bluuebunny/crossref_metadata_2025 huggingface dataset:
A Stochastic, Fuzzy, Neural Network for Unknown Dynamic Systems
Authors: Jing Zhongliang , Luo Albert C. J. , Tomizuka M.
Published: January 2022

A stochastic, fuzzy, neural network (SFNN) to model unknown nonlinear dynamic systems is developed. In this network, a non-singleton fuzzifier with Gaussian membership functions instead of the singleton fuzzifier in the fuzzy logic is introduced. Based on these membership functions, an online supervised parameter learning algorithm of the SFNN is proposed to overcome the local minimum of learning process in current neural networks, and an off-line algorithm for the structure learning of the SFNN is presented to reduce the amount of computation of the SFNN. This new network provides a universal approximator and it is also applicable to stochastic control and decision systems and the identification of chaos in nonlinear systems.
A New Simplified Model of Shrouded Blisk and its Dynamic Behaviour
Authors: Li Lin , Baumgartner Manfred
Published: January 2022

A model of a cyclic two-dimensional spring-mass-damper substructure of a bladed disc is presented. The method considers the shroud interlock angle and the direction of the blade motion. This is an improvement of the cyclic 1 DOF substructure modelling. The equations of motion for the mechanical replacement system are presented in the paper. The dynamic behaviour of the system especially the effect of the interlock angle are investigated.
Dimension Reduction of Singular Perturbation Problems of Spinning Rectangular Beams
Authors: Lee K. H. , Ong E. H.
Published: January 2022

This paper describes a new reduction principle which can be used to solve singular perturbation problems arising from the nonlinear dynamics of spinning rectangular beams which are much suffer in one of the transverse directions. With this approach, the vibration in the suffer direction is considered as a singular perturbation to that in the less stiff direction. The reduction principle enables the outer solution (the long term behaviour) of the equations of motion to be obtained easily without the “stiffness” often associated with singular perturbation problems. The reduction in dimension from a four-dimensional to a two-dimensional vector field also facilitates the use of analytical tools like Mel’nikov’s method for predicting the onset of chaos for beams with von Karman nonlinearity. Examples involving simply-supported spinning rectangular beams under external periodic excitation, parametric excitation and quasi-periodic excitation are used to demonstrate the effectiveness of the reduction principle and the corresponding dimension reduction.
The Effect of Tool Rotation on Regenerative Chatter in Line Boring
Authors: Li Chen-Jung , Ulsoy A. Galip , Endres William J.
Published: January 2022

Line boring uses a rotational boring bar such that the cutting forces rotate and are repetitive. This is quite different from turning, or boring with stationary boring bars, in which the force directions are fixed. Although the subject of chatter analysis of rotating tools has been extensively studied in milling, the cutting forces are typically intermittent, and the methods used are either analytically approximate or via time domain simulation. This paper will use an analytical method for chatter analysis of line boring, which can also be applied to other full-immersion machining processes with a rotating tool. The analytical results show that the stability lobes for boring with a rotating boring bar are quite different than those for boring with a stationary boring bar, and an explanation is given. Furthermore, results and a qualitative explanation are given to show the discrepancy in stability between the exact and approximate solutions, especially at low spindle speeds. The importance of the results is to provide stability lobes for line boring to help select chatter-free cutting conditions.
Dynamic Simulation of Reaming: Theory, Methods and Application to the Problem of Lobed Holes
Authors: Young Keith A. , Bayly Philip V. , Halley Jeremiah. E.
Published: January 2022

Reaming is a very common machine tool operation, which is performed to enlarge previously drilled holes to a precise size. If a reamer with evenly spaced teeth oscillates transversely as it cuts, the resulting hole is not round. Typically the hole profile exhibits N-1 or N+1 “lobes”, where N is the number of cutting flutes on the tool. This type of profile is caused by periodic motion, or “whirl”, of the tool at N cycles/revolution (the tooth passing frequency). From kinematics, it is clear that the direction and frequency of whirl determines the number of lobes on the hole profile. However, the mechanism that causes the oscillation has remained unclear, especially when the tooth passing frequency is well below the natural frequency of the tool. In this paper, a simplified model of the reamer is proposed which includes cutting forces and forces on the sides and clearance faces of the flutes. The cutting forces include a time-delayed component due to the effect of the previous tooth’s passage. In order to study efficiently the response of the tool at low speeds, a quasi-static numerical method is used. A Newton-Raphson method is used to solve the nonlinear equations of static equilibrium at every point in the simulation. The model remains dynamic because of the regenerative effect of the time delay, and successfully predicts the qualitative behavior of the reamer under several different cutting conditions.
Galloping of Lightly Iced Conductors: An Explanation
Authors: Venkatasubramanian S. H. , White Warren N. , Lam K. Y. , Liu G. R.
Published: January 2022

