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为了在大范围数学模型中合理有效地模拟码头桩基等小尺度建筑物附近的潮流场,采用非结构网格建立了渤海二维有限元潮流数学模型.在面积达85 700 km2的模型范围中将码头桩基概化为面积约20-30 m2的不透水单元,用于直接模拟桩基附近的复杂潮流场.在此基础上,对渤海曹妃甸海域10万吨级LNG(液化天然气)码头布置的走向进行了优化.结果表明:数学模型模拟的潮位和流速等水动力特征与实测结果一致,LNG码头布置的优化结果合理可信.表明建立的能够直接模拟小尺度建筑物的渤海二维有限元数学模型可应用于码头工程布置及优化的潮流场模拟研究. 相似文献
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为研究根式基础在电塔基础上的受力特性,采用透明土与粒子图像测速(particle image velocimetry, PIV)技术,分析3种根式基础受上拔、水平荷载时的荷载-位移(Q-s)关系曲线,以及极限荷载条件下透明土的位移矢量变化,通过数值模拟探究不同根键长度对基础承载力的影响。结果表明:相同工况下,单层根式基础竖向抗拔承载性高于双层根式基础,但单层根式基础抗水平承载性低于双层根式基础。根键竖向间距为0.02 m双层根式基础位移矢量图显示,位移较大区域符合经典摩尔-库仑理论中的剪切破坏理论。数值模拟结果显示,双层根键竖向布置间距范围为0.83~1.25倍基础直径、根键长度为0.6 m时,抗拔承载性能较优。 相似文献
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以实现回热加热器动态模拟为目的,建立600 MW超临界机组回热加热器动态模型。该模型依据直流锅炉回热加热器结构与全负荷情况下直流锅炉600 MW超临界机组参数,建立由回热加热器集总参数模型、过热区模型和蒸发区模型组成的超临界机组回热加热器分段动态模型,利用该模型实现回热加热器动态模拟。实验结果表明:该模型计算回热加热器过热区温度与仿真软件模拟数值完全相同,具备较高的可靠性。当直流锅炉开度增加时,其回热加热器过热区和蒸发区的主蒸汽流量和主蒸汽温度均呈现上升趋势;当直流锅炉负荷下降时,其回热加热器蒸发区水冷壁流量受省煤器和水冷壁阻力系数影响呈现波动趋势。 相似文献
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设计了一种热泵驱动的溴化锂溶液深度除湿机组,该机组适用于无回风可利用、低湿度需求的场合.机组的性能测试结果显示,当室外温度为28~31℃,含湿量为11~14g/kg时,机组的送风温度为1.6~2.6℃,含湿量为2.6~3.0g/kg,系统COP为1.8.测试时发现了一个造成冷热溶液混合损失的管路链接问题,并对其进行修改.然后,对修改后的新机组进行了性能测试,结果显示,在室外温度为25~32℃,含湿量为18~21g/kg时,机组的送风温度为3.2~4.0℃,含湿量为3.4~3.6g/kg,系统COP为2.8.最后,对机组建立数学模型,并将模拟结果与实测数据进行比较,结果表明管路改动使机组性能提升约20%. 相似文献
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《赤峰学院学报(自然科学版)》2017,(13)
基于归一化方法,将风电机组平均输出功率和额定风速转化为无量纲,建立了容量系数和归一化功率关于归一化额定风速的数学模型,并且提出以风速与机组匹配指数最大为目标的机组参数确定方法.通过工程算例验证了该方法是合理可行的,对其他风电场机组优化选型提供了理论依据. 相似文献
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《浙江大学学报(A卷英文版)》2016,(9)
目的:少量任意布置冻结管冻结的稳态温度场无解析解。建立任意布置少量管冻结稳态温度场模型,获得解析解,解决人工冻结温度场理论问题。创新点:1.基于势函数叠加原理,确立人工地层冻结中少量管冻结稳态温度场的通用求解方法;2.建立任意布置的3根和4根非等温冻结管下冻结稳态温度场数学模型,获得其解析解通解及特解。方法:1.通过理论分析,将冻结管简化为热汇点源,确定人工地层冻结热势的拉普拉斯方程表述;2.应用势函数叠加原理建立少量管冻结稳态温度场的通用求解方法;3.建立少量管冻结稳态温度场的数学模型,通过理论推导获得温度场解析解;4.通过数值模拟,验证所提方法、数学模型和解析解的正确性和准确性。结论:1.将冻结管简化为点源(热汇),其冻结形成的热势场服从拉普拉斯方程,其解即为热势函数;2.多根冻结管冻结时,将单根冻结管的热势函数叠加,由冻结管的位置决定每根冻结管的热流,再根据边界条件定解。这一方法(即势函数叠加法)可以用于任意布置冻结管冻结稳态温度场解析解的求解;3.将冻结管简化为点源导致获得的解析解存在一定的误差,但误差仅发生在冻结管附近极小的范围内,并且误差微小,完全满足工程上的精度要求。 相似文献
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Computational fluid dynamics simulation of formaldehyde emission characteristics and its experimental validation in environment chamber 总被引:1,自引:0,他引:1
We investigated the effect of supply air rate and temperature on formaldehyde emission characteristics in an environment chamber. A three-dimensional computational fluid dynamics (CFD) chamber model for simulating formaldehyde emission in twelve different cases was developed for obtaining formaldehyde concentration by the area-weighted average method. Laboratory experiments were conducted in an environment chamber to validate the simulation results of twelve different cases and the formaldehyde concentration was measured by continuous sampling. The results show that there was good agreement between the model prediction and the experimental values within 4.3% difference for each case. The CFD simulation results varied in the range from 0.21 mg/m3 to 0.94 mg/m3, and the measuring results in the range from 0.17 mg/m3 to 0.87 mg/m3. The variation trend of formaldehyde concentration with supply air rate and temperature variation for CFD simulation and experiment measuring was consistent. With the existence of steady formaldehyde emission sources, formaldehyde concentration generally increased with the increase of temperature, and it decreased with the increase of air supply rate. We also provided some reasonable suggestions to reduce formaldehyde concentration and to improve indoor air quality for newly decorated rooms. 相似文献
