With the advent and development of precision machining and manufacturing, the necessity to ensure quality of the produced parts for their longevity has grown as fast the advances in technology. One of the ways of achieving higher product lives has been through tighter tolerances on size and form characteristics. Thus, it is imperative that designers, manufacturers and quality inspectors understand the mathematical principles guiding these dimensional and form characteristics, and further utilize them, to the greatest degree possible, in the inspection equipment and tooling. One of the greatest benefits to mankind was the invention of wheel. It is inarguably evident how much of our lives depend on machines with rotating parts. From power stations to power tools, from the smallest watch to the largest car, all contain round components. In precision machining of cylindrical parts, the measurement and evaluation of roundness (also called circularity in ASME Geometric Dimensioning & Tolerancing, GD&T Y14.5) is an indispensable component to quantify form tolerance. Based on reference circles, this paper focuses on the four modeling methods of roundness. These are (1) Least Squares Circle (LSC), (2) Maximum Inscribed Circle (MICI), (3) Minimum Circumscribed Circle (MCCI) and (4) Minimum Zone or Minimum Radial Separation Circles. These methods have been explained in the context of their implications on design applications, advantages and disadvantages. This article also explores how these multitudes of parameters are to be understood and be incorporated into undergraduate engineering curriculum, and be taught as an improved toolkit to the aspiring engineers, process engineers and quality control professionals.

The automotive industry is one of the fastest growing industries worldwide with millions of vehicle productions and sales every year globally. Some of the vehicles have their engines in rear end, which means there is no incoming airflow from the front and the engine cannot cool down efficiently. The main aim of the research is to study the flow behavior for a duct that can detour the incoming air to the radiator for vehicles those have their engines located at the back. The duct collects the incoming air from the front of the vehicle and detour it to the engine located at the back. This helps in cooling down the engine in order to protect it from being overheated. The research is conducted to understand the detailed parameters to be accounted for while designing such a prototype. It is important to understand the essence of a cooling effect as the efficiency of the vehicle engine can only be maintained under a stable temperature. The research is important as it can be applied to diverse engineering problems. There are three cases for the experiment, each with different lengths. However, the inlet and outlet have identical dimensions for all three cases. There is a certain scale factor used to scale down the dimensions from a previously studied CAD model. These scaled down dimensions are then utilized to fabricate the prototype. Once the model has been constructed, a mesh is located at the outlet, which helps recording velocity magnitude and direction at each of the respective node of the mesh. One of the key elements of the research is to extensively understand the type of flow at different points of the duct and how they affect the efficiency of the design. For example, the curved parts where channels are installed along the length of the duct experience turbulent air flow. Hence, it is important to understand the influence of these flows on the efficiency of the design.

The design of a novel micro-propulsion system for small satellites of the nano-satellites class (1–10kg) that is low-cost, non-toxic, non-flammable, and no-pressurized at launch conditions is currently being developed at the University of Arkansas. The goal of the present micro-propulsion system is to achieve milli-Newton thrust levels with specific impulses on the order of 100s. The proposed propellant is the water-propylene glycol. However, little data is available for its fluid and thermal characteristics at the gaseous state, nor the evolution of similar mixtures through micro/nano-channels. This paper will present experimental methods of measuring the mass flow rate of the water-glycol mixtures through micro/nano-channels. A MEMS fluidic chamber fabricated with a nano-channel is used to quantify the mass flow through optical tracking of liquid interfaces confined in the chamber. The dimensions of the channels are designed with the purpose to act as a passive throttling valve that prevent liquid-phase fluids from entering into the nozzle in order to achieve a simple water-based cold-gas propulsion system.

