bluuebunny/crossref_metadata_2025 huggingface dataset:
Superposition Effect of the Leading Edge Film on the Downstream Film Cooling of a Turbine Vane Under Combustor Swirling Outflow
Authors: Wu Zhuang , Zhu Hui-ren , Liu Cun-liang , Li Lin , Wang Ming-rui
Published: November 2021

To investigate the superposition effect of the leading edge (LE) film on the downstream film cooling under swirling inflow, numerical simulations with three vane models (vane with films on the leading edge only, vane with films on the pressure side (PS), and suction side (SS) only, full-film cooling vane), two inlet conditions (axial inlet and swirling inlet) are conducted. The results indicate that the leading edge is the area where the film is most affected by the swirling inflow. For full-film cooling vane, the film on the leading edge does not always improve or even reduce the downstream film cooling. Flow mechanism analysis shows that the velocity direction near the downstream wall is governed by the interaction between the direction of swirling inflow and the direction of film hole incidence on the leading edge. A new type of leading-edge film proposed by the author is also investigated, with the dividing line of the counterinclined film-hole row coinciding with the twisted stagnant line to ensure that all films are incident at angles inverse to the direction of the swirling inflow. The new leading-edge film successfully changes the velocity direction near the downstream wall and suppresses the deflecting effect on the downstream film. The new leading-edge film can increase the overall area-averaged cooling effectiveness (η) of the full-film cooling vane by 10%, 15%, 18% and reduce the inhomogeneity by 13%, 19%, 27% over the traditional design, as the coolant mass flow increases.
Importance of Seismic SSI in 3-D Tunnels Assuming Inelastic Material Behavior
Authors: Hatzigeorgiou G. D. , Beskos D. E.
Published: November 2021

This paper investigates the importance of seismic soil-structure interaction in three-dimensional lined tunnels, assuming inelastic material behavior for both the concrete liner and the soft rock type of soil. The seismic response of the soil-structure system is obtained by the finite element method in the time domain. Viscous absorbing boundaries are used in conjunction with the discretization of the rock medium. Both the rock medium and the concrete liner are assumed to behave inelastically on the basis of the continuum damage mechanics theory. The seismic waves are assumed to have any arbitrary time variation and direction of propagation. The system is analysed with and without soil-structure interaction in order to assess its importance on the response of the system.
Compressive Instabilities in Braided Textile Composites
Authors: Quek Shu Ching , Waas Anthony M. , Agaram Venkatesh , Shahwan Khaled
Published: November 2021

This paper discusses the results of a finite element (FE) based study of the compressive instabilities of braided glass fiber composites. The micromodel was based on a 2-unitcell size 3-D FE model. Computational tests were carried out to first determine the elastic moduli of the system. Once the computational model was validated with experimental data for the elastic moduli, the compressive response of the micromodel was established using the RIKS method option available in the ABAQUS commercial FE code. The present approach is different from that reported in the literature where classical methods based on the technique of homogenization is used to model the elastic and inelastic response of braided composites. In the present work, explicit account of the braid microstructure (geometry and packing) and the inelastic properties of the matrix are accounted for via the use of the FE method. The macromechanical data pertaining to the braided composites were obtained through traditional means. Tensile tests were performed on the composites through the usage of ASTM D 3039 standard to obtain the macroscopic orthotropic moduli and response. For each test, 3 samples were used to ensure accuracy and the average data is reported in this paper. A separate test was conducted to obtain the in-situ matrix properties of the glass braided composites. The computational model provides a means to assess the compressive strength of braided composites and its dependence on various microstructural parameters. It also serves as a tool to assess the most significant parameter that affects compressive strength. Furthermore, the model is useful to understand the response of braided composites under multiaxial loads.
A New 3D Dynamic Tire/Road Friction Model for Vehicle Control and Simulation
Authors: Claeys Xavier , Yi Jingang , Alvarez Luis , Horowitz Roberto , de Wit Carlos Canudas
Published: November 2021

In this paper a 3D dynamic tire/road friction model is presented. This model is based on the LuGre dry friction model and tire dynamics. The longitudinal and lateral forces, and tire self-aligning torque are determined through several first-order dynamic systems. The main advantage of this model is that it can be easily used and identified for vehicle control and simulation. Furthermore, calibration of model parameters and comparison with “magic formula”, which is widely used in area, are presented to validate the model.
Co-Simulation of Algebraically Coupled Dynamic Subsystems
Authors: Gu Bei , Asada H. Harry
Published: November 2021