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A detailed mathematical model of a direct internal reforming solid oxide fuel cell (DIR-SOFC) incorporating with simulation of chemical and physical processes in the fuel cell is presented. The model is developed based on the reforming and electrochemical reaction mechanisms, mass and energy conservation, and heat transfer. A computational fluid dynamics (CFD) method is used for solving the complicated multiple partial differential equations (PDEs) to obtain the numerical approximations.The resulting distributions of chemical species concentrations, temperature and current density in a cross-flow DIR-SOFC are given and analyzed in detail. Further, the influence between distributions of chemical species concentrations, temperature and current density during the simulation is illustrated and discussed. The heat and mass transfer, and the kinetics of reforming and electrochemical reactions have significant effects on the parameter distributions within the cell. The results show the particularchar acteristics of the DIR-SOFC among fuel cells, and can aid in stack design and control. 相似文献
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为了研究高大空间建筑喷口送风系统的吹风感分布,在大空间实验室中进行了夏季工况的实验测试,得到了喷口高度为4m时人体活动区域温度场、速度场和吹风感的分布.然后,采用计算流体力学的方法对实验工况进行模拟计算.将室内垂直温度和冷吹风感分布的计算结果和实测数据进行对比验证,结果显示吻合良好.在此基础上进行了不同喷口高度处工况的模拟计算,通过分析3个工况下人体活动区域的吹风感和温度,获得了较理想的送风工况.模拟结果显示,喷口高度为5m时吹风感分布较为理想,温度场和速度场较为均匀. 相似文献
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分析了4类风口模型(即基本模型、盒子模型、N点动量模型、主流区风口模型)在计算流体动力学中的应用以及在实际工程案例中的运行情况.在环境舱内进行了足尺实验,利用全方位热风速表测量了环境舱内的气流速度和温度场,并与4类风口模型的模拟结果进行比较.结果表明:基本模型与盒子模型并不适用于结构复杂的送风口模拟;基于N点动量模型和主流区风口模型的流体速度在工作区的模拟值与实测值的相对误差小于20%;在主流区风口模型中,送风口附近的气体速度模拟值与实测值的最大相对误差小于15%.证明主流区风口模型相对于其他3类风口模型而言,对于结构复杂的送风口模拟更准确,应用性更强. 相似文献
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Jun Li Ying-wei Kang Guang-yi Cao Xin-jian Zhu Heng-yong Tu Jian Li 《浙江大学学报(A卷英文版)》2008,9(7):961-969
A detailed mathematical model of a direct internal reforming solid oxide fuel cell (DIR-SOFC) incorporating with simulation of chemical and physical processes in the fuel cell is presented. The model is developed based on the reforming and electrochemical reaction mechanisms, mass and energy conservation, and heat transfer. A computational fluid dynamics (CFD) method is used for solving the complicated multiple partial differential equations (PDEs) to obtain the numerical approximations. The resulting distributions of chemical species concentrations, temperature and current density in a cross-flow DIR-SOFC are given and analyzed in detail. Further, the influence between distributions of chemical species concentrations, temperature and current density during the simulation is illustrated and discussed. The heat and mass transfer, and the kinetics of reforming and electrochemical reactions have significant effects on the parameter distributions within the cell. The results show the particular characteristics of the DIR-SOFC among fuel cells, and can aid in stack design and control. 相似文献
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综述了CFD数值模拟在调节阀中的应用,对某一广泛应用的套筒型调节阀应用三维建模软件内部流场建立模型,通过前处理器生成计算网格,应用CFD软件中的k-ε模型进行求解,得到调节阀内部流场的压力和速度的可视化图形。 相似文献