Stability of a stranded, sagged, lightly iced electrical power transmission cable subjected to aerodynamic forces and moment is studied. Small oscillations in three Cartesian directions about wind loaded equilibrium position and torsional oscillations are considered. A finite element analysis of the linearized coupled differential equations is performed. Stability is determined by the sign — stable if negative — of the real parts of the eigenvalues of the linear system. It is shown that a lightly iced cable without inertial coupling that is Den Hartog stable and subjected to an aerodynamic moment having a positive slope can still be unstable due to the combined effect of stranded nature of cable construction, wind, and aerodynamic coefficients. It appears that this effect is less significant if the fundamental torsional frequency is well separated from the first few vertical mode frequencies.
Fluid Mechanics and Heat Transfer in Zero-Mean Oscillatory Flows in Short Channels
Authors: Li P. , Yang K. T.
Published: January 2022

The fluid mechanics and heat transfer of zero-mean oscillatory flows at low frequencies and large amplitudes in essentially two dimensional short channels are studied numerically, and the associated heat transfer enhancement depends strongly on the conditions imposed on the channel ends. The results show that intracycle oscillations do also occur, and that such oscillations are different from those for long ducts. In the case of sudden pressure changes as the flow reverses at the ends, the intracycle oscillations are found to occur in the acceleration phase of the oscillatory cycle and are responsible for the heat transfer enhancement. These results compare favorably with previously obtained experimental data.
Transition to Chaotic Flow in a Radially Heated Taylor-Couette System
Authors: Kedia R. , Hunt M. L. , Colonius T.
Published: January 2022

Numerical simulations have been performed to study the stability of heated, incompressible Taylor-Couette flow for a radius ratio of 0.7 and a Prandtl number of 0.7. As Gr is increased, the Taylor cell that has the same direction of circulation as the natural convection current increases in size and the counter-rotating cell becomes smaller. The flow remains axisymmetric and the average heat transfer decreases with the increase in Gr. When the cylinder is impulsively heated, the counter-rotating cell vanishes and n = 1 spiral is formed for Gr = 1000. This transition marks an increase in the heat transfer due to an increase in the radial velocity component of the fluid. By slowly varying the Grashof number, the simulations demonstrate the existence of a hysteresis loop. Two different stable states with same heat transfer are found to exist at the same Grashof number. A time delay analysis of the radial velocity and the local heat transfer coefficient time is performed to determine the dimension at two Grashof numbers. For a fixed Reynolds number of 100, the two-dimensional projection of the reconstructed attractor shows a limit cycle for Gr = −1700. The limit cycle behavior disappears at Gr = −2100, and the reconstructed attractor becomes irregular. The attractor dimension increases to about 3.2 from a value of 1 for the limit cycle case; similar values were determined for both the local heat transfer and the local radial velocity, indicating that the dynamics of the temperature variations can be inferred from that of the velocity variations.
Turbulent Instability Prediction in Low-Pressure Last Stage Steam Turbine Blades
Authors: Wang K. D. , Amano R. S.
Published: January 2022

The last stage blades of a low-pressure (LP) steam turbine were reported to have been experiencing flow instability associated with higher than normal back pressure level. The phenomenon is identified as one of the serious potential causes of last stage blade failures and, therefore, can be one of the major factors that limit the operational flexibility of steam turbines. Thus, for failure prevention, it becomes necessary to determine the operating conditions under which turbulent instability is likely to occur.

This paper presents a novel approach that can quantitatively predict turbulent flow instability by comparing aerodynamic damping and structural damping. To assess its applicability, turbulent flow instability was investigated in conjunction with three fundamental vibration modes of last stage blades of a LP steam turbine. The stability considerations were based on a quasi-steady power-per-vibration-cycle approach. The aerodynamic work per cycle of vibration mode of a bladed disk was calculated from the time integral of the product of the periodic time varying force and the specified harmonic vibration amplitude. A finite element based blade model was constructed to obtain modal characteristics at an operating speed. The aerodynamic forces were obtained from a two-dimensional cascade analysis for viscous compressible flow with a second-order Reynolds-stress model. The computational nodes were generated by employing a body-fitted algebraic grid generation technique. The unsteady compressible Navier-Stokes equations were solved for the flows around the blade airfoil region to determine aerodynamic damping. The nonlinear material damping energy of the bladed disk was calculated as a function of the vibration amplitude by using the Lazan’s power law. The turbulent instability was determined by the net power flow to die bladed disk at various amplitudes of vibration. Some computed results for die last stage of a LP steam turbine are presented in this paper.
Optimization of Fin Spacing to Enhance Falling Film Evaporation of Seawater on Vertical Plane Walls or Tubes
Authors: Schröder Jens J. , Bode Andreas , Fast Peter , Sander-Beuermann Wolfgang
Published: January 2022

In a review over eight years of our experimental research on falling film evaporation it is shown that by using non-integral fins in flow-direction, the evaporation heat transfer coefficient for water and seawater can be enhanced several times compared to flat surfaces. The optimum spacing of the fins is 5 mm for pure water and 8.6 mm for salt solutions. In our experiments the evaporation temperatures ranged from 40 °C to 80 °C and heat fluxes were well below the start of nucleate boiling.