This paper analyzes the problem of Co-Simulation. The term Co-Simulation is used to describe a large dynamic system that is simulated by running a group of independently coded subsystem simulators. Very commonly, the Co-Simulation of subsystems faces incompatible boundary conditions, i.e., causal conflicts. These causal conflicts cannot be directly resolved, due to the nonlinearity and/or difficulties in modification of coded subsystem simulators. Causal conflicts result in algebraic constraints. Boundary Condition Coordinators (BCCs) are designed to calculate boundary conditions based on subsystem models and their algebraic constraints. The Co-Simulation, which is modeled as Differential Algebraic Equations, then relies on BCC to provide compatible boundary conditions for subsystem simulators. The high index constraint is reduced to index one by defining a sliding manifold. Different ways of enforcing the sliding manifold are discussed: A new Discrete-Time Sliding Mode (DTSM) controller is devised to serve as a BCC, enforcing sliding manifolds and providing boundary conditions. The multi-rate scheme can guarantee Co-Simulation stability at any given step size of all subsystem simulators, provided the subsystem simulators are tested stable at that step size. An example is given to demonstrate the DTSM method. Advantages and possible future improvements are discussed.
A Method for the Frequency Domain Design of PWM-Controlled Pneumatic Systems
Authors: Barth Eric J. , Zhang Jianlong , Goldfarb Michael
Published: November 2021

This paper presents a rigorous analysis and design method for PWM-based control of pneumatic systems. An equivalent analytical model incorporating the effects of a finite PWM switching period is formulated. This equivalent model was motivated by a lack of control design and analysis techniques needed to treat the inherently non-analytical switching models associated with PWM-based systems. The equivalent model enables the design of a loop compensator that rigorously addresses control design issues of stability robustness, disturbance rejection, insensitivity to sensor noise, performance bandwidth and actuator saturation. Simulation of this compensator with both the equivalent design model and a full nonlinear switching model for a particular pneumatic robot application is presented which demonstrates and validates the proposed method.
Delay-Dependent Induced L2Norm Analysis and Control for LPV Systems With State Delays
Authors: Wu Fen
Published: November 2021

In this paper, we address the analysis and state-feedback synthesis problems for linear parameter-varying (LPV) systems with parameter-varying time delays. It is assumed that the state-space data and the time delays depend on parameters that are measurable in real-time and vary in a compact set with bounded variation rates. We explore the delay-dependent stability and the induced L2 norm performance of these systems using parameter-dependent Lyapunov functions. In addition, the state-feedback control synthesis problem is examined when a variable state delay is present. Both analysis and synthesis conditions are formulated in terms of linear matrix inequalities (LMIs) that can be solved via efficient interior-point algorithms.
Adaptive Nonlinear Control for Spacecraft With Coupled Translational and Attitude Dynamics
Authors: Pan Haizhou , Kapila Vikram
Published: November 2021

In this paper, we address a tracking control problem for the coupled translational and attitude motion of a spacecraft. Specifically, a nonlinear adaptive control law is developed to ensure global asymptotic tracking of the desired translational and attitude trajectories in the presence of unknown mass and inertia parameters of spacecraft. Using the vectrix formalism the translational and attitude dynamics of spacecraft is modeled, where the mutual coupling in the translational and attitude motion induced by their gravitational interaction is duly accounted. The four-parameter quaternion representation is employed to describe the attitude kinematics of spacecraft in order to enable large orientation maneuvers. Based on the structure of the resulting system dynamics, the filtered translational and attitude tracking error dynamics are developed, which facilitate the transformation of second-order translational and attitude motion error dynamics as first-order equations, thus providing a considerable simplification in control law synthesis/analysis. With the aid of two linear operators, the open-loop filtered tracking error dynamics is parameterized such that the unknown mass and inertia parameters of spacecraft are isolated and can be estimated on-line. Using a Lyapunov framework, nonlinear control and adaptation laws are designed that ensure the global asymptotic convergence of the translational and attitude position tracking errors, despite the presence of unknown mass and inertia parameters of spacecraft. In addition, the form of the filtered tracking error reveals the convergence of translational and attitude velocity tracking errors of spacecraft. An illustrative numerical simulation is presented to demonstrate the effectiveness of the proposed control design methodology for the coupled translational and attitude motion control of spacecraft.
Adaptive AQM Routers Supporting TCP Flows
Authors: Chait Yossi , Oldak Salomon , Hollot C. V. , Misra Vishal
Published: November 2021

This paper describes the development of an adaptive algorithm for active queue management (AQM) routers supporting a dynamically varying number of long-lived TCP flows. We use a nonlinear dynamic model of TCP behavior which was recently developed from fluid-flow and stochastic differential equation analysis. We first show that the high-frequency gain of the linearized plant model is inversely proportional to the network load factor which can easily vary by an order of magnitude. The motivation for adaptation follows from the direct relation between the plant’s high-frequency gain and stability margins and speed of response. Our adaptive algorithm — the Externally Excited Adaptive Loop (EEAL) — is shown to achieve improved queue level management compared with that achieved using RED AQM and the recently proposed PI AQM.
Autonomous Decentralized Control
Authors: Šiljak Dragoslav D. , Stipanović Dušan M.
Published: November 2021

A decentralized control law is called autonomous if the resulting closed-loop interconnected system is connectively stable, that is, the system remains stable despite structural perturbations whereby subsystems are disconnected and again connected in an unpredictable way during operation. The objective of the paper is to propose an LMI scheme for design of autonomous decentralized controllers and observers for output control of complex systems. An interesting feature of the proposed observer-based controllers is that they do not impose any communication overhead since only the locally available output information is required.
A Method for the Study of Position in Highly Redundant Multibody Systems in Environments With Obstacles
Authors: Zelaia Josu Agirrebeitia , González Rafael Avilés , de Bustos Igor Fernandez , Martin Enrique Amezua San
Published: November 2021