Breastfeeding provides both nutrients and immunities necessary for infant growth. Understanding the biomechanics of breastfeeding requires capturing both positive and negative pressures exerted by infants on the breast. This clinical experimental work utilizes thin, flexible pressure sensors to capture the positive oral pressures of 7 mother-infant dyads during breastfeeding while simultaneously measuring vacuum pressures and imaging of the infants oral cavity movement via ultrasound. Methods for denoising signals and evaluating ultrasound images are discussed. Changes and deformations on the nipple are evaluated. The results reveal that pressure from the infant’s maxilla and mandible are evenly distributed in an oscillatory pattern corresponding to the vacuum pressure patterns. Variations in nipple dimensions are considerably smaller than variations in either pressure but the ultrasound shows positive pressure dominates structural changes during breastfeeding. Clinical implications for infant-led milk expression and data processing are discussed.

We consider modeling of single phase fluid flow in heterogeneous porous media governed by elliptic partial differential equations (PDEs) with random field coefficients. Our target application is biotransport in tumors with uncertain heterogeneous material properties. We numerically explore dimension reduction of the input parameter and model output. In the present work, the permeability field is modeled as a log-Gaussian random field, and its covariance function is specified. Uncertainties in permeability are then propagated into the pressure field through the elliptic PDE governing porous media flow. The covariance matrix of pressure is constructed via Monte Carlo sampling. The truncated Karhunen–Loève (KL) expansion technique is used to decompose the log-permeability field, as well as the random pressure field resulting from random permeability. We find that although very high-dimensional representation is needed to recover the permeability field when the correlation length is small, the pressure field is not sensitive to high-oder KL terms of input parameter, and itself can be modeled using a low-dimensional model. Thus a low-rank representation of the pressure field in a low-dimensional parameter space is constructed using the truncated KL expansion technique.

As it has been shown previously, the blood flow in the heart and the main vessels is a self-organizing tornado-like flow of a viscous fluid, exhaustively described by the particular solution of nonstationary hydrodynamic equations coined in 1986. This solution is implemented in a local dynamic cylindrical coordinate system, which origin moves with the flow. Streamlines of these flows are characterized with an axial symmetry and determine certain restrictions to the geometry of the flow channels. It has been proved, that the experimentally measured orientations of intraventricular trabeculae and dynamic geometric characteristics of the aortic flow channel during the cardiac cycle satisfy the conditions for the self-organization of tornado-like blood flow. This enables to obtain relative estimates of the flow parameters using the geometric characteristics of the flow channel. For this, a set of experimentally measured quasi-invariant anatomical marks was used, which static and dynamic parameters are utterly determined by the structure of the dominant blood jet. Such marks are the position of the embouchures of pulmonary veins and the left atrium auricle, the directions of the trabecular profile on the left ventricle streamlined surface, the dynamic geometry of the mitral and aortic valves, the length and radial elasticity of the aorta, etc. These marks allow a formal localization of the dynamic coordinate system position of a swirling blood flow in the investigated part of the cardiovascular channel and more accurate estimation of the jet structural parameters evolution. Basing on these parameters, a consistent theory of the initiation and evolution of swirling blood jet in the flow channel beginning from the left atrium to the aorta and its main branches has been proposed. The result of the study is a concept, integrating the measured characteristics of the heart and the aorta flow channel (dynamic dimensions, elasticity) and the structural parameters of swirling blood flow. It was shown that flow channel pathological changes significantly affect the flow structure.

The present in vitro study aims at comparing the ablation volume obtained with commercially available RITA’s StarBurst ® XL (dry type) and StarBurst ® Xli-e (wet type) multi-tine electrodes during radiofrequency ablation (RFA) procedure. The experiments have been conducted on polyacrylamide based tissue-mimicking phantom gel whose thermo-electric properties are similar to that of the soft tissues. A temperature-controlled RFA has been performed utilizing AngioDynamics RITA 1500X ® radiofrequency generator. The maximal longitudinal and maximal transverse dimensions of the coagulated phantom gels have been measured from which the derived ablation volume has been calculated. Further, the temperature distribution and power delivered with the dry type and wet type electrodes have been compared. The in vitro study revealed that the efficacy of wet type electrode is more pronounced as compared to the dry type electrode. Moreover, it has been found that both the electrodes are capable enough of producing ablation volume up to 5 cm in diameter.

