bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Two Methods to Measure the Frequency-Wavenumber Spectrum of the Wall Pressure Field Beneath a Turbulent Boundary Layer
Authors: Giovannelli G. , Hespeel D. , Forestier B. E. , Pognant M.
Published: January 2022

The wavevector-frequency spectral estimation of wall pressure fluctuations by means of multiple Fourier transform processing of multi point data is discussed. This paper compares two methods to estimate the ω-k spectrum. In the first method, fluctuating pressure field measurements are made synchronously. In the Wills (1970) method the fluctuating pressure data are issued from two movable probes. The spectral level at low wavenumbers has been previously evaluated by Iddir (1997) and Giovannelli et al (1997). We use both these experiments in the subconvective domain and the present measurements in the convective part to fit the parameters of Chase’s model (1991) of the wall pressure spectrum. We show that the bias introduced by the discrete Fourier transform estimation on Chase’s model integrated over the transverse wavenumbers is about 5 dB. The addition of Chase’s model and the acoustic excitation of the facility is close to experimental frequency-wavenumber spectral densities. The Maximum Likelihood Method is also performed on the pressure data and on the model.
Wavenumber-Frequency Spectrum Measurement of Wall Shear Stress Fluctuations Beneath a Planar Turbulent Boundary Layer
Authors: Hespeel D. , Giovannelli G. , Forestier B. E.
Published: January 2022

The majority of past and recent works on the wall pressure spectrum of a turbulent boundary layer considers that the wall shear stress effects are negligible. To estimate the contribution of the shear stress dipoles to the wall pressure generation, instantaneous fluctuations of streamwise wall shear stress have been measured using hot-element probes in a planar turbulent boundary layer. Considering various factors such as heat loss to the probe substrate, frequency response of the probes, spanwise averaging and length to diameter ratio of the heated element, the wall shear stress frequency spectra have been studied and the measured relative intensity τrms/τ¯=34% reevaluated to 40%. The wall shear stress correlations show a lower convection velocity and a greater coherence loss than for wall pressure fluctuations. The difference between the wall pressure and the wall shear stress wavenumber-frequency spectra is about 21 dB at the convective maxima and reduces to a few dB at the low wavenumbers.
Subjective Evaluation of the Noise at the Operator’s Ear Position in Earth Moving Machines: A Preliminary Investigation
Authors: Carletti Eleonora , Pedrielli Francesca
Published: January 2022

Laboratory listening tests have been carried out in order to compare the objective parameters commonly used for assessing the noise at the operator’s ear position in the cabin of an earth moving machine, with the subjective perception. The results, although affected by limitations inherently the initial state of the study, show that the parameter that has to be measured in accordance with the international standards currently in force, is not adequate to describe the physical phenomena determining the subjective auditory perception. A further investigation should address the identification of descriptors which better represent the hearing sensation.
Damage Characterization Around a Bullet Hole in Composites
Authors: Baig Zahid I. , Dayal Vinay
Published: January 2022

The ballistic impact of a bullet on thin and thick composites has been studied in this work. Vibration modal analysis was used to ascertain the effect of bullet hole and damage on the change in natural frequency of the laminate. Ultrasound was used to determine the actual extent of damage in the laminate and a quasi-static Finite Element model is employed to determine the development of interlaminar shear stresses and failure in the laminate.
Nondestructive Ply-Layup Identification for Fiber Reinforced Composites Using Genetic Algorithm
Authors: Balasubramaniam Krishnan , Rao Navin S.
Published: January 2022

For multi-oriented layered composite laminates, ply lay-up (stacking sequence) identification is an essential exercise. Lay-up identification falls under the realm of nonlinear inverse problems. Few attempts in this direction are quoted in literature. Of note are the works of Komsky and co-workers [1], where shear wave transmission signals have been used in conjunction with theoretical models or neural networks.
Geometric and Material Influences on the Forward Stage of the Elastic Identification Problem
Authors: Ayorinde Emmanuel O. , Yu Lin
Published: January 2022

This paper looks at the characteristics of frequency response and frequency sensitivity of elastic constants in completely free rectangular plates of varying aspect ratios, fiber angle orientations and material orthotropy ratios. These are important considerations in the procedures currently widely applied for the elastic identification and damage analysis of composite materials.
Low Velocity Impact Response of Thin Walled Graphite/Epoxy Cylinders
Authors: Vaidya Uday K. , Jones Michael V. , Kamath Mohan V. , Evans Robert , Vandiver Terry
Published: January 2022

