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Rate Constitutive Theories of Orders n and 1n for Internal Polar Non-Classical Thermofluids without Memory
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作者 Karan S. Surana Stephen W. Long J. N. Reddy 《Applied Mathematics》 2016年第16期2033-2077,共45页
In recent papers, Surana et al. presented internal polar non-classical Continuum theory in which velocity gradient tensor in its entirety was incorporated in the conservation and balance laws. Thus, this theory incorp... In recent papers, Surana et al. presented internal polar non-classical Continuum theory in which velocity gradient tensor in its entirety was incorporated in the conservation and balance laws. Thus, this theory incorporated symmetric part of the velocity gradient tensor (as done in classical theories) as well as skew symmetric part representing varying internal rotation rates between material points which when resisted by deforming continua result in dissipation (and/or storage) of mechanical work. This physics referred as internal polar physics is neglected in classical continuum theories but can be quite significant for some materials. In another recent paper Surana et al. presented ordered rate constitutive theories for internal polar non-classical fluent continua without memory derived using deviatoric Cauchy stress tensor and conjugate strain rate tensors of up to orders n and Cauchy moment tensor and its conjugate symmetric part of the first convected derivative of the rotation gradient tensor. In this constitutive theory higher order convected derivatives of the symmetric part of the rotation gradient tensor are assumed not to contribute to dissipation. Secondly, the skew symmetric part of the velocity gradient tensor is used as rotation rates to determine rate of rotation gradient tensor. This is an approximation to true convected time derivatives of the rotation gradient tensor. The resulting constitutive theory: (1) is incomplete as it neglects the second and higher order convected time derivatives of the symmetric part of the rotation gradient tensor;(2) first convected derivative of the symmetric part of the rotation gradient tensor as used by Surana et al. is only approximate;(3) has inconsistent treatment of dissipation due to Cauchy moment tensor when compared with the dissipation mechanism due to deviatoric part of symmetric Cauchy stress tensor in which convected time derivatives of up to order n are considered in the theory. The purpose of this paper is to present ordered rate constitutive theories for deviatoric Cauchy strain tensor, moment tensor and heat vector for thermofluids without memory in which convected time derivatives of strain tensors up to order n are conjugate with the Cauchy stress tensor and the convected time derivatives of the symmetric part of the rotation gradient tensor up to orders 1n are conjugate with the moment tensor. Conservation and balance laws are used to determine the choice of dependent variables in the constitutive theories: Helmholtz free energy density Φ, entropy density η, Cauchy stress tensor, moment tensor and heat vector. Stress tensor is decomposed into symmetric and skew symmetric parts and the symmetric part of the stress tensor and the moment tensor are further decomposed into equilibrium and deviatoric tensors. It is established through conjugate pairs in entropy inequality that the constitutive theories only need to be derived for symmetric stress tensor, moment tensor and heat vector. Density in the current configuration, convected time derivatives of the strain tensor up to order n, convected time derivatives of the symmetric part of the rotation gradient