Variable Cross-sectional Area Research Articles

Systematic oil flow modeling in the Quasi-3D approximation yields additional terms that allows for variable cross-section area tubing

A systematic model development for oil flow in quasi-3D (1D + 2D) is presented. Our approach provides a unified modeling scheme. Besides, additional terms are obtained, which allows for tubing area variation along the flow direction. The area variation can be modeled as analytic function or random fluctuation, as it could be the result of deposits or tubing internal surface roughness. The proposed approach can be used to obtain analytic solutions which provide physical insight into the phenomena under scrutiny, including the validation of software tools, sensor development and sensor placement. One starts from conservation laws as given by kinetic theory and applies the transverse averaging technique (TAT) to extract the one-dimensional approximation in formal grounds. To demonstrate its application, the steady-state Ramey's model, the Hasan's transient model and a simple two-phase model are generated from the obtained equations.

Thermal rectification enhancement of bi-segment thermal rectifier based on stress induced interface thermal contact resistance

Thermal rectification is the phenomenon that heat flows much easier from forward direction than reverse direction across the structure. Materials with temperature-dependent thermal conductivity and/or variable cross section area segments are always adopted to utilize obvious thermal rectification effect. Previous studies often ignored the effect of thermal contact resistance between the two segments of traditional bi-segment thermal rectifier. Since interface thermal contact resistance also contributes significantly to the total effective thermal conductivity of the rectifier, the present paper proposed a finite element scheme to simulate the thermomechanical coupling problem caused by the stress-dependent thermal contact resistance. The proposed method is verified and validated with analytical and experimental examples respectively, and numerical results show the effect of thermal contact resistance on the optimization of thermal rectification ratio. Several key parameters such as the initial gap between the two segments and the thermal contact resistance model parameters are investigated numerically, and the present paper provide a novel approach and design guidance to manipulate heat flux through stress-dependent thermal contact resistance.

Relation between muscle architecture and first metacarpal morphology, and its implications for human hand evolution.

Previous studies have proposed that our ability to produce and use stone tools was the primary selective pressure explaining the evolution of the human hand. Derived traits in humans include a robust first metacarpal and longer thumbs relative to the other fingers. Along with other anatomical peculiarities, humans can exert forceful precision and have powerful grips, and can resist loads during tool production and use. Despite this biomechanical explanation for the morphology of the human hand, limited work has been done on the soft tissue and, therefore, the relationship between the hand bones and the muscles most heavily relied upon during tool-related behaviours still requires thorough investigation. For this purpose, we have dissected 23 forearms and hands of fresh human cadavers of known sex and age at death, and dissected all the muscles attached at the first metacarpal (the first dorsal interosseous, opponens pollicis, and abductor pollicis longus muscles). Variations in physiological cross-sectional area, muscle mass, and fibre length were compared with metacarpal anatomy. In no case bone traits were a significant predictor of muscle features. In contrast, sex and age predicted muscle architecture in several cases, thus substantially affecting the functional analysis based on linear measurements of this bone. The data, therefore, failed to provide a deductive framework for predicting muscle recruitment based on measurements of bone from the fossil record.

Impact of Viscosity Variation, and Flow Rate on Coefficient of Discharge in Venturimeter Utilizing Taguchi Methodology

Most of the industries are concerned with flow measurement and accurate measurement of fluid is important to obtain specific proportion as per process requirement. Generally Venturimeter (VM) is utilized in enterprises due to notable highlights offered by it. VM works on the principle of pressure difference i.e. Bernoulli’s principle. By varying cross sectional area of flow, it creates pressure difference along its length which is used to calculate theoretical discharge. Head loss in VM is less as compared to other flow measuring apparatus. Because of its specific geometry eddies formation is avoided causing less head loss. The coefficient of discharge (Cd ) is an important parameter always referred in case of flow measuring devices. For VM it varies from 0.95 to 0.99. Tests have been performed in accordance to Taguchi L9 O-A on cast iron pipe to examine the impact of variations of viscosity, and rates of flow on the Cd .