Helical and hoop wound graphite/epoxy (Gr/Ep) composite cylinders have been tested under low velocity impact under simply supported boundary conditions, in two phases. In Phase I, the impact energy levels ranged from 1 to 6 ft-lbs, (1 ft-lb = 1.35J) while in Phase II, the impact energy levels ranged from 35 ft lbs-50 ft lbs. Pre- and Post-impact ultrasonic C-scans have been conducted. The fiber bundles and the winding angle(s) are well resolved through the C-scans. Vibration based NDE has been conducted prior to and after impact to determine modal response of the composite cylinders under a simply supported boundary condition. The modal density of the helical wound cylinders is found to be higher than the hoop wound, while the hoop wound cylinders exhibit higher stiffness. The microstructure of some of the cylinders has been studied by sectioning them at impact locations.
Effect of 3D Reinforcement on the Low-Velocity Impact Response of S2-Glass/Vinyl Ester Composite Laminates
Authors: Hosur M. V. , Vaidya U. K. , Abraham A. , Jeelani S.
Published: January 2022

Due to their inherent weakness in thickness direction, laminated fiber reinforced composites are susceptible to undergo large delamination damage when subjected to transverse loading. Low-velocity impact loading is one such case. Low-velocity impact occurs due to tool-drops during manufacturing, maintenance, and service, runway debris during landing and takeoff and hailstorm. In the current work an effort is made to improve the transverse strength by providing 3D reinforcement in the form of pins and stitching the laminate in thickness direction. Laminates were made of S2-Glass/Vinyl Ester. Specimens of size 3 × 4 inch were subjected to drop-weight impact at energy levels of 20, 31 and 41 Joules. The impacted panels were subjected to vibration tests to determine the stiffness loss through vibration based frequency response function (FRF) measurements. Effect of impact damage on interlaminar shear strength was studied. Results indicate that there is considerable improvement in damage tolerance due to 3D reinforcement.
Effective Dynamical Properties
Authors: Barbone Paul E.
Published: January 2022

We discuss effective dynamical properties of complicated vibratory subsystems. A complicated vibratory subsystem is one in which the resonance structure contains a lot of fine detail. The first part of this paper describes an analogy between the effective vibratory subsystem theory and the effective medium equations used to model composite materials. The second part of this paper presents an example application of the effective vibratory subsystem theory. The effective subsystem theory is used to model a continuous elastic rod. Features of the nonuniform limit ω → ∞ are shown to be reproduced by the effective vibratory sub-system theory.
Rational Interpolation of Sampled Frequency Response Calculations Based on Sophisticated Vibration Theory
Authors: McDaniel J. Gregory , Pierce Allan D.
Published: January 2022

This paper presents a new method for enhancing and extending finite element analyses of structures in the frequency domain. When a finite element model is used to predict the response of a vibrating structure to a time-harmonic excitation, the number of degrees of freedom necessary for a convergent answer scales with the frequency of excitation. At higher frequencies, inversion of the matrix equations of motion for the response vector is computationally expensive and, given a finite amount of computer resources, the response at any particular point on the structure is coarsely sampled in frequency. Direct computation of the modal vectors and natural frequencies is similarly cost prohibitive. The method presented here is intended to increase the frequency resolution of response data over a frequency band by estimating the resonant frequencies which lie in the band and their corresponding modal vectors. These estimates are obtained by inserting into Rayleigh’s Principle a trial modal vector that is a linear combination of the response vectors evaluated at frequencies inside the band. An eigenvalue problem is thereby obtained whose rank is equal to the number of sampled frequencies, which is chosen to be much smaller than the number of degrees of freedom of the structure. The method is demonstrated on a vibrating beam, where it is shown to accurately predict the displacement anywhere over a frequency band which contains four modes.
Numerical Implementation of Inflow/Outflow Conditions for Time-Harmonic Turbomachinery Flows
Authors: Golubev Vladimir V. , Atassi Hafiz M.
Published: January 2022

An efficient numerical scheme is developed to implement the inflow/outflow conditions for unsteady turbomachinery flows. The formulation gives exact non-reflective conditions which can be used with a time-harmonic code for calculating the unsteady flow about blades as well as the acoustic radiation. The method is applied to flows with a mean swirl. Upstream and downstream from the blade row, an asymptotic behavior of the scattered unsteady disturbances is obtained from an eigenmode analysis of the unsteady linearized Euler equations. The inflow/outflow conditions are developed as a filter which selects the physically acceptable modes and thus provides a non-reflective solution throughout the physical space of the annular blade row passage. The direct numerical implementation of the non-reflective conditions may lead to ill-conditioned matrices. An approach is proposed based on matrix factorization which enhances the convergence properties.
Approximations of Power Flow Between Two Coupled Beams Using Statistical Energy Methods
Authors: Tan Y. C. , Castanier M. P. , Pierre C.
Published: January 2022

The present work is concerned with predicting the power flow between two coupled substructures with parameter uncertainties. The power flow is averaged over an ensemble of systems due to the variation of the system parameters. The ultimate aim is to develop a statistical method which may be applied to the mid-frequency range of vibration for a complex structure. The system considered in this paper is two coupled, nominally identical beams on simple supports, with a torsional spring attached at the coupling point. Various methods are presented to calculate the power flow for this system. The Parameter-based Statistical Energy Method (PSEM) is applied to a classical modal solution and a wave solution. The wave approach appears to be more accurate and computationally efficient for this one-dimensional system. The power flow formulated by applying Component Mode Synthesis (CMS) is also presented. It is seen that the CMS formulation may provide a framework for the efficient numerical analysis of power flow in a general complex structure, which may be modeled by the finite element method.
Free Vibration Analysis of Viscoelastic Moving Belts
Authors: Zu Jean W. , Zhang Lixin
Published: January 2022

