Advances in Mechanical Engineering The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Characteristics of Large-Scale Structures in Supersonic Planar Mixing Layer with Finite Thickness Tue, 02 Sep 2014 12:16:12 +0000 Nanoparticle-based planar laser scattering (NPLS) experiments and large eddy simulation (LES) were launched to get the fine structure of the supersonic planar mixing layer with finite thickness in the present study. Different from the turbulent development of supersonic planar mixing layer with thin thickness, the development of supersonic planar mixing layer with finite thickness is rapidly. The large-scale structures of mixing layer that possess the characters of quick movement and slow changes transmit to downriver at invariable speed. The transverse results show that the mixing layer is strip of right and dim and possess 3D characteristics. Meanwhile the vortices roll up from two sides to the center. Results indicate that the higher the pressure of the high speed side is, the thicker the mixing layer is. The development of mixing layer is restrained when the pressure of lower speed side is higher. The momentum thickness goes higher with the increase of the clapboard thickness. Through increasing the temperature to change the compression can affect the development of the vortices. The present study can make a contribution to the mixing enhancement and provide initial data for the later investigations. Hailong Zhang, Jiping Wu, Jian Chen, and Weidong Liu Copyright © 2014 Hailong Zhang et al. All rights reserved. Numerical Study on the Effect of Tube Rows on the Heat Transfer Characteristic of Dimpled Fin Tue, 02 Sep 2014 09:51:10 +0000 The dimpled fin has excellent heat transfer performance and has attracted a lot of attention to apply on the fin and tube heat exchanger. A study presents to investigate the effects of number of tube rows on the air-side heat transfer characteristics of dimpled fin for velocity ranging from 1 to 3 m/s. The and are used to evaluate the heat transfer performance of the heat exchanger. The results show that the dimpled arrangement can change the mainstream direction, increase the disturbance, and enhance the heat transfer. With the increase of the number of tube rows, the average Nusselt number decreases and and increase gradually. Compared with the multipipe tube rows, the performance of two-row tube is better. Xuehong Wu, Lihua Feng, Dandan Liu, Hao Meng, and Yanli Lu Copyright © 2014 Xuehong Wu et al. All rights reserved. Using of Multiwall Carbon Nanotube Based Nanofluid in the Heat Pipe to Get Better Thermal Performance Mon, 01 Sep 2014 12:14:55 +0000 Thermal performance of a cylindrical heat pipe is investigated numerically. Three different types of water based nanofluids, namely, Al2O3 + Water, Diamond + Water, and Multi-Wall Carbon Nano tube (MWCNT) + Water, have been used. The influence of using the simple nanofluids and MWCNT nanofluid on the heat pipe characteristics such as liquid velocity, pressure profile, temperature profile, thermal resistance, and heat transfer coefficient of heat pipe has been studied. A new correlation developed by Bakhshan and Saljooghi (2014) for viscosity of nanofluids has been implemented. The results show, a good agreement with the available analytical and experimental data. Also the results show, that the MWCNT based nanofluid has lower thermal resistance, higher heat transfer coefficient, and lower temperature difference between evaporator and condenser sections, so it has good thermal specifications as a working fluid for use in heat pipes. The prepared code has capability for parametric studies also. Y. Bakhshan, S. Motadayen Aval, F. Kamel, and A. Hajhossini Copyright © 2014 Y. Bakhshan et al. All rights reserved. Sequence Planning and Tool Selection for Bending Processes of 2.5D Sheet Metals Mon, 01 Sep 2014 12:14:11 +0000 Planning of an appropriate bending sequence is one of the most important aspects in the processing of sheet metals as the appropriateness of the plan affects correct selection of bending tools and feasibility of bending processes. This study aims to propose a set of principles to be followed for the planning of bending sequences and selection of bending tools for 2.5D sheet metals. To this end, we first define basic bending patterns by characterizing each pattern with a set of operation rules. The sheet metal is then decomposed into a series of bending patterns that is in turn used in the planning of bending sequences. In order to select the bending tools, we combine the contours of each bending operation, choose appropriate bending punches from the bending-tool database, and then undertake an interference check with the bending