velocity and temperature are analyzed.
From Sub-Channel Analysis to Two-Phase Flow CFD: Improving Thermal-Hydraulics Analysis of Nuclear Reactor Cores
Authors: Clerc Sebastien , Agee Lance , Harrison Jim
Published: November 2021

For safety analyses of nuclear reactor cores, a correct prediction of the thermal-hydraulic characteristics is crucial. These predictions are all the more difficult as the flows generally involve liquid and vapor phases simultaneously. Moreover, the geometry of nuclear cores is often quite complex. The typical situation is that of a rod bundle, the characteristic length of the gap between two rods being much smaller than the size of the bundle.

The traditional approach to the simulation of such flows is called the sub-channel analysis. The flow is assumed to have a privileged direction, and the cross-flow inertia effects are neglected. Moreover, a lumped-geometry approach is generally adopted, whereby a single discretization cell is used to represent the volume between several rods. This leads to efficient solution methods but forbids a precise description of local or global three-dimensional effects.

As the computational power of modem computers steadily increases, a finer description of the flows in nuclear reactor cores becomes possible. Indeed, there is a current trend in the nuclear industry toward a CFD-like description of these flows as shown by Paillère, et al., (1998) and Rautaheimo, et al., (1999). However, the numerical method used for the simulation must satisfy some specific requirements:

• The use of unstructured meshes must be possible to allow an easy description of the geometry between the rods.

• The numerical method must be suitable for variable density (thermally expandable) flows.

Cavendish, Hall, and Porsching (1994) present a covolume method designed to meet these requirements. This method relies on the construction of a dual or Voronoi mesh. The pressure and the thermodynamic variables are computed at the vertices of the primal mesh. Additionally, the velocities are computed in the normal direction to each face of the primal mesh, or, equivalently, along each edge of the dual mesh. The continuity equation is integrated by parts on the dual polytopes, while the momentum equations are discretized by finite differences on the primal mesh.

This Cavendish, Hall, and Porsching covolume numerical method has been used to solve typical problems of nuclear reactor thermal-hydraulics analysis. The physical models are those of the CORETRAN code (1999). The first numerical results demonstrate the efficiency of the method and validate the new approach.
ATR Flow Blockage Tests and CFD Simulations
Authors: Oh Chang H. , Atkinson Steve A.
Published: November 2021

Steady state flow channel blockage tests were conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) as part of the safety basis upgrade program for the Advanced Test Reactor (ATR). The tests were sponsored by the U.S. Department of Energy (DOE). This study was aimed at carrying out flow blockage tests, establishing a base case to compare test results with numerical results using a computational fluid dynamics code, calculating temperature profiles for blockage cases, and determining whether or not the ATR core would be exposed to core melting due to blockage of the inlet of a fuel cooling channel.

The test section consisted of three parallel channels and two side channels along the side plate. Three cases were selected to evaluate flow blockage events in the channels. A base case with all the channels open, Case 1 where the inlet of the middle channel is blocked, and Case 2 where both the middle channel and the side channel are blocked.

Laser Doppler anemometer (LDA) was used to measure velocities in the channel. Velocities were measured at 2.54-mm intervals in the channel width, and every 1.27-mm around side windows in the flow direction for three parallel channels.

LDA measured velocity profiles for the base case and Case 1 indicated good agreement with predicted velocity profiles from the CFD model. The channel velocity in the blocked channel is about 70% of the velocity in the unblocked, adjacent channel in between the top and second side channel vents. Additional flow redistribution occurs into the blocked channel at the second side channel vent.

Temperature calculations for the base case were made to compare with benchmark temperatures calculated with the ATR SINDA model and CFD calculations underpredicted benchmark plate temperatures by less than 10% while it predicted bulk temperatures very well. The same heat flux and boundary conditions were incorporated for Case 1 and Case 2. The results for both cases indicated that core melt would not occur in the postulated ATR flow channel blockage events simulated for this study. Peak fuel plate temperature is about 20% greater than the peak temperature for the unblocked case just upstream of the second side channel vent.
Numerical Study of Transient Conjugate Heat Transfer in a Long Two-Phase Pipeline
Authors: Fairuzov Yuri V. , Arvizu Dal Piaz Hector
Published: November 2021

