bluuebunny/crossref_metadata_2025 huggingface dataset:
Multibody Dynamic Analysis of a 6-DOF Parallel Robot
Authors: Almonacid Miguel , Agrawal Sunil K. , Aracil Rafael , Saltarén Roque J.
Published: November 2021

This paper presents the dynamic analysis of a six-degree of freedom (dof) parallel robot based on multibody dynamics. The robot is also known as Stewart-Gough platform. The inverse and forward dynamic analysis is presented based on the Newton-Euler formulation with the imposition of the constraints through Lagrange multipliers and the application of the principle of virtual work. The singularity problem within the workspace is also focused and 3D surfaces where the robot reach singular configurations are shown. Finally, simulations for the inverse and forward dynamic of the robot have been carried out showing the computational cost.
The Motion of a Compliantly Suspended Rigid Body Constrained by a Frictional Surface
Authors: Huang Shuguang , Schimmels Joseph M.
Published: November 2021

In this paper, the quasistatic motion of an elastically suspended, unilaterally constrained rigid body is studied. The motion of the rigid body is determined, in part, by the position controlled motion of its support base and the behavior of the elastic suspension that couples the part to the support. The motion is also determined, in part, by contact with a frictional surface that both couples the rigid body to unilateral constraint surfaces and generates a friction force. The unknown friction force, however, is determined in part by the unknown direction of the rigid body motion. We derive a solvable set of equations that simultaneously determines both the friction force and the resulting rigid body motion. This set of equations requires that the friction and motion at the point of contact are oppositely directed. Solution involves the use of rigid body kinematics, the Coulomb friction coefficient, the commanded motion of the support, and the spatial elastic behavior of the coupling.
An Approach for the Design of Walking Humanoid Robots Having Different Leg Mechanisms and Using Dynamic Gaits
Authors: Bruneau Olivier , Ben Ouezdou Fethi , Fontaine Jean-Guy
Published: November 2021

This article describes a method to design humanoid robots and to generate their dynamic gaits. Firstly, the global design process which defines structures able to carry out dynamic locomotion tasks is explained. Secondly, a set of leg mechanisms are described to generate these tasks. The third section describes a method to produce intrinsic smooth motions for fest walking gaits of bipedal robots having different leg mechanisms. Finally, some simulation results are given.
Position Control of an Underactuated Planar 2R Manipulator
Authors: Rosas-Flores José A. , Alvarez-Gallegos Jaime , Castro-Linares Rafael
Published: November 2021

In this paper the problem of regulation of an underactuated planar 2R manipulator is solved by tracking appropriate planned trajectories. A class of parametric trajectories is propossed to reach a desired configuration. The parameters of the trajectories are found by using an optimization algorithm. Besides, a feedback control is proposed to regulate the manipulator under error modeling and small desviations on the initial conditions. By using simulations, it is illustrated that if the coordinates of the underactuated system track the planned trajectories then the system reaches the desired configuration.
From Human Arms to a New Generation of Manipulators: Control and Design Principles
Authors: Koeppe Ralf , Hirzinger Gerd
Published: November 2021

With the knowledge of the biological design of the human arm, we lay out the mechatronic design of a new generation of advanced light-weight robot manipulators with human-like dynamic characteristics. To achieve this property, the manipulator does not have to revert to a human-like, bionic design. A serial link manipulator, control technology, and sensorized joint actuators can generate a kinesthesis enabling high fidelity interaction of the robot with its environment. The design and control of the DLR light-weight robot is based on these principles. Based on generic properties governing the dynamic behavior of any arm, we discuss the difference between the human and the advanced robot arm. The mechatronic design of the advanced robot has to make use of these properties in a very different way than its biological counterpart to achieve a similar dynamic behavior.
Miniature Vapor Compression Refrigeration Systems for Active Cooling of High Performance Computers
Authors: Heydari Ali , Russell Kathy
Published: November 2021

A small refrigeration system for cooling of computer system components is evaluated. A thermodynamic model describing the performance of the cycle along with a computer simulation program is developed to evaluate its performance. The refrigeration system makes use of a miniature reciprocating vapor compression compressor. Due to space limitations in some high performance computer servers, a miniature refrigeration system composed of a compressor, capillary tube, a compact condenser, and a cold-plate evaporator heat exchanger are used. Mathematical multi-zone formulation for modeling thermal-hydraulic performance of heat exchanger for the condenser and evaporator are presented. The throttling device is a capillary tube and there is presented a mathematical formulation for predicting refrigerant mass flow rate through the throttling device. A physically based efficiency formulation for simulating the performance of the miniature compressor is used. An efficient iterative numerical scheme with allowance for utilization of various refrigerants is developed to solve the governing system of equations. Using the simulation program, the effects of parameters such as the choice of working refrigerant, evaporating and condensing temperatures on system components and overall efficiency of system are studied. In addition, a RAS (reliability, availability and serviceability) discussion of the proposed CPU-cooling refrigeration solution is presented. The results of analysis show that the new technology not only overcomes many shortcomings of the traditional fan-cooled systems, but also has the capacity of increasing the cooling system’s coefficient of performance.
Computational and Experimental Study of Thermo-Mechanics in a New Design of a Transceiver for High-Speed Telecommunications
Authors: Pryputniewicz Ryszard J. , Weller Steven A. , Shaw Sam R. , Herb William L.
Published: November 2021