contours. Alan C. Lin and Chao-Fan Chen Copyright © 2014 Alan C. Lin and Chao-Fan Chen. All rights reserved. CFD Numerical Simulation of the Complex Turbulent Flow Field in an Axial-Flow Water Pump Mon, 01 Sep 2014 12:04:48 +0000 Further optimal design of an axial-flow water pump calls for a thorough recognition of the characteristics of the complex turbulent flow field in the pump, which is however extremely difficult to be measured using the up-to-date experimental techniques. In this study, a numerical simulation procedure based on computational fluid dynamics (CFD) was elaborated in order to obtain the fully three-dimensional unsteady turbulent flow field in an axial-flow water pump. The shear stress transport (SST) k-ω model was employed in the CFD calculation to study the unsteady internal flow of the axial-flow pump. Upon the numerical simulation results, the characteristics of the velocity field and pressure field inside the impeller region were discussed in detail. The established model procedure in this study may provide guidance to the numerical simulations of turbomachines during the design phase or the investigation of flow and pressure field characteristics and performance. The presented information can be of reference value in further optimal design of the axial-flow pump. Wan-You Li, Xiang-Yuan Zhang, Zhi-Jun Shuai, Chen-Xing Jiang, and Feng-Chen Li Copyright © 2014 Wan-You Li et al. All rights reserved. Safety Control on the Chocking Process of Supercritical Carbon Dioxide Pipeline Mon, 01 Sep 2014 08:47:52 +0000 Transportation safety of supercritical CO2 pipeline is a key aspect of carbon capture and storage (CCS). For reducing the high pressure in supercritical pipeline when accidental cases arise, man-made release will be applied using chocking process. The downstream parameters of chocking process can be predicted based on the adiabatic process assumption. In the critical chocking process, the critical velocity at outlet is sonic. A chocking pipe can be designed for buffering between different chocking orifices according to the length of turbulence area produced by jetting momentum. For the effect of noise hazard produced by large jetting velocity, a muffler can be applied at the outlet of final stage orifice to atmosphere. For the influence of impurities on the chocking process of anthropogenic CO2 pipeline, the presence of SO2 as an impurity is helpful for increasing the downstream temperatures through the chocking device to prevent the frozen hazard, whereas the presence of N2 as an impurity indicates a lower downstream temperature. The higher initial temperature can prevent the dry ice formation at the outlet of vent pipe when the multistage chocking is applied. Qing Zhao, Yuxing Li, and Shunli Li Copyright © 2014 Qing Zhao et al. All rights reserved. Pump and Pumping System Mon, 01 Sep 2014 08:34:19 +0000 Weidong Shi, Wang Zheng-Wei, Li Ren-Nian, Leqin Wang, and Shibo Kuang Copyright © 2014 Weidong Shi et al. All rights reserved. Collaborative Synchronization Digital Control for Double Hydraulic Cylinders Mon, 01 Sep 2014 07:23:59 +0000 By researching the synchronization motion of double hydraulic cylinders controlled by high-speed on-off valve, the paper aims to solve the shortage of current hydraulic synchronization system with low synchronization precision. The flow characteristic of high-speed on-off valve with pulse width-frequency modulation is researched compared with pulse width modulation. The mathematical equations of the double hydraulic cylinders are formulated with bulk-cavity-node method in MATLAB/Simulink. The collaborative synchronization control is analyzed and the compound algorithm of collaborative synchronization control and pulse width-frequency modulation is simulated compared with collaborative synchronization control. The hydraulic loop is set up to verify the simulation result with the proposed control algorithm on the FESTO platform. The research finds that (1) the pulse width-frequency modulation control can be linear to the flow of high-speed on-off valve on the duty bound of 0~100%; (2) the collaborative synchronization control is effective to eliminate the displacement error between the double cylinders which results from the different load environment and other disturbance. Zhi-hao Liu, Qin-he Gao, Chuan-qiang Yu, Xiang-yang Li, Wen-liang Guan, and Gang-feng Deng Copyright © 2014 Zhi-hao Liu et al. All rights reserved. Thermal Performance Analysis and Empirical Correlations for Laminar Forced Convection over 30° V-Baffled Square Channel Mon, 01 Sep 2014 06:19:32 +0000 Thermal performance analysis for laminar forced convection in an isothermal wall square channel with 30° V-baffle is presented