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S. Eiamsa-ard S. Pattanapipat P. Promvonge 《Journal of Mechanical Science and Technology》2013,27(7):2199-2208
Laminar periodic flow and heat transfer in a three-dimensional channel with triangular wavy baffles (TWBs) have been numerically investigated. The baffles with three different angles of attack: 30°, 45° and 60° have been considered for Reynolds numbers ranging from 100 to 1000. For a better understanding in the heat transfer mechanisms, the pressure contour, secondary flow pattern, streamlines of impinging flow, wall streamline and iso-surface are also reported. Apparently, each wavy baffle generates two counter-rotating vortices. The 30° and 45° baffles generate vortices with comparable intensities which are considerably higher than that caused by 60° baffles. At similar conditions, the 30° and 45° baffles give comparable Nu/Nu0 values which are considerably higher than that provided by the 60° baffles, but the 30° baffles cause lower f/f 0 than the 45° and 60° baffles. For the range determined, the maximum thermal performances achieved by using baffles with the attack angles of 30°, 45° and 60° are 2.3, 2.2, and 1.88, respectively. 相似文献
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Mass conservation is a key issue for accurate streamline and stream surface visualization of flow fields. This paper complements
an existing method (Feng et al., 1997) for CFD velocity fields defined at discrete locations in space that uses dual stream
functions to generate streamlines and stream surfaces. Conditions for using the method have been examined and its limitations
defined. A complete set of dual stream functions for all possible cases of the linear fields on which the method relies are
presented. The results in this paper are important for developing new methods for mass conservative streamline visualization
from CFD data and using the existing method. 相似文献
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The research on the dynamic performance of flowmeters has great significance for the accurate measurement of flow onsite. A simulation method for dynamic characteristics of turbine flow sensor was proposed in this study. This method was used to investigate the dynamic performance of three turbine flow sensors with different diameters. The amplitude-frequency characteristic, phase-frequency characteristic, transfer function, and step response are analyzed based on the results of the simulation. The results indicate that turbine flow sensors can be analyzed as a first-order system. The frequency of pulse flow is the main factor affecting the sensor's performance. The phase difference increases as the frequency increases, and the maximum phase difference reaches 50°. The gain of the small-diameter turbine flow sensor is susceptible, while the phase difference and time constant of the large-diameter turbine flow sensor are susceptible. For step flow, the time constant generated by the negative step is larger than that by the positive step. The analysis results provide bases for evaluating the dynamic performance of turbine flow sensors used online. 相似文献
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Sang-Joon Lee Hak-Lim Kim Jin-Pyung Lee Sundara Rajagopalan 《Journal of Mechanical Science and Technology》2012,26(12):4007-4016
The flow characteristics of jets issued from a sinusoidal nozzle with in-phase and 180° out-of-phase exit configurations were investigated using PIV (particle image velocimetry) and flow visualization techniques. The experiments were carried out at a Reynolds number of about 6300 based on the mean width of the jet nozzle. Compared to a normal rectangular jet, the sinusoidal nozzle jets have smaller velocity deficits as the flow goes downstream. In addition, the turbulence intensity is suppressed in the horizontal center plane. For the case of in-phase wavy nozzle jet, the length of the potential core exhibits small variations along the lateral direction, while the 180° out-of-phase wavy nozzle jet shows large lateral variation in the length of potential core. The turbulent kinetic energy of the 180° out-ofphase nozzle jet also shows sinusoidal variation in the horizontal planes. Large-scale vortices shed from the sinusoidal edge of the nozzle interact strongly and migrate toward the center plane as the flow develops downstream. 相似文献
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利用计算流体力学软件FLUENT对一种气井专用的电磁阀内部流场进行了计算和分析,结果表明:阀芯后部存在低速区,下部出口管内存在两个明显的涡流区,涡流区的出现加大了流动的阻力;随着阀芯开度的增大,阀芯后部低速区仍然存在,涡流区的旋转强度减弱,阀体内的湍动能和湍能耗散率减小,电磁阀的总压降减小;锥形阀座壁面和下游出口管下部壁面剪应力较大,其它区域剪应力较小,因此在阀芯锥面以及阀座锥形壁面和下游出口管下部的壁面处容易磨损。研究结果为电磁阀内部结构的设计提供了指导。 相似文献
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计算流体动力学是解决三维流动问题的有效手段.为解决某型柴油机水流分配器两个出口流量不均匀、出口流动阻力大等问题,提出了改进设计方案.为了验证改进方案是否满足使用要求,建立了三维计算模型,运用CFD前处理软件Gambit划分网格,同时采用标准k-ε模型及SIMPLEC算法,对水流分配器内流场进行了数值模拟分析.通过分析,得到了水流分配器的出口流量以及内流场压力、速度分布特性,找出了改进方案中存在的缺陷,并提出了进一步的改进建议. 相似文献
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基于标准k-ε湍流模型对四组不同阀芯结构(平底、小弧、大弧、波浪形)调节阀流阻性能进行研究,分析流场内速度流线、压力云图,得到流动规律及阀前后压力损失,流阻系数ξ。研究表明:随着阀芯开度增加,阀内流阻系数逐渐减小。10%开度时平底阀芯结构调节阀内流阻系数最大,大弧形与波浪形阀芯结构调节阀的流阻系数最小,对比发现大弧形与波浪形阀芯结构调节阀的截阻性能较平底阀芯调节阀的流阻系数值减小9.71%;全开度下大弧、小弧阀芯以及波浪形阀芯调节阀内部流阻系数相近,平底阀芯全开度下流阻系数相较于其他三组减小了14.69%。表明该工况下,阀芯处于全开度时,平底阀芯截阻性能具有一定的优势,因此,调节阀在小开度工况下工作时可选用大弧阀芯与波浪形阀芯结构。 相似文献
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J.-H. Song S.-Y. Hong Y. Kang H.-G. Kil 《Journal of Mechanical Science and Technology》2011,25(3):567-576
This study concerns the transmission of vibrational energy through beam-plate junctions by energy flow analysis, which is
an analytic tool for predicting the frequency averaged vibration response of built-up structures in the medium to high frequency
ranges. A semi-infinite beam perpendicularly connected to an infinite plate is studied using the wave transmission approach.