The present article looks at a method of analysing the behaviour of highly redundant multibody systems (e.g. in the case of cellular adaptive structures of variable geometry) in environments with obstacles. It is sought to solve the inverse problem in successive positions of variable-geometry structures, avoiding the obstacles in its work environment; i.e. the computation of the increment that has to be assigned to the actuators throughout the movement of the multibody system so that it does not collide with obstacles, as one or more nodes perform a pre-established function (e.g. a certain path). The multibody systems are modelled via rod-type finite elements, both deformable and indeformable, and the coordinates of their nodes are chosen as variables. The obstacles are modelled via a mesh of points that exert repulsive forces on the nodes of the multibody, so that interference between the two is avoided. Such forces have been chosen inversely proportional to the Nth power of the distance between the corresponding points of the obstacle and of the multibody system. The method is based on a potential function and on its minimization using the Lagrange Multiplier Method. The solution of the resulting equations is undertaken iteratively with the Newton-Raphson Method. The 2D and 3D examples provided attest to the good performance of the algorithms and procedure here set forth.
Design of Haptic Interfaces to Assess the Driving Capabilities of People With Disabilities
Authors: Zekri S. , Pernalete N. , Dubey R. V. , Gage A.
Published: November 2021

Transportation is an area that needs to be studied from a disability perspective. Different types of barriers exist when it comes to enabling persons with disability to comfortably perform routine activities such as driving a vehicle.

Some of these barriers are due to lack of quantitative assessment techniques that will determine physical capabilities and ergonomic parameters related to the disabled person. The objective of this paper is to design an intelligent haptic interface for quantitative assessment of driving capabilities of persons with disabilities.

A twenty two year old subject with Muscular Dystrophy was introduced to the task of steering wheel control. This task tested the subject’s ability to control different steering wheel diameters, angles of orientation, and fatigue after an extended control period.
Robotic Assembly Based on Human Perception and Action
Authors: Chung Byunghoon , Lee Sooyong
Published: November 2021

Force guided assembly is a control scheme to guide a workpiece based on a stored map from forces to a correction of motion. Based on the geometry of the workpiece and its kinematic behavior in interacting with the environment, the functional map relating the correction of motion to force measurements is generated and stored as a control law. Central to the design of force guided control is how to synthesize this functional map. Although these explicit force-guided controls are a useful concept, particularly for the monitoring of assembly processes, there are inherent difficulties in applying it to real world problems.

In real assembly lines, pipe insertion task, for instance, has been performed only by human workers. Skilled workers insert pipes by perturbing the pipes in order to avoid jamming as well as to determine which way to correct the motion. According to them, the skilled workers monitor obstructing forces in response to the applied perturbation, and modify their motion accordingly. The proposed perturbation/correlation method was motivated by this human perception and action : perturbing the pipe, observing the reaction to the perturbation and correcting the trajectory.

In this paper, we propose a novel technique for acquiring effective force information despite sensor noise and friction. Instead of simply receiving force signals from the process, we give perturbation to the robot and measure the reaction forces to the perturbation. By taking the correlation between the perturbation signal and the reaction forces, reliable and useful information for guiding the robot would be extracted. It is expected that this perturbed force measurement provides much richer force information than that of stationary measurement. The perturbation/Correlation method presented in this paper is not only effective for reducing friction, but also effective for obtaining useful information for guiding the robot towards a desired direction. Preliminary experimental results with one directional perturbation are shown in this paper. Extensive mathematical analysis shows the potential application to assemblies in higher dimension.
Attitude Control of a String and Rigid Bodies System
Authors: Nohmi Masahiro , Terumichi Yoshiaki , Sogabe Kiyoshi
Published: November 2021

Applications of mechanical systems of a string with a rigid bodies subsystem have various possibilities for the engineering in extreme environment conditions, for example, in space or in ocean. This rigid bodies subsystem can be used as a robot subsystem. This paper discusses about attitude control of the rigid bodies subsystem, especially around an equilibrium point of the whole system. The control technique is consists of attitude control with reaction wheels and angular momentum control with manipulation of the rigid bodies subsystem. In order to confirm the effectiveness of the control approach, numerical simulations have been done, under condition that the shape of the string is described by the finite-element formulation, selecting a linear interpolation Also, from the view point of natural frequency analysis of the controlled system, characteristics of the control approach have been examined.
Direct Simulation of Electrorheological Suspensions
Authors: Wang Aijun , Singh Pushpendra , Aubry Nadine
Published: November 2021