Deterioration of environment caused by the release of harmful greenhouse gases (mainly CO 2 ) from the power plants has become an area of growing concern. At the present, various methods are being investigated for capturing and storing CO 2 . Current technologies require a huge amount of energy leading to reduction in overall efficiency. The introduction of Allam cycle, which uses high pressurized super critical CO 2 as working fluid has added a new dimension to solve this problem. This is an innovative oxy-fuel power cycle which ensures a near zero emission through inherent capture of all CO 2 . This paper concentrates on performance modeling of an Allam cycle. The effects of various input parameters are analyzed for achieving highest efficiency. Performance of each component in the cycle is investigated separately and combined therefore to get the overall performance of the cycle. The impact of using an ASU without intercooling and then supplying the high temperature outlet gases except oxygen to the recuperator is investigated. Although, a high power is consumed within ASU, the overall energy requirement decreases as extra energy becomes available in the recuperator to preheat the recycled CO 2 . An efficiency of 55% is predicted for the cycle.

The Stirling engine is a high efficiency and high reliability energy converter which is expected to be a solution for future space power generation and commercial applications. One of the key components in a Stirling engine, to keep high efficiency, is the regenerator. Currently, woven screens or random fibers are mostly used as the regenerator material. However, since both woven screen and random fiber regenerators are composed of wires, the flow across the wires is similar to cylinders in cross flows. As a result, flow separation occurs and the regenerator results in high friction losses and thermal dispersion. In the previous study, a robust foil type regenerator is designed and CFD analysis of the regenerator was conducted to predict the friction coefficient and the thermal efficiency under oscillating flow conditions. In this research, a regenerator test bench was designed and constructed to investigate the friction coefficient and thermal efficiency of the regenerator. The experiment conditions are decided based on the one-dimension thermodynamic modeling software SAGE. The experiment result shows that the friction coefficient of the experiment is close to CFD prediction at high Reynolds number.

While driving a FCV during acceleration, many sorts of sounds could be heard, which influence the interior sound quality. A typical FCV is taken as a sample, four interior noises generated under the acceleration operation are collected in the whole vehicle semi-anechoic chamber, and the noise sample database of diesel engine radiation noise is established after preprocessing. Based on sound quality theory (physical and psychoacoustic features), the Kernel Principal Component Analysis (KPCA) is used to extract the key objective features mainly influencing the sound quality, which realize the dimension reduction target; the variations of objective features are analyzed to qualitatively analyze the law of the sound quality varying during acceleration. According to the objective evaluation of FCV interior sound quality, combining with FCV operating parameters, the influencing law of the FCV sound quality could be obtained.

Previous efforts to model the effectiveness of heat input and extraction from a thermal storage unit have generally been based on the definition of a constant conductance of heat from the working fluid to the phase change storage material. In order to capture the effects of changing thermal resistance between the working fluid and melt front location, this paper presents a method using a resistor network analogy to account for thermal conductance as a function of melt fraction. This expression for thermal conductance is then implemented in an existing numerical framework. Results are validated by comparing calculations for a single unit cell using a quasi-steady Stefan problem approach, a finite difference scheme, and more general form solutions from literature. The variable approach is then compared with an average value for overall thermal conductivity, U, to characterize the performance of a thermal energy storage unit consisting of a series of these unit cells. Overall effectiveness in the thermal energy storage device is found to be within 0.6% agreement when comparing these methods, though local percent deviation can be as high as 113%. Depending on the needed accuracy and use case for such a numerical framework, suggestions are provided on whether an average value for U is sufficient for characterizing such a thermal energy storage device. Discussion is also provided on the flexibility of the computation schemes described by testing the sensitivity of the results via changes in dimension-less input parameters.

