采用标量联合PDF(probability density function)方法结合修正的k-ε湍流模型、EMST小尺度混合模型以及GRI3.0化学反应机理对甲烷-氢气混合燃料(体积比为1∶1)高温伴流射流J HC(jet in hot coflow)火焰进行数值模拟.比较分析了高温伴流...采用标量联合PDF(probability density function)方法结合修正的k-ε湍流模型、EMST小尺度混合模型以及GRI3.0化学反应机理对甲烷-氢气混合燃料(体积比为1∶1)高温伴流射流J HC(jet in hot coflow)火焰进行数值模拟.比较分析了高温伴流中氧气质量分数分别为3%,6%和9%时的3种不同的MILD(moderate andintense lowoxygen dilution)燃烧火焰,3种火焰的计算结果与实验值符合得较好.展开更多
为了探索高温伴流射流(jet in hot coflow,JHC)无焰燃烧(moderate or intense low oxygen dilution,MILD)建立的条件,利用数值模拟的方法研究了JHC火焰在不同伴流温度与伴流氧气质量分数下的火焰特性。使用商业CFD软件ANSYS FLUENT 15.0...为了探索高温伴流射流(jet in hot coflow,JHC)无焰燃烧(moderate or intense low oxygen dilution,MILD)建立的条件,利用数值模拟的方法研究了JHC火焰在不同伴流温度与伴流氧气质量分数下的火焰特性。使用商业CFD软件ANSYS FLUENT 15.0,开展稳态RANS(Reynolds averaged Navier-Stokes)模拟,湍流模型采用标准κ-ε双方程模型,化学反应采用DRM 22详细反应机理,湍流与化学反应的相互作用采用涡耗散概念(EDC)模型。模拟结果表明:提高伴流温度加强了火焰内部的传热过程;降低氧气浓度减小了化学反应释放的热量,显著降低了火焰亮度,使火焰锋面变得模糊,氧气浓度在转变燃烧状态时起到更加明显的作用;燃料主射流的初始速度决定了反应区域的湍流时间尺度,伴流温度通过影响湍流时间尺度影响宏观燃烧状态;降低伴流氧气浓度增加了化学反应时间尺度,使宏观燃烧更均匀温和,燃烧模式的转变过程更加规律可控。展开更多
In this paper,the Johnson-Holmquist concrete(JHC)constitutive model is adopted for modeling and simulating the fracture of dolomite.A detailed step-by-step procedure for determining all required parameters,based on a ...In this paper,the Johnson-Holmquist concrete(JHC)constitutive model is adopted for modeling and simulating the fracture of dolomite.A detailed step-by-step procedure for determining all required parameters,based on a series of experiments under quasi-static and dynamic regimes,is proposed.Strain rate coefficients,failure surfaces,equations of state and damage/failure constants are acquired based on the experimental data and finite element analyses.The JHC model with the obtained parameters for dolomite is subsequently validated using quasi-static uniaxial and triaxial compression tests as well as dynamic split Hopkinson pressure bar(SHPB)tests.The influence of mesh size is also analyzed.It shows that the simulated fracture behavior and waveform data are in good agreement with the experimental data for all tests under both quasi-static and dynamic loading conditions.Future studies will implement the validated JHC model in small-and large-scale blasting simulations.展开更多
The Johnson-Holmquist constitutive ceramic model is re-implemented into the LS_ DYNA3D program to simulate the penetration of long rod projectile into ceramic/armor steel composite targets. The damage evolution, fract...The Johnson-Holmquist constitutive ceramic model is re-implemented into the LS_ DYNA3D program to simulate the penetration of long rod projectile into ceramic/armor steel composite targets. The damage evolution, fracture propagation, and spall damage in the ceramic/armor targets is represented during the simulation procedure and the accuracy of the penetration depth comparing between the simulating and experimental results is reliable with an error less than 8 %. The relationship between the mass efficiency factor, differential factor and ceramic tiles thickness is given out for the penetration results with/without a cover plate.展开更多
文摘采用标量联合PDF(probability density function)方法结合修正的k-ε湍流模型、EMST小尺度混合模型以及GRI3.0化学反应机理对甲烷-氢气混合燃料(体积比为1∶1)高温伴流射流J HC(jet in hot coflow)火焰进行数值模拟.比较分析了高温伴流中氧气质量分数分别为3%,6%和9%时的3种不同的MILD(moderate andintense lowoxygen dilution)燃烧火焰,3种火焰的计算结果与实验值符合得较好.
文摘为了探索高温伴流射流(jet in hot coflow,JHC)无焰燃烧(moderate or intense low oxygen dilution,MILD)建立的条件,利用数值模拟的方法研究了JHC火焰在不同伴流温度与伴流氧气质量分数下的火焰特性。使用商业CFD软件ANSYS FLUENT 15.0,开展稳态RANS(Reynolds averaged Navier-Stokes)模拟,湍流模型采用标准κ-ε双方程模型,化学反应采用DRM 22详细反应机理,湍流与化学反应的相互作用采用涡耗散概念(EDC)模型。模拟结果表明:提高伴流温度加强了火焰内部的传热过程;降低氧气浓度减小了化学反应释放的热量,显著降低了火焰亮度,使火焰锋面变得模糊,氧气浓度在转变燃烧状态时起到更加明显的作用;燃料主射流的初始速度决定了反应区域的湍流时间尺度,伴流温度通过影响湍流时间尺度影响宏观燃烧状态;降低伴流氧气浓度增加了化学反应时间尺度,使宏观燃烧更均匀温和,燃烧模式的转变过程更加规律可控。
文摘In this paper,the Johnson-Holmquist concrete(JHC)constitutive model is adopted for modeling and simulating the fracture of dolomite.A detailed step-by-step procedure for determining all required parameters,based on a series of experiments under quasi-static and dynamic regimes,is proposed.Strain rate coefficients,failure surfaces,equations of state and damage/failure constants are acquired based on the experimental data and finite element analyses.The JHC model with the obtained parameters for dolomite is subsequently validated using quasi-static uniaxial and triaxial compression tests as well as dynamic split Hopkinson pressure bar(SHPB)tests.The influence of mesh size is also analyzed.It shows that the simulated fracture behavior and waveform data are in good agreement with the experimental data for all tests under both quasi-static and dynamic loading conditions.Future studies will implement the validated JHC model in small-and large-scale blasting simulations.
文摘The Johnson-Holmquist constitutive ceramic model is re-implemented into the LS_ DYNA3D program to simulate the penetration of long rod projectile into ceramic/armor steel composite targets. The damage evolution, fracture propagation, and spall damage in the ceramic/armor targets is represented during the simulation procedure and the accuracy of the penetration depth comparing between the simulating and experimental results is reliable with an error less than 8 %. The relationship between the mass efficiency factor, differential factor and ceramic tiles thickness is given out for the penetration results with/without a cover plate.
