For the in-situ gas-injection mining technology of oil shale by process,a numerical simulation method with flow-thermo-solid coupling is proposed in this paper.This method adopts separate simulations and step-by-step ...For the in-situ gas-injection mining technology of oil shale by process,a numerical simulation method with flow-thermo-solid coupling is proposed in this paper.This method adopts separate simulations and step-by-step coupling simulation ideas combined with the advantages of the finite element method and the finite volume method.The numerical simulation of flow-thermo-solid coupling is decomposed into two parts:flow-solid coupling and thermo-solid coupling.Considering the Fuyu oil shale in-situ production test area in Songliao Basin as an example,it is concluded that the oil shale has undergone four heating stages:a rapid temperature rise,a steady temperature rise,a slow temperature rise,and heat preservation.It takes about 10 years for the stress-strain state of the oil shale layer to reach a steady-state through the thermo-solid coupling.The main strain zones of the oil shale layer are distributed near the fracturing fractures connected to the gas injection well and at the edge of the fracturing fractures.The areas with the plastic deformation in the oil shale layer predominantly appear near the gas injection wells,production wells,and fracturing channels.The areas with the largest fracture strength are mostly distributed near the edge of the fracturing fractures with low flow velocity and low temperature.展开更多
In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin proj...In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.展开更多
砂土液化是常见的地震灾害,目前应用于研究砂土液化动力特性的室内试验以及模型试验还不能全面反映土体液化全过程。计算流体动力学(computational fluid dynamics,CFD)与离散元法(discrete element method,DEM)耦合模拟方法能够准确地...砂土液化是常见的地震灾害,目前应用于研究砂土液化动力特性的室内试验以及模型试验还不能全面反映土体液化全过程。计算流体动力学(computational fluid dynamics,CFD)与离散元法(discrete element method,DEM)耦合模拟方法能够准确地模拟各类水土耦合问题。通过二次开发的CFD-DEM流固耦合模块实现离散元软件PFC3D与计算流体力学软件OpenFOAM之间的力学信息交互,利用颗粒水下自由沉降验证该方法的可行性。利用PFC3D软件模拟室内循环三轴试验标定出具有真实饱和砂土动力特性的数值砂样。根据已有的参数信息以及耦合模拟方法建立了饱和砂土的场地液化模型。模拟结果表明,离散元法能够复现室内砂土液化试验,标定参数可应用于场地液化模拟;单颗粒沉降速度与理论解一致验证了CFD-DEM耦合方法的准确性;峰值加速度0.25g下不同深度处土体均会发生液化,液化时超孔压比无法达到1,超孔压累计值由浅层往深层递增;液化后土体强度自下而上逐渐恢复,再固结的场地土体结构呈现均匀化发展趋势。展开更多
Modeling has become phenomenal in developing new products.In the case of filters,one of the mos applied procedures is via the construction of idealized physical computational models bearing close semblance to real fil...Modeling has become phenomenal in developing new products.In the case of filters,one of the mos applied procedures is via the construction of idealized physical computational models bearing close semblance to real filter media.It is upon these that multi-physics tools were applied to analvze the fow of fuid and the resulting typical performance parameters.In this work,two 3D filter membranes were constructed with MATLAB:one had a random distribution of unimodal nanofibers,and the other,a novel modification,formed.a bimodal distribution:both of them had similar dimensions and solid volume fractions.A comparison of their performance in a dust-loading environment was made by using computational fluid dynamic-discrete elemen method(CED-DEM)coupling technique in STAR-CCM+.It was found that the bimodal nanofiber membrane greatly improved the particle capture efficiencv.Whereas this increased the pressure drop,the gain was not toosignificant.Thus.overall,the results of the figure of merit ptoved that adopting a bimodal formation improved the filter's quality.展开更多
The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical m...The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical method based on computational fluid mechanics(CFD).The transient aerodynamic behaviors when opening door under various flight altitudes and the corresponding structure deformation evolution in the unsteady flow fields are analyzed respectively and presented.The rules of aircraft attitude parameters′impacting to the responses of structure and the bay-door′s opening process are obtained by comparing with the analysis results.These rules can be applied to the structure design of bay-door and route specification of missile when disengaged and launched from within store.展开更多
过滤器内部的水沙运动复杂且多变,初始状态下沙粒分布的不均导致滤芯产生局部堵塞,改变了水流流态并进一步影响后续沙粒运动和分布。本文以CFD-DEM(Computational fluid dynamics,CFD;Discrete element method,DEM)耦合模拟Y型网式过滤...过滤器内部的水沙运动复杂且多变,初始状态下沙粒分布的不均导致滤芯产生局部堵塞,改变了水流流态并进一步影响后续沙粒运动和分布。本文以CFD-DEM(Computational fluid dynamics,CFD;Discrete element method,DEM)耦合模拟Y型网式过滤器内部流场变化与沙粒运动及分布,直观地反映了滤芯对水流的流动阻力特性与对沙粒运动分布影响。结果表明,过滤器内部存在明显的回流区、旋涡区及滞流区,导致各过滤面流速不均,出口一侧流速大,进口一侧流速小,两者相差39%;随着时间的变化,过滤器内流场变化明显,沙粒堆积依次出现在出口侧下端面、出口侧上端面、进口侧下端面、进口侧上端面上,最终布满整个滤芯;在滤芯的4个过滤面中,出口侧上端面流速大而沙粒堆积最少,进口侧上端面流速小而沙粒堆积最多,由此可见出口侧上端面具有更好的过滤性能,可适当提高该处过水面积,以提高过滤器过滤效率。展开更多
基金Supported by Project of Science and Technology Department of Jilin Province(No.20170201001SF)。
文摘For the in-situ gas-injection mining technology of oil shale by process,a numerical simulation method with flow-thermo-solid coupling is proposed in this paper.This method adopts separate simulations and step-by-step coupling simulation ideas combined with the advantages of the finite element method and the finite volume method.The numerical simulation of flow-thermo-solid coupling is decomposed into two parts:flow-solid coupling and thermo-solid coupling.Considering the Fuyu oil shale in-situ production test area in Songliao Basin as an example,it is concluded that the oil shale has undergone four heating stages:a rapid temperature rise,a steady temperature rise,a slow temperature rise,and heat preservation.It takes about 10 years for the stress-strain state of the oil shale layer to reach a steady-state through the thermo-solid coupling.The main strain zones of the oil shale layer are distributed near the fracturing fractures connected to the gas injection well and at the edge of the fracturing fractures.The areas with the plastic deformation in the oil shale layer predominantly appear near the gas injection wells,production wells,and fracturing channels.The areas with the largest fracture strength are mostly distributed near the edge of the fracturing fractures with low flow velocity and low temperature.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2141254 and U23B6009)。
文摘In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.