tensor up to orders 1n, temperature gradient tensor and temperature are considered as argument tensors of all dependent variables in the constitutive theories based on entropy inequality and principle of equipresence. The constitutive theories are derived in contravariant and covariant bases as well as using Jaumann rates. The nth and 1nth order rate constitutive theories for internal polar non-classical thermofluids without memory are specialized for n = 1 and 1n = 1 to demonstrate fundamental differences in the constitutive theories presented here and those used presently for classical thermofluids without memory and those published by Surana et al. for internal polar non-classical incompressible thermofluids. 展开更多
关键词 Rate Constitutive Theories Non-Classical thermofluids Without Memory Convected Time Derivatives Internal Rotation Gradient Tensor Generators and Invariants Cauchy Moment Tensor
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Application of machine learning to develop a real-time air-cooled condenser monitoring platform using thermofluid simulation data 被引量:1
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作者 Rashid A.Haffejee Ryno Laubscher 《Energy and AI》 2021年第1期151-166,共16页
A data-driven surrogate model is proposed for a 64-cell air-cooled condenser system at a power plant.The surro-gate model was developed using thermofluid simulation data from an existing detailed 1-D thermofluid netwo... A data-driven surrogate model is proposed for a 64-cell air-cooled condenser system at a power plant.The surro-gate model was developed using thermofluid simulation data from an existing detailed 1-D thermofluid network simulation model.The thermofluid network model requires a minimum of 20 min to solve for a single set of in-puts.With operating conditions fluctuating constantly,performance predictions are required in shorter intervals,leading to the development of a surrogate model.Simulation data covered three operating scopes across a range of ambient air temperatures,inlet steam mass flow rates,number of operating cells,and wind speeds.The surrogate model uses multi-layer perceptron deep neural networks in the form of a binary classifier network to avoid ex-trapolation from the simulation dataset,and a regression network to provide performance predictions,including the steady-state backpressure,heat rejections,air mass flowrates,and fan motor powers on a system level.The integrated surrogate model had an average relative error of 0.3%on the test set,while the binary classifier had a 99.85%classification accuracy,indicating sufficient generalisation.The surrogate model was validated using site-data covering 10 days of operation for the case-study ACC system,providing backpressure predictions for all 1967 input samples within a few seconds of compute time.Approximately 93.5%of backpressure predictions were within±6%of the recorded backpressures,indicating sufficient accuracy of the surrogate model with a significant decrease in compute time. 展开更多
关键词 COOLING Air-cooled condensers Data-driven surrogate modelling thermofluid network modelling Neural networks Multilayer perceptron networks
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矿井火灾燃烧区热阻力的研究 被引量:12
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作者 李传统 王省身 《中国矿业大学学报》 EI CAS CSCD 北大核心 1996年第4期8-11,共4页
根据热流体学理论,结合矿井火灾特点研究了矿井火灾燃烧区产生的热阻力,得出了倾斜(或垂直)巷道及水平巷道内火灾燃烧区热阻力系数的表达式,还给出了两种井下固体可燃物在水平巷道内燃烧时热阻力系数随无因次加热准则变化的实验结果。
关键词 矿井火灾 热阻力 火风压 燃烧区
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热阻力概念的修正及计算方法 被引量:9
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作者 程小虎 曾艳华 《防灾减灾工程学报》 CSCD 2006年第4期404-408,共5页