numerically. The parameters of the V-baffle, blockage ratio (b/H, BR), pitch ratio (P/H, PR), flow direction (V-Downstream and V-Upstream), and arrangement (in-line and staggered), are studied and compared with the previous works, 20° and 45° V-baffle. The Reynolds number based on the hydraulic diameter of the channel (), Re = 100–2000, is used in range study. The results show that the flow configurations of 30° V-baffle are found similar as 20° and 45° V-baffle. The fully developed periodic flow and heat transfer are created around 7th-8th module, while the periodic flow and heat transfer profiles are found at 2nd module in all cases. Except for the periodic concept, the 30° V-baffle can help to reduce the pressure loss around 2.3 times in comparison with the 45° V-baffle at the maximum value (BR = 0.3, PR = 1, V-Downstream). The optimum thermal enhancement factor for the 30° V-baffle is found around 4.25 at BR = 0.15, PR = 1, and Re = 2000 for V-Downstream case with in-line arrangement. Amnart Boonloi and Withada Jedsadaratanachai Copyright © 2014 Amnart Boonloi and Withada Jedsadaratanachai. All rights reserved. CFD and Experimental Analysis of a Falling Film outside Smooth and Helically Grooved Tubes Sun, 31 Aug 2014 07:21:29 +0000 Simultaneous heat and mass transfer are investigated in a falling film outside grooved and smooth tubes. A numerical analysis of the helically trapezoidal-grooved and reference smooth tube was performed in the computational fluid dynamics program “Ansys Fluent 14.” The three-dimensional model drawings in the , , and coordinates are used, and the effects of the falling film outside the helically grooved tube on the surface temperature and surface heat transfer coefficient are determined. The average surface temperature, heat transfer coefficient, and Nu values are determined experimentally for a constant heat flux. An uncertainty analysis and Nu correlation for the grooved tube are also provided in this study. The Reynolds number varied between 50 and 350 for the falling film and between 1500 and 3500 for air. Using a computational fluid dynamics (CFD) analysis for the reference smooth tube, the experimental results are validated within 2–12% difference. The experimental results are also within 6–13% of the grooved tubes. Cenk Onan, Derya Burcu Ozkan, and Serkan Erdem Copyright © 2014 Cenk Onan et al. All rights reserved. Study on Detection and Localization Algorithm of Traffic Signs from Natural Scenes Sun, 31 Aug 2014 07:15:01 +0000 Automatic detection and location of traffic signs is an important part of intelligent transportation, especially for unmanned vehicle technology research. For the morphological feature of China road traffic signs, we propose a traffic sign detection method based on color segmentation and shape analysis. Firstly, in order to solve the problems of traffic signs color cast, distortion, and cross-color in natural scenes, the images are processed by white balance, Retinex color enhancement, and affine transformation. Then, the type of traffic signs is discriminated and detected, according to the color and shape characteristics of traffic signs. The experimental results show that this method can effectively detect and recognize traffic signs. Xian-Zhong Han, Chen Chen, Ke-Jian Wang, Yingchun Yuan, and Yulong Song Copyright © 2014 Xian-Zhong Han et al. All rights reserved. Defect Characterization Based on Eddy Current Technique: Technical Review Thu, 28 Aug 2014 12:31:27 +0000 Eddy current testing is widely used for nondestructive evaluation of metallic structures in characterizing numerous types of defects occurring in various locations. It offers remarkable advantages over other nondestructive techniques because of its ease of implementation. This paper presents a technical review of Eddy current technique in various scope of defect detection. The first part presents Eddy current evaluation on various defects location and orientation such as steam generator tubes, stress crack corrosion, and fatigue cracks. The next section analyzes the use of pulsed Eddy current and pulsed Eddy current thermography as an alternative method for monitoring the growth of cracks with the aid of computational techniques for postsignal analysis. Ruzlaini Ghoni, Mahmood Dollah, Aizat Sulaiman, and Fadhil Mamat Ibrahim Copyright © 2014 Ruzlaini Ghoni et al. All rights reserved. Formalization of Matrix Theory in HOL4 Thu, 28 Aug 2014 12:12:20 +0000 Matrix theory plays an important role in modeling linear systems in engineering and science. To model and analyze the intricate behavior of complex systems, it is imperative to formalize matrix theory in a metalogic setting. This paper presents the higher-order logic (HOL) formalization of the vector space and matrix theory in the HOL4 theorem proving system. Formalized theories include formal definitions of real vectors and matrices, algebraic properties, and determinants, which are verified in HOL4. Two case studies, modeling and verifying composite two-port networks and state transfer equations, are presented to demonstrate the applicability and effectiveness of our work. Zhiping Shi, Yan Zhang, Zhenke Liu, Xinan Kang, Yong Guan, Jie Zhang, and Xiaoyu Song Copyright © 2014 Zhiping Shi et al. All rights reserved. Shift Performance Test and Analysis of Multipurpose Vehicle Thu, 28 Aug 2014 11:20:32 +0000 This paper presented an analysis of the gear shifting performances of a multipurpose vehicle transmission in driving condition by Ricardo’s Gear Shift Quality Assessment (GSQA) system. The performances of the transmission included the travel and effort of the gear shift lever and synchronizing time. The mathematic models of the transmission including the gear shift mechanism and synchronizer were developed in MATLAB. The model of the gear shift mechanism was developed to analyze the travel map of the gear shift lever and the model of the synchronizer was developed to obtain the force-time curve of the synchronizer during the slipping time. The model of the synchronizer was used to investigate the relationship between the performances of the transmission and the variation of parameters during gear shifting. The mathematic models of the gear shift mechanism and the synchronizer provided a rapid design and verification method for the transmission with ring spring. Can Yang, Lin Hua, Zhou Wang, and Yaohua He Copyright © 2014 Can Yang et al. All rights reserved. Research on the Vibration Characteristics of the New Type of Passive Super Static Vibratory Platform Based on the Multiobjective Parameter Optimization Thu, 28 Aug 2014 11:10:55 +0000 In order to reduce impact on payload due to vibration, the new type of passive super static vibratory platform and its dynamic mathematical model were established. In order to obtain the best performance of this platform, the method of multiobjective parameter optimization was applied to decide the parameters such as stiffness coefficient and damping coefficient. Then studying the dynamics inherent characteristic of the platform, the result shows the new type of passive super static vibratory platform has relatively low natural frequency and can effectively reduce the vibration of the high frequency range that means this new type of passive super static vibratory platform was suitable for the satellite payload work environment. Based on the simulation, the experimental platform was manufactured and tested on the platform with random forced vibration; the result shows the new type of passive super static vibratory platform has an obvious vibration damping effect. Jiaqiang E, Cheng Qian, Teng Liu, and Guanlin Liu Copyright © 2014 Jiaqiang E et al. All rights reserved. Responses of a Highly Accelerated Life Test System to Impacts from Different Designs of Hammers Thu, 28 Aug 2014 09:44:51 +0000 The response of a table to the impact of its driving hammer in the highly accelerated life test (HALT) system depends on, among other things, the location of the hammer, the presence of multiple hammers, and the angle at which the hammer is mounted to the table. The present study investigated the response of a table to a variety of impacts from different combinations of hammers. It began with a theoretical analysis of the forces of impact exerted by hammers which led to the calculation of the corresponding displacement. These theoretical calculations revealed the mechanics of the HALT system to help explain the working principles behind this complex system. Then a simulation model was built to check the accuracy of the theoretical results. Finally, the accelerations of a table in a real HALT system were measured. These data showed good agreement with the experimental results and computer simulation. The responses of HALT systems have not been investigated thoroughly to date. The current study can help equipment designers and end users better understand the working principles of this kind of systems. It can be considered a breakthrough in terms of improving the performance of reliability testing with this kind of system. Yeong-Shu Chen and Le Hong Chuong Copyright © 2014 Yeong-Shu Chen and Le Hong Chuong. All rights reserved. Numerical Study of Natural Supercavitation Influenced by Rheological Properties of Turbulent Drag-Reducing Additives Thu, 28 Aug 2014 06:27:54 +0000 Natural supercavitations in water and turbulent drag-reducing solution were numerically simulated using unsteady