High-speed telecommunications require ever increasing data rates, pushing the limits of existing hardware and driving the development of new data handling hardware. This paper addresses thermo-mechanical issues in a new Input/Output (I/O) device for high-speed telecommunications. This device is a surface mount-compatible fiber optic transceiver developed as the Small Form-Factor Pluggable (SFP) System. The development of the SFP System is supported by virtually every leading fiber optic transceiver manufacturer in the industry in accordance with the Multi Source Agreement (MSA). We describe the new MSA-compliant SFP System, develop a FEM model to simulate its thermal behavior under a variety of operating conditions, and present results of the simulation which are validated by selected experimental measurements.
Flow Characteristics of a Powder Lubricant in a Slider Bearing
Authors: Pappur Manjunath , Khonsari M. M.
Published: November 2021

This paper deals with a systematic development of theory of powder lubrication with the appropriate formalism based on the fundamentals of fluid mechanics. The theory is capable of predicting flow velocity, fluctuation (pseudo-temperature), powder volume fraction, and slip velocity at the boundaries. An extensive set of parametric simulations covering particle size, surface roughness, volumetric flow, load and speed are performed to gain insight into the performance of a powder lubricated thrust bearing. The results of simulations are compared to the published experimental results. Good agreement between the theory and experiment attests to the capability of the model and its potential for design of powder lubricated bearings.
Optimizing the Performance of a Fuel Induced Flue Gas Recirculation (FIR) System for Low Nox Boiler Burner Applications
Authors: Lorra Michael A. , Bussman Wes , Smith Joseph , Webster Tim
Published: November 2021

New burner design technologies are using the momentum of fuel gas injection to entrain flue gas for the purpose of diluting the combustible mixture in order to reduce NOX emissions. Using an eductor, these designs entrain flue gas from above the convection section of a furnace stack and mix with the fuel downstream of the eductor. This diluted fluegas/fuel mixture results in lower local adiabatic flame temperatures providing a reduction in NOX emissions. Test results show that NOX reduction performance is strongly dependent on the mass ratio of flue-gas to fuel. An entrainment mass ratio of flue-gas/fuel typically ranges between 2 to 3 pound flue-gas per pound fuel, leading to a NOX reduction of approximately 50 to 70 % for boiler burner applications. The flue gas entrainment performance is effected by pressure drop through the upstream and downstream FIR piping system. This paper describes optimization of an existing FIR system not meeting initial design performance. To improve the entrainment ratio several tools were used to re-design and optimize the FIR system. These tools included Computational Fluid Dynamics (CFD), semi-empirical modeling and cold flow test results. A detailed description and discussion of the results are presented.
NOx Emissions in a Steel Reheat Furnace Firing By-Product Fuels
Authors: Adams Bradley R. , Wang Dave H.
Published: November 2021

A DOE-funded program was used to understand the mechanisms that control the formation of NOx during the combustion of steelmaking by-product fuels and to investigate possible low-cost control options to minimize the NOx emissions. This paper discusses the CFD modeling results of NOx emissions in a reheat furnace. The reheat furnace has a total of 20 burners distributed over three firing zones. The furnace is fired at a rate of 250 × 106 Btu/hr and an overall stoichiometric ratio of 1.06 (fuel lean). Fuels with heating values of approximate 500 Btu/SCF were examined, including coke oven gas (COG), blast furnace gas (BFG) and a blend of COG, BFG, natural gas (NG) and nitrogen. A good range of process variables was modeled to examine effects of fuel type, air preheat, stoichiometric ratio, firing rate and burner stoichiometry distribution on NOx emissions.

Modeling results indicated that NOx formation in the reheat furnace is dominated by thermal NO, with some variation depending on the fuel fired. Temperature profiles showed an effective separation of the furnace interior into top and bottom zones as a result of the steel slab barrier. Higher temperatures characterized the bottom zone and elevated NOx levels as a result of the confined space and enhanced fuel air mixing provided by the slab supports. Results also showed that reburning of NOx plays a significant role in final NOx emissions with 30–40% of NOx formed being reduced by reburning in most cases. Modeling identified that operating the side burners in each burner zone slightly substoichiometric (while maintaining the overall furnace stoichiometry at 1.06) provided significant NOx reduction via reburning. NOx reductions of 23% and 30% were predicted when firing with COG and COG-NG-Air fuels, respectively. Overall furnace exit temperatures and heat flux profiles were not significantly affected by the biased firing.
Physical Scaling of Fire Suppression by Water Mist
Authors: Su G. , Quintiere J. G. , Schultz N.
Published: November 2021