For pure water and suitable film Reynolds numbers capillary waves with high frequencies are permanently rewetting dry patches and drastically enhance evaporation.

For salt solutions instead it is mainly the gradient of surface tension that permanently renews the boundary of the liquid phase causing transfer coefficients that in extremum can be better than with pure water under optimum conditions. There is a strong dependence of the heat transfer coefficient on heat flux in this case.
Industry-University Interaction: A Win-Win Scenario
Authors: Nasr Karim J. , AbdulNour Bashar S.
Published: January 2022

Kettering University (formerly GMI Engineering & Management Institute) has had a strong link with industry due to its co-op approach to engineering education. This paper presents an extension of this link by collaborating with industry under two different programs: The Ford University Research Program (URP) and the Sloan Faculty Co-op Program. This paper describes the two programs and the various reasons for interaction, documents the nature of the collaborations, outlines potential benefits, and describes the manner by which the relationships were initiated. The paper focuses on the outcomes, makes recommendations towards successful and mutually beneficial relationships, and exhibits conditions for a continuing partnership. It concludes with an outline for a successful collaboration, its implications, and proposes ideas to other institutions for developing similar programs.
Effect of Density Change on Melting of Unfixed Rectangular Phase-Change Material Under Low-Gravity Environment
Authors: Asako Y. , Faghri M.
Published: January 2022

An enthalpy method is employed to solve transport processes associated with the effect of density change on melting of unfixed rectangular phase change material (PCM) under low-gravity environment. This method permits the phase-change problems to be solved within fixed numerical grids, hence eliminating the need for coordinate transformation. The PCM, initially and its melting temperature, is placed inside a rectangular enclosure. The lower surface of the enclosure is then exposed to a uniform temperature higher than the PCM melting temperature. The difference in densities of solid and liquid causes a force imbalance on the solid. In the case where the density of the solid phase exceeds that of the liquid, the solid continually moves downwards as melting progresses and hence generates a flow field within the liquid. The problem is formulated as a one-domain problem and the effect of density change at the solid/liquid interface is treated via source and sink terms at interface and the outflow boundaries. The governing equations are discretized by using a control-volume-based finite difference scheme. The results are presented in form of parametric study of the effects of solid/liquid density ratio, Archimedes number, Stefan number, Prandtl number and the geometric parameters on the melt thickness, the downward solid velocity, the elevation of the top surface and the volume of the solid PCM. In general, the effect of solid/liquid density ratio is small on melting characteristics in low-gravity environment.
Effects of Mesh Size in a Flat Evaporator and Condenser Cooling Capacity on the Thermal Performance of a Capillary Pumped Loop
Authors: Boo J. H. , Chun M. S.
Published: January 2022

The thermal performance of a flat evaporator for capillary pumped loop (CPL) applications was investigated. Two to four layers of coarse wire screen wicks were placed onto the heated surface to provide irregular passages for vapor flow. The evaporator and condenser were separated by a distance of 1.2 m and were connected by individual liquid and vapor lines. The wall material was copper and the working fluid was ethanol. The experimental facility utilized a combination of capillary and gravitational forces for liquid return, and distribution over the evaporator surface. The tubing used for the vapor and liquid lines was 0.935 cm or less in diameter and heat removal from the condenser was by convection of air.

A heat flux of up to 4.9 × 104 W/m2 was applied to a flat evaporator having dimensions of 100 mm by 200 mm, 20 mm thick. The thermal resistance of the system as well as the temperature characteristics of the system was investigated as the evaporator heat flux and the condenser cooling capacity varied. The performance of the evaporator and the effect of condenser cooling capacity were analyzed and discussed.
Experimental and Analytical Study of Reduction in Aircraft Fuel Consumption With Recovery Energy From the Cabin Air
Authors: Asfia F. J. , Buzza T. G. , Wiles S. A.
Published: January 2022

In an existing aircraft air conditioning system, high temperature and pressure air from the engine core compressor enters the air conditioning packs to reach the desired cabin temperature and pressure. This conditioned cabin air is discharged to the outside ambient. A significant amount of energy is wasted by this process. In order to recover some of this energy, a new air conditioning pack was designed, analyzed and tested. In the new pack, the cabin out-flow air passes through an out-flow turbine which is shaft connected to a compressor. The compressor receives the ambient air and delivers it to a heat exchanger, where it is cooled by out-flowing turbine air and is passed on to the cabin. Experiments were performed to verify the new concept of using the out-flow turbine. In the experiments, an automobile turbo-compressor was used. A series of T-type thermocouples, 10 pressure transducers and five orifice flowmeters were used to measure the temperature, pressure and flowrate at different locations. A 32.5 m3 tank, simulating the aircraft cabin, was connected to the turbo-compressor as well as a pressurized air duct, simulating the in-flow from the other existing packs. The turbine outlet was connected to a low pressure 4.2 m3 tank, simulating altitude condition, and the compressor inlet was connected to another low pressure 2.1 m3 tank, simulating ram air condition (total pressure and temperature). It should be noted that due to the aircraft speed the ram air pressure is higher than the ambient pressure. During each test, three pressure control valves were used to maintain the pressure of the three tanks nearly constant with time.