A growing number of multiphase technology applications stimulate the development of reliable methods for modeling transient processes in two-phase systems in which the temperature field in the moving fluid and the temperature field in the bounding walls are directly dependent on each other. This situation presents a conjugate heat-transfer problem since the heat-transfer rate at the wall-fluid interface and local fluid conditions are not known a priori, and therefore need to be simultaneously calculated. Examples of such processes include the direct heating of multiphase pipelines, a change of heat load in evaporators of two-phase thermal control systems, startup or shutdown of systems with a two-phase working fluid. In this paper, direct electrical heating of a long two-phase pipeline has been modeled. The modeling of transient two-phase flow and heat transfer in the pipeline is based on two different mathematical formulations. In the first formulation, the transient heat conduction and the forced convection effects are rigorously taken into account. The second formulation assumes that the pipe wall and the fluid are in local thermal equilibrium. The effect of the thermal capacity of the pipe wall is taken into account by an additional term in the energy equation for the fluid flow. Such an approach allows significant simplifying the problem and reducing the computer running time. Numerical simulation of the sudden heat input to the pipe wall has been performed using both formulations of field equations. The practical significance of the results obtained is discussed.
Steady-State Operation of a Loop Heat Pipe With Analytical Prediction
Authors: Watson Heather , Gerhart Charlotte , Mulholland George , Gluck Donald
Published: November 2021

The steady-state performance of an 800W, sintered nickel powder wick, loop heat pipe (LHP) has been analyzed using a modified Dynatherm LHP Thermal Model. Results from characterization tests of this LHP performed at the Air Force Research Laboratory in Albuquerque, NM are used as the basis for comparison and discussion of results for the analytical model. The analytical predictions gave excellent correlation to the measured data for power levels ranging from 50 to 1500W at condenser chiller settings between −40°C and 20°C, with the LHP in a horizontal orientation.
Passive Cooling of Permafrost Foundation Soils Using Porous Embankment Structures
Authors: Goering Douglas J.
Published: November 2021

Permafrost (permanently frozen ground) underlies approximately 25% of the world’s land surface. Construction of surface facilities in these regions presents unique engineering challenges due to the alteration of the thermal regime at the ground surface. Even moderate disturbance of the pre-existing ground surface energy balance can induce permafrost thawing with consequent settlement and damage to buildings, roadways, or other man-made infrastructure.

The present work examines the thermal characteristics of embankments constructed of unconventional, highly porous materials. Using these materials, a passive cooling effect can be achieved due to the unstable density stratification and resulting natural convection that occur during winter months. The convection enhances transport of heat out of the embankment, thus cooling the lower portions of the embankment and underlying foundation soil and preserving the permafrost layer. Numerical results obtained with an unsteady two-dimensional finite element model are compared to experimental measurements taken in full-scale field installations for the cases of open and closed (impermeable) side-slope boundary conditions.
Multi-Mode Heat Transfer in a Randomly Packed Bed of Cylindrical Rods Using a Finite Volume Scheme
Authors: Murthy J. Y. , Mathur S. R.
Published: November 2021

In this paper, calculations of mixed-mode heat transfer in beds of randomly-packed cylinders are presented. An unstructured finite volume method is employed. Random packing is addressed by meshing a periodic module, and creating the bed by stacking and random lateral translation of modules. The ability of the finite volume scheme to employ arbitrary polyhedra is exploited in addressing the resulting non-conformal interfaces. Conduction and radiation are considered, but convection is ignored. Results are presented for conducting and semi-transparent cylinders for a range of fluid and solid conductivities and solid refractive indices and establish the viability and versatility of the method.
A Hybrid Finite Volume/PDF Monte Carlo Method to Capture Sharp Gradients in Unstructured Grids
Authors: Li Genong , Modest Michael F.
Published: November 2021

The hybrid finite volume/PDF Monte Carlo method has both the advantages of the finite volume method’s efficiency in solving flow fields and the PDF method’s exactness in dealing with chemical reactions. It is, therefore, increasingly used in turbulent reactive flow calculations. In order to resolve the sharp gradients of flow velocities and/or scalars, fine grids or unstructured solution -adaptive grids have to be used in the finite volume code. As a result, the calculation domain is covered by a grid system with very large variations in cell size. Such grids present a challenge for a combined PDF/Monte Carlo code. To date, PDF calculations have generally been carried out with large cells, which assure that each cell has a statistically meaningful number of particles. Smaller cells would lead to smaller numbers of particles and correspondingly larger statistical errors. In this paper, a particle tracing scheme with adaptive time step and particle splitting and combination is developed, which allows the PDF/Monte Carlo code to use any grid that is constructed in the finite volume code. This relaxation of restrictions on the grid makes it possible to couple PDF/Monte Carlo methods to all popular commercial CFD codes and, consequently, extend existing CFD codes’ capability to simulate turbulent reactive flow in a more accurate way. To illustrate the solution procedure, a PDF/ Monte Carlo code is combined with FLUENT to solve a turbulent diffusion combustion problem in an axisymmetric channel.
Feature Variation and Its Impact on Structural Acoustic Response Predictions
Authors: Cunefare Kenneth A.
Published: November 2021