The objective of the project is to develop water mist extinguishments design by scaling. The report describes the requirement and criteria of scaling fire, scale model, and the results of suppression for a developing water mist system design. The Maritime Safety Committee Draft Circular, MSC 914 is used as a basis test to evaluate a water mist design. A series of three full-scale tests related to MSC 914 were performed: fire only, fire with steel trailers, and fire with steel trailers and combustible commodities. A simulation was accordingly studied. Then, a scaled water mist design was tested in the scale model to find the characteristics needed for suppression in terms of pressure, water flow rate, droplet size, and the spray momentum. Based on these characteristics, a candidate nozzle will be selected for the full-scale MSC 914 test. The results so far show that the water mist system can effectively suppress the fire in scaled MSC 914 model. The full-scale MSC 914 is scheduled for September 2001. Therefore, the final answer is still pending until then. Scaling results are confirmed for temperatures, heat flux and flow for the MSC 914 fire without water add in.
A Comparison of Diffusion Flame Stability in One and Two Spatial Dimensions Near Cold, Inert Surfaces
Authors: Vance Robert , Wichman Indrek S.
Published: November 2021

A linear stability analysis is performed on two simplified models representing a one-dimensional flame between oxidizer and fuel reservoirs and a two-dimensional “edge-flame” between the same reservoirs but above a cold, inert wall. Comparison of the eigenvalue spectra for both models is performed to discern the validity of extending the results from the one-dimensional problem to the two-dimensional problem. Of primary interest is the influence on flame stability of thermal-diffusive imbalances, i.e. non-unity Lewis numbers. Flame oscillations are observed when Le > 1, and cellular flames are witnessed when Le < 1. It is found that when Le > 1 the characteristics of flame behavior are consistent between the two models. Furthermore, when Le < 1, the models are found to be in good agreement with respect to the magnitude of the critical wave numbers. Results from the coarse mesh analysis of the two-dimensional system are presented and compared to the one-dimensional eigenvalue spectra. Additionally, an examination of low reactant convection is undertaken. It is concluded that for low flow rates the behavior in one and two dimensions are similar qualitatively and quantitatively.
Large-Scale Laboratory Fire Whirls and Their Numerical Simulations
Authors: Satoh Kohyu , Naian Liu , Shinohara Masahiko , Yang K. T.
Published: November 2021

Fire whirls have been observed in large-scale forest and city fires, which are likely accompanied by strong winds and heavy damages such as loss of lives and physical properties. Despite the general interest in the research of fire whirls, their detailed mechanisms and physical effects still remain largely unknown. One reason is that such real fire whirls are of large size and their direct studies are obviously not feasible. On the other hand, CFD-based fire field models, despite their inherent deficiencies, do provide a rational means to scale the fire sizes. It is desirable, or even necessary, to study larger-scale fire whirls with higher whirling flames in the laboratory, along with their numerical simulations. If success in the numerical simulations for the larger fire whirls can again be demonstrated, we will then approach more closely to have a quantitative tool in the use of the fire field model to simulate and study the truly large real-life fire whirls. The purpose of the present study is to attempt to create a stable six-meter class whirling flame in the laboratory, and then compare the measured data with what can be simulated with a fire field model.
A Perspective on Combustion-Driven Flows With Circulation
Authors: Battaglia Francine , Rehm Ronald G. , Baum Howard R. , Hassan Mohamed I. , Saito Kozo
Published: November 2021

Perhaps the most dramatic example of surprising behavior when circulation is imposed on a combustion-driven flow is the fire whirl, where the burning gases form a tall slender column. Relatively few studies have addressed the influence of circulation on the development of combustion-driven flows. Three dimensionless parameters characterize this interplay: the Froude number, the swirl number and the Reynolds number. It is surprising that for most studies, even with plausible assumptions concerning the experiments, not enough information is given to determine the values of these parameters. We will experimentally reconstruct these studies in an effort to characterize parametrically these interactions. Both buoyancy-driven and momentum-driven combustion processes will be investigated to determine the influence of circulation. Theoretical studies will occur in conjunction to provide the most complete parametric investigation.
A Mixture Fraction Combustion Model for Large Scale Fire Modeling
Authors: McGrattan Kevin , Floyd Jason , Hostikka Simo
Published: November 2021

A numerical fire model, Fire Dynamics Simulator (FDS), is being developed at NIST to study fire behavior and to evaluate the performance of fire protection systems in buildings. To date, about half of the applications of the model have been for design of smoke handling systems and sprinkler/detector activation studies. The other half consists of residential and industrial fire reconstructions. Improvements are being made to address the second set of applications, most importantly a mixture fraction combustion model and a finite volume radiation transport algorithm using either a gray gas or a wide band assumption. The methods will be discussed and a sample calculation presented.
Transient Measurements of Gas Species Concentrations and Soot Properties in Pool Fires
Authors: Murphy Jeffrey J. , Shaddix Christopher R.
Published: November 2021