Stability of One-Dimensional Steady Flows with Detonation Wave in a Channel of Variable Cross-Sectional Area

The stability of one-dimensional steady flows of an ideal (inviscid and non-heat-conducting) gas in channels of variable cross section with combustion in a structurally stable detonation wave is studied. The detonation wave represents a discontinuity surface propagating normally to the axis of the channel. It was previously established that, in this formulation, steady flows with combustion in a Chapman–Jouguet detonation wave are always unstable, in contrast to combustion flows in an overcompressed detonation wave. The stability analysis of such flows is reduced to the numerical solution of an initial-boundary value problem describing the evolution of finite flow perturbations between the moving detonation wave and the minimal nozzle cross section (in the case of a sudden contraction) or the exit nozzle cross section. The problem is solved by applying a modified Godunov scheme of higher order accuracy. More specifically, a Riemann solver with switching (between the overcompressed and Chapman–Jouguet detonation waves) with an explicitly represented detonation wave is created. Examples of stable flows and flows collapsing due to large initial perturbations are given, and their dynamics with transitions to a Chapman–Jouguet detonation wave and back are computed.

Biologically Inspired Catheter for Endovascular Sensing and Navigation

Minimally invasive treatment of vascular disease demands dynamic navigation through complex blood vessel pathways and accurate placement of an interventional device, which has resulted in increased reliance on fluoroscopic guidance and commensurate radiation exposure to the patient and staff. Here we introduce a guidance system inspired by electric fish that incorporates measurements from a newly designed electrogenic sensory catheter with preoperative imaging to provide continuous feedback to guide vascular procedures without additional contrast injection, radiation, image registration, or external tracking. Electrodes near the catheter tip simultaneously create a weak electric field and measure the impedance, which changes with the internal geometry of the vessel as the catheter advances through the vasculature. The impedance time series is then mapped to a preoperative vessel model to determine the relative position of the catheter within the vessel tree. We present navigation in a synthetic vessel tree based on our mapping technique. Experiments in a porcine model demonstrated the sensor’s ability to detect cross-sectional area variation in vivo. These initial results demonstrate the capability and potential of this novel bioimpedance-based navigation technology as a non-fluoroscopic technique to augment existing imaging methods.

In Memoriam: Professor Ephraim Maurice Sparrow

In Memoriam: Professor Ephraim Maurice Sparrow

Multi-objective optimization of orthogonal TLCDs for reducing fatigue and extreme loads of a floating offshore wind turbine

Floating offshore wind turbines have substantial potential to harness energy in deep-water locations, however, compared to fixed-bottom offshore wind turbines, they also have more complicated dynamic behavior that may lead to larger structural loads. In this paper, structural control using tuned liquid column dampers (TLCDs) is applied to a tension leg platform type floating offshore wind turbine in order to improve the structural response and reliability of the system. A structural control module in the aero-hydro-servo-elastic wind turbine simulator, FASTv8, is developed that enables the analysis of passive orthogonal tuned liquid column dampers with variable cross-sectional areas. Multi-objective optimization using the nondominated sorting genetic algorithm II is solved to provide an optimal Pareto front that can be used to select designs of the orthogonal TLCDs. With the optimal designs, non-linear fully-coupled time marching simulations are conducted to evaluate the impacts of the orthogonal TLCDs on reducing fatigue and extreme loads. The simulation results demonstrate the effectiveness of the orthogonal TLCDs on reducing the fore-aft and side-to-side fatigue and extreme loadings.

Effects of the heating surface structure of phase change chamber on boiling-condensation coexisting phase change heat transfer

The influences of the heating surface structure of phase change chamber on heat transfer characteristics are studied by using smooth, equal-width and variable cross-sectional area grooved heating surfaces, and visualization is made of the boiling-condensation coexisting phase change phenomena inside the chamber. The experimental results confirm that there is an optimum working fluid filling ratio for the phase change chamber to acquire its best performance. The optimum filling ratio for the smooth and equal-width grooved heating surface phase change chamber is found to be 36.0% and 11.4%, respectively. The experimental results also disclose that the equal-width grooved heating surface has the best performance and the overall heat transfer coefficient of the phase change chamber is augmented by more than 44% over the smooth heating surface. Although the thermal resistance of condensation is the dominant of the overall heat transfer resistance, it is proved that enhancing boiling is still an efficient way due to the strong interactions between the boiling and condensation processes inside the phase change chamber.