This paper presents a screening technique to assess the impact on model fidelity introduced by variations in the properties or positions of features in harmonically forced fluid-loaded structural acoustic models. While fluid-loading is included, it is not a requirement or restriction to the methods presented. The perspective taken is one of knowledge of a reference state, with a desire to determine the impact on the total radiated acoustic power due to perturbations in the reference state. Such perturbations change the predicted resonance frequencies of a structure under consideration, and hence, change the predicted response amplitudes. The method uses a single degree of freedom response model in the local region of each fluid-loaded resonance, coupled with eigenvalue sensitivities or variations, to estimate the perturbation impact. The SDOF model argues for the use of proportional bandwidth analyses. Elements of the analysis method are not necessarily restricted to model perturbations nor acoustic power, rather they may be used to assess the perturbation of any quadratic response quantity of interest due to changes in resonance frequency. The SDOF analysis method is limited by its assumption of constant modal forcing between the reference and perturbed states.
An Investigation of Power Flow in the Mid-Frequency Range for Systems of Co-Linear Beams Based on a Hybrid Finite Element Formulation
Authors: Zhao Xi , Vlahopoulos Nickolas
Published: November 2021

A hybrid finite element analysis (hybrid FEA) is employed for investigating power flow characteristics for systems of co-linear beams in the mid-frequency range. The importance of capturing power re-injection and power re-radiation effects in the solution is demonstrated. The dependency of the power flow characteristics of a system in the mid-frequency range on the rigidity, mass, and damping properties of its components is determined. Both the hybrid FEA and analytical solutions are employed for analyses in order to establish the viability of the hybrid FEA as a simulation technology in the mid-frequency range.
A Hybrid Finite Element Formulation for Mid-Frequency Analysis of Systems With Excitation Applied on Short Members
Authors: Zhao Xi , Vlahopoulos Nickolas
Published: November 2021

A hybrid finite element method for computing mid-frequency vibrations is presented. In the mid-frequency region a system is comprised by some members that contain several wavelengths and some members that contain a small number of wavelengths within their dimensions. The former are considered long members and they are modeled by the Energy Finite Element Analysis (EFEA). The latter are considered short and they are modeled by the Finite Element Analysis (FEA). In this paper the excitation is considered to be applied on the short members. The hybrid formulation computes the response of the entire system. The characteristics of the long members affect the behavior of the short members and the amount of power flow between the members of the system. The resonant characteristics of the short members and the boundary conditions imposed by the long members determine the amount of input power into the system. The interaction between members is described by a set of equations between the FEA and the EFEA primary variables at the interfaces between long and short members. The equations for the short and the long members and the interface equations are solved simultaneously. A theoretical formulation and a numerical implementation for systems that contain one wave type is presented. Analytical solutions for several co-linear beam configurations are compared to numerical results produced by the hybrid finite element method. Good correlation is observed for all analyses.
Laser-Induced Acoustic Waves for Measurement and Imaging
Authors: Li Wen , Roy Ronald A. , Cleveland Robin O. , Berg Lawrence J. , DiMarzio Charles A.
Published: November 2021

A short pulse of laser light can act as a source of acoustic energy for acoustic imaging. Although there are a number of mechanisms by which the light pulse may generate sound, all require a pulse of high peak power density and short duration. In this work, we address examples where the material is highly absorbing at the laser wavelength, and the sound is generated near the surface. In these cases, there exist two different mechanisms which can convert the light to sound. The first is heating followed by expansion, and the second is generation of a plasma in the air above the surface. In the first case, sound generation occurs in the medium of interest and the energy efficiency can be very high, in the sense that no reflection losses occur. We present two applications from our own research.
Vibration and Acoustic Evaluation of a Large Centrifugal Wastewater Pump, Part 2: Modeling and Interpretation
Authors: Abbot Philip , Gedney Charles , Morton David , Celuzza Stephen , Dyer Ira , Ehlers Peter , Vaicaitis Rimas , Brown James , Guinzburg Adiel , Hodgson William
Published: November 2021