In recent years it has been discovered that besides non-uniform flow excitation such as from stator wakes; acoustic pressure pulsation can be a concern, especially for high pressure centrifugal compressor impellers. This has been termed “triple coincidence” and explains rare failures and likely a reason, at least partially, for some previous undocumented failures. Bladed disk interaction resonance discovered by the author in the mid 1970’s can be avoided such as for centrifugal impellers as needed, depending on vibratory mode involved, available damping, and potential excitation level. Especially for stages having vanes in the diffuser near impeller tips, concern for high cycle fatigue is very high as certain numbers of vanes combined with number of rotating blades can give correct phase to excite a highly responding mode. Intentional mistuning of disk-dominated modes has potential for reducing response. A similar but more complex interaction is with transverse acoustic modes having a specific number of nodal diameters. In this case acoustic gas modes in cavities at sides of impellers can match rotating acoustic pulsations at BPF (blade passing frequency) and/or harmonics, termed Tyler-Sofrin modes with increased noise. Also acoustic mode matching impeller structural mode can give the triple coincidence causing resonant response of the impeller. The concern for this coincidence is often difficult to evaluate. For some cases, calculations give enough evidence to modify number of vanes or blades to correct a possible cause of a fatigue failure. This coincidence can add to the direct response, e.g. from either upstream wakes or downstream diffuser vane interacting “potential flow” excitation, herein termed “quadruple coincidence resonance”. Dimensions of impeller side cavities are axisymmetric and are set by aerodynamics, so that outer and inner radii define transverse modes with small radial dimensional changes available. Often a minor aerodynamic performance compromise can be used to change designs to avoid serious resonances, e.g. revise numbers of vanes and/or blades, avoid the response of a matching diameter mode or have a different less responsive mode to alleviate concern. Besides turbomachinery e.g. compressors and pumps, some other methods as described could be utilized for any cavity that has diametrical mode shapes, or possibly other patterns for pressure pulsation frequencies. These modification(s), including patent-pending method, PCT/US2018/020880 described herein can alleviate if not eliminate concern for any mechanism having structural vibration excitation and/or environmental noise issues.

Stiffened panels are commonly used in aircraft structures in order to resist high compression and shear forces with minimum total weight. Minimization of the weight is obtained by combining the optimum design parameters. The panel length, the stringer spacing, the skin thickness, the stringer section type and the stringer dimensions are some of the critical parameters which affect the global buckling allowable of the stiffened panel. The aim of this study is to develop a design tool and carry out a geometric optimization for panels having a large number of stringers. The panel length and the applied compression-shear loads are assumed to be given. In the preliminary part, a simplified panel with minimized number of stringers is found. This panel gives the same equivalent critical buckling load of panels having larger number of stringers. Additionally, the boundary conditions to be substituted for the outer stringer lines are studied. Then the effect of some critical design parameters on the buckling behavior is investigated. In the second phase, approximately six thousand finite element (FE) models are created and analyzed in ABAQUS FE program with the help of a script written in Phyton language. The script changes the parametric design variables and analyzes each skin-stringer model, and collect the buckling analysis results. These design variables and analysis results are grouped together in order to create an artificial neural network (ANN) in MATLAB NNTOOL toolbox. This process allows faster determination of buckling analysis results than the traditional FE analyses.

This study outlines the design and optimization processes for the development of a multipurpose urban firefighting and disaster relief unmanned aerial vehicle (UAV). The design strives to attack and suppress fires that occur in high rise structures at heights greater than can be reached by ladder truck. The design also strives to deliver a payload of disaster relief supplies to affected areas, reducing risk to ground transport efforts. The study outlines the design and optimization of design components utilizing SolidWorks and testing of these components using SolidWorks Simulation and Flow Simulation packages. This study details the development of the final propeller and frame design, and the range of tests performed within SolidWorks to ensure the design can perform to the required standards. Given the dimensional advantages and torque cancellation capabilities a coaxial octocopter frame is developed. In designing and testing a propeller the proposed design is capable of producing a maximum thrust of 118 lbf. with a minimum factor of safety of 2.238. The propeller spacings are optimized to produce maximum thrust in both the coaxial and in-plane directions which are 23.6 inches and 25.6 inches respectively. For urban firefighting the selected hose and nozzle combination are capable of supplying 60 GPM of water at a height of 150 ft. from the ground. At this loading the minimum factors of safety of the frame and propeller are determined to be 2.238 and 3.034 respectively. The corresponding fatigue lives under prescribed number of cycles are determined to be infinite for both frame and propeller. Using rotorcraft theory, the theoretical hover time that the UAV can maintain in firefighting is determined to be 1.7 hours. Using a combination of SolidWorks Flow Simulation and aerodynamics theory the maximum velocity of the UAV at a pitch of 30 degrees from vertical, hauling a box with dimensions capable of carrying 200 lbs. of relief goods, is determined to be 85 mph. At disaster relief payload capacity the designed frame and propeller are capable of maintaining factors of safety of 3.226 and 3.034 respectively. These factors of safety correlate to fatigue lives of the frame and propeller of 15.98 years and 19.12 years respectively, under prescribed loading. The theoretical flight time the UAV can maintain for disaster relief is determined to be 1.618 hours. This study provides optimized propeller and frame designs along with selections of engines and other important components for building a multipurpose UAV.