The nonlinear free vibration of viscoelastic moving belts is studied. Based on the linear viscoelastic differential constitutive law, the generalized equation of motion is derived for a moving belt with geometric nonlinearities. The method of multiple scales is applied directly to the governing equation which is in the form of continuous autonomous gyroscopic systems with weakly nonlinearity. This direct treatment does not involve a prior assumption regarding the spatial solutions. The nonlinear natural frequencies and free response amplitude for autonomous systems are predicted by the perturbation method. The results obtained with the quasi-static assumption and those without this assumption are compared. The effects of elastic and viscoelastic parameters, axial moving speed, and the geometric nonlinearity on natural frequencies and amplitudes of the free response are investigated from numerical examples.
Flow Induced Vibration of Submerged and Inclined Concentric Pipes With Different Lengths
Authors: Wang Xiaodong , Bloom Frederick
Published: January 2022

In this paper, we formulate a mathematical model to study the dynamics of submerged, inclined concentric pipes with different lengths. The governing equations of motion for the inner pipe are derived under small deformation assumptions and with the consideration of gravitational forces, turbulent boundary layer thickness of external flow, fluid frictional forces, and inertia! effects. We obtain discretized dynamical equations using spatial finite difference schemes and calculate the resonant frequencies of a particular pipe system design. In addition, by varying the operating conditions, we identify a few critical parameters pertaining to the proper design of such pipe systems.
Flow Visualization of Oscillating Rectangular Prisms Arranged in Arrays and in Isolation
Authors: Kerenyi K. , Hillisch S. , Drobir H. , Staubli T.
Published: January 2022

This study examines the flow around an isolated rectangular prism as well as around and through an array of equidistant bars. These prisms are excited to oscillate by the flow for certain experimental parameters due to a lightly damped suspension. The experiments with suspension allowing oscillations with mechanically uncoupled, orthogonal degrees of freedom are described, as is the hydrogen bubble technique employed for visualization. A first interpretation of flow images is given starting with the stationary, single bar at various incidence angles of the flow. In a next step the oscillating isolated bar is discussed followed by arrays of five (non-oscillating) and three bars (oscillating). Special focus is put on the influence of the bar spacing and its influence on the excitation of oscillations. It is demonstrated that oscillation can be avoided by appropriately choosing the spacing.
Time-Optimal Input Sequences for Residual Vibration Reduction
Authors: Teo C. L. , Ong C. J. , Xu M.
Published: January 2022

In this article, a method of designing an input sequence to move a flexible structure without residual vibration is presented. The vibration suppression problem is formulated as an optimization problem to find the input sequence that minimizes the time taken for a point-to-point motion. The requirement for zero residual vibration is imposed on the optimization problem as suitable constraints. Other constraints resulting from physical limits existing in the actual system can also be easily incorporated. The only requirement is that the natural frequency and damping ratio of the system be known. However additional robustness constraints can be added to ensure that the solution will be insensitive to slight variations in these parameters. Simulations and experimental results show that the inputs developed here are effective to reduce the residual vibration. In addition, the proposed solution shows a marked insensitivity to errors in natural frequency and damping ratio estimates if the additional robustness constraints are included.
Stability Analysis of Flexible Cam Follower Systems
Authors: Dehghani M. , Hamidzadeh H. R.
Published: January 2022

Dynamic stability of a flexible cam-follower is considered. The shaft-cam-follower assembly is modeled by a single degree of freedom system. In the analysis, transverse and rotational flexibilities of the camshaft along with flexibility of the follower are taken into consideration. This gives rise to a system governed by a linear, second-order, ordinary differential equation with time-dependent coefficients. In general, this class of equations is known as second order Hill’s equation. The time responses of the cam-follower system for an eccentric cam under different rotational speeds are determined. In addition, the stability analysis based on Hill’s infinite determinant is performed, and the effects of operational speed and damping on the stability are determined. For the special case of the cam-follower system that has been considered, it has been found that the system is stable for lower values of the angular speed of the cam. As the speed is increased gradually, a few unstable regions occur. In general, damping shows a significant effect on stabilizing the cam-follower system.
Stability Analysis of Multiple Delayed Resonator Vibration Absorbers
Authors: Jalili Nader , Olgac Nejat
Published: January 2022