A new distributed multiplier/fictitious (DLM) domain method is developed for direct simulation of electrorheological (ER) suspensions subjected to spatially uniform electrical fields. The method is implemented both in two and three dimensions. The fluid-particle system is treated implicitly using the combined weak formulation described in [1,2]. The governing Navier-Stokes equations for the fluid are solved everywhere, including the interior of the particles. The flow inside the particles is forced to be a rigid body motion by a distribution of Lagrange multipliers. The electrostatic force acting on the polarized spherical particles is modeled based on the point-dipole approximation. Using our code we have studied the time evolution of particle-scale structures of ER suspensions in channels subjected to the pressure driven flow. In our study, the flow direction is perpendicular to that of the electric field. Simulations show that when the hydrodynamic force is zero, or very small compared to the electrostatic force, the particles form chains that are aligned approximately parallel to the direction of electric field. But, when the magnitude of hydrodynamic force is comparable to that of the electrostatic force the particle chains orient at an angle with the direction of the electric field. The angle between the particle chain and the direction of the electric field depends on the relative strengths of the hydrodynamic and electrostatic forces.
Parallel Computing of Magnetically-Induced Flows and Microstructure Formation During Solidification Processing
Authors: Govindaraju N. , Li B. Q.
Published: November 2021

Solidification starts with nucleation that comes from the clustering of molecules, followed by deposition of molecules upon the nuclei or grain growth. In materials dynamics, these events are modeled at a spatial scale of microns and a temporal scale of micro seconds. On the other hand, the electrodynamic, fluid flow and heat transfer phenomena in solidifying metals are observable and thus modeled at a scale of millimeters (or sometimes centimeters) and a fraction of a second. An integrated macro/micro model is developed to represent the evolution of complex electrodynamic and transport phenomena and microstructure formation in solidifying metals with electromagnetic stirring applied to affect the solidification micrstructures. The model development is based on the hybrid boundary/finite element solution of the Maxwell equations and the finite element solution of the momentum and thermal transport equations, in combination with the Monte-Carlo-Cellular-Automaton representation of the evolution of solidification microstructure formation. Parallel computing has been applied to speed up the microstruture formation simulation, which is the most time consuming part of the calculations. The model should be useful to further our fundamental understanding of flow and microstructure formation in electromagnetically-assisted processes such as electromagnetic casting, arc welding, and vacuum refining.
Comparison of a Hydraulic Vane Actuator With Oil and Water
Authors: Raneda Albert , Siuko Mikko , Virvalo Tapio
Published: November 2021

The aim of this paper is to compare the performance of a hydraulic vane actuator with oil and water as the pressure medium. If the same performance level can be achieved with water and oil hydraulics, water as the pressure medium is preferred in applications where external oil leakage is not allowed or in applications that need fireproof fluids.

In order to compare the performance, a theoretical analysis of the actuator characteristics is carried out. The analysis includes a linear model of the hydraulic drive and allows identifying which factors should be analyzed in detail. As a result of this study, the parameters that greatly affect the performance of a hydraulic drive are identified (mainly, natural frequency, leakage, friction, damping and servovalve behaviour).

To experimentally verify the influence of these factors on the behaviour of the vane actuator, a set of measurements is designed to be able to identify the critical parameters.

During this study, special attention is paid to friction and leakage effects. Due to the lower water viscosity, sealing of the fluid chambers is difficult and internal leakage is difficult to avoid.
Thermal and Fluid Dynamic Structures of a Laboratory-Scale Fixed-Frame Fire-Whirl
Authors: Hassan Mohamed I. , Helali A. , Saito Kozo
Published: November 2021

Fire whirl is one of the most destructive phenomena in mass fires. To study thermal and fluid dynamic structures of a fire whirl in a laboratory, a fire whirl generator consisting of two vertically oriented split-cylinders were placed in an asymmetric position to form a compartment leaving two open slits in each end. A 5-cm diameter liquid pool fire was placed at the center of the compartment floor, the fire generated buoyancy flow moved upwardly, and fresh air entered to the compartment creating swirl motion. The visible flame height of the generated fire whirl was measured by a video camera, 2-D azimuthal velocity profiles at several different heights by particle image velocimetry (PIV), and the average heat flux input to the fuel surface by a Gardon gauge type heat flux meter.
A Study of Effects of Combustion on the Noise Generated by a Circular Jet Flow
Authors: Singh Kapil K. , Frankel Steven H. , Gore Jay P.
Published: November 2021

The noise generated by the standard Sandia Non-premixed Turbulent Flame Workshop (TNF) DLR-A and DLR-B flames was experimentally studied and compared with the noise generated by a cold air jet from same burner with identical exit Reynolds Numbers (Re). The axial and radial variations were studied for both reacting and non-reacting jets and compared.
Simultaneous Measurements of Droplet Size, Temperature, and Velocity Using an Integrated Phase-Doppler/Rainbow Thermometer
Authors: Donnell Matt O’ , Acharya Sumanta
Published: November 2021

This work summarizes efforts to determine the accuracy and performance characteristics of a new and novel laser diagnostic to measure instantaneous, in flight, droplet temperatures. The instrument uses the location of the rainbow peak to deduce the refractive index of the droplet, which in turn is related to the droplet temperature. Preliminary experiments were undertaken in order to understand the fundamental operating principles and limitations of the instrument. These experiments measured the temperature of an isothermal, single stream of monodisperse droplets. These measurements indicate that the mean refractive index can be measured with a standard deviation as low as 0.0001m.