以隧道火灾为背景,对一维加热管流中的热阻力进行了研究。通过压力场数值模拟与理论分析,直接证实了热阻力的存在,并表明传统概念上的热阻力明显大于实际的能量损失。根据能量方程提出水平无粘管流的热阻力应等于气流经过加热区的全压力... 以隧道火灾为背景,对一维加热管流中的热阻力进行了研究。通过压力场数值模拟与理论分析,直接证实了热阻力的存在,并表明传统概念上的热阻力明显大于实际的能量损失。根据能量方程提出水平无粘管流的热阻力应等于气流经过加热区的全压力降,而非静压力降;等截面管流的热阻力大小应为传统热阻力值的1/2。这一修正使热阻力概念具有了严格的流体力学意义。在定义新的热阻力系数基础上,建立了2个热阻力系数表达式及低马赫数条件下热阻力的近似表达式。将该近似表达式与热损失方程进行对比,表明两者在低马赫数条件下具有一致性。研究成果进一步发展了热阻力理论体系,对隧道火灾及其它相关工程热物理问题的研究与应用都具有重要价值。 展开更多
关键词 隧道火灾 热阻力 热流体学 压力场
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Ordered Rate Constitutive Theories for Non-Classical Thermoviscoelastic Fluids with Internal Rotation Rates 被引量:1
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作者 K. S. Surana S. W. Long J. N. Reddy 《Applied Mathematics》 2018年第8期907-939,共33页
The paper presents constitutive theories for non-classical thermoviscoelastic fluids with dissipation and memory using a thermodynamic framework based on entirety of velocity gradient tensor. Thus, the conservation an... The paper presents constitutive theories for non-classical thermoviscoelastic fluids with dissipation and memory using a thermodynamic framework based on entirety of velocity gradient tensor. Thus, the conservation and the balance laws used in this work incorporate symmetric as well as antisymmetric part of the velocity gradient tensor. The constitutive theories derived here hold in coand contra-variant bases as well as in Jaumann rates and are derived using convected time derivatives of Green’s and Almansi strain tensors as well as the Cauchy stress tensor and its convected time derivatives in appropriate bases. The constitutive theories are presented in the absence as well as in the presence of the balance of moment of moments as balance law. It is shown that the dissipation mechanism and the fading memory in such fluids are due to stress rates as well as moment rates and their conjugates. The material coefficients are derived for the general forms of the constitutive theories based on integrity. Simplified linear (or quasi-linear) forms of the constitutive theories are also presented. Maxwell, Oldroyd-B and Giesekus constitutive models for non-classical thermoviscoelastic fluids are derived and are compared with those derived based on classical continuum mechanics. Both, compressible and incompressible thermoviscoelastic fluids are considered. 展开更多
关键词 RATE CONSTITUTIVE Theories Non-Classical thermofluids With Memory Convected Time Derivatives Internal Rotation Gradient TENSOR Generators and INVARIANTS CAUCHY MOMENT TENSOR
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热流体力学及其应用 被引量:1
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作者 过增元 《力学进展》 EI CSCD 北大核心 1990年第2期145-158,共14页
热流体力学是一门涉及传热学、流体力学和热力学的交叉学科,并把重点放在讨论热过程对流体流动的影响。它由5部分组成:①热阻力。在某些情况下热阻力的存在对通道中的流体流量和换热系数有重大影响。借助于热阻力系数的定义和分析表达式... 热流体力学是一门涉及传热学、流体力学和热力学的交叉学科,并把重点放在讨论热过程对流体流动的影响。它由5部分组成:①热阻力。在某些情况下热阻力的存在对通道中的流体流量和换热系数有重大影响。借助于热阻力系数的定义和分析表达式,不仅可以预示单相通道流中的压力降,而且能用简便的方法预示气-液两相通道流中的压力降和临界热流。②热绕流。运用“虚质量源”和“热偶极子”的概念,对热绕流现象进行了分析和数值研究。它可在热除尘、粒子样品收集和热设备中流量分配等方面获得广泛的应用。③热驱动。不仅在重力场中,而且在如离心力场、表面张力场和电磁力场中也存在着热驱动流。着重讨论了流体运动的起因及其带来的后果,它包括环境污染、传热强化和同位素分离系数的提高等,④热不稳定性。重点讨论了热不稳定性的物理机理。用各种动力学方法所得到的流动不稳定性的临界准则对材料加工、热减阻、水源热污染等都是十分重要的。⑤热优化。研究了基于熵产生最小(热力学第二定律)为目标函数的流动和传热过程的优化。探讨了在一定条件下热力学第一定律效率和第二定律效率的内在联系。 展开更多
关键词 热流体力学 流体
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波兰硫矿藏的开发利用 被引量:1
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作者 姚绍德 《中国矿业》 1993年第6期74-78,共5页
本文叙述了作者在波兰进行非金属矿开发利用实地考察的一方面内容,即波兰Tarnobrzeg天然硫矿床地下热熔开采的生产方式、工艺流程、井点布置和废水净化处理方式,特别着重介绍了流体动力法和热流体法新工艺的具体技术措施。
关键词 波兰 地下热熔开采 硫矿床
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河北宣化“战国红”玛瑙矿床地质特征及成因分析 被引量:1
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作者 徐文华 许新成 +1 位作者 杨丽丽 武海燕 《宝石和宝石学杂志》 CAS 2017年第3期1-11,共11页