Researchers at Sandia National Laboratories have been investigating large-scale pool fires, both experimentally and numerically, for several years, because of the risk that these fires pose to critical engineered systems during transport accident scenarios [1]. In addition, Sandia recently implemented an insulated, water-cooled fiber optic probe that used a combined HeNe-laser-absorption, 2-color emission technique to determine soot volume fraction distributions and soot temperatures over a 2-cm sampling distance within 5-m diameter JP-8 pool fires [2].
Heat and Charge Conductivities in Superlattices: Two-Scale Measuring and Modeling
Authors: Travkin V. S. , Catton I.
Published: November 2021

Conventional reasoning and established procedures for measurement of heat and charge conductivities at the continuum micrometer scale, or higher scales, results in a number of variables and physical entities being the subject of measurement. These variables themselves are not point values if to define them with the lower scale concepts. When the media overall properties are sought, their dependence on lower (smaller) scale physical phenomena and their mathematical descriptions need to be considered and incorporated into the higher (larger) scale description and mathematical modeling. This is not a new problem. How to treat or solve multi-scale problems is the issue. Effective scaled heat and charge conductivity are studied for a morphologically simple 1D layered heterostructure with the number of components being n ≥ 2, the effective scaled heat and charge conductivities. It is a two-scale media with the lower scale physics of energy and charge carriers being described by commonly used models. A continuum ↔ continuum description of ηm ↔ μm transport of electron-phonon energy fields, as well as the electromagnetic and temperature fields for ηm scale coupled with the microscale (μm) mathematical models are studied. The medium is heterogeneous because it has multiple phases, volumetric phases 1, 2, 3 .... and (n+m) phases that are the interfaces between volumetric phases. The fundamental peculiarities of interface transport and hierarchical mathematical coupling bring together issues that have never actually been addressed correctly. It is shown that accurate accounting for scale interactions and, as is inevitable in scaled problems, application of fundamental theorems to a scaled description of the Laplace and ▽ operators bring to the upper scales completely different mathematical governing equations and models. We have conducted and report some preliminary quantitative assessment of the differences between the static upper scale and transient nanoscale transport coefficients and show how the lattice morphology and its irregularities influence the effective conductivities.
Transient Radiation Element Method for Three-Dimensional Scattering, Absorbing, and Emitting Media
Authors: Guo Zhixiong , Kumar Sunil , Maruyama Shigenao
Published: November 2021

In this study transient radiative heat transfer is investigated in scattering, absorbing, and emitting media. The radiation element method is formulated for the first time to solve the transient radiative transfer equation in 3-D geometries. The sensitivity and accuracy of the method are examined. A good agreement of temporal transmittance predicted by the present method and Monte Carlo method is found. The characteristics of transient analysis are investigated via various problems of radiative transfer in inhomogeneous cubes. It is found that the transmitted signals are strongly affected by the inhomogeneous properties of the media through which the radiation has passed. In the position where the radiation travels a larger optical thickness, the broadening of the transmitted pulse width is more obvious and the magnitude of the transmittance is smaller.
Performance Modelling of Solid Oxide Fuel Cells
Authors: Cooper Richard J. , Billingham John , King Andrew C. , Kendall Kevin
Published: November 2021

Fuel cells are a clean and efficient alternative to existing methods of energy production. Solid oxide fuel cells produce electricity directly from the combustion of methane or other hydrocarbons. We present a mathematical model for a tubular solid oxide fuel cell, which includes consideration of advection, diffusion and electrochemical activity. The chemical reaction scheme includes both steam reforming and partial oxidation of methane, as well as carbon deposition on the anode surface. In the steady state, an asymptotic analysis is performed to find the composition of the exhaust gas. The results are compared with experimental data and good agreement is obtained.
The Feasibility of Using Photothermal Deflection Spectroscopy to Measure Thermal Contact Resistance in a Film on Substrate System
Authors: Foley Jason R. , Avedisian C. Thomas
Published: November 2021

In this paper we extend the theory of photothermal deflection spectroscopy for an isotropic film-on-substrate system to include the thermal contact resistance between the two materials and absorption of energy in the film and substrate. The model is formulated as a three-domain system (gas, film and substrate) with coupling conditions at the various interfaces, including a thermal contact resistance. Closed form expressions are obtained for the temperatures in each domain.