Once the operation of the refractometer was proved under isothermal conditions, the measurement of droplet temperatures in a swirl-stabilized combustor was performed. These measurements indicate that the strength of the rainbow signal is significantly hampered by the noise induced by the flame. Preliminary temperature measurements with the combustor equipped with 45° vanes showed relatively constant radial temperature profiles (∼55–60°C) at locations less than 2 inches from the nozzle exit. A detailed examination of the temperature correlation with velocity and diameter revealed that larger and faster moving droplets dominate the distributions. Thus, the smaller droplets that are suspected of having the highest temperatures are inadequately represented in the mean droplet temperature.
Extinction Limits of Nonadiabatic, Catalyst-Assisted Flames in Stagnation-Point Flow
Authors: Margolis Stephen B. , Gardner Timothy J.
Published: November 2021

Because combustion is essentially an Arrhenius process, premixed flames generally can only exist within certain parameter ranges, or extinction limits, that correspond to a rate of heat production that is sufficient to sustain the reaction in a given flow geometry. Nonetheless, it is frequently desirable to extend these limits, often for the purpose of increasing fuel efficiency and/or reducing the rate of formation of pollutant species. Another emerging motivation is to allow combustion to be sustained in relatively small volumes, which are characterized by larger surface-to-volume ratios, that would otherwise lead to extinguishing levels of heat loss. Surface catalysts are widely used to achieve such enhancements with respect to efficiency and pollutant formation, and we wish to now consider the role catalysts might play with respect to nonadiabatic flames.
A Two-Phase and Multi-Component Model for the Cathode of PEM Fuel Cells
Authors: You Lixin , Liu Hongtan
Published: November 2021

A two-dimensional, two-phase and multi-component flow and transport model has been developed to simulate the flow and transport phenomena in the cathodes of PEM fuel cells. First, the governing equations based on a “two-phase mixture model” are derived by using a unified approach that describes the flow and transport in the gas channel and gas diffuser simultaneously. Then, the detailed boundary conditions are discussed especially at the gas diffuser/catalyst layer interface, which couples the flow, transport, potential and current density in the anode, the catalyst layer and membrane. Next, the model is validated by comparing the modeling results with experimental data. Further, typical distributions of oxygen and water-mass fraction in the “two-phase mixture,” as well as water vapor mass fraction, liquid saturation and liquid velocity vector are presented. Finally, the model is used to study the influences of two of the most critical issues of PEM fuel cell operation: i.e., the water and the thermal management on the two-phase flow. It was found that the two-phase flow characteristics in the cathode depend on some of the following factors: current density, operating temperature, and cathode and anode humidification temperatures. The dependence of the formation and the distribution of the two-phase flow in the gas diffuser and gas channel on these factors is explored. By studying the effects of these parameters on the two-phase flow and the fuel cell performance, the model can be used to study a water and thermal management scheme.
Ultrafast Deformation in Femtosecond Laser Heating
Authors: Tzou D. Y. , Beraun J. E. , Chen J. K.
Published: November 2021

The hot-electron blasting model is extended in this work to describe the ultrafast deformation in thin metal films in the sub-picosecond to picosecond domain. The driving force depends on both the temperature and temperature gradient in the hot electron gas, while the metal lattices remain thermally undisturbed in this highly non-equilibrium regime. The dominating parameters characterizing the ultrafast deformation are identified. The phonon-electron interaction model is used to describe the electron temperature, while renormalization of elastic moduli is accommodated in the dynamic equation of motion. Method of lines is used to solve the nonlinearly coupled equations describing ultrafast deformation in the sub-picosecond domain.
High-Temperature Electron Emission From Diamond Films
Authors: Shin S. H. , Fisher T. S. , Walker D. G. , Strauss A. M. , Kang W. P. , Davidson J. L.
Published: November 2021

This work examines the electron field emission characteristics of polycrystalline diamond films at high temperatures. Diamond is an excellent material as a field emitter because its high mechanical hardness and chemical inertness enable robust reliability. Diamond is also a wide-band gap semiconductor, increasing the probability for selective emission of higher-energy electrons. In recent years, considerable interest has developed in energy conversion applications of polycrystalline diamond films. However, little work has been considered for the field emission characteristics of diamond at elevated temperatures. The motivation behind this study involves direct energy conversion applications in power generation systems, where high temperatures exist. N-doped polycrystalline diamond films were grown by plasma-enhanced chemical-vapor deposition (PECVD). To investigate the effect of increased temperatures on field emission, current-voltage measurements were taken from the same diamond film at varying temperatures. Results from these measurements indicate a decrease in the turn-on voltage with increasing temperature. Further analysis of the temperature dependency of diamond was achieved through the parameter estimation of the effective emitting area, field enhancement factor, and work function. These results suggest that high-energy electrons are responsible for improved emission at high temperature. The resulting possibilities for direct energy conversion via diamond field emission are considered and discussed.
Numerical Solution of Melting Processes for Fixed and Unfixed Phase Change Material in the Presence of Magnetic Field: Simulation of Low Gravity Environment
Authors: Asako Y. , Gonçalves E. , Faghri M. , Charmchi M.
Published: November 2021