Summary of developing a test stand for realistic emulation of the cross-sectional area variation of hot rolled wire

Abstract The development of innovative measuring technology for process optimization in hot rolling mills becomes more and more relevant because of increasing demands on product quality. Measurement technology for high-resolution non-contact cross-sectional area measurement has shown that the variation in cross-sectional area contains information about the rolling process. This information can be used for the development of new measurement devices and analytical methods for process optimization. The harsh environmental conditions and strict safety regulations result in great effort when implementing a new sensor prototype in hot rolling mills. For this reason, this work presents a mechatronic test stand that can simulate the cross-sectional area variation under laboratory conditions realistically.

Joint Effect of the Nonlinearity of Elastic Foundations and the Variation of the Inertia Ratio on Buckling Behavior of Prismatic and Nonprismatic Columns Using a GDQ Method

In this paper, we present a simple, powerful, yet efficient and easily applicable technique based on the GDQ method for solving nonlinear problems. The proposed technique is implemented to some nonlinear engineering problems in structure analysis. The results reveal that the proposed technique is effective. Then, the proposed technique is used to explain the effects of the variation of cross section area on the nondimensional critical buckling loads for columns with and without elastic foundation for three sets of boundary conditions. Finally, the proposed technique is used to investigate the effect of the nonlinearity term of Winkler elastic foundation on the nondimensional critical buckling loads of nonuniform columns resting on elastic foundations. The effectiveness of the proposed technique is validated through comparing the present results with exact solutions and other numerical results available in references. The proposed method benefits the optimum design of columns against buckling in engineering applications. The most important conclusions from this paper can be summarized as follows. When the inertia ratio varies parabolically, the nondimensional critical buckling loads increase in comparison with varying linearly. Moreover, the nondimensional critical buckling loads increase in the presence of the elastic foundation.

Thermal rectification mechanism of one-dimensional composite structure with interface thermal contact resistance

Thermal rectification refers to the phenomenon that heat fluxes or equivalent thermal conductivities are different under the same temperature difference when temperature gradient directions are different. The nature of the thermal rectification is that the structure has different effective thermal conductivities in different directions. Most of previous studies focused on thermal rectification of temperature-dependent thermal conductivity materials or variable cross section area structure, and the effect of thermal contact resistance at the interface was investigated very rarely. In the present paper we present the analytical and finite element numerical solution of temperature field and thermal rectification ratios of a composite structure with variable cross section area and thermal conductivity under different interface thermal contact resistances. The prescribed temperature boundary condition is introduced by penalty method, and the temperature jump condition at the interface is implemented by the definition of thermal contact resistance directly. The nonlinear heat conduction problem caused by temperature-dependent thermal conductivity and interface thermal contact resistance is then solved with a direct iteration scheme. Comparisons between experimental results and the present theoretical and numerical results show the feasibility of the proposed model. Then parameter investigations are also conducted to reveal the effect of some key geometric and material parameters. Numerical results show that thermal contact resistance plays an important role in the temperature field and thermal rectification ratio of the two-segment thermal rectifier. With the increase of the length ratio, thermal ratification ratio increases first and decreases then, and the optimal length ratio varies with both thermal contact resistance and cross-section radius change rate of the two segments. In general, the existence of thermal contact resistance can increase the total thermal resistance of the rectifier and magnify the distinction of the heat flux in forward and reverse cases. However, if the thermal contact resistance is too large, this distinction will decrease and correspondingly the thermal rectification ratio becomes low. With the increase of the boundary temperature difference, thermal rectification ratio increases due to the effect of temperature-dependent thermal conductivity. In the present study, we propose a theoretical and numerical approach to designing and optimizing the length ratio, cross-section radius change rate, thermal conductivity, boundary temperature difference and interface thermal contact resistance to obtain the maximal thermal rectification ratio of a bi-segment thermal rectifier, as well as the manipulation of thermal flux in engineering applications.