The analysis for probe beam deflection is confirmed by comparison to well-known limits of infinite film thickness, zero film thickness, zero contact resistance, and a thin absorbing layer at the surface of the film. The formulations are tested against NIST standard reference materials (SRM) using numerically generated beam deflection data to extract thermal diffusivity of a bulk material, and of two SRMs pressed together to extract thermal contact resistance. The results show the feasibility of using to determine the thermal contact resistance of a layered sample from beam deflection data.
A Review of Micro Heat Exchanger Flow Physics, Fabrication Methods and Applications
Authors: Bowman W. Jerry , Maynes Daniel
Published: November 2021

A review of the literature in the area of micro heat exchangers is presented to provide a concise overview of the recent advances in this field of study. The review is divided into six sections. The first section reviews research focused on understanding friction and heat transfer in microchannels. The second section deals with heat exchanger design, optimization and comparison studies. The third section deals with fabrication methods used for constructing micro heat exchangers. The fourth section reviews applications of micro heat exchangers. The last two sections of the paper deal with miscellaneous topics and other reviews on the subject. The total review focuses on advances made after the early 1990’s.
Thermal Modeling of a Liquid-Cooled Electric Machine
Authors: Jih Edward , Chen Kanghua , Abraham Thomas , Liang Feng
Published: November 2021

The future of the Hybrid Electric Vehicle and Fuel Cell Electric Vehicle is very promising for the automotive industry. In order to take a full advantage of those vehicles, a better thermal performance of the electric motor is required. A series of CFD analyses were performed in this study for the design of a liquid-cooled PM electric motor. Based on the results of this study, the thermal contact resistance of thermal interface between stator & housing is critical for the design of this PM electric motor. The effect of thermal conductivity of slot filling epoxy & stator core lamination on the peak temperature of stator winding is small. Improving the heat transfer capability of the air gap between stator & rotor can reduce the peak rotor temperature. The cooling of rotor magnet at the higher rotor speed is essential since the rotor temperature increases significantly due to higher power loss at rotor.
Reconstruction of the Temperature Profile Along an Optical Fiber Thermometer
Authors: Jones Matthew R.
Published: November 2021

A blackbody optical fiber thermometer consists of an optical fiber whose sensing tip is given a metallic coating. The sensing tip of the fiber forms an isothermal cavity, and the emission from this cavity is approximately equal to the emission from a blackbody. Temperature readings are obtained by measuring the spectral radiative flux at the end of the fiber at two wavelengths. The ratio of these measurements is used to infer the temperature at the sensing tip. However, readings from blackbody optical fiber thermometers are corrupted by self-emission when extended portions of the probe are exposed to elevated temperatures. This paper describes an alternative approach for using blackbody optical fiber thermometers that avoids the problems due to self-emission. In the alternative approach, an inverse method incorporating spectral measurements is used to reconstruct the temperature profile along the fiber. A genetic algorithm is used as the basis for the inversion method.
Turbulent Heat Transfer Over a Free Rotating Disk: Analytical and Numerical Predictions Using Solutions of Direct and Inverse Problems
Authors: Shevchuk I. V.
Published: November 2021

All known analytical solutions of the integral equation of the turbulent thermal boundary layer for a rotating disk have been obtained for the case of direct problem. This means finding the Nusselt number at a given distribution of the wall temperature. This distribution is described by power law and is monotone (derivative of wall temperature with respect to the radial coordinate does not change its sign). Outlined in this paper is an analytical form of non-monotone distribution of the wall temperature, which provided a new analytical solution for the turbulent Nusselt number including earlier known equations as a specific particular case. The solution is based on the integral method, which proved to be more precise than known Dorfman’s approach. Chosen for validation of the proposed method were turbulent heat transfer experiments of Northrop and Owen (1988). Predictions presented include analytical studies using inverse and direct problem solutions as well as numerical simulations using polynomial approximations of the experimental wall temperature distributions.
Analysis and Multi-Disciplinary Optimization of Internal Coolant Networks in Turbine Blades
Authors: Martin Thomas J. , Dulikravich George S.
Published: November 2021

This paper presents the theoretical methodology, conceptual demonstration, and validation of a fully automated computer program for the inverse design and optimization of internal convectively cooled three-dimensional axial gas turbine blades. A parametric computer model of the three-dimensional internal cooling network was developed, including the automatic generation of computational grids. A boundary element computer program was written to solve the steady-state non-linear heat conduction equation inside the internally cooled and thermal barrier-coated turbine blade. A finite element algorithm was written to model an arbitrary network of internal coolant passages for the calculation of the internal heat transfer coefficients, pressure losses, local flow rates, the effects of centrifugal pumping, heating of the coolant fluid, and forced convection from the thermal model of the solid to the coolant fluid. The heat conduction and internal flow analyses were iteratively coupled to account for the heat balance between the blade and the coolant fluid. The computer-automated design and optimization system was demonstrated on the second high-pressure turbine blade row of the Pratt & Whitney F100 engine. The internal cooling configuration and local heat transfer enhancements (boundary layer trip strips and pin fins) inside the three-dimensional blade were optimized for maximum cooling effectiveness and durability against corrosion and thermo-mechanical fatigue.
Cooling Effectiveness on Film Cooled Turbine Blades
Authors: Derrar M. , Nagler J. , Koschel W. W.
Published: November 2021