Transport processes associated with melting of an electrically conducting Phase Change Material (PCM), placed inside a rectangular enclosure, under low-gravity environment, and in the presence of a magnetic field is simulated numerically. Electromagnetic forces damp the natural convection as well as the flow induced by sedimentation and/or floatation, and thereby simulating the low gravity environment of outer space. Computational experiments are conducted for both side-wall heating and top-wall heating under horizontal magnetic field. The governing equations are discretized using a control-volume-based finite difference scheme. Numerical solutions are obtained for true low-gravity environment as well as for the simulated-low-gravity conditions resulted by the presence of a horizontal magnetic field. The effects of magnetic field on the natural convection, solid phase floatation/sedimentation, liquid-solid interface location, solid melting rate, and flow patterns are investigated. It is found that the melting under low-gravity environment can reasonably be simulated on earth via applying a strong horizontal magnetic field. However, the flow patterns obtained for the true low-gravity cases are not similar to the corresponding cases solved for the simulated-low-gravity environment.
Effect of Squealer Geometry Arrangement on Gas Turbine Blade Tip Heat Transfer
Authors: Azad Gm Salam , Han Je-Chin , Bunker Ronald S. , Lee C. Pang
Published: November 2021

This study investigates the effect of a squealer tip geometry arrangement on heat transfer coefficient and static pressure distributions on a gas turbine blade tip in a five-bladed stationary linear cascade. A transient liquid crystal technique is used to obtain detailed heat transfer coefficient distribution. The test blade is a linear model of a tip section of the GE E3 high-pressure turbine first stage rotor blade. Six tip geometry cases are studied: 1) squealer on pressure side, 2) squealer on mid camber line, 3) squealer on suction side, 4) squealer on pressure and suction sides, 5) squealer on pressure side plus mid camber line, and 6) squealer on suction side plus mid camber line. The flow condition corresponds to an overall pressure ratio of 1.32 and exit Reynolds number based on axial chord of 1.1 × 106. Results show that squealer geometry arrangement can change the leakage flow and results in different heat transfer coefficients to the blade tip. A squealer on suction side provides a better benefit compared to that on pressure side or mid camber line. A squealer on mid camber line performs better than that on a pressure side.
Heat Transfer Enhancement With Inclined Baffles and Ribs Combined
Authors: Khan Jamil A. , Hinton Jason , Baxter Sarah C.
Published: November 2021

Common heat transfer enhancement techniques are found in many of today’s processes. Devices such as inclined baffles, rib turbulators, jet impingement, etc are all used in order to augment the thermal transfer of a process. Inclined baffles have been studied along with the combination of jet impingement techniques. Inclined baffles enhance heat transfer by enhancing large-scale fluid bulk motion and through tripped boundary layer flow separation. Impinging jets, created by perforating the baffle, create additional heat transfer through flow impingement on the heated surface. Rib turbulators create heat transfer augmentation by disturbing the thermal boundary layer, unlike baffles; ribs enhance heat transfer in areas near the heat transfer surface leaving the core flow largely undisturbed. This investigation investigates experimental heat transfer of turbulent flow in a rectangular channel with inclined solid and perforated baffles combined with rib turbulators for isoflux heating at the top surface of the channel. Combining ribs with baffles yielded an increase in average Nusselt Number, albeit, with a pressure drop penalty. In situations where rate of heat transfer is critical to the performance of a device combining ribs with baffle is a viable solution.
Numerical Solution of Alloy Solidification and Columnar Eutectic Growth Using a Phase-Field Model
Authors: Judson Ward , Paolucci Samuel
Published: November 2021

Near-eutectic alloys freeze with a macroscopically discrete solid-liquid interface at a temperature below the equilibrium eutectic temperature. The velocity dependence of the freezing temperature results from the microscale species diffusion for microstructures with coupled eutectic growth characteristic of a near-eutectic alloy composition. At solidification rates that are representative of gravity permanent mold and die casting processes, consideration of the nonequilibrium conditions at the interface affects the prediction of the macroscale thermal field, and it in turn affects microscale properties.

A phase-field formulation is presented to model the alloy solidification which implicitly links the interface temperature to the interface speed. The utility of the method is well-suited for complex evolving solid-liquid interfaces and the velocity-dependent freezing temperature is satisfied implicitly.