Flows of real gas in nozzles with unsteady local energy supply

When gas flows at a high speed in a channel with a variable cross sectional area and high-intensity energy supply, it experiences complicated physical and chemical processes producing high-temperature gas effects. High-temperature gas effects are a key issue related to design and optimization of nozzles of plasmatron of alternating current. The finite volume method is applied to solve unsteady compressible Euler equations with high-temperature gas effects. Solutions of some benchmark test cases are reported, and comparison between computational results of chemically equilibrium and perfect air flowfields is performed. The results of numerical simulation of one-dimensional and two-dimensional under- and over-expanded nozzle flows with a moving region of energy supply are presented. Output nozzle parameters are calculated as functions of a number and time of burning of plasmatron arcs. The results obtained show a qualitative pattern of gas dynamics and thermal processes in the nozzle with unsteady energy supply demonstrating the displacement of the nozzle shock wave towards the nozzle outlet in the over-expanded nozzle flow in comparison to perfect gas flow.

Cutting transport simulation in a horizontal borehole near tool joints

In the presented study, we investigated the influence of cuttings transport in a channel with variable cross-section area to determine the pressure drop and obtain preliminary data on tool joint effect on solids deposition. The influence of boundary conditions at the channel’s inlet on flow regimes was analysed. The average particle concentration over the cross-section significantly reduced due to increasing the velocity in the narrowing area on the tool joint. Behind the tool joint, particles deposition appeared due to the reverse flow, which manifested itself as a local maximum in concentration distribution along the channel. The impact of a tool joint on the pressure drop in a single-phase flow has been more pronounced if compared to one in a two-phase flow at the given conditions.

On the longest reach problem in large deflection elastic rods

The longest reach problem of an elastic cantilevered rod subjected to a tip load is here revisited. It has been investigated for the first time recently (Wang, 2016). In this paper, two extensions of the problem are covered: the case of rods of extensible axis and of variable cross sectional area distribution. The problem is stated and solved numerically by means of the shooting method. Further distances with respect to those obtained in the literature can be reached employing decreasing bending rigidity along the rod axis.

Heterogeneous and dynamic lumen remodeling of the entire infrainguinal vein bypass grafts in patients

ObjectiveTo examine the regional variation and temporal change in lumen size along the entire autogenous vein bypass graft used for treating arterial occlusive disease in lower extremity and to explore the factors associated with graft expansive or constrictive remodeling. MethodsPatients were prospectively scanned using contrast-enhanced computed tomography at 1 week and 1, 6, and 12 months postoperatively to obtain lumen cross-sectional areas at 1-mm intervals along the entire grafts. Graft lumen remodeling characteristics and the associated demographic and clinical factors were examined. ResultsFifty-six patients with at least two consecutive computed tomography scans were analyzed. Patients with a composite or longer graft, or with diabetes, had a larger lumen cross-sectional area variation along the graft. The mean lumen cross-sectional areas of all the grafts demonstrated no significant changes through 12 months. However, individually, graft remodeling was time dependent and there was a more dramatic change in lumen cross-sectional area within the first postoperative month. At 12 months, a near equal distribution between expansive and constrictive grafts existed. A negative relation between the initial lumen diameters and the subsequent lumen diameter changes was observed. Eleven grafts failed within 12 months; failed and patent grafts had similar mean lumen cross-sectional areas at all four time points, but failed grafts had a larger maximal local cross-sectional area reduction from 1 week to 1 month (58.0 ± 6.7% vs 38.1 ± 3.1%, mean ± standard error of the mean, failed vs patent, P = .004). Black patients had a smaller mean lumen cross-sectional area than white patients at all four time points and also had a higher early percent mean area reduction (−20.5 ± 6.3% vs −1.0 ± 3.7%, black vs white, P = .018). Cilostazol use was associated with early expansive graft remodeling. ConclusionsVein grafts remodel heterogeneously and dynamically. Remodeling is associated with initial graft lumen size, race, and cilostazol use. It is found that remodeling that produces some critical minimum area or maximal percent reduction during the first postoperative month may predispose to vein graft failure. These findings offer insight into further investigation to examine the underlying mechanisms and opportunities to improve graft remodeling and durability.