This paper presents experiments on the cooling effectiveness obtained for two different injection locations on the suction side of a turbine blade at transonic flow conditions. Previous results of a computational analysis and flow visualization indicated that a separation bubble is present on the suction side at a location x/L = 0.43 and the location x/L = 0.575 corresponds to a shock-boundary interaction zone [9]. The scientific interest is primarily focused on the realization of high film cooling efficiencies and its relevant parameters under these flow conditions. Streamwise aligned as well as inclined angled film coolant hole configurations have been investigated for each location. Due to the high number of interacting parameters the experimental simulation of turbine blade film cooling is extremely complex, which can only be solved by a simultaneous modeling using the experimentally measured results. Test rig, instrumentation and data analysis are described in detail. The goal of the investigations is to determine the optimum location of the film coolant injection.
Heat Transfer of a Chordwise-Oriented Internal Cooling Passage Around a Turbine Airfoil
Authors: Chyu M. K. , Ojo O. B. , Yen C. H. , Nordlund R. S.
Published: November 2021

An innovative design of closed-loop cooling system for a stator airfoil consists of a number of internal cooling passages wrapping around both pressure and suction sides of the airfoil. The cooling passages feature (1) jet impingement post a sharp 90-degree turn at the passage inlet, (2) turbulators on the outermost wall, and (3) a nearly 180-degree turn in the trailing edge. In addition, the passage has an irregular cross-section and varies throughout its entire length. A series of heat transfer tests have been performed at Re = 17,000 ∼ 61,000, compared to this tests which uses a new approach, so-called the hybrid liquid crystal technique. The magnitude of local heat transfer coefficient rises sharply in three regions. The first maximum occurs in the region subjected to direct jet impingement as the flow turns into the channel. Compounded with the inlet effect, this maximum, in fact, is the highest heat transfer coefficient over the entire passage. The second and third peaks, both are comparable in magnitude, locate near the trailing edge of the airfoil where the flow experiences a 180-degree turn and near the passage exit with a 90-degree turn. The average value of heat transfer coefficient over the entire passage is about 1.9∼ 2.5 times higher than that with fully developed turbulent flow in a straight channel. This level of enhancement is comparable to that of the conventional ribturbulators with a 90-degree angle-of-attack.
Characteristics of Continuous CVD of Silicon With a Moving Susceptor
Authors: Yoo Hoseon , Jaluria Yogesh
Published: November 2021

This paper deals with continuous chemical vapor deposition of silicon in a horizontal cold wall reactor, focusing on a moving susceptor. A two-dimensional numerical model, accounting for variable properties, thermal diffusion, radiative exchange among surfaces, and conjugate heat transfer between the gas and susceptor, is developed and validated. Scale analysis for the susceptor energy balance makes it possible to identify the characteristic parameters and infer their qualitative effects a priori, which proves to be consistent with numerical predictions. The results show that the present continuous system is characterized by two newly defined parameters: conductance ratio and susceptor parameter. A pair of performance curves that relate the deposition efficiency to each parameter successfully provide susceptor-related design conditions. It is also revealed that there exists an optimum length of heating zone that maximizes the deposition efficiency.
Localized Electron Evolution Induced by Femtosecond Laser Pulses in Water
Authors: Fan C. H. , Sun J. , Longtin J. P.
Published: November 2021

Optical breakdown by ultrashort laser pulses in dielectrics presents an efficient method to deposit laser energy into materials that otherwise exhibit minimal absorption at low laser intensities. During optical breakdown, a high density of free electrons is formed in the material, which dominates energy absorption, and, in turn, the material removal rate during ultrafast laser-material processing. Classical models assume spatially uniform electron population and constant laser intensity in the focal region, which results in a time-dependent expressions only, i.e., the rate equations, to predict electron evolution induced by nanosecond and picosecond pulses. For femtosecond pulses, however, the small spatial extent of the pulse requires that the pulse propagation be considered, which results in inhomogeneous plasma and localized electron formation during optical breakdown. In this work, a femtosecond breakdown model is combined with the classical rate equations to determine both time- and position-dependent electron density during femtosecond optical breakdown in water. The model exhibits good agreement when compared with experimental results. For other transparent or moderately absorbing dielectric media, the model also shows promise for determining the time- and position-dependent electron evolution induced by ultrashort laser pulses. Another interesting result is that the maximum electron density formed during femtosecond-laser-induced optical breakdown can exceed the conventional limit imposed by the plasma frequency.
Application of Affordable Composite Materials and Processes on UCAV (Extended Abstract)
Authors: Schwedt Steve J.
Published: November 2021