In Part 1, an extensive series of vibration and acoustic measurements conducted on a large centrifugal wastewater pump at a municipal pump station was discussed. In Part 2, the vibration data are evaluated with a physics-based model to estimate the individual contributions from the pump and an acoustic resonance. The results of the measurements, combined with the model, suggest that the primary mechanisms for the pump bearing vibration are: the near-field hydrodynamic pressures generated by the pump itself within the volute, and to a lesser extent, the acoustic resonance excited by the pump’s BPF.
Field Demonstration of a Boiler Feedwater Pump Upgraded to Reduce Vibration and Acoustic Emissions Without Compromising Performance
Authors: Marchi John F. , Bush R. Frank
Published: November 2021

The high-energy boiler feedwater pump is the heart of the steam-generation cycle in modern high-pressure boiler systems. These multi-stage centrifugal pumps are engineered to produce system pressures from 12 MPa (1800 lb/in2) to 45 MPa (6500 lb/in2) at temperatures ranging from 150°C (300°F) to 312°C (600°F).

To optimize pump hydraulic performance, pump designers have focused on impeller and diffuser vane angles, hydraulic passageway shapes and minimized impeller-to-diffuser vane clearances to maximize performance within a narrow range of operation. This was the approach that had been applied successfully on lower energy pump design of an earlier era.

However, in the mid-1980s, in response to market forces, operators began to cycle and operate plants over a wide range of loads, which was contrary to the original plant designs. This new operating paradigm has resulted in unacceptable vibration and acoustic emissions that are often attributable to impeller-to-diffuser vane interaction (a result of the minimized clearances referenced previously). Efforts to reduce these emissions by changing the design must always be balanced with the potential impact on hydraulic performance.

This paper uses operating field data taken from boiler feedwater pumps to prove that by:

• optimizing hydraulic passageways and

• changing the internal geometry, specifically, impeller-to-diffuser vane combinations,

vibration and acoustic emissions are reduced without compromising hydraulic performance.
Computational Methods for the Detection of the Source of Acoustical Noise
Authors: DeLillo Thomas , Isakov Victor , Valdivia Nicolas , Wang Lianju
Published: November 2021

Computational methods for the inverse problem of detecting the source of acoustical noise in an interior region from pressure measurements in the nearfield are discussed. The methods are based on a single layer potential representation of solutions to the Helmholtz equation. Regularization is peformed using the singular value decomposition and the conjugate gradient method.
Damage Modeling in Honeycomb Panels for Tap Testing
Authors: Dayal Vinay , Mir Gohar M. , Hsu David K.
Published: November 2021

Effect of damage on Composite Honeycomb panel due to low speed impact is of significance. The result of such impact is damage such as crushing or buckling of the core, core to face de-bonding and local de-lamination of the plies. The damage, however, may be invisible to human eye but can result in significant degradation of stiffness and strength of Honeycomb structure. Of all the NDE techniques available, Tap Test seems to be the cheapest and most suited for the detection of damage in face-sheets, the face-sheet to core de bonding, and core damage. Instrumented Tap Testing with scanning capability makes it a very attractive NDE tool. This work is concerned with modeling the Tap Test on composite honeycomb panels by Finite Elements in both static and dynamic modes.

Interactive Finite Element model has been developed having option of creating multiple defects of varying size at desired location within the core material. Model is generated using Graphite/Epoxy quasi-isotropic laminate as face sheet material with Nomex paper core, simulating condition of crushed core. The model was analyzed by applying point load (equivalent force of the impacting projectile) at the node of concern. The defect is modeled as a gap in the core.

Samples were made having defects at different core height and were analyzed using Finite Element Methods (ANSYS) and by Tap Testing under same boundary conditions and loading. The sensitivity of FE model and Tap Test to damage location and size has been studied and the results are presented.
An Efficiency Study of Laser-Induced Thermoelastic Wave Generation in Layers
Authors: Wu Ji , Cetinkaya Cetin , Li Chen
Published: November 2021

The elastic wave generation and the efficiency of the thermal-to-mechanical energy conversion process of elastic wave generation by laser excitation are studied. A previously developed transfer matrix formulation [3, 4] is reviewed and the transient response in a silicon layer is computed by employing FFT. The transient thermal and mechanical response of a layer are considered, and the transient temperature, stress, acceleration and mechanical power are obtained under micro-second level excitation. The generation efficiency for the elastic wave components, which are utilized to evaluate the state of layered structures, is examined for a silicon layer. The results presented are useful in determining instrument specification, such as laser power, receiver dynamic range, and test set-up design.
Inspection of Concrete-Metal Rod Interface Using Guided Waves
Authors: Na Won-Bae , Kundu Tribikram , Ehsani Mohammad R.
Published: November 2021