This paper is on the use of multiple identical Delayed Resonator (DR), a recently introduced active vibration absorber, in suppressing tonal vibration of multi-degree-of-freedom mechanical structures. The DR methodology forces the conventional mass-spring-damper passive absorbers into marginally stable resonators which absorb all the vibratory energy at their points of attachment. Control forces in the form of proportional acceleration feedback with variable gains and time delays are considered here. Elimination of tonal vibration, real-time tunability, and stand-alone nature of these actively controlled absorbers are already proven features. The stability of the primary structure combined with multiple DR’s is addressed in this paper, following a stability chart strategy. A “peeling-off” procedure is adopted to eliminate successively the highest order delay terms in the characteristic equation of the system at each step. Consequently, the stability charts are constructed to reveal the operable zones. An example case of two identical DR’s on a 3-DOF system is presented.
The Effect of Spatially Nonuniform Thermal Fields on the Vibration Frequencies of EDM Wires
Authors: Murphy Kevin D. , Lin Zhengmao
Published: January 2022

This is an investigation into the effect of spatially nonuniform temperature fields on the undamped, free vibration characteristics of the wire electrode in the wire electro-discharge machining (EDM) process. In particular, a nonlinear multi-mode structural model is developed for the translating wire along with a thermal model which accounts for heat input (from sparking), axial conduction, radial convection, and energy storage. The two models are then coupled through the internal thermal stress terms of the structural model.

Using these combined models, an eigenvalue analysis is performed to examine the behavior of the natural frequencies (Im(λ)) as a function of the transport speed. It is shown that both divergence and Hopf bifurcations occur in this system. Specifically, the system is unstable at low transport speeds due to thermal buckling, stable at intermediate speeds, and unstable at high speeds due to a series of transport instabilities. Furthermore, it is shown that the frequency loci for a given mode decreases as the input discharge energy and, hence, the mean wire temperature are increased. This lowers the critical transport speed associated with the transport instability.
Laminar Natural Convection in Isosceles Triangular Enclosures Heated From Below and Symmetrically Cooled From Above
Authors: Holtzman Gary A. , Hill Roger W. , Ball Kenneth S.
Published: January 2022

A numerical study of natural convection in an isosceles triangular enclosure with a heated horizontal base and cooled upper walls is presented. Nearly every previous study conducted on this subject to date has assumed that the geometric plane of symmetry is also a plane of symmetry for the flow. This problem is re-examined over aspect ratios ranging from 0.2 to 1.0 and Grashof numbers from 103 to 105. It is found that a pitchfork bifurcation occurs at a critical Grashof number for each of the aspect ratios considered, above which the symmetric solutions are unstable to finite perturbations whereas two steady mirror image solutions are stable. Results are presented detailing the occurrence of the pitchfork bifurcation in each of the aspect ratios considered and the resulting flow patterns are described. Local and mean heat transfer coefficients are presented, and discrepancies with previously published results in which a symmetric flow pattern is assumed are discussed.
Heat Transfer to Two-Phase: Air, Power-Law Fluid Flows Over a Hot Cylinder
Authors: Rao B. K.
Published: January 2022

Circumferential temperatures for two-phase: air and aqueous polymer (purely viscous) solutions flowing over a horizontal cylinder were measured experimentally. The cylinder was heated by passing direct electric current through it. The peripherally averaged heat transfer coefficient for purely viscous non-Newtonian fluids, at any fixed flow rate, decreases with increasing polymer concentration. A new correlation is proposed for predicting the Nusselt number for two-phase: air and power-law fluid flows over a heated cylinder in cross flow.
Effect of Jet Characteristics on Heat Transfer by Impingement of Submerged-Confined Water Jet
Authors: Abou-Ziyan H. Z. , Radwan M. S. , Swidan M. M. , Ibrahim T. A.
Published: January 2022

Single phase forced convection and subcooled flow boiling due to impingement of confined submerged, fully turbulent liquid jet are experimentally investigated at atmospheric pressure. Heat transfer measurements are made along a uniformly heated surface onto which a jet is impinged orthogonal or at angles of inclination upstream into the cross flow. The experiments are performed at heat fluxes of 80–700 kW/m2, for cast iron and cast steel stabilized surfaces. The experimental parameters used in this investigation include: fluid temperatures (50, 60, 70 and 90°C), jet velocities (1, 2, and 3 m/sec), jet diameters (4.6, 8.6, and 10 mm), jet inclination angles (46°, 59°, and 90°), dimensionless nozzle-to-plate spacing distances, x/L (0.25, 0.5 and 1) with the duct heights, L of 10, 30 and 40 mm which provide confined walls aspect ratios (height/width) of 0.2, 0.6, and 0.8, respectively. Such conditions explore the effect of jet characteristics on cooling of engine cylinder heads by water impinging technique.