The dimensionless governing equations are solved numerically with a fixed-grid Galerkin finite element method. After demonstrating sufficient numerical accuracy, temperature, phase field, and interface position results are presented for a square domain and three-dimensional casting geometry. Limitations of the phase-field method are discussed, and the conjugate heat transfer problem is studied to address boundary condition issues.
Fundamental and Application of High Precision Laser Micro-Bending
Authors: Zhang X. Richard , Xu Xianfan
Published: November 2021

This paper presents the technique of high precision microscale laser bending and the study of the thermomechanical phenomena involved. The use of pulsed and CW lasers for microscale bending of ceramics, silicon, and stainless steel is demonstrated. Experimental studies are conducted to find out the relation between bending angles and laser operation parameters. Bending results obtained by a pulsed and a CW laser are compared. Changes of surface composition after laser irradiation are analyzed. Numerical calculations based on thermo-elasto-plastic theory are conducted and results are compared with the experimental data Examples of industrial applications of high precision laser bending are given.
Affordable Integrated Helicopter Fuselage Structure — Full-Scale Article (Extended Abstract)
Authors: Burpo Steven J. , Sen Joyanto K. , Renieri Gary D. , Froeschner Neal A. , Kollmansberger Ronald B.
Published: November 2021

The Boeing Company and the US Army Aviation Applied Technology Directorate Missile are working under a cooperative agreement to re-engineer the center fuselage of the Longbow Apache Helicopter using an integrated design and manufacturing approach. The program is aggressively applying advanced composite manufacturing processes to a 14-foot portion of the Longbow fuselage. The goal of the program is to reduce recurring manufacturing labor costs by 25% and structural weight by 15% as compared to a 1994 Composite Baseline Design. This paper presents the accomplishments on the program.
A Model for Nonisothermal Healing of Thermoplastic Polymers During Fusion Bonding
Authors: Yang Fuzheng , Pitchumani Ranga
Published: November 2021

Polymer healing, referring to the intermolecular diffusion across the interfaces of thermoplastic tape layers in intimate contact, is one of the important steps in fusion bonding responsible for the development of interlaminar bond strength, and is strongly influenced by the temperature history. In this paper, a model for the healing process under non-isothermal conditions is developed starting from a fundamental formulation of the reptation of polymer chains. Considering the temperature dependence of the reptation time, the bond strength is described as a function of temperature history. Parametric studies and comparison of the model with available models in the literature are presented.
A Simplified Modeling Scheme for Design Sensitivity Study of Thermal Solution Utilizing Heat Pipe and Vapor Chamber Technology
Authors: Prasher Ravi S. , Shipley James , Devpura Amit
Published: November 2021

This paper introduces a simplified modeling scheme for the prediction of heat transport capability of heat pipes and vapor chambers. The modeling scheme introduced in this paper enables thermal designers to model heat pipes and vapor chambers in commercially available conduction modeling tools such as Ansys™ and IcePak™. This modeling scheme allows thermal designers to perform design sensitivity studies in terms of power dissipation of heat pipes and vapor chambers for different scenarios such as configurations, heat sink resistance for a given temperature drop between the heating source and the ambient. This paper also discusses how thermal designers can specify requirements to heat pipe/vapor chamber suppliers for their thermal design, without delving into the complete thermofluidic modeling of this technology.
Numeric Modeling of Ultrasonic Acoustic Streaming Cooling Effect on IC Chips
Authors: Wan Q. , Kuznetsov A. V.
Published: November 2021

This paper investigates enhancement of cooling of an IC chip by acoustic streaming induced by a PZT-covered vibrating beam, which is placed underneath the chip. Vibration of the beam induces acoustic streaming in the gap between the chip and the beam. The governing equations are asymptotically decomposed into the first order harmonic equations and second order time-independent acoustic streaming equations by the infinite small parameter defined as the ratio of characteristic beam vibration velocity and the local sound speed. The first order harmonic equations are numerically solved in the reduced wave equation form. The steady acoustic streaming equations are driven by the first order harmonic field and are solved by SIMPLER method. The cooling effect on the uniform heat flux from the chip is also analyzed and behavior of the cooling effect on the uniform heat generation within a chip with finite thickness is also estimated.
Design and Development of a Jet Impingement Facility for Experimental Studies
Authors: Allen Jason R. , Anderson Ann M.
Published: November 2021

This paper describes the design and development of a facility for the study of jet impingement heat transfer. The facility was designed to teach undergraduate students about the relation between fluid mechanics and convective heat transfer. It consists of a heated surface mounted perpendicular to a 9.8 by 3.8 cm slot jet nozzle on an adjustable base. A small compact blower serves as the air supply and is also mounted on the base. The jet to surface gap distance can be varied from 0 to 25 cm and the jet velocity can be varied from 2 to 15 m/s. The system uses particle image velocimetry (PIV) to measure the impinging flow velocities and liquid crystal thermography (LCT) to measure the temperatures on the heated surface. This paper will discuss the design constraints, the design options, and several analyses used to size the jet nozzle and the heat transfer surface. The final design will be presented as well as some typical PIV and LC results which illustrate the jet impingement cooling phenomena.
Use of Lamb Waves to Predict Current Damaged State of Mortar
Authors: Keller Michael S. , Kundu Tribikram , Desai Chandrakant S.
Published: November 2021