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An inter-phasing pulse tube cooler (IPPTC) consists of two pulse tube units, which are connected to each other at hot ends of the pulse tubes through a needle valve. This paper presents the computational fluid dynamic (CFD) results of an IPPTC using a 2D axis-symmetrical model. General results such as the phase difference between pressure and velocity at cold end and hot end, the temperature profiles along the wall, the available lowest temperature as well as its oscillations and the coefficient of performance (COP) for IPPTC are presented. The formation of DC flow and its effects on the performance of the cooler are investigated and analyzed in detail. Turbulence, which is partially responsible for the poor overall performance of a single orifice pulse tube cooler (OPTC), is found to be much reduced in IPPTC and its performance is improved significantly compared with the single OPTC. 相似文献
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In this study, we present a thermal optimization method using the overall lumped parameter (LP) and partial computational fluid dynamics (CFD) modeling for a 600-kW permanent magnet traction motor developed for high-speed trains. The motor is totally enclosed forced ventilated to achieve high power density, high efficiency, and low maintenance requirements. Considering the electro-magnetic performance, bogie space, and thermal capacity, we propose a ventilation structure with zigzag plates in sector cross-section. We focus particularly on the ventilation channels and propose an overall LP model for thermal optimization, in which the full consideration of the influence of turbulent flow is given by using a partial CFD model. Given the specific critical parameters from the optimization results, we present a complete 3D CFD model of the whole motor to obtain an accurate temperature distribution and the maximum temperature rises in local points. The benefit of zigzag plates is studied extensively using both the LP and the complete CFD models and the results are verified by equivalent thermal experiments under rated operations. Experimental results indicate that the ventilation structure fulfills the normal operational demands of high-speed trains by improving thermal performance by more than 15%. Additionally, we propose an engineering method to estimate iron loss constraint with the complete CFD model to guide the control system design. 相似文献
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采用格子-Boltzmann方法对平行平板间甲醇水蒸气重整反应过程进行模拟,其中包括反应、对流、扩散。模拟中假设化学反应对流场没有影响,流场、温度场和组分场可分别利用演化方程进行求解,利用多尺度技术可分别将演化方程回归到对应的宏观方程。在低Ma的条件下格子-Boltzmann方法模拟的结果与传统Navier-Stokes方程数值计算结果进行对比,吻合得较好,证明了格子-Boltzmann方法的可靠性。 相似文献
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Inspired by the successful applications of biological non-smoothness, we introduced bionic non-smooth surfaces as appendices
into vehicle body design, aiming to further reduce aerodynamic drag. The size range of the non-smooth units with pits and
grooves was determined according to our analysis with the mechanisms underlying non-smooth unit mediated aerodynamic drag
reduction. The bionic non-smooth units reported here were designed to adapt the structure of a given vehicle body from the
point of boundary layer control that reduces the burst and the loss of turbulent kinetic energy. The engine cover lid and
vehicle body cap were individually treated with the non-smooth units, and the treated vehicles were subjected to aerodynamic
drag coefficient simulation tests using the computational fluid dynamics (CFD) analysis method. The simulation results showed
that, in comparison with smooth surfaces, properly designed non-smooth surfaces can have greater effects on drag reduction.
The mechanism underlying drag reduction mediated by non-smooth surfaces was revealed by further analyses, in which the effects
of non-smooth and smooth surfaces were directly compared. 相似文献