The Unmanned Combat Air Vehicle (UCAV) program is an Advanced Technology Demonstration Program funded by DARPA and the Air Force. As a part of the program two demonstration air vehicles were fabricated and assembled for flight test and for demonstrating the affordability of UCAVs. Using advanced design and manufacturing toolsets, the first vehicle, 27 feet long with a 34-foot wingspan, was designed and delivered in 18 months. In addition, unique fabrication, tooling, and assembly techniques were used to produce these vehicles. This presentation will discuss the techniques used that led to the success of the program.
A Micro/Macro Integrated Model for Melt Flow and Non-Equilibrium Solidification for Thermal Spraying
Authors: Wang X. Y. , Zhang H. , Zheng L. L. , Sampath S.
Published: November 2021

In this paper, a micro/macro-integrated model based on the VOF scheme is presented that accounts for free surface movement, thermal contact resistance, and fluid instability. A sub-model is developed to include the non-equilibrium solidification phenomena at the solid/liquid interface. In the combined model, the free surface location and movement are captured by the VOF technique, and the movement of the solidification interface is determined from the energy balance and the kinetic correlation of the interface velocity and temperature on the interface. The melt flow is incorporated into the microscopic model through interpolation of melt velocities on the macroscopic grids using prescribed velocity profiles. To improve the efficiency of the integration between the melt flow and microscopic model, a relational database has been developed and applied to the integrated micro/macro model. Three velocity profiles, e.g., linear, parabolic, and cubic velocity profiles, are investigated and the results were compared with that from the diffusion model.
Performance Evaluation of Serrated Plate Fins for Under-Carriage Electronics Cooling in Transportation Application
Authors: Shwaish Ibraheem K. , Murthy Jayathi Y. , Amon Cristina H. , Bains Diep
Published: November 2021

Serrated plate fins are commonly used in the cooling of under carriage electronics in people movers and other rail transportation systems. Here, a bank of electronic equipment consisting of diods, IGBT’s, and other power and control devices reside in an electronics box attached to the under-carriage. Plate fin heat sinks are typically attached to underside and along the sides of the box; typically flow through the heat sink is regulated by enclosing the sink in a channel with an open inlet and outlet for the flow. The heat sink is shown in Fig. 1. Even though water is used for cooling in Europe, the primary cooling fluid in the United State is forced air supplied by a blower and/or by the train motion. The problem is unsteady because of the train starts and stops, changing the load on the electronics and resulting in changes in the power dissipation.
Nanoscale Thermal Imaging of Thermionic Devices Using Scanning Thermal Microscopy
Authors: Tan Kwong-Luck , Miner Andrew , Fan Xiaofeng , LaBounty Chris , Zheng Gehong , Bowers John E. , Croke Edward T. , Shakouri Ali , Majumdar Arun
Published: November 2021

Ever increasing importance of cooling and precise temperature control in microelectronics and optoelectronics has driven recent development of integrated thermoelectric and thermionic cooling structures. Previous studies have investigated SiGe/Si superlattice thermionic coolers experimentally using thermocouples that were 50 μm in diameter. However, the relative size of these thermocouples as compared to the devices sizes (30–100 μm) makes surface and cross-section temperature measurement of the SiGe/Si superlattice thermionic coolers not possible. In this work, a sub 100 nm probe was used to measure the surface and cross-sectional temperature of the SiGe/Si superlattice thermionic coolers using scanning thermal microscopy. Two sets of superlattice thermionic coolers were used in this study and their cooling curves (temperature vs current) are presented. Each set consists of six devices of different sizes. A comparison of device cooling performance is examined. A mechanism for studying thermionic cooling in the superlattice coolers is discussed through an analysis of the cooler cross-section temperature profile.
Capillary Pumped Loop Heat Spreader for Electronics Cooling
Authors: Chung Jaewon , Grigoropoulos Costas P. , Greif Ralph
Published: November 2021

As cooling requirements for electronic devices, e.g. computer processor units, power modules, etc. increase beyond the capabilities of air-cooling, interest has moved to several alternatives such as thermoelectric coolers, impinging jets and heat exchangers with phase change. Included among these, the capillary pumped loop is a very competitive cooling device, because of its performance reliability, no power requirements and low manufacturing cost. In this paper, a heat spreader employing capillary pumped loop principles was made of aluminum and copper and tested. The copper CPL heat spreader with heat sinks and fans on the condenser (86mm thick, 60mm wide, 181mm long) has demonstrated a cooling capacity of 640W at atmospheric pressure in the vertical orientation and maintains a difference between TIHE (temperature of the interface between heater and evaporator) and TAMB (ambient temperature) lower than 100°C.
Development of a Health Monitoring Capability for FRP Using Optical Fiber Sensors
Authors: Cassino Christopher , Duke John , Borinski Jason
Published: November 2021

Fiber reinforced polymers (FRP) are an efficient and relatively inexpensive method of repairing or replacing deteriorating and damaged infrastructure. FRP sheets can be applied to spalling bridge sections to prevent further deterioration and increase stiffness. Pre-fabricated FRP decks can also be used to replace weak portions of the bridge superstructure. However, the effect of the environment on long-term durability of FRP and how the various mechanisms of deterioration initiate and develop are not known.