A general and rapid method for performance evaluation of enhanced heat transfer techniques

Evaluation of the comprehensive performance of different heat transfer technologies and selection the best enhanced surface to meet the requirements are of great significance for efficient energy recovery. In this paper, based on the previous research results from our group, a rapid multi-criterion comprehensive evaluation method of enhanced heat transfer surfaces was first proposed; it realizes the rapid evaluation of heat transfer performance under the condition of equal flow rate, equal pressure drop and equal pump power constraints. Three baselines divide evaluation plot into six zones, namely zone 1 (non-energy-saving zone), zone 2 (relative energy-saving zone), zone 3 (value-added energy-saving zone), zone 4 (ideal energy-saving zone), zone 5 (pure energy-saving zone), and zone 6 (simple energy-saving zone). A simplified evaluation plot was then developed to overcome the dependence on the correlations of the reference surface. Next, the prediction results of the evaluation plot under the condition of variable minimum flow cross-section area, variable total heat transfer area, variable equivalent diameter, and variable tube bundle arrangement were compared with the traditional method to verify the applicability and accuracy of the evaluation plot. Finally, numerical simulations and engineering application of typical heat transfer surfaces were conducted to compare the energy-saving effectiveness of different enhanced surfaces and to analyze the effect of geometry and operation parameters on comprehensive performance. The results showed that the evaluation chart established in this paper can be successfully applied to the comprehensive comparison of multiple evaluation criteria and has a high prediction accuracy. Compared with the common evaluation methods, this method has excellent practicability and visualization, and contributes to the rapid development of new enhanced surfaces and efficient utilization of energy.

LQR Based Optimal Tuning of PI Controller for a Conical Tank Level Process

The liquid level control in conical tank is tough task owing to variable cross-sectional area. The replica of the conical tank is recognized using standard step test technique and is approximated to be FOPTD model. In this paper, PSO based LQR-PI controller has been wished-for conical tank system. The PI controller gains are formulated as the optimal state-feedback gains. A PSO has been accustomed optimally to discover the weighting matrices, related to the various optimum state- feedback regulator design whereas minimizing ISE and the controller effort. The performance of the proposed PSO based LQR-PI controller is contrasted with those of GA-LQR-PI and LQR-PI controllers.

The Vibration Reduction in Multilevel Structure Model with the addition of Tuned Liquid Column Damper (TLCD):Study of the Influence of variations in TLCD’s mass ratio & orifice cross-sectional area

The multilevel buildings are vulnerable to the excitation forces such as winds and earthquakes. The analysis of vibration reduction in multilevel building is established in this study. The experimental and simulation method are conducted in laboratory scale. The multilevel structure model is design to be two-floor building model. The Tuned Liquid Column Damper (TLCD) is placed on first-floor of the building model and then it is placed on second-floor of the building model. The TLCD’s mass ratio and its orifice cross-sectional area are varied. The experimental results correspond well to the simulation results. The TLCD’s mass ratio does not provide significant difference, while the variation of orifice cross-sectional area provides significant differences.

Mathematical Model Analysis of Dispersion and Loss in Photonic Crystal Fibers

Abstract This study has deeply investigated the basic equations analysis of dispersion and loss in photonic crystal fibers (PCF) within the operating wavelengths of 850, 1,300, and 1,550 nm. The confinement loss, effective refractive index, and effective cross-section area of PCF are also studied. The variations of total dispersion and losses against hole diameter and distance between holes variations in PCF are clarified. Confinement loss, effective refractive index, and effective cross-section area variations for PCF are sketches with the variations of the operating wavelength.