In the experiments the cabin pressure, ambient pressure and ram pressure were varied parametrically simulating different altitudes. Data were taken at altitudes ranging from 6000 to 9000 m. In the experiments, the simulated in-flow air from the other packs fluctuated by 10%. From the obtained data, it was observed that by placing a flow control valve in the compressor outlet duct the cabin pressure could be controlled within 0.4% while the in-flow air flowrate was varied 10%.

The analytical results as well as experimental data show that nearly 56% of the delivered air to the cabin can be provided by this new pack. This decrease of the extracted engine air by 56% results in a significant reduction of fuel consumption.
Assessment of Coupled Natural Convection and Radiation Within Enclosed Vertical Annuli
Authors: Sanders Joseph C.
Published: January 2022

An independent investigation of heat transfer in enclosed vertical storage tubes housing plutonium metal within DOE Standard 3013-compliant storage container systems was performed to determine whether this storage configuration could effectively remove the internally generated heat from pure plutonium metal. Alpha-phase plutonium metal, if allowed to exceed approximately 239°F, will transition to beta-phase metal and undergo a volumetric expansion which could rupture the storage container system. Significant temperature drops occurred in two regions. Both regions were gas-filled vertical annuli with heat flux boundary conditions on the inner surfaces and fixed temperature boundary conditions on the outer surfaces. The thermal resistance method was employed to evaluate radial heat transfer across each annulus, coupling natural convection, radiation, and conduction. Correlations from Thomas and deVahl Davis (1970) and Keyhani et al. (1983) were used to evaluate the degree of natural convective enhancement. Multi-dimensional finite element modeling of these regions was also performed employing both buoyant and radiative effects. Both models accurately predicted the measured temperature changes from an experimental investigation by Hopkins et al. (1997) which used a larger diameter storage tube with a 38% higher heat loading.
Detailed Heat Transfer Measurements in an Engine Representative Impingement Cooling System Using Liquid Crystals
Authors: Son Changmin , Michaelis Mark , Robertson Andrew , Ireland Peter , Bather Simon
Published: January 2022

In the present study the cooling performance of an impingement array representative of the type used in some nozzle guide vanes has been investigated. The geometry tested consists of a staggered impingement hole array in which the hole size increases in the direction towards the array outlet. The array geometry parameters are in the range x/d = 3 – 4.8, y/d = 3.75 – 6 and z/d = 1.875 – 3. Heat transfer experiments have been carried out using the transient liquid crystal technique with 3 narrow band thermochromic liquid crystals. Using the transient technique, full surface local heat transfer coefficient distributions have been determined. To calculate local jet Reynolds numbers, a simplified analytic model of the flow field through the impingement channel, which accounts for the effect of different jet hole diameters, has been used. Comparison of the model local pressure distributions with experimentally determined mass flows verify this approach. Local heat transfer coefficients distributions at very high data resolution have been presented for a range of jet Reynolds number between 17,000 and 32,000. The peak in local heat transfer is consistently located at the stagnation point beneath the jets. The high-resolution data also revealed a very repeatable change in the slope of the heat transfer coefficient distribution at a radial distance from the hole axis of 1–1.5 diameters. Stagnation point Nusselt numbers, which rise with increasing local jet Reynolds number and cross-flow to jet flow ratio, show excellent agreement with an earlier correlation.
Computational Simulation of the In Situ Formation in Melts of Electrical Pathways Among Particles Transported by Two-Dimensional Chaotic Mixing
Authors: Danescu R. I. , Zumbrunnen D. A.
Published: January 2022

Recently, fine-scale structures have been constructed from initially large clusters of micron-size particles by inducing chaotic motion within cavities filled with polymer melts. Upon solidification, the structures can render the resulting composite material electrically conducting if conducting particles are used. The transport of particles and the formation of these structures by chaotic mixing in an eccentric cylindrical cavity is simulated computationally in order to assess the influence of key parameters. The general equation for particle motion in response to drag and colloidal forces was derived and dimensionless parameters were identified which characterize the process. Computational tracking of individual particles was performed under conditions where global chaotic mixing prevailed. Two levels of complexity were considered. In the first case, particles were assumed to move passively. In the second case, colloidal and drag forces were present. After mixing, networks comprising interconnected particles were identified as electrical pathways. Formation mechanisms are described at various stages of mixing and the networks are characterized statistically.
An Improved Transient Model of Tool Temperatures in Metal Cutting
Authors: Jen Tien-Chien , Anagonye Aloysius U.
Published: January 2022