充填熔岩气孔形成的玛瑙并非不常见,但形成具规模矿床的不多。河北宣化"战国红"玛瑙就是这类矿床的典型,解剖该矿床具有一定的理论及勘查意义。通过矿区勘查发现,该类玛瑙产于近水平中侏罗统髫髻山组四段粗面熔岩中,为充填厘... 充填熔岩气孔形成的玛瑙并非不常见,但形成具规模矿床的不多。河北宣化"战国红"玛瑙就是这类矿床的典型,解剖该矿床具有一定的理论及勘查意义。通过矿区勘查发现,该类玛瑙产于近水平中侏罗统髫髻山组四段粗面熔岩中,为充填厘米级浑圆气孔之产物,矿体含矿率达0.7~1.2kg/m^3;矿体上覆髫髻山组五段火山集块岩、角砾岩。显微结构观察揭露浑圆状玛瑙矿石由韵律式隐晶燧石环带组成,环带间被细粒显晶石英及少量方解石充填;内含斑点状铁质、锰质杂质。扫描电子显微镜面扫描结合拉曼光谱分析表明,杂质的质量分数及成分变化造就丰富多彩的玛瑙颜色。综合矿区地质、显微结构特点,该类玛瑙为晚期爆发式火山活动形成的富硅流体快速沉淀于先存熔岩气孔中的结果。每一韵律式燧石条带代表一次火山-流体活动,韵律间的粗晶石英或方解石代表火山爆发间隙。 展开更多
关键词 玛瑙 髫髻山组 粗面熔岩 气孔 火山流体
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导弹发射箱发射过程热流固耦合数值模拟
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作者 邹长星 邓春丽 袁森 《机械与电子》 2022年第7期22-26,共5页
为研究导弹热发射过程中发射箱结构应力与变形分布规律,建立了发射箱内流场域、外流场域和结构域1/4对称模型。采用域动分层法和单向热流固耦合技术模拟导弹发射,得到发射箱内外壁的压强、温度变化。仿真结果表明:导弹发射过程中,由于... 为研究导弹热发射过程中发射箱结构应力与变形分布规律,建立了发射箱内流场域、外流场域和结构域1/4对称模型。采用域动分层法和单向热流固耦合技术模拟导弹发射,得到发射箱内外壁的压强、温度变化。仿真结果表明:导弹发射过程中,由于高温高压燃气流的烧蚀和冲击,在发射0.0200 s时刻发射箱前端加强筋处应力最大,为7209.10 MPa;在发射0.0200 s时刻发射箱前端处变形最大,为27.24 mm。该仿真验证为箱体结构优化设计与制造提供了数据支持及理论依据。 展开更多
关键词 发射箱 应力 变形 域动分层法 热流固耦合技术
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Bifurcation and hysteresis phenomena in the two-phase natural circulation system
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作者 YAO Wei KUANG Bo XU Ji-jun (Department of Nuclear Power Engineering and Automation, School of Power and Anergy Engineering, Shanghai Jiaotong University, Shanghai, 200050) 《Nuclear Science and Techniques》 SCIE CAS CSCD 2001年第1期61-67,共7页
The static bifurcation of the two-phase natural circulation (TPNC) system was studied theoretically and numerically. By the DERPAR algorithm the solution diagram was calculated, which shows that the static bifurcation... The static bifurcation of the two-phase natural circulation (TPNC) system was studied theoretically and numerically. By the DERPAR algorithm the solution diagram was calculated, which shows that the static bifurcation occurs under some conditions in the TPNC systems. Also, it shows that, in a region of multiple solutions, the static instability may occur. It is defined as a region of thermal-siphon instability induced flow rate jumping. By means of the solution diagram, the stability margin can be determined in this region. Furthermore, the heat input at the peak of the solution diagram is defined as the maximum capacity Of heating load that can be used to judge the capacity of the TPNC of a given geometry topological structure. Meanwhile, it is interesting that the TPNC systems have the hysteresis phenomenon defined as thermal-siphon hysteresis. Some parametric effects related were also studied. 展开更多
关键词 沸腾水反应堆 双相自然环流系统 磁滞现象
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地下热熔法采硫工艺与新技术应用 被引量:1
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作者 姚绍德 《武汉工业大学学报》 CSCD 1993年第1期70-76,共7页
本文以作者国外实地考察为依据,介绍了用地下热熔法开采自然硫矿的主要工艺和流体动力法、热流体法新技术在开采实践中的应用,同时对其理论原理进行了分析探讨,提供了一些可供参考的技术数据和技术措施。
关键词 地下热熔法 采矿 硫矿 热流体法
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平面电机散热器热流建模与尺寸-拓扑并行优化设计 被引量:1
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作者 赵家琦 张鸣 +4 位作者 朱煜 成荣 李鑫 王磊杰 胡楚雄 《清华大学学报(自然科学版)》 EI CAS CSCD 北大核心 2022年第3期400-407,共8页
为了提高平面电机水冷散热器热流性能,该文构建了散热器热流模型并开展了"结构尺寸-流道拓扑"并行优化设计。首先,构建了散热器3层热流模型,该模型囊括了盖板与流固混合层的流动/传热耦合效应以及散热器厚度方案对热流场的影... 为了提高平面电机水冷散热器热流性能,该文构建了散热器热流模型并开展了"结构尺寸-流道拓扑"并行优化设计。首先,构建了散热器3层热流模型,该模型囊括了盖板与流固混合层的流动/传热耦合效应以及散热器厚度方案对热流场的影响。其次,基于3层热流模型,引入孔隙度域来描述流道拓扑,构建了包含流道拓扑变量与层厚变量的连续伴随结构优化模型,并提出了相应的散热器层厚与流道拓扑并行优化方案。最终,数值案例部分评估了3层热流模型准确性及计算效率、"层厚-流道拓扑"并行优化设计结果热流性能和"尺寸-拓扑"并行优化方案。结果表明:相较于全3D热流模型,所构建的3层热流模型仅需少于10%的计算时间获得了近乎一致的温度场;相较于基准设计,所优化的散热器结构新颖且展现出高达30.82%的目标性能改善;相较于离散优化方案,所提出的并行优化方案高效且取得了具有竞争力的设计。 展开更多
关键词 散热器 热流建模 多层模型 拓扑优化 尺寸优化 并行优化
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