The feasibility of detecting interface degradation and separation of steel rebars in concrete beams using Lamb waves is investigated in this paper. It is shown that Lamb waves can easily detect these defects. A special coupler between the steel rebar and ultrasonic transducers has been used to launch non-axisymmetric guided waves in the steel rebar. This investigation shows that the Lamb wave inspection technique is an efficient and effective tool for health monitoring of reinforced concrete structures because the Lamb wave can propagate a long distance along the reinforcing steel bars embedded in concrete as the guided wave and is sensitive to the interface debonding between the steel rebar and concrete.
Ultrasonic Guided Waves in Thin Orthotropic Layers: Exact and Approximate Analyses
Authors: Datta Subhendu K. , Mukdadi Osama
Published: November 2021

Exact and approximate analyses of ultrasonic guided wave propagation in thin orthotropic layers are presented in this work. Exact solutions to the equations governing the dependence of guided wave propagation speeds on the elastic constants characterizing the anisotropic properties of the layers are presented and compared with the predictions of first order approximate theories for extensional and flexural waves in thin plates. Comparison with available experimental results for dispersion of these waves in thin sheets of different types of papers leads to the confirmation or modification of the elastic constants and density reported for these papers. A particular focus of this study is the coupling of three types of guided waves (extensional (S), flexural (A), and shear-horizontal (SH)) due to anisotropy of the material. It is shown that there are significant changes in the dispersion characteristics of these modes at certain frequencies, which can be exploited to measure the in-plane elastic properties of thin layers. Another focus is to study the limitations of approximate results when compared with exact solutions for wave propagation in different directions. In general good agreements are found at low frequencies.
Review of Basic Models in Fire Dynamics
Authors: Kim Hyeong-Jin , Lilley David G.
Published: November 2021

The ultimate goal of this study is to improve scientific understanding of fire behavior leading to flashover in structural fires. This document summarizes important information in five topic areas: burning rates, radiant ignition, fire spread rates, ventilation limit imposed by size of opening, and flashover criteria.

These are the main components related to the scientific understanding of the fire growth and flashover problem involved in real-world structural fires. Within each topic area, there are four subsections dealing with background, theory, comments, and references. Main components of the study are to develop improved mathematical simulations so as to improve the accuracy of theoretical calculation and to develop and extend the range of knowledge and modeling capability so as to extend the range of available experimental data.
Investigation of Spectral Radiation Heat Transfer and NOx Emission in a Glass Furnace
Authors: Golchert B. , Zhou C. Q. , Chang S. L. , Petrick M.
Published: November 2021

A comprehensive radiation heat transfer model and a reduced NOx kinetics model were coupled with a computational fluid dynamics (CFD) code and then used to investigate the radiation heat transfer, pollutant formation and flow characteristics in a glass furnace. The radiation model solves the spectral radiative transport equation in the combustion space of emitting and absorbing media, i.e., CO2, H2O, and soot and emission/reflection from the furnace crown. The advanced numerical scheme for calculating the radiation heat transfer is extremely effective in conserving energy between radiation emission and absorption. A parametric study was conducted to investigate the impact of operating conditions on the furnace performance with emphasis on the investigation into the formation of NOx.
The Practical Application of CFD in the Design of Industrial Centrifugal Compressors
Authors: Sorokes James M. , Hutchinson Bradley R.
Published: November 2021

In the development of industrial turbomachinery, the aerodynamic designer is faced with many complex fluid flow problems. In the mid to late 1980’s, Computational Fluid Dynamics (CFD) software was developed to assist in the solution of these flow fields. Initially applied only by high end gas turbine or jet engine designers, these sophisticated tools eventually found their way to engineers at industrial turbomachinery manufacturers. However, it has only been in the last five to ten years that industrial users have begun to make more widespread use of CFD. There are a variety of reasons for this slow adoption.
Problem Diagnosis and Aerodynamic Improvement of a Field Pipeline Compressor
Authors: Liu Zheji , Hill D. Lee , Biba Yuri I.
Published: November 2021