A model for predicting cutting tool temperatures under transient conditions is presented. The model of Stephenson et. al (1997) is extended to include the initial transient response to the tool temperature, non-uniform heat flux distributions and the convective cooling due to the use of coolant. The main goal in this paper is to be able to accurately predict the initial transient tool temperature response, or temperatures in interrupted cutting for cases where the cutting time is short. A method to predict the true transient energy partitioning instead of quasi-steady energy partitioning (Stephenson et. al, 1997), without seeking the full numerical analysis, has been developed. In this paper, the transient energy partitioning is obtained through a fixed-point iteration process by modifying the quasi-steady energy partitioning method presented by Loewen and Shaw (1954). The predicted transient tool temperatures are compared quantitatively to the experimental data. Utilizing a semi-empirical correlation for heat flux distribution along the tool-chip interface, the temperature distribution is calculated and compared qualitatively to existing experimental data.
A Periodic Surface Heating Method for the Thermal Characterization of Dielectric Thin Films
Authors: Indermuehle Scott W. , Peterson Richard B.
Published: January 2022

This paper presents a phase sensitive measurement technique for determining two independent thermal properties of a thin dielectric film. The technique involves measuring a specimen’s front surface temperature response to a periodic heating signal produced by passing current through a 50 nm thick layer of nichrome deposited on the specimen’s surface. The temperature response is measured with a HgCdTe infrared detector operating at 77 K. The phase shift of the temperature response with respect to the heating signal is fit to an analytical model using thermal diffusivity and effusivity as fitting parameters. From these two parameters, the thermal conductivity and specific heat can be calculated. The method has been applied to 1.72 μm-thick films of SiO2 that were thermally grown on a silicon substrate. One interesting outcome stemming from analysis of the experimental data is the ability to extract both thermal conductivity and specific heat of a thin film from phase information alone. All film thermal conductivities determined so far by this method show a slight decrease with respect to the bulk values. Specific heats were found to be similar to bulk values. Both of these results are consistent with past work on thermally grown films of SiO2.
Heat Transfer in a Matrix With Embedded Particles
Authors: Vick Brian , Scott E. P.
Published: January 2022

The transient heat transfer characteristics of heterogeneous materials consisting of a microstructure of relatively small particles embedded in a matrix is investigated. A constitutive model is developed where heat is initially transferred to the matrix and is then transferred to small, separated particles embedded throughout the matrix. The heat exchange between the matrix and particles is characterized by a contact conductance. This physical model leads to a system of coupled diffusion equations for the matrix and particles, similar to the parabolic two-step model used to describe the electron-lattice interactions in microscale heat transfer. In the current investigation, a one-dimensional model with an applied surface heat flux is used.

A numerical solution to the coupled system of equations using the control volume based finite difference method is developed. This method readily allows for the inclusion of any combination of material properties, particle sizes and contact conductance. Case studies reveal that the property ratios and contact conductance can lead to a thermal lag where the temperature response to an applied heat flux is markedly different than that predicted with a homogeneous conduction model. An effective thermalization time can also be inferred from this modeling of the heterogeneous microstructure.
Predicting Thermal Boundary Resistance Using Monte Carlo Simulation
Authors: De Bellis Lisa , Prasher Ravi S. , Phelan Patrick E.
Published: January 2022

The Acoustic Mismatch Model (AMM) and the Diffuse Mismatch Model (DMM) have traditionally been used to predict the thermal boundary resistance, Rb, across the interface of two adjoining materials at temperatures well below the Debye temperatures of the materials in question. Both models, however, fall short when compared to experimental data. The development of these models involves limiting assumptions in order to simplify the mathematical evaluation. A Monte Carlo (MC) Model is proposed and developed as a compliment to the AMM and DMM models. Using the statistical approach eliminates the need of addressing complicated expressions, thereby allowing us to lift some of the limiting assumptions. Furthermore, for the first time, the AMM and DMM are combined into a single, mixed model which determines Rb based on a net heat transfer calculated from both specular and diffuse transmission. As expected, the results in this instance lay between those of the AMM and DMM models.
A Critical Evaluation of the Monte Carlo Method for Application to the Inverse Heat Conduction Problem
Authors: Ganesa-Pillai Madhu , Haji-Sheikh A.
Published: January 2022

The solutions of the Inverse Heat Conduction Problem using the Monte Carlo method, Green’s Function Solution Equation and the Alternative Green’s Function Solution Equation are compared. The Monte Carlo method is a simple technique that provides a method of determining the source of error and placement of sensors. However, in comparison with the exact solution, if attainable, the cost is a higher error in the solution. All the three methods use the function specification method in the sense that a functional form for the surface heat flux or temperature is assumed and the parameters defining the function are evaluated by minimizing the error functional. In the alternative method, the functional form also satisfies the boundary conditions, the unknown quantity in the problem. The input data for this comparison are experimentally measured temperatures in a stainless steel disk subjected to spray cooling.
The Function Decomposition Method and its Application in Thermal Inverse Analysis
Authors: Osborne G. E. , Frankel J. I. , Keyhani M.
Published: January 2022

The use of inverse analysis for both function reconstruction-estimation and thermal design problems represents a developing area for which a wealth of studies can be performed. These two classes of thermal inverse problems are both ill-posed and differ mainly in the nature of the data prescribed at the over-specified boundary surface, i.e., discrete or continuous data.