Reynolds averaged Navier-Stokes (RANS) scheme with mixture-multiphase model. The Cross viscosity equation was adopted to represent the fluid property of aqueous solution of drag-reducing additives. The characteristics of natural supercavity configuration and overall resistance of the navigating body were presented, respectively. The numerical simulation results indicated that, at the same cavitation number, the length and diameter of supercavity in drag-reducing solution are larger than those in water, and the drag coefficient of navigating body in solution is smaller than that in water; the surface tension plays an important role in incepting and maintaining the cavity. Turbulent drag-reducing additives have the potential in enhancement of supercavitation, drag reduction, and decrease of turbulent vortex structures. Numerical simulation results are consistent with the available experimental data. Chen-Xing Jiang and Feng-Chen Li Copyright © 2014 Chen-Xing Jiang and Feng-Chen Li. All rights reserved. Comparisons of Hydraulic Performance in Permanent Maglev Pump for Water-Jet Propulsion Thu, 28 Aug 2014 05:56:25 +0000 The operation of water-jet propulsion can generate nonuniform inflow that may be detrimental to the performance of the water-jets. To reduce disadvantages of the nonuniform inflow, a rim-driven water-jet propulsion was designed depending on the technology of passive magnetic levitation. Insufficient understanding of large performance deviations between the normal water-jets (shaft) and permanent maglev water-jets (shaftless) is a major problem in this paper. CFD was directly adopted in the feasibility and superiority of permanent maglev water-jets. Comparison and discussion of the hydraulic performance were carried out. The shaftless duct firstly has a drop in hydraulic losses (), since it effectively avoids the formation and evolution of the instability secondary vortex by the normalized helicity analysis. Then, the shaftless intake duct improves the inflow field of the water-jet pump, with consequencing the drop in the backflow and blocking on the blade shroud. So that the shaftless water-jet pump delivers higher flow rate and head to the propulsion than the shaft. Eventually, not only can the shaftless model increase the thrust and efficiency, but it has the ability to extend the working range and broaden the high efficiency region as well. Puyu Cao, Yang Wang, K. X. Qian, and Guidong Li Copyright © 2014 Puyu Cao et al. All rights reserved. Compositional Simulation on the Flow of Polymeric Solution Alternating CO2 through Heavy Oil Reservoir Thu, 28 Aug 2014 00:00:00 +0000 Water-alternating-gas (WAG) method provides superior mobility control of CO2 and improves sweep efficiency. However, WAG process has some problems in highly viscous oil reservoir such as gravity overriding and poor mobility ratio. To examine the applicability of carbon dioxide to recover viscous oil from highly heterogeneous reservoirs, this study suggests polymer-alternating-gas (PAG) process. The process involves a combination of polymer flooding and CO2 injection. In this numerical model, high viscosity of oil and high heterogeneity of reservoir are the main challenges. To confirm the effectiveness of PAG process in the model, four processes (waterflooding, continuous CO2 injection, WAG process, and PAG process) are implemented and recovery factor, WOR, and GOR are compared. Simulation results show that PAG method would increase oil recovery over 45% compared with WAG process. The WAG ratio of 2 is found to be the optimum value for maximum oil recovery. The additional oil recovery of 3% through the 2 WAG ratio is achieved over the base case of 1 : 1 PAG ratio and 180 days cycle period. Moon Sik Jeong, Jinhyung Cho, Jinsuk Choi, Ji Ho Lee, and Kun Sang Lee Copyright © 2014 Moon Sik Jeong et al. All rights reserved. Numerical Simulation of Frost Heave in Soils around the Buried Oil Pipeline in Island Talik Permafrost Region Wed, 27 Aug 2014 11:43:30 +0000 A systematic method to obtain the freezing characteristics and the amounts of frost heave in the soils around a buried oil pipeline in island talik permafrost region is presented on the basis of the simulation of soil temperature fields and a classic segregated potential frost heave model. The finite thermal effect domain and the equivalent heat capacity method were adopted to analyze the heat transfer process with phase change. The calculation parameters were derived from the China-Russia Crude Oil Pipeline engineering. The developments of the annual maximum freezing circles and frost penetrations emerging in typical years within the pipeline operation life cycle under different oil temperature, different