The results revealed that the heat flux is enhanced with degree of subcooling, flow velocity, jet diameter, jet inclination angle and confined wall aspect ratio. Correlations of forced convection, incipient boiling, partial subcooled flow boiling and fully developed subcooled boiling are obtained. These correlations are useful in designing the cooling system of the critical areas which cooled by jet impinging technique. The results showed that this technique can save 50% to 92% of the required cooling water when compared with the classical cooling technique.
Energy Dissipation in Sheared Granular Flows
Authors: Karion Anna , Hunt Melany L.
Published: January 2022

Flows of granular materials play an important role in industry and in nature. This research focuses on shear flows of particles of the same size and of two different sizes and the energy dissipation associated with these flows. The study was performed using a two dimensional discrete element computer simulation of a bounded, gravity-free Couette flow of particles. The heat dissipation rate per unit area in these flows is presented as a function of position in the flow as well as overall solid fraction. Results compare favorably with kinetic theory results from Jenkins and Richman (1985) for rough disks. The heat dissipation rate is also measured for binary mixtures of particles as a function of position in the flow and solid fraction ratio of small to large particles. These results are presented for diameter ratios of ten, five, and two. Results show that dissipation rates increase significantly with overall solid fraction and local strain rates and granular temperatures.
Experiments and Numerical Simulations of Swirling Fires due to 2 × 2 Flames in a Channel With a Single Corner Gap
Authors: Satoh Kohyu , Yang K. T.
Published: January 2022

Fire whirls are known to cause loss of lives and extreme property damages in large urban fires such as earthquake fires. This study focuses on the swirling flames generated by placing four identical symmetrical fires in a square channel with a single corner gap on one of the channel walls. The effects of the inter-fuel pan distance were examined experimentally and also numerically simulated by a field model. The numerical simulations show the existence of both the strong rotating flames and the vertical buoyant swirling flames, as also observed in the experiments. Furthermore, the simulations also show strong inflow from the channel top opening, resulting in extremely complex flow patterns inside the channel due to flow instabilities.
The Effect of Forcing on Scalar Transport in a Co-Axial Combustor Geometry
Authors: Chandra P. R. , Acharya S. , Sebastijanovic N. , Panigrahi P.
Published: January 2022

This paper investigates open-loop control of the mixing between an inner heated stream and an outer unhealed stream in coaxial combustor geometry. The inner and outer streams mimic the gaseous fuel and primary air stream in a gas turbine combustor. Of specific interest in this study is the behavior of the coherent structures, and the mixing in these coherent structures under the effect of controlled perturbation of the primary air stream. Two perturbation or forcing frequencies are studied: the preferred mode or fundamental frequency of the unforced flow which is measured to be 500 Hz, and the subharmonic frequency of 250 Hz. At each forcing frequency, three different forcing levels were examined. At the high-forcing level, the preferred mode forcing produces an increase in the spreading rate of both the inner and the outer jets. This is associated with increased entrainment into the coherent structures and increased mixing of the heated inner and unheated outer jet. With subharmonic forcing, a similar behavior is observed due primarily to the emergence of the fundamental as a dominant mode. At low-level forcing, the velocity profiles are only marginally affected, but the temperature profiles indicate a decrease in mixing. It is speculated that this is associated with increased coherence but without an associated increase in entrainment into the coherent structures.
A Numerical Study of Short Residence Time FCC Riser Flows With a New Flow/Kinetics Modeling Technique
Authors: Chang S. L. , Lottes S. A. , Petrick M. , Zhou C. Q.
Published: January 2022

Fluid Catalytic Cracking (FCC) technology is the most important process used by the refinery industry to convert crude oil to valuable lighter products such as gasoline. New and modified processes are constantly developed by refinery companies to improve their global competitiveness and meet more stringent environmental regulations. Short residence time FCC riser reactor is one of the advanced processes that the refining industry is actively pursuing because it can improve the yield selectivity and efficiency of an FCC unit. However, as the residence time becomes shorter, the impact of the mixing between catalyst and feed oil at the feed injection region on the product yield becomes more significant. Currently, most FCC computer models used by the refineries perform sophisticated kinetic calculations on simplified flow field and can not be used to evaluate the impact of fluid mixing on the performance of an FCC unit. Argonne National Laboratory (ANL) is developing a computational fluid dynamic (CFD) code ICRKFLO for FCC riser flow modeling. The code, employing hybrid hydrodynamic-chemical kinetic coupling techniques, is used to investigate the effect of operating and design conditions on the product yields of FCC riser reactors. Numerical calculations were made using the code to examine the impacts of the operating and design conditions on the product yields. The controlling parameters under investigation include the residence time, reaction temperature, and catalyst/oil ratio. This paper describes the CFD code, presents computational results, and discusses the effects of operating conditions on the performance of short residence time FCC riser reactors.
Effects of Surface Patterning in Thin Film Structures on the Thermal Radiative Properties During Rapid Thermal Processing
Authors: Tada Haruna , Abramson Alexis R. , Miaoulis Ioannis N. , Wong Peter Y. , Nieva Patricia , Zavracky Paul
Published: January 2022

