bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dimension Reduction of Singular Perturbation Problems of Spinning Rectangular Beams
Authors: Lee K. H. , Ong E. H. 
Published: January 2022

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.