A new and robust technique is presented that eliminates the need for multiple analytical approaches. The innovative procedure, called the Function Decomposition Method (FDM), is proposed and demonstrated in this paper. This technique provides stable and accurate results without the need for specification of an external Tikhonov regularization parameter, thereby reducing the complexity of the solution algorithm. The methodology may be readily extended to nonlinear problems by utilizing quasilinearization.

The results presented in this paper focus on problems in which discrete temperature data are provided at the boundary. To illustrate the Function Decomposition Method as it is applied to inverse heat conduction, the classic Beck’s problem is considered. The first case uses exact data as input while the remaining cases employ data with noise introduced.
Inverse Radiation Heat Transfer Within Enclosures With Nonisothermal, Non-Gray Participating Media
Authors: França Francis H. R. , Oguma Masahito , Howell John R.
Published: January 2022

This work considers the inverse problem where both the net radiative heat flux and temperature distributions on the design surface of a rectangular enclosure are imposed, the remaining surfaces being adiabatic. The enclosure is filled with a non-gray, absorbing, emitting, non-scattering medium, whose temperature and volumetric heat generation distributions are unknown, and have to be determined such that the two specified conditions on the design surface are attained. The heat transfer is considered to be purely radiative, and is evaluated by the zoning method combined with the weighted-sum-of-gray-gases model. The resulting system of equations is non-linear and ill-conditioned. It is solved by an iterative procedure, where the truncated singular value decomposition method (TSVD) is applied at each iteration step.
Automotive Heater Core Boundary Conditions Identification
Authors: Moultanovsky Alexander V.
Published: January 2022

This paper centers on the first ever research of inverse problem of an automotive heating thermal system, which mostly operates in cold weather modes of Heating, Ventilating, and Air Conditioning system. Heat fluxes or heat transfer coefficients between an automotive heater core and fluids are intended to be identified by means of Inverse Heat Transfer Problem solution. The estimation of heat transfer with the inverse heat transfer methods, first and foremost makes it possible to get accurate results of heat transfer coefficient (or heat flux) because one calculates it with the most exact statistical methods on the basis of real temperature measurements. Secondly, the identified boundary conditions would be very precise since its value is calculated based on temperatures, which appear already as a product of all heat transfer between coolant and air.
Heat Transfer and Thermal Pattern in Two-Phase Flow
Authors: Hetsroni G. , Mosyak A. , Rozenblit R. , Yarin L. P.
Published: January 2022

This study deals with heat transfer in vertical, horizontal, and inclined tubes with water-air mixture flowing in them. We obtain and analyze a thermal pattern on the heated wall, which makes it possible to establish the connection between the flow parameters and heat transfer. The experimental technique is based on the infrared thermography of an electrically heated wall of the tube, providing both visualization of the temperature field and measurements of the local wall temperature. We consider first the results concerning a horizontal tube only. These results serve as a reference basis for the studies on inclined and vertical tubes. The heat transfer coefficient in inclined tubes is drastically enhanced, as compared to that in a horizontal one. In a vertical tube, it is observed that the streaky thermal pattern on the wall is destroyed by the bubbles. This pattern was partially recovered with slug flow. The heat transfer coefficient was observed to increase substantially.
Symbol Statistics: A New Tool for Understanding Multiphase Flow Phenomena
Authors: Daw C. S. , Finney C. E. A. , Nguyen K. , Halow J. S.
Published: January 2022

We discuss data symbolization as a tool for identifying temporal patterns in complex measurement signals. We describe the basic concepts involved and illustrate their application for the analysis of gas-bubble injection data. Specific issues addressed include selection of symbolization parameters, construction of symbol-sequence histograms, and statistical characterization and comparison of these histograms. We demonstrate that symbol-sequence statistics can reveal unique information about deterministic patterns. Such information may be useful for developing flow diagnostics and comparing computational models with experiments.
Observations on Chaos in Upward Gas-Liquid Flow
Authors: Langford Heather M. , Beasley Donald E. , Ochterbeck Jay M.
Published: January 2022