An extensive investigation surrounding a performance shortfall of a pipeline compressor is presented. Regions of high aerodynamic loss are identified from an extensive flange-to-flange numerical investigation. Special attention is placed on understanding the impact of the interface model between the rotating and stationary components on the performance of each individual component and the whole machine. This process lead to the redesign of the radial inlet, the diffuser region, and the volute. Upon numerical validation of the proposed design changes, the components were manufactured and installed into the compressor that was already operating in the field. “Field” testing showed the new design to have a peak efficiency improvement of 4 points surpassing the contract guarantee.
An Experimental Setup for Measuring Unstable Thermo-Mechanical Behavior of a Shape Memory Alloy Wire
Authors: ladicola Mark A. , Shaw John A.
Published: November 2021

An experimental arrangement is demonstrated that overcomes some difficulties in thermo-mechanical testing of thin Shape Memory Alloy (SMA) wires under uniaxial tension. It is now well known that stress-induced transformations in some SMAs under uniaxial loading can lead to mechanical instabilities and propagating phase transformation fronts. Critical parameters, such as nucleation barriers are difficult to measure by conventional testing techniques and are often masked by unavoidable stress concentrations at grips. In addition, simultaneous full field measurements of localized deformation and temperature fields are difficult to obtain for different ambient conditions. The current scheme uses a temperature-controlled conduction block and a non-uniform temperature field induced by thermoelectric modules to uncover the underlying thermo-mechanical response of the wire. The approach also allows access for optical and infrared imaging of the specimen deformation and temperature fields.
Effect of Feedback Control on the Power Consumption of Induced-Strain Actuators
Authors: Chandrasekaran Sriram , Lindner Douglas K. , Leo Don
Published: November 2021

In this paper we study the closed loop power flow characteristics between a controlled piezoelectric actuator and a current controlled drive amplifier for two different structural control laws. We determine the real and reactive power flow through the structure and actuator into the amplifier when the structure is excited with a sinusoidal disturbance force under both control laws. The dependence of the real and reactive components of the power on the material properties of the actuator, structure and the configuration of the controller is presented. These real and reactive power estimates are useful for sizing the drive amplifier for the actuator.
A General Magneto-Elastic Model of Terfenol-D Particle Actuated Composite Materials
Authors: Armstrong William D.
Published: November 2021

A new theory is presented of the nonlinear multi-axial magneto-elastic behavior of magnetostrictive particle actuated composite materials. The analysis assumes a uniform external magnetic field is operating on a large number of well distributed, crystallographically and shape parallel ellipsoidal magnetostrictive particles encased in an elastic, nonmagnetic composite matrix. Comparisons between experimental and model magnetostriction results show that the model is able to provide a quantitatively correct dependence on particulate volume fraction and longitudinal stress and quantitatively accurate magnetostriction curves for both homogenous Terfenol-D rod and magnetically ordered Terfenol-D particulate actuated epoxy matrix composites over experimentally applied field ranges.
An Active-Passive Piezoelectric Vibration Absorber for Structural Control Under Harmonic Excitations With Time-Varying Frequency
Authors: Morgan Ronald A. , Wang K. W.
Published: November 2021

It has been shown that piezoelectric materials can be used as passive electromechanical vibration absorbers when shunted by electrical networks. Semi-active piezoelectric absorbers have also been proposed for suppressing harmonic excitations with varying frequency. However, these semi-active devices have limitations that restrict their applications. The design presented here is a high performance active-passive alternative to semi-active absorbers that uses a combination of a passive electrical circuit and active control actions. The active control consists of three parts: an adaptive inductor tuning action, a negative resistance action, and a coupling enhancement action. A formulation for the optimal tuning of the piezoelectric absorber inductance on a multiple degree of freedom (MDOF) structure is derived. The effectiveness of the proposed system is demonstrated experimentally on a system under a variable frequency excitation. Extensive parameter studies are also carried out to show that the proposed design offers superior performance and efficiency compared to other state-of-the-art control methods.
A New Twisting and Bending Coupled Piezoelectric Actuator Using Shaped Electrodes
Authors: Kwak Seung-Keon , Washington Gregory
Published: November 2021

In this research, a new twisting and bending coupled piezoelectric actuator based on the spatial aperture shading technique is introduced. The shaped electrode twisting actuator consists of two layers of PZT-5H (lead zirconate titanate) and one middle layer of steel shim. The directionally shaped electrode technique is applied to achieve the both twisting and bending motions of the actuator. The comparison of an analytical model, a numerical analysis, and actual experimental results for the actuator are given. The generalized functions are used to determine the discontinuous forcing function of the actuator in the analytical model. For the numerical analysis, the actuator is modeled utilizing a multi-layered integrated finite element model. The models show good agreement with experimental research.