Thermal processing is used in various stages of microelectronics fabrication. One of the heating processes may be rapid thermal processing (RTP), which involves high temperatures and heating rates, and short durations. Temperature control and uniformity within a few degrees is a requirement in RTP. Prediction, measurement, and control of wafer temperatures during RTP have been a challenge due to the highly non-linear radiative properties of the wafers. These properties are functions of temperature, wavelengths, doping level, surface patterns, and thin-film structures. A numerical model has been developed to determine the wafer radiative properties, taking into account bandgap, free carrier, and lattice absorption effects, as well as thin-film interference near the surface and partial transparency within the wafer thickness. Experimental measurements of spectral reflectivity of different pattern sizes were made for SiO2 stripes on Si wafer. Results indicate that the radiative properties of patterned wafers for pattern sizes down to 4 μm can be adequately predicted by the average reflectivity of Si and SiO2, weighted according to their relative areas. This was found to be true regardless of the diffractive effects seen visually. The numerically determined radiative properties were used in a model of radiantively heated patterned wafer to find the temperature distribution at steady-state. For the model wafer having 2550 Å SiO2 film on Si, with SiO2 and Si stripe patterns, the patterns created regions of high and low temperatures on the wafer, which can lead to significant thermal stresses and defects in the wafer.
An Investigation of Corrosion in Liquid-Metal Heat Pipes
Authors: Adkins Douglas R. , Rawlinson K. Scott , Andraka Charles E. , Showalter Steven K. , Moreno James B. , Moss Timothy A. , Cordiero Patricia G.
Published: January 2022

Research is underway to develop a 75-kW heat pipe to transfer solar energy from the focus of a parabolic dish concentrator to the heater tubes of a Stirling engine. The high flux levels and high total power level encountered in this application have made it necessary to use a high-performance wick structure with fibers on the order of 4 to 8 microns in diameter. This fine wick structure is highly susceptible to corrosion damage and plugging, as dissolved contaminants plate out on the evaporator surface. Normal operation of the heat pipe also tends to concentrate contaminants in localized areas of the evaporator surface where heat fluxes are the highest. Sandia National Laboratories is conducting a systematic study to identify procedures that reduce corrosion and contamination problems in liquid-metal heat pipes. A series of heat pipes are being tested to explore different options for cleaning heat-pipe systems. Models are being developed to help understand the overall importance of operating parameters on the life of heat-pipe systems. In this paper, we present our efforts to reduce corrosion damage.
Filtration of Aircraft Cabin Air Odors in 100% Relative Humidity, Low Temperature Conditions
Authors: Penrod Samuel L. , Unger Pete D. , Rohrbach Ronald P. , Bause Daniel E. , Xue Lixin , Dondero Russ A.
Published: January 2022

Aircraft cabin air is frequently contaminated by low concentration odor causing compounds. Activated carbon has a long history of effective application in gas stream treatment. However, little information is available on removing low concentration odor causing compounds in high humidity, cold air environments. Previous research suggests that high relative humidity would severely reduce the effectiveness of activated carbon filters. Operating conditions in aircraft low pressure water separators typically run at 100% relative humidity and 2°C.

Effluent or “breakthrough” curves at 5 ppmv toluene resulted in an adsorption capacity of 0.3 g toluene per gram media at 100% relative humidity compared to a 33% increase at less than 5% relative humidity, i.e. 0.4. Breakthrough analyses were performed at 5 to 40 ppmv toluene at face velocities of 50 to 180 m/min. These results indicate that carbon fiber based filter media hold the promise of effective odor control under conditions of high humidity and low temperature.
Analysis of Soil Heat Exchangers for Thermal Management of Outdoor Electronic Cabinets
Authors: Hegab Hisham E. , Zimmerman Eric B. , Colwell Gene T.
Published: January 2022

Telephone companies utilize densely packed electronics in outdoor metal cabinets for routing calls between customers. As a result of the increasing power densities of electronics, companies are looking for innovative methods of providing system level cooling such as using soil heat exchangers. Numerical simulation using a system of lumped thermal capacitances coupled to a soil finite element model is used to predict the transient thermal behavior of a cabinet. The cabinet model has been verified in previous studies by comparison with experimental measurements on a commercial telecommunications cabinet and is shown to predict temperature trends well. The effects of transient heat load, soil properties, and heat exchanger geometry are examined. Results reveal soil heat exchangers have the capability to provide the necessary cooling for relatively low power outdoor cabinets. However, the temperature of the soil surrounding the heat exchanger may increase daily if the number and spacing of pipes is not adequate to handle the desired heat dissipation load.
Study of Combined Method to Enhance Convective Heat Transfer
Authors: Chen Li
Published: January 2022

Experimental study of convective heat transfer in a tube with the combination of spring coil and flag-type inserts was performed to investigate the characteristics of heat transfer and flow drag. The test tube was a ϕ28 × 2 × 700 mm copper tube, and the working fluid was No.30 turbine oil. A piece of spring with the length of 100mm (wire diameter of 1.5mm and the pitch of 4mm) was set at the inlet of test tube, behind the spring 1–3 pieces of trapezoid shaped flag-type inserts made of stainless steel having a sweep angle of 76° length of 20mm width of 22mm and thickness of 0.3mm were hinged on a ϕ1.0 mm stainless steel vertical stick. It was shown that by means of the combined method heat transfer coefficient was greatly increased and the ratio of h/h0 was mostly higher than Δp/Δp0, also h/h0 increased in both the low and high Re regions. It was concluded that the advantages of these two components were combined and their disadvantages were reduced.
Heat Pipe Vapor Chamber Cold Plate Modeling, Fabrication and Testing
Authors: Zuo Z. Jon , Dussinger Peter M.
Published: January 2022