To calculate the power transmission and the reflection coefficients of the beam-plate junction, compatibility and equilibrium
conditions are applied when each wave component is incident on the beam and plate, respectively. Power coefficients are calculated
and plotted against frequencies for different dimensions and the directivity pattern of the scattered waves in the plate show
close agreement with that of the rigid inclusion as the frequency increases. The results obtained are applied to the finite
beam and the circular plate coupled structure, and the energy densities obtained from energy flow analysis show better agreement
with analytic solution results as frequencies are increased. 相似文献
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Installation effects were considered with the help of computational fluid dynamics (CFD). The information obtained by numerical simulation was much more extensive than in experimental data investigations. Using standard turbulence models, reasonable agreement with experimental data was achieved. The use of advanced turbulence models improves the agreement drastically but needs far more computer resources. Visualization of calculated flows was performed with the aid of an advanced graphic system. The assessment of the validation procedure was found to be dependent on various aspects which are discussed in detail. The influence of flow disturbances on various ultrasonic flow meters was numerically investigated. 相似文献
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A fundamental study on Co-based metallic glasses has been conducted. The study focused on understanding the changes of the properties and structures of an Fe-B-Si glass as a function of Co, Co-Ni, Co-Mn, and Co-Ni-Mo additions. The separate addition of Co, Co-Ni, Co-Mn, and Co-Ni-Mo elements was successful in such a way that four new metallic glasses were produced. The compositions of the new glasses are Fe66Co18B15Si1, Co66Fe4B14Si15, Co76Fe2Mn4B12Si6, and Co69Fe4Mo2B12Si12. Consequently, an evaluation of the physical and magnetic properties was determined. Furthermore, the internal and surface structures of the glasses have been characterized by a transmission electron microscope (TEM), and a scanning tunneling microscope (STM), respectively. A comparison between the internal and surface structures of the glasses was carried out on both amorphous and crystalline forms. As a result, a correlation between the properties and structures of the glasses is established. 相似文献
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Flow field distribution plays a vital role in electrochemical machining (ECM) because it can directly affect the machining stability and accuracy of ECM. In counter-rotating electrochemical machining (CRECM), the uniformity of the flow field is difficult to control due to the complicated and changeable flow channel shape. Through the simulation of the conventional lateral fluid flow pattern, it is found that the complexity of the flow channel with grid structures makes the flow field of machining area strongly disordered, which leads to the low velocity zones and dead zones. Based on the simulation results, a new electrolyte flow pattern with an auxiliary internal fluid is proposed, which can remarkably improve the uniformity of flow field by apply supplementary electrolyte to the machining area. Experimental results show that the new flow pattern effectively improves the machining stability of CRECM, and enhances the machining precision of grid structures, the sidewall taper angle is reduced from 29.3° to 7.7°. 相似文献
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Numerical analysis of the influence of electrode position on fluid flow in 2-D rectangular duct flow
Suwimon Saneewong Na Ayuttaya Chainarong Chaktranond Phadungsak Rattanadecho 《Journal of Mechanical Science and Technology》2013,27(7):1957-1962
This paper numerically examines the influence of electrode arrangements and number of electrodes on fluid flow under electric field. The distance between the electrode and ground positions varies in the vertical direction (i.e., H = ?1 cm to 1 cm) and horizontal direction (i.e., L = 2 cm to 8 cm). Electrical voltage and inlet velocity are employed at 20 kV and 0.5 m/s, respectively. Numerical results show that swirling flow occur at H ≠ 0 cm and its direction depends on the location of H. When the distance L decreases, the swirling becomes smaller and the vorticity becomes stronger because of the higher and denser electric field intensity. Increasing the number of electrodes also increases the electric field, thus causing larger and more violent swirling. Comparisons of the flow visualization show that the simulation results are in good agreement with the experiment results. 相似文献
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为解决流场中的问题,采用CFD方法,对某汽车发动机舱内的前端局部流场进行分析,包括:机舱前端设计不合理,存在漏风、热气回流等。基于CFD的分析结果,有针对性地提出了多个优化方案,对前端模块,风扇进行重新设计,并增设导流板,解决了上述问题,提高了冷却模块的流量。 相似文献