Due to high stiffness/weight ratio, composite materials are widely used in aerospace applications such as motor case of rockets which can be regarded as a pressure vessel. The most commonly used method to manufacture the pressure vessels is the wet filament winding. However, the mechanical performance of a filament wound pressure vessel directly depends on the manufacturing process, manufacturing site environmental condition and material properties of matrix and fiber. The designed ideal pressure vessel may not be manufactured because of the mentioned issues. Therefore, manufacturing of filament wound composite structures are based on manufacturing experience and experiment. In this study, the effect of layer-by-layer thickness and fiber volume fraction variation due to manufacturing process on the mechanical performance was investigated for filament wound pressure vessel with unequal dome openings. First, the finite element model was created for designed thickness dimensions and constant material properties for all layers. Then, the model was updated. The updated finite element model considered the layer-by-layer thickness and fiber volume fraction variation. Effects of the thickness and fiber volume fraction on the stress distribution along the motor axial direction were shown. Also hydrostatic pressurization test was performed to verify finite element analysis in terms of fiber direction strain through the motor case outer surface. Important aspects of analyzing a filament wound pressure vessel were addressed for designers.

In the Suspended ThermoReflectance (STR) technique a microcantilever is heated with a laser power at the free end of the microcantilever and as heat propagates through it, another laser is used to measure the temperature along the beam.[1] In this paper, the heat equation is solved for two-dimensional heat flow in the microcantilever to determine the material’s thermal conductivity and heat capacity. Two of the dimensions of the microcantilever, width and length, are significantly greater than the third dimension, the thickness, leading to the two-dimensional approximation. Two boundaries along the length of the structure and one boundary along the width are assumed to be under Dirichlet boundary conditions, while the other boundary has Neumann condition. The Neumann or flux condition has a Gaussian profile due to the nature of laser beam intensity. The heat equation is solved using under 3 different flux conditions: (1) Steady-state, (2) Transient, and (3) Periodic. A steady-state condition mimics the experimental condition when a continuous wave laser is used to heat the microcantilever’s tip. A transient condition is possible when quickly removing or adding the continuous wave laser’s flux from the microcantilever’s tip using a chopper. Finally, a periodic condition can be achieved when an electro-optic modulator is utilized experimentally. Closed form analytical expressions are evaluated against the finite element model and experimental results for microcantilever beams and micro-structures of Si that have lengths on the order of a mm, width on the order of 100 microns, and thicknesses of 1 micron or less.