Heat pipe vapor chamber cold plates (HPVCCP) utilize highly efficient two-phase flow heat transfer to distribute concentrated heat to larger surface areas for effective dissipation. Because of the isothermal heat transfer characteristics, the HPVCCP is particularly suited for effective cooling of electronics. This paper presents the results of a recently completed study by Thermacore, Inc. on HPVCCP modeling, analysis, design, fabrication, processing, and testing. A two-dimensional numerical model was developed to calculate the liquid flow pressure distribution in the porous wick structure that is critical to determining the wick capillary limitation. A thermal network model was developed to calculate the temperature differences between the heating and cooling surfaces. Prototype, large size HPVCCP design, fabrication and testing issues are also discussed in the paper.
Natural Harmonic Locking of Sea–Gulf Systems and Effect of Their Artificial Instability on Mass Transfer
Authors: Kovinskaya Svetlana I. , Sofronov Valentin V. , Amromin Eduard L.
Published: January 2022

An analysis of water oscillation in the several sea-gulf systems on the base of shallow water theory and the actual bottom relief data was provided. Computation was carried out for each part of every system independently, and their amplitude responses were compared. The numerical analysis manifests that the sea oscillations have an influence on the gulf oscillations, and the inverse influence takes place too. Harmonic locking of oscillations in both part of the sea-gulf system is established. Tuning of the sea-gulf system oscillations is effected by the depth distribution only, but a correlation between gulf narrowness places and nodes of the main seiche modes is found. The amplitude responses and modes of three coupled sea systems are presented.

The influence of the large-scale engineering activity in the gulf of the Finland (a dam construction at its head near St.-Petersburg) on the gulf amplitude response are estimated. The results of the numerical analysis show the amplitude response changes as the dam effects. Besides, the nodes of the modes have displaced. Nowadays the dam effect introduces an artificial instability, but harmonic locking must lead to a restoration of the gulf amplitude response, with an according change of the bottom relief and of the shoreline as the long-term environmental effect of the dam construction. This change is a large-scale, long-term mass transfer in the environment caused by engineering.
A Discretization Approach for Conjugate Heat Transfer and Application to Turbomachinery Flows
Authors: Papanicolaou Elias L. , Giebert Dietmar , Koch Rainer , Schulz Achmed
Published: January 2022

A numerical procedure is presented to simulate conjugate heat transfer in generalized coordinates and used in some typical turbomachinery applications. The discretized equations at the solid-fluid interface are obtained using energy conservation principles and computational nodes are placed exactly on that interface, thus yielding the corresponding temperatures directly, without the need for inter- or extrapolation from neighboring nodes. The temperature field over both the fluid and the solid domains is computed implicitly, i.e., without iterating between the two. The computer code used for the computations is based on the finite-volume method and the SIMPLE algorithm along with various turbulence models. Both a version of the low-Reynolds-number k-ϵ model suitable for recirculating flows with heat transfer and the standard k-ϵ have been used, with suitable modifications.

The successful treatment of the boundary condition at the solid-fluid interface has been verified by comparing against analytical solutions for laminar, conjugate heat transfer over a flat plate of finite thickness. The agreement was found to be quite good, when temperature profiles were compared at various streamwise distances from the leading edge. Further applications have been sought in the field of turbomachinery and as the main test case, the turbulent flow and heat transfer in labyrinth seals has been selected. Two such configurations have been considered, a straight-through and a stepped labyrinth seal. Results were compared with measured data obtained for the same configurations and the agreement was found to be satisfactory. In addition, the applicability of the current method to a film-cooling problem and the merits of it are being demonstrated.
Prediction of Unsteady Wake-Passing Effects on Boundary Layer Development
Authors: Kim Kyoungjin , Crawford Michael E.
Published: January 2022

A boundary layer on the surface of a turbine blade can be significantly affected by the presence of periodic wake-passing from upstream blade rows, leading to a special form of transition mode from the high turbulence in the periodic wakes. In an effort to predict the evolution of wake-induced transition, time-resolved calculations were carried out using an unsteady two-dimensional boundary layer code and a newly developed transition model. The model is based on the theory of turbulent spot propagation and its subsequent growth. As a benchmark for the model, a single turbulent spot was simulated and compared with measurements. The results yielded the two-dimensional characteristics of the turbulent spot, as well as the becalmed region behind the spot. By imposing successive turbulent strips and freestream velocity defects in the time-space domain, the process of wake-induced transition was predicted for several test cases. The results showed good agreement on both the time-resolved and time-averaged measurements for the boundary layer quantities. In addition, predictions reproduced many details of the flow structure of wake-disturbed boundary layers and transition process.
A Performance Analysis Modeling for a Plate Heat Exchanger
Authors: Lee Jaeyong , Yoon Seokmann , Kim Chongbo , Jung Dongsoo , Seo Taebeom , Chun Wongee
Published: January 2022

Heat transfer characteristics and performance of a plate heat exchanger have been investigated through numerical modeling techniques. A 3-D finite volume technique has been utilized to solve the proposed numerical model. Flow passage turnings between upper and lower corrugated plates in the exchanger are assumed because two corrugated plates face each other with different channel angles where working fluid flows between two plates. The effects of flow channel angles and cross-sectional shapes of exchanger plates have been investigated to determine the optimum design parameters for the exchanger.