Systems for health monitoring are being sought as a means of managing transportation structures as assets in light of modern life cycle cost concepts. This paper will describe the efforts to develop a method to monitor the structural integrity of FRP materials utilizing an optical fiber sensor developed by Luna Innovations. This sensor is capable of detecting both transient, acoustic emission strain events as well as the accumulated strain in the components to which it is attached. The fact that this sensor is impervious to electromagnetic radiation makes it ideal for monitoring FRP in transportation applications.
Stochastic Properties of Anisotropic Materials
Authors: Peterson Michael “Mick” , Sun Miao
Published: November 2021

Extensive research has been directed toward the development of methods for the optimal recovery of elastic properties from ultrasonic measurements. For a number of applications both the elastic and damping characteristics of the materials are required in design. The use of the optimal recovery does present challenges when applied to either man-made or natural anisotropic materials. In many cases manufacturing variability results in a need for a statistical description of the elastic and damping properties. In addition, errors in material lay-up or growth patterns may result in mis-orientation of the principle materials axes with respect to the geometrical axes. In this work, an examples is shown that demonstrates the recovery of the elastic properties of a natural material when stochastic properties are required. Statistical descriptions of the materials properties are obtained for wood of two different types of material. Results are shown assuming a nominally orthotropic orientation, although the existence of curvilinear coordinates is acknowledged.
Use of Computational Intelligence for Corrosion Damage Assessment of Aging Aircraft Panels
Authors: Palakal M. J. , Huang J. , Pidaparti R. M. , Peeler D. T. , Rebbapragada S.
Published: November 2021

This paper describes computational methods that have been developed to automatically detect and quantify corrosion on images of aircraft panels obtained using nondestructive inspection (NDI) techniques. Images obtained from NDI techniques are not directly suitable for corrosion analysis. We propose a multi-resolution wavelet analysis to segment the NDI images to isolate the corroded regions from the undamaged regions. Wavelet coefficients were extracted from each segment and subjected to a multivariate data analysis to obtain the most relevant features. These features are then used to identify the corroded region on the images and also to estimate the extent of damage, in terms of material loss, using backpropagation neural networks. Experiments were conducted to test the developed modules on images obtained from the Air Force Research Lab in Dayton, Ohio. The results obtained prove the feasibility and robustness of our approach in detecting the damaged regions and for estimating the material loss due to corrosion.
Heat Transfer and Pressure Drop Characteristics of Angled Spiralling Tape Inserts in a Heat Exchanger Annulus
Authors: Coetzee H. , Liebenberg L. , Meyer J. P.
Published: November 2021

The purpose of this paper was to determine the single phase heat transfer and pressure drop characteristics of an angled spiralling tape inserted into the annulus of a tube-in-tube heat exchanger. Experimental measurements were taken on four setups: a normal tube-in-tube heat exchanger used as a reference and three heat exchangers with different angled spiralling tape inserts. From the results correlations were developed that can be used to predict the heat transfer and pressure drop characteristics. It was concluded that the angled spiralling tape inserts resulted in an increase in the heat transfer and pressure drop characteristics as can be expected.
Corrosion Resistance of Structural Steel Processed Using Electro-Plasma Methods
Authors: Schilling Paul J. , Herrington Paul D.
Published: November 2021

Electro-plasma cleaning and deposition is a recently developed electrolytic method for cleaning mill scale and other debris from steel surfaces, and depositing protective metal coatings. Structural steel was processed using these methods and tested for corrosion resistance. Samples included freshly cleaned steel coupons and samples coated with a metallic zinc layer. Tests included linear polarization resistance, QUV weathering, salt fog exposure, and electrochemical impedance spectroscopy. Steel samples cleaned by electro-plasma methods exhibited superior corrosion resistance to those cleaned by shot-blasting. The zinc metal coatings demonstrated potential for long-term corrosion protection.
Active Draft Cushioning in Unit Train Service
Authors: Hodges Richard N.
Published: November 2021

Since the 1960’s, end-of-car cushioning has been a critical technology for rail cars that carry fragile commodities such as automobiles, airplane components, newsprint or coiled metal rolls. Because the primary benefit of the technology has been in impact protection, these units have historically returned back to the draft stops after an impact in order to maximize the protection available for subsequent impacts. This technology often did not provide the best protection for the car during in-train service, when buff and draft slack action put significant shocks into the car and cargo. Once returned to the draft stops, the cushioning unit offers no further protection from draft slack action during train movement. This results in potentially high draft coupler forces. A new cushioning technology, called active draft preload, provides improved control of in-train forces by positioning the cushioning device several inches from the draft stops so that adequate protection is provided for the in-train environment. Testing conducted in unit train service has documented the improvement in ride quality obtained from active draft cushioning applied to the rail cars.