thickness of thermal insulation layer, and different water content of soils were investigated. The maximum frost heaves in four typical sections of island talik were predicted. The results can be used to further mechanical calculation and can provide references for risk evaluation and site management of the buried pipelines in island talik permafrost regions. Zaiguo Fu, Bo Yu, Yu Zhao, and Yasuo Kawaguchi Copyright © 2014 Zaiguo Fu et al. All rights reserved. Development of a New Platoon Dispersion Model considering Turning Vehicles in Urban Road Environment Wed, 27 Aug 2014 11:08:20 +0000 By considering turning vehicles of a platoon that travels on arterial link, a new procedure for calibrating dispersion parameter α of Robertson’s model is proposed. Upstream edge of channelized section is served as the boundary and the link between two adjacent intersections is divided into two sections, which are road section and channelized section. Typical investigation site is selected in Changchun city and data are collected to study the relationship between α and internal frictions, such as traffic volume and turning proportion. Double Gaussian function and logistic function are used to fit the curves among optimum values of α and internal frictions in the two sections, respectively, which allow the determination of α that varies as the volumes and turning proportions change. The study results are of great importance for arterial progression because Robertson’s model can depict platoon movements more accurately using the calibrated values of α. Yiming Bie, Zhiyuan Liu, Yan Li, and Yulong Pei Copyright © 2014 Yiming Bie et al. All rights reserved. Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan Wed, 27 Aug 2014 08:51:14 +0000 An aerodynamic and aeroacoustic investigation of the multiblade centrifugal fan is proposed in this paper, and a hybrid technique of combining flow field calculation and acoustic analysis is applied to solve the aeroacoustic problem of multiblade centrifugal fan. The unsteady flow field of the multiblade centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS) equations with conventional computing techniques for fluid dynamics. The principal noise source induced is extracted from the calculation of the flow field by using acoustic principles, and the modeled sources on inner and outer surfaces of the volute are calculated with multiregional boundary element method (BEM). Through qualitative analysis, the sound pressure amplitude distribution of the multiblade centrifugal fan in near field is given and the sound pressure level (SPL) spectrum diagram of monitoring points in far field is obtained. Based on the analysis results, the volute tongue structure is adjusted and then a low-noise design for the centrifugal fan is proposed. The comparison of noise tests shows the noise reduction of improved fan model is more obvious, which is in good agreement with the prediction using the hybrid techniques. Shuiqing Zhou and Jun Wang Copyright © 2014 Shuiqing Zhou and Jun Wang. All rights reserved. An Experimental Investigation of Ethanol-Diesel Blends on Performance and Exhaust Emissions of Diesel Engines Wed, 27 Aug 2014 08:45:57 +0000 Ethanol is a promising alternative fuel, due to its renewable biobased origin. Also, it has lower carbon content than diesel fuel and it is oxygenated. For this reason, ethanol is providing remarkable potential to reduce particulate emulsions in compression-ignition engines. In this study, performance of ethanol-diesel blends has been investigated experimentally. Tested fuels were mineral diesel fuel (E0D100), 15% (v/v) ethanol/diesel fuel blend (E15D85), and 30% (v/v) ethanol/diesel fuel blend (E30D70). Firstly, the solubility of ethanol and diesel was experienced. Engine tests were carried out to reveal the performance and emissions of the engine fuelled with the blends. Full load operating conditions at various engine speeds were investigated. Engine brake torque, brake power, brake specific fuel consumption, brake thermal efficiency, exhaust gas temperature, and finally exhaust emissions were measured. Performance of the tested engine decreased substantially while improvement on smoke and gaseous emissions makes ethanol blend favorable. Tarkan Sandalcı, Yasin Karagöz, Emre Orak, and Levent Yüksek Copyright © 2014 Tarkan Sandalcı et al. All rights reserved. A Numerical Study of Aerodynamic Performance and Noise of a Bionic Airfoil Based on Owl Wing Wed, 27 Aug 2014 07:21:36 +0000 Noise reduction and efficiency enhancement are the two important directions in the development of the multiblade centrifugal fan. In this study, we attempt to develop a bionic airfoil based on the owl wing and investigate its