Within a plate heat exchanger, the flow passage is being determined due to flow interactions between the corrugated plates. Since the working fluid flows along the rather complicated flow path in actual situation, it is simplified that the flow from one direction changes its direction after colliding with the flow coming from the other direction due to the chevron angle of the plate. Various numbers of flow passage turnings are assumed for comparisons in order to obtain optimum performance conditions for the plate heat exchanger. The effects of cross-sectional shapes to the exchanger performance is also investigated.
Heat Transfer and Flow Friction Characteristics of a Compact Plate-Type Condenser
Authors: Cheng Lixin , Chen Tingkuan
Published: January 2022

Condensation heat transfer Experiments in a Model BRS08 plate-type condenser were conducted. The geometry parameters of the condenser are as follows: the gap between plates of vapor channel is 5.88mm and the average equivalent diameter is 10.16mm. The gap between plates of cooling channel is 3.87mm and the average equivalent diameter is 6.7mm; the available heat transfer area of a single plate is 0.802m2; the tested condenser consists of 4 vapor channels and 4 cooling water channels. The Reynolds number of cooling water was varied from 1400 to 16000. The vapor was condensed at an absolute pressure of 0.2Mpa. The experimental data were reduced to obtain correlations for heat transfer coefficient and friction factor.
Measurement of Flow Field in the Translational Region of a Twin-Screw Extruder: Effect of Material Behavior
Authors: Bakalis Serafim , Karwe Mukund V.
Published: January 2022

Laser Doppler anemometry (LDA) was used to measure velocity distributions in a table-top, co-rotating, self-wiping, twin-screw extruder having a Plexiglas barrel. Velocity measurements were made in the translational region of a 14 mm pitch forward conveying screw element. Axial (along the screw axis) and tangential (normal to the axis) velocity components were measured using a Newtonian (heavy corn syrup) and a pseudoplastic (CMC solution) fluid. The variation of velocity with screw rotation was similar for both fluids. The tangential velocity component for both fluids was higher closer to the screw flights and smaller in the middle of the screw channel. The axial velocity component was close to zero near the screw flights. Maximum values of the axial component were measured in the middle of the of the screw channel.
Measurement of Laser-Induced Shock Wave in Thin Nickel Foil
Authors: Song Kevin H. , Xu Xianfan
Published: January 2022

A polyvinylidene fluoride (PVDF) piezoelectric transducer is used for time-resolved measurements of shock waves generated by a KrF excimer laser irradiating a thin Nickel foil. Pressure loading due to both thermal expansion and surface evaporation is measured. The peak pressure of the shock wave increases with laser fluence, and the stress behind the shock reaches 390 bar at a laser fluence of 3.7 J/cm2. The mechanical coupling efficiency during laser-metal interaction is estimated for laser fluences between 0.72 and 3.7 J/cm2. The measurement results reveal prolonged pressure loading at the target surface after the termination of laser pulse, which is due to superheating of the surface layer during laser ablation.
Double Diffusive Velocity Measurement During the Solidification Process Using Particle Image Velocimetry
Authors: Wang S. Y. , Liu Y. Z. , Lin C. X. , Ebadian M. A.
Published: January 2022

This paper discusses the advanced technique, Particle Image Velocimetry (PIV), used to measure the velocity distribution of double diffusive convection of a binary mixture during the solidification process. The experiments were conducted using ammonium chloride solution in a rectangular enclosure. It was found that the double diffusive flow is stronger at the beginning of solidification and decays as solidification proceeds.
Axisymmetric Mixed Convection in the Annulus Between Vertical Concentric Cylinders With Axial Translation
Authors: Gagnon Daniel R. , Hill Roger W. , Ball Kenneth S.
Published: January 2022

Mixed convection in an air-filled annular enclosure between vertical concentric cylinders, which is driven by combined heating and axial translation of the inner cylinder, is simulated numerically. Both cylinders are assumed to be isothermal with an imposed temperature difference between them. The flow is assumed to be axisymmetric and the Boussinesq approximation is employed. The conservation equations for momentum and energy are solved using a spectral Chebyshev collocation technique utilizing a pressure Poisson influence matrix approach to maintain a solenoidal velocity field. The buoyancy driven flow observed at low Re is displaced by a forced convection cell that grows with increasing translational velocity until it fills the entire cavity at high Re. High heat transfer rates are observed for cases in which the air flow is dominated by either buoyancy or shear forces while low heat transfer rates result from flow driven by competing forces.