Porous media like open celled metal foams inherently provide a high heat transfer area per unit volume due to their interconnected cellular structure and are lightweight. High pore density metal foam because of its small overall dimensions and micro feature size shows promise in thermal packaging of compact electronics. An experimental study was carried out to evaluate thermal performance of high porosity (95%) and high pore density (90 PPI) copper foam of size 20 mm × 20 mm × 3 mm in buoyancy induced flow conditions and compared with a baseline smooth surface. The enhanced surface showed about 15% enhancement in average heat transfer coefficient over the baseline case. To optimize the performance further, the foam sample was cut into strips of 20 mm × 5 mm × 3 mm and attached symmetrically on the central 20 mm 2 base surface area with inter-spacing of 2.5 mm. This new configuration led to further 15% enhancement in heat transfer even with 25% lesser heat transfer area. This is significant as heat transfer is seen as a strong function of permeability to flow through the structure over heat conduction through it. To test this hypothesis, a third configuration was tested in which the strips were further cut into blocks of 4 mm × 4 mm × 3 mm and attached in a 3 × 3 array on to the base surface. Here, only 36% of the central 20 mm 2 base surface area was covered with foam. The heat transfer performance was found to be within ± 10% of the initial metal foam configuration, thereby, supporting the hypothesis. Performance was seen to decrease with increase in inclination from 0° to 30° to 90° with respect to the vertical.

Meeting the stringent requirements on fuel economy and emissions is still a challenge for automotive original equipment manufacturers (OEMs). In this study, we consider the light weighting opportunities of a heavy commercial truck by evaluating the various requirements of its anti-roll bar. First, an MSC.ADAMS model of the truck is analyzed under some standard vehicle dynamics maneuvers and a target for the anti-roll bar is set. A topology optimization study is then performed using Solid Isotropic Material with Penalization (SIMP) method to determine its dimensions and material to meet this target. For this purpose, a finite element (FE) model of the anti-roll bar is developed in order to determine its torsional stiffness using MSC.Nastran commercial software. The advantages and disadvantages of various optimization results are discussed. Finally, fatigue performance of the anti-roll bar is assessed under the road load data coming from various road simulations. The results prove that the simulation tools and optimization methods offer great capabilities to meet challenging requirements of automotive industry.

Magnetic levitation (maglev) concepts are applied to a variety of industries such as the automotive, aerospace, or energy in order to accomplish different tasks: suspension and propulsion in maglev trains, rocket propulsion and spacecraft attitude control, centrifuge of nuclear reactors. In this paper, maglev is implemented in environmentally friendly hydrokinetic energy harvesting to achieve contactless bearing, thus, minimizing friction and improving efficiency. Generally, maglev systems exhibit higher efficiency and reduced maintenance while providing longer lifetime and higher durability when appropriate engineering design and control are applied. A Flow Induced Oscillation (FIO) energy-harvesting converter is considered in this work. To minimize friction in the support of the cylinder in FIO (vortex induced vibrations and galloping) due to high hydrodynamic drag, a maglev system is proposed. In the proposed configuration, a ferromagnetic core (element 1), of known dimensions, is considered under the effects of an externally imposed magnetic field. A second ferromagnetic element, of smaller dimensions, is then placed adjacent to the previous considered core. This particular configuration results in a non-homogenous magnetic field for element 1, caused by dimensional disparity. Specifically, the magnetic flux does not follow a linear path from the ferromagnetic core to element 2. A general electromagnetic analysis is conducted to derive an analytical form for the magnetic field of element 1. Subsequent numerical simulation validates the obtained formula. This distinct expression for the magnetic field is valuable towards calculating the magnetic energy of this specific configuration, which is essential to the design of the FIO energy harvesting converter considered in this work.

There are different types of uncertainty sources in the Complex System Thermal-Hydraulics Codes calculations resulting in inaccurate computations. The sources include boundary and initial condition, model structure, their corresponding parameters, user inputs, the numerical techniques and the errors in the validation test data. Regarding the codes structure, the uncertainty sources are utilization of simplified mathematical models expressing conservation laws, thermodynamics laws, state equations applicability, discretization of governing equations, and physical characteristics of the simulated system. The Edwards high-pressure test tube is a well-known test for verifying the results of simulating complex numerical codes. On the other hand, the existence of deterministic values in the initial, boundary conditions and geometric dimensions can challenge the results of this experiment. In this study, a probabilistic approach is utilized to study the behavior of the Edwards High-Pressure pipe using RELAP5 Complex System Thermal-Hydraulics Code. A probabilistic distribution is estimated with appropriate accuracy for the experiment uncertainties. An efficient approach consisting of Wilks sampling method is implemented to quantify the uncertainty of experimental results.