aerodynamic performance and noise-reduction mechanism at the relatively low Reynolds number. Firstly, according to the geometric characteristics of the owl wing, a bionic airfoil is constructed as the object of study at Reynolds number of 12,300. Secondly, the large eddy simulation (LES) with the Smagorinsky model is adopted to numerically simulate the unsteady flow fields around the bionic airfoil and the standard NACA0006 airfoil. And then, the acoustic sources are extracted from the unsteady flow field data, and the Ffowcs Williams-Hawkings (FW-H) equation based on Lighthill’s acoustic theory is solved to predict the propagation of these acoustic sources. The numerical results show that the lift-to-drag ratio of bionic airfoil is higher than that of the traditional NACA 0006 airfoil because of its deeply concave lower surface geometry. Finally, the sound field of the bionic airfoil is analyzed in detail. The distribution of the A-weighted sound pressure levels, the scaled directivity of the sound, and the distribution of dP/dt on the airfoil surface are provided so that the characteristics of the acoustic sources could be revealed. Xiaomin Liu and Xiang Liu Copyright © 2014 Xiaomin Liu and Xiang Liu. All rights reserved. The Influence of Operation Pressure on the Long-Term Stability of Salt-Cavern Gas Storage Wed, 27 Aug 2014 07:21:15 +0000 The operation pressure of underground salt-cavern gas storage directly affects its stability. Because of seasonal demand and other emergency reasons, the gas storage working pressures always change from high to low or from low to high cyclic variation. In order to analyze the effect of gas storage pressure changing on its long-term stability, considering the salt rock creep, a 3D finite element model was built using the software Abaqus. Moreover, the deformation and analyzed results of the storage under 0 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa, and 12 MPa and also circulating changes pressure operation were given in the 10-year creep. It concluded that how working pressures have effect on long-term stability of salt-cavern gas storage. The research results indicated that the long-term creep performance of underground salt cavern gas storage is affected by internal pressure, the smaller the internal pressure creep is, the more obvious the creep and the greater deformation of gas storage are. The greater the internal pressure is, the smaller the deformation of the gas storage is. The low pressure and excessive high pressure must be avoided during the operation of gas storage. These results have an important significance on determining the reasonable pressure of gas storage operation and ensure the long-term stability of gas storage. Jianjun Liu and Qiang Xiao Copyright © 2014 Jianjun Liu and Qiang Xiao. All rights reserved. Drag Reduction of a Pipe Flow Using Nata de Coco Suspensions Wed, 27 Aug 2014 07:04:58 +0000 The addition of drag-reducing agents to reduce pipe friction loss has attracted attention as a method to conserve energy. In addition to reducing drag, these agents are required to have a low environmental load and conserve natural resources. Therefore, naturally occurring biopolymer additives, which are considered to have a low environmental load, have recently received much attention. Here we focused on nata de coco, a type of biopolymer that exhibits low mechanical degradation, and found that it reduced drag by up to 25% at a concentration of 50 ppm. With respect to the drag reduction (DR) mechanism, we investigated the relation between DR phenomena and the fiber structure of nata de coco by visualization. As a result, we found that the DR effect appeared only when a network of nata de coco fibers was formed in the suspension. In addition, DR increased as the size of the network of nata de coco fibers increased. Satoshi Ogata, Gunawan, Jun Warashina, and Yanuar Copyright © 2014 Satoshi Ogata et al. All rights reserved. Motion of Passive Scalar by Elasticity-Induced Instability in Curved Microchannel Wed, 27 Aug 2014 06:19:49 +0000 This paper presented a direct numerical simulation (DNS) study on the elasticity-induced irregular flow, passive mixing, and scalar evolution in the curvilinear microchannel. The mixing enhancement was achieved at vanishingly low-Reynolds-number chaotic flow raised by elastic instabilities. Along with the mixing process, the passive scalar transportation carried by the flow was greatly affected by the flow structure and the underlying interaction between microstructures of viscoelastic fluid and flow structure itself. The simulations are conducted for a wide range of viscoelasticity. As the elastic effect exceeds the critical value, the flow tends to a