In the present investigation, statistical and chaos analysis techniques were implemented to evaluate pressure dynamics in air-water, vertical pipe flow. The purpose of the analysis is to relate the statistical and chaos measures to the flow physics. Pressure measurements were achieved in a 22 mm ID aluminum and quartz tubing test section. Four water superficial velocities (0.0055, 0.055, 0.165 and 0.329 m/s) were examined for a range of air superficial velocities. Detailed statistical and chaos results are presented for signals representing slug flow, churn flow, and annular flow. Statistical analyses included qualitative evaluation of the shape of histograms, calculation of normalized statistical moments, and implementation of a nonlinearity test. Kolmogorov entropy and attractor dimension estimates (maximum-likelihood correlation dimension and correlation dimension) comprised the chaos analysis measures. The non-integer values of maximum-likelihood correlation dimension and correlation dimension are consistent with chaotic systems. Additionally, the positive, non-infinite values of Kolmogorov entropy, ranging from 5 to 107 bits/s, provide further evidence of the chaotic nature of the air-water vertical upflow.
Application of Capacitance Sensors for Monitoring Oil-Water Separation Processes
Authors: Jaworski Artur J. , Dyakowski Tomasz , Davies Graham A.
Published: January 2022

This paper describes the construction and experimental evaluation of a novel capacitance based instrument for monitoring oil-water separation processes. The electronic circuitry to measure the electrical capacitance, originally developed by UMIST for tomographic applications, is based on the charge-discharge principle. The evaluation of the developed system took place in the existing transparent oil-water separator in the Pilot Plant facility at UMIST. During the experiments, the dynamic behaviour of the multiphase flow within the packed bed of inclined separator plates has been monitored in-situ and on-line for various total flow rates as well as varying oil/water ratios in the mixture. The applied capacitance sensor enabled the measurement of the thickness of oil and water layers along the length of the separator plates as well as the emulsion phase, which is a critical parameter from the viewpoint of the separator’s efficiency.
Radial Profiles of Local Solids Distribution in a High-Loaded Riser-Reactor Measured With X-Ray Computed Tomography
Authors: Wirth K.-E. , Grassler T.
Published: January 2022

Since years high-loaded riser-reactors have been used successfully for different commercial applications, e.g. for fluid catalytic cracking. The fundamental study of hydrodynamics of such reactors will help to improve the design and operating conditions of existing plants and may lead to higher conversion rates and selectivity. The solids concentration distribution of a riser with an inner diameter of 0.19 m and 15 m height is investigated with x-ray computed tomography with a minimum spatial resolution of 0.2 mm and 0.4 mm thickness. A number of experiments have been carried out with narrowly size distributed glass beads between 50 and 70 μm at superficial gas velocities from 2 to 7 m/s. Even at higher circulation rates obtained radial solids concentration profiles still show a typical core-annulus structure, which gets more uniform at higher elevations.
An Homogenization Method for Solid-Liquid Phase Change During Directional Solidification
Authors: Ganaoui M. El , Bontoux P.
Published: January 2022

Homogeneous formulation for Navier-Stokes and energy equations is extended to the directional solidification problems. The solid-liquid mixture is represented as a single continuous medium. A two-phase intermediate zone modelled as a porous medium is involved. A finite volume approximation is used with a fixed mesh. The technique is validated with respect to an interface tracking method. The applications concern the interaction of steady and oscillatory melts with the interface during Bridgman crystal growth. The amplification of oscillatory instability in the melt is studied in the case of inverted Bridgman configuration (heated from bellow). Various solutions (steady symmetric and asymmetric, time-periodic, aperiodic ...) are analyzed.
Non-Intrusive Heat Transfer Coefficient Determination in Highly Porous Metal/Ceramic Foams
Authors: Jones Stanley , Catton Ivan
Published: January 2022

An experimental program has been developed by which one may non-intrusively measure the heat transfer coefficient of highly porous metal/ceramic foams. Under steady one-dimensional flow conditions, the solid phase is subjected to a step change in heat generation rate via induction heating. By measurement of the gas phase temperature response, one may determine the heat transfer coefficient based upon the volume-averaged equations for gas and solid phase energy. These equations are developed and solved numerically to determine the heat transfer coefficient from the gas phase temperature response.

The media in question is a highly porous (0.75–0.90) reticulated structure that, due to small gas pathways (25–160 pores per linear inch) and narrow solid ligaments, makes direct temperature measurement impractical, intrusive and inaccurate. Not only does this technique alleviate the need for complicated gas and solid phase temperature measurements, the heat generation rate does not require determination. Therefore, at no point is the fluid/solid porous media interaction disturbed by the presence of temperature sensors and the experimentalist avoids the calibration difficulty of an inductively-coupled, sample specific, heat generation system.
Non-Intrusive, Spatially Resolved Temperature Measurements Using Coherent Anti-Stokes Raman Spectroscopy (CARS)
Authors: Kearney Sean P. , Lucht Robert P. , Jacobi Anthony M.
Published: January 2022