This paper describes the experimental and analytical results for the development of a methodology for predicting the current state of simulated concrete (mortar) in infrastructure. The nondestructive Lamb wave technique is used to experimentally identify the disturbance (damage) before and after mechanical testing of mortar specimens, which is used in the initial research as a substitute for concrete. The mortar specimens are tested to measure their stress-strain response under uniaxial compression and tension loading. The results of the nondestructive and mechanical stress-strain testing are correlated to develop the model based on the Disturbed State Concept (DSC), a unified approach for modeling material behavior. This model can allow evaluation of the deformation moduli, strength and degradation (damage) at a given state during the life of the material. This information can be used to design rehabilitation strategies. It can also lead to the development of new computer based equipment that can be used in the field for defining the remaining life. At this time, the research involved one-dimensional testing. The proposed methodology can, however, be extended and improved by conducting two- and three-dimensional testing of concrete specimens.
Individualization of exosuit assistance based on measured muscle dynamics during versatile walking
Authors: Nuckols R. W. , Lee S. , Swaminathan K. , Orzel D. , Howe R. D. , Walsh C. J.
Published: November 2021

An ankle exosuit tuned to the measured muscle dynamics of the user during multiple walking tasks improves energy economy.
Streamlined Whole-Genome Sequencing of Mumps Virus for High-Resolution Outbreak Analysis
Authors: Bryant Patrick , Caldwell Haley , Lamson Daryl M. , Yildirim Tugba , St. George Kirsten
Published: November 2021

Since 2015, the United States has experienced a resurgence in the number of mumps cases and outbreaks in fully vaccinated populations. These outbreaks have occurred predominantly in close-quarter settings, such as camps, colleges, and detention centers.
Comparative Performance of Genomic Methods for the Detection of Pyrazinamide Resistance and Heteroresistance in Mycobacterium tuberculosis
Authors: Whitfield Michael G. , Engelthaler David M. , Allender Christopher , Folkerts Megan , Heupink Tim H. , Limberis Jason , Warren Robin M. , Van Rie Annelies , Metcalfe John Z.
Published: November 2021

Pyrazinamide is an important component of both drug-susceptible and drug-resistant tuberculosis treatment regimens. Although approximately 50% of rifampin-resistant isolates are also resistant to pyrazinamide, pyrazinamide susceptibility testing is not routinely performed due to the challenging nature of the assay.
MicroRNA-376b-3p Promotes Porcine Reproductive and Respiratory Syndrome Virus Replication by Targeting Viral Restriction Factor TRIM22
Authors: Chen Jing , Zhao Shijie , Cui Zhiying , Li Wen , Xu Pengli , Liu Huimin , Miao Xinyong , Chen Yu , Han Fangfang , Zhang Hongying , Xia Pingan , Zhang Yina
Published: November 2021

Porcine reproductive and respiratory syndrome virus (PRRSV) causes enormous economic losses each year in the swine industry worldwide. MicroRNAs (miRNAs) play important roles during viral infections via modulating the expression of viral or host genes at the posttranscriptional level.
A Structurally Conserved RNA Element within SARS-CoV-2 ORF1a RNA and S mRNA Regulates Translation in Response to Viral S Protein-Induced Signaling in Human Lung Cells
Authors: Basu Abhijit , Penumutchu Srinivasa , Nguyen Kien , Mbonye Uri , Tolbert Blanton S. , Karn Jonathan , Komar Anton A. , Mazumder Barsanjit
Published: November 2021

Specific RNA elements in the genomes of RNA viruses play important roles in host-virus interaction. For SARS-CoV-2, the mechanistic insights on how these RNA elements could sense the signals from the host cell are lacking.
Characterization of Apicomplexan Amino Acid Transporters (ApiATs) in the Malaria Parasite Plasmodium falciparum
Authors: Wichers Jan Stephan , van Gelder Carolina , Fuchs Gwendolin , Ruge Julia Mareike , Pietsch Emma , Ferreira Josie L. , Safavi Soraya , von Thien Heidrun , Burda Paul-Christian , Mesén-Ramirez Paolo , Spielmann Tobias , Strauss Jan , Gilberger Tim-Wolf , Bachmann Anna
Published: November 2021

Malaria parasites live and multiply inside cells. To facilitate their extremely fast intracellular proliferation, they hijack and transform their host cells.
Positive and Negative Ions Potently Inhibit the Viability of Airborne Gram-Positive and Gram-Negative Bacteria
Authors: Comini Sara , Mandras Narcisa , Iannantuoni Maria Rita , Menotti Francesca , Musumeci Andrea Giuseppe , Piersigilli Giorgia , Allizond Valeria , Banche Giuliana , Cuffini Anna Maria
Published: November 2021

Indoor air is a well-established vehicle for direct and indirect spread of a wide variety of human pathogens—as bioaerosols are composed of bacteria, viruses, fungi, and other types of organisms—that may trigger some pathologies. Plasmacluster ionizers are known for their ability to generate positively or negatively charged air ions (PAIs and NAIs, respectively) that can kill/inactivate indoor airborne pathogens, through oxidative stress-induced damage, in various environments.
A Distinct, Flocculent, Acidogenic Microbial Community Accompanies Methanogenic Granules in Anaerobic Digesters
Authors: Mills Simon , Trego Anna Christine , Lens Piet N. L. , Ijaz Umer Zeeshan , Collins Gavin
Published: November 2021

Complex microbial communities in engineered environments can aggregate to form surface-attached biofilms. Others form suspended biofilms, such as methanogenic granules.