chaotic state, while the evolution of scalar gets strong and fast, showing excellent agreement with experimental results. For the temporal changing of scalar gradients, they vary rapidly in the form of isosurfaces, with the shape of “rolls” in the bulk and evolving into “threads” near the wall. That indicates that the flow fields should be related to the deformation of viscoelastic micromolecules. The probability distribution function analysis between micromolecular deformation and flow field deformation shows that the main direction of molecular stretching is perpendicular to the main direction of flow field deformation. It implies they are weakly correlated, due to the confinement of channel wall. Xiao-Bin Li, Hong-Na Zhang, Yang Cao, Marie Oshima, and Feng-Chen Li Copyright © 2014 Xiao-Bin Li et al. All rights reserved. Numerical Thermodynamic Analysis of Two-Phase Solid-Liquid Abrasive Flow Polishing in U-Type Tube Wed, 27 Aug 2014 05:53:28 +0000 U-type tubes are widely used in military and civilian fields and the quality of the internal surface of their channel often determines the merits and performance of a machine in which they are incorporated. Abrasive flow polishing is an effective method for improving the channel surface quality of a U-type tube. Using the results of a numerical analysis of the thermodynamic energy balance equation of a two-phase solid-liquid flow, we carried out numerical simulations of the heat transfer and surface processing characteristics of a two-phase solid-liquid abrasive flow polishing of a U-type tube. The distribution cloud of the changes in the inlet turbulent kinetic energy, turbulence intensity, turbulent viscosity, and dynamic pressure near the wall of the tube were obtained. The relationships between the temperature and the turbulent kinetic energy, between the turbulent kinetic energy and the velocity, and between the temperature and the processing velocity were also determined to develop a theoretical basis for controlling the quality of abrasive flow polishing. Junye Li, Zhaojun Yang, Weina Liu, and Zemin Qiao Copyright © 2014 Junye Li et al. All rights reserved. Numerical Analysis and Design of Thermal Management System for Lithium Ion Battery Pack Using Thermoelectric Coolers Wed, 27 Aug 2014 00:00:00 +0000 A new design of thermal management system for lithium ion battery pack using thermoelectric coolers (TECs) is proposed. Firstly, the 3D thermal model of a high power lithium ion battery and the TEC is elaborated. Then the model is calibrated with experiment results. Finally, the calibrated model is applied to investigate the performance of a thermal management system for a lithium ion battery pack. The results show that battery thermal management system (BTMS) with TEC can cool the battery in very high ambient temperature. It can also keep a more uniform temperature distribution in the battery pack than common BTMS, which will extend the life of the battery pack and may save the expensive battery equalization system. Yong Liu, Shichun Yang, Bin Guo, and Cheng Deng Copyright © 2014 Yong Liu et al. All rights reserved. A Finite Element Procedure with Poisson Iteration Method Adopting Pattern Approach Technique for Near-Incompressible Rubber Problems Wed, 27 Aug 2014 00:00:00 +0000 A finite element procedure is presented for the analysis of rubber-like hyperelastic materials. The volumetric incompressibility condition of rubber deformation is included in the formulation using the penalty method, while the principle of virtual work is used to derive a nonlinear finite element equation for the large displacement problem that is presented in a total-Lagrangian description. The behavior of rubber deformation is represented by hyperelastic constitutive relations based on a generalized Mooney-Rivlin model. The proposed finite element procedure using analytic differentiation exhibited results that matched very well with those from the well-known commercial packages NISA II and ABAQUS. Furthermore, the convergence of equilibrium iteration is quite slow or frequently fails in the case of near-incompressible rubber. To prevent such phenomenon even for the case that Poisson’s ratio is very close to 0.5, Poisson’s ratio of 0.49000 is used, first, to get an approximate solution without any difficulty; then the applied load is maintained and Poisson’s ratio is increased to 0.49999 following a proposed pattern and adopting a technique of relaxation by monitoring the convergence rate. For a given Poisson ratio near 0.5, with this approach, we could reduce the number of substeps considerably. Young-Doo Kwon, Soon-Bum Kwon, Xiaozhe Lu, and Hyun-Wook Kwon Copyright © 2014 Young-Doo Kwon et al. All rights reserved.