This paper describes the use of a dual-broadband, pure-rotational coherent anti-Stokes Raman spectroscopy (CARS) technique for non-intrusive, spatially resolved temperature measurements in convective-heat-transfer boundary layers. CARS is an optical, laser diagnostic technique that has often been used for temperature and species concentration measurements in high-temperature combustion applications. This work is one of the first applications of CARS to convective heat transfer. The basics of the CARS technique are discussed and the method is compared to other temperature measurement techniques used in convective-heat-transfer work. Dual-broadband, pure-rotational CARS was used to measure mean temperature profiles in a low-Reynolds-number, turbulent boundary layer. Shot-averaged temperature data were acquired as close as 50 μm (±25 μm) to the wall, with a spatial resolution of 50 μm normal to the heat transfer surface, and a precision limit of ±4 K. Results, presented for three representative Reynolds numbers, display good agreement with the thermal law of the wall for zero-pressure-gradient flows.
MRI Model Generation and Inverse Tumor Temperature, Vascular Flow and Perfusion Estimation During Hyperthermia Using a Computational Steering Tool: SCIRun
Authors: Shelkey J. D. , Luke E. J. , Weinstein D. , Roemer R. B. , Clegg S. , Johnson C.
Published: January 2022

SCIRun (Johnson and Roemer, 1997), a general framework for computational steering, is currently being modified to become a universally applicable and flexible package for simulating hyperthermia treatments. This package will integrate a highly interactive user interface with the following five modular programs: 1) the creation of a finite element mesh of either patient anatomies from medical imaging procedures or idealized anatomies from computational theoretical geometries; 2) the creation of a power deposition model applied to the FE mesh; 3) the solution of the resulting system of equations for the tissue temperatures; 4) the use of inverse techniques to estimate unknown parameters of the governing equation and 5) the visualization of the resulting solution. The first application of this package will be to investigate the hypothesis that pretreatment MR perfusion distribution measurements can be scaled to accurately simulate hyperthermia treatment temperatures using Pennes bio heat transfer equation (Pennes, 1948).
Model for Ultrasonic Heating of Chest Wall Recurrences
Authors: Moros Eduardo G. , Fan Xiaobing
Published: January 2022

Ultrasonic and biothermal numerical models for a simplified 3D chest wall anatomy were developed for a more accurate analysis of power deposition patterns and resulting temperature distributions during hyperthermic therapy of recurrent breast cancer. Four different media were considered: water, muscle tissue, bone tissue (ribs and cartilage), and lung tissue. Results are presented for planar insonation at normal incidence in a typical chest wall section at 1.0 and 3.5 MHz; frequencies that are routinely used clinically. Transient profiles show that the initial rate of temperature rise in bone tissue is much larger than in muscle tissue; however, the temperature difference between these two media decays after the first two minutes of insonation. Steady state results showed that the highest temperatures were induced at the soft tissue-bone interfaces and inside the bone tissue at 1.0 MHz, while at 3.5 MHz these were located in the muscle tissue a few mm in front of the bone. Strategies for treatment planning and optimization are discussed.
Effect of Fluid-Mechanical and Chemical Environments on Cell Function and Tissue Growth: Experimental and Modeling Studies
Authors: Neitzel G. Paul , Nerem Robert M. , Sambanis Athanassios , Smith Marc K. , Wick Timothy M. , Brown Jason B. , Hunter Christopher , Jovanovic Ivana , Malaviya Prasanna , Saini Sunil , Tan Sanda
Published: January 2022

Bioreactors are widely used for the growth and maintenance of tissue-engineered constructs. In this paper, we report on work directed toward a better understanding of the chemical and fluid-mechanical environments that are needed to enhance cell function and tissue growth in bioreactors. We have conducted cell-growth studies in well-controlled flow conditions that indicate the effect of shear stress and oxygen tension on cellular function. In more complicated bioreactors, like the NASA rotating-wall vessel bioreactor, we have done experimental and numerical fluid-mechanical studies that quantify the velocity and shear-rate fields near a three-dimensional construct suspended by the flow inside the bioreactor. All of these results will be used to develop the tools needed to properly design and operate bioreactors for the optimal growth of tissue substitutes.
Effects of Fluid Dynamics and Mass Transfer on Cell Migration and Growth in Confined Geometry
Authors: Peng Ching-An
Published: January 2022

We consider a mathematical model of the physical and biological processes involved in the bioreactors for cultivating tissues. In a laminar flow duct bioreactor, the Navier-Stokes and convective-diffusion equations are solved to obtain the concentration distribution of chemoattractant secreted from the stromal cells. Then, it is concoitmently used to solve the proposed chemotactic model and stem cell growth kinetics. The simulation results elucidate the spatio-temporal distribution of cells is governed by the interaction of cell chemotactic migration and cell mitosis. A dimensionless number that balances these two effects predicts the extent of non-uniformity in duct chambers. That is, if the directed cell migration rate is much larger than the cell growth rate, the cells will have enough time to move toward the side walls and proliferate rapidly causing prominent non-uniform growth. On the contrary, if the directed cell migration rate is much smaller than the cell growth rate, the cell growth on the cell bed is in comparison more uniform.