This study explores free convective heat transfer in an electrically conducting nanofluid flow over a moving semi-infinite flat plate under the influence of an induced magnetic field and viscous dissipation.The veloci...This study explores free convective heat transfer in an electrically conducting nanofluid flow over a moving semi-infinite flat plate under the influence of an induced magnetic field and viscous dissipation.The velocity and magnetic field vectors are aligned at a distance from the plate.The Spectral Relaxation Method(SRM)is used to numerically solve the coupled nonlinear partial differential equations,analyzing the effects of the Eckert number on heat and mass transfer.Various nanofluids containing Cu,Ag,Al_(2)O_(3),and TiO_(2) nanoparticles are examined to assess how external magnetic fields influence fluid behavior.Key parameters,including the nanoparticle volume fraction ϕ,magnetic parameter M,magnetic Prandtl number Prm,and Eckert number Ec,are evaluated for their impact on velocity,induced magnetic field,and heat transfer.Results indicate that increasing the magnetic parameter reduces velocity and magnetic field components in alumina-water nanofluids,while a higher nanoparticle volume fraction enhances the thermal boundary layer.Greater viscous dissipation(Ec)increases temperature,and Al_(2)O_(3) nanofluids exhibit higher speeds than Cu,Ag,and TiO_(2) due to density differences.Silver-water nanofluids,with their higher density,move more slowly.The SRM results closely align with those from Maple,confirming the method’s accuracy.展开更多
Although the classical spectral representation method(SRM)has been widely used in the generation of spatially varying ground motions,there are still challenges in efficient simulation of the non-stationary stochastic ...Although the classical spectral representation method(SRM)has been widely used in the generation of spatially varying ground motions,there are still challenges in efficient simulation of the non-stationary stochastic vector process in practice.The first problem is the inherent limitation and inflexibility of the deterministic time/frequency modulation function.Another difficulty is the estimation of evolutionary power spectral density(EPSD)with quite a few samples.To tackle these problems,the wavelet packet transform(WPT)algorithm is utilized to build a time-varying spectrum of seed recording which describes the energy distribution in the time-frequency domain.The time-varying spectrum is proven to preserve the time and frequency marginal property as theoretical EPSD will do for the stationary process.For the simulation of spatially varying ground motions,the auto-EPSD for all locations is directly estimated using the time-varying spectrum of seed recording rather than matching predefined EPSD models.Then the constructed spectral matrix is incorporated in SRM to simulate spatially varying non-stationary ground motions using efficient Cholesky decomposition techniques.In addition to a good match with the target coherency model,two numerical examples indicate that the generated time histories retain the physical properties of the prescribed seed recording,including waveform,temporal/spectral non-stationarity,normalized energy buildup,and significant duration.展开更多
随着我国山区高速公路建设的不断推进,弃渣场地的稳定性及致灾机制成为工程建设评估的重要因素之一。为了实现弃渣场的稳定性、失稳灾害动力学全过程的分析,基于面向GPU并行高性能计算软件CoSim中的物质点法(material point method,简称...随着我国山区高速公路建设的不断推进,弃渣场地的稳定性及致灾机制成为工程建设评估的重要因素之一。为了实现弃渣场的稳定性、失稳灾害动力学全过程的分析,基于面向GPU并行高性能计算软件CoSim中的物质点法(material point method,简称MPM),引入强度折减法(strength reduction method,简称SRM)开展相关研究工作。为了验证算法的合理性,以典型均质边坡为例,采用基于MPM的强度折减法与极限平衡法(limit equilibrium method,简称LEM)进行了对比,表明两者无论在稳定系数Fs还是在潜在滑动面上均具有良好的一致性。在此基础上,以云南某高速公路弃渣场降雨诱发失稳灾害为例,对其在天然工况和暴雨工况下稳定性和失稳过程进行了分析。结果表明,该弃渣场边坡在天然状态下处于稳定状态,而在暴雨工况下会发生失稳和大变形滑动;数值模拟和现场调查结果吻合较好,表明了提出的方法在弃渣场边坡稳定性与大变形失稳动力学分析中有强大的优势,可以实现斜坡的“稳定性→大变形→流动→堆积”的全过程分析。展开更多
文摘This study explores free convective heat transfer in an electrically conducting nanofluid flow over a moving semi-infinite flat plate under the influence of an induced magnetic field and viscous dissipation.The velocity and magnetic field vectors are aligned at a distance from the plate.The Spectral Relaxation Method(SRM)is used to numerically solve the coupled nonlinear partial differential equations,analyzing the effects of the Eckert number on heat and mass transfer.Various nanofluids containing Cu,Ag,Al_(2)O_(3),and TiO_(2) nanoparticles are examined to assess how external magnetic fields influence fluid behavior.Key parameters,including the nanoparticle volume fraction ϕ,magnetic parameter M,magnetic Prandtl number Prm,and Eckert number Ec,are evaluated for their impact on velocity,induced magnetic field,and heat transfer.Results indicate that increasing the magnetic parameter reduces velocity and magnetic field components in alumina-water nanofluids,while a higher nanoparticle volume fraction enhances the thermal boundary layer.Greater viscous dissipation(Ec)increases temperature,and Al_(2)O_(3) nanofluids exhibit higher speeds than Cu,Ag,and TiO_(2) due to density differences.Silver-water nanofluids,with their higher density,move more slowly.The SRM results closely align with those from Maple,confirming the method’s accuracy.
基金National Key Research and Development Program of China under Grant No.2023YFE0102900National Natural Science Foundation of China under Grant Nos.52378506 and 52208164。
文摘Although the classical spectral representation method(SRM)has been widely used in the generation of spatially varying ground motions,there are still challenges in efficient simulation of the non-stationary stochastic vector process in practice.The first problem is the inherent limitation and inflexibility of the deterministic time/frequency modulation function.Another difficulty is the estimation of evolutionary power spectral density(EPSD)with quite a few samples.To tackle these problems,the wavelet packet transform(WPT)algorithm is utilized to build a time-varying spectrum of seed recording which describes the energy distribution in the time-frequency domain.The time-varying spectrum is proven to preserve the time and frequency marginal property as theoretical EPSD will do for the stationary process.For the simulation of spatially varying ground motions,the auto-EPSD for all locations is directly estimated using the time-varying spectrum of seed recording rather than matching predefined EPSD models.Then the constructed spectral matrix is incorporated in SRM to simulate spatially varying non-stationary ground motions using efficient Cholesky decomposition techniques.In addition to a good match with the target coherency model,two numerical examples indicate that the generated time histories retain the physical properties of the prescribed seed recording,including waveform,temporal/spectral non-stationarity,normalized energy buildup,and significant duration.