文摘砂土液化是常见的地震灾害,目前应用于研究砂土液化动力特性的室内试验以及模型试验还不能全面反映土体液化全过程。计算流体动力学(computational fluid dynamics,CFD)与离散元法(discrete element method,DEM)耦合模拟方法能够准确地模拟各类水土耦合问题。通过二次开发的CFD-DEM流固耦合模块实现离散元软件PFC3D与计算流体力学软件OpenFOAM之间的力学信息交互,利用颗粒水下自由沉降验证该方法的可行性。利用PFC3D软件模拟室内循环三轴试验标定出具有真实饱和砂土动力特性的数值砂样。根据已有的参数信息以及耦合模拟方法建立了饱和砂土的场地液化模型。模拟结果表明,离散元法能够复现室内砂土液化试验,标定参数可应用于场地液化模拟;单颗粒沉降速度与理论解一致验证了CFD-DEM耦合方法的准确性;峰值加速度0.25g下不同深度处土体均会发生液化,液化时超孔压比无法达到1,超孔压累计值由浅层往深层递增;液化后土体强度自下而上逐渐恢复,再固结的场地土体结构呈现均匀化发展趋势。
基金the Chang Jiang Youth Scholars Program of China(No.51773037)the National Natural Science Foundation of China(Nos.51803023 and 61771123)+2 种基金the Shanghai Sailing Program(No.18YF1400400)the China Postdoctoral Science Foundation(No.2018M640317)the Fundamental Hesearch Funds for the Central Universities(No.2232018A3-11)。
文摘Modeling has become phenomenal in developing new products.In the case of filters,one of the mos applied procedures is via the construction of idealized physical computational models bearing close semblance to real filter media.It is upon these that multi-physics tools were applied to analvze the fow of fuid and the resulting typical performance parameters.In this work,two 3D filter membranes were constructed with MATLAB:one had a random distribution of unimodal nanofibers,and the other,a novel modification,formed.a bimodal distribution:both of them had similar dimensions and solid volume fractions.A comparison of their performance in a dust-loading environment was made by using computational fluid dynamic-discrete elemen method(CED-DEM)coupling technique in STAR-CCM+.It was found that the bimodal nanofiber membrane greatly improved the particle capture efficiencv.Whereas this increased the pressure drop,the gain was not toosignificant.Thus.overall,the results of the figure of merit ptoved that adopting a bimodal formation improved the filter's quality.
文摘The coupling behavior of the imbedded weapon store occurring between the local unsteady flow field round the store and the structure response on the processing of opening its bay-door is simulated by using numerical method based on computational fluid mechanics(CFD).The transient aerodynamic behaviors when opening door under various flight altitudes and the corresponding structure deformation evolution in the unsteady flow fields are analyzed respectively and presented.The rules of aircraft attitude parameters′impacting to the responses of structure and the bay-door′s opening process are obtained by comparing with the analysis results.These rules can be applied to the structure design of bay-door and route specification of missile when disengaged and launched from within store.
文摘过滤器内部的水沙运动复杂且多变,初始状态下沙粒分布的不均导致滤芯产生局部堵塞,改变了水流流态并进一步影响后续沙粒运动和分布。本文以CFD-DEM(Computational fluid dynamics,CFD;Discrete element method,DEM)耦合模拟Y型网式过滤器内部流场变化与沙粒运动及分布,直观地反映了滤芯对水流的流动阻力特性与对沙粒运动分布影响。结果表明,过滤器内部存在明显的回流区、旋涡区及滞流区,导致各过滤面流速不均,出口一侧流速大,进口一侧流速小,两者相差39%;随着时间的变化,过滤器内流场变化明显,沙粒堆积依次出现在出口侧下端面、出口侧上端面、进口侧下端面、进口侧上端面上,最终布满整个滤芯;在滤芯的4个过滤面中,出口侧上端面流速大而沙粒堆积最少,进口侧上端面流速小而沙粒堆积最多,由此可见出口侧上端面具有更好的过滤性能,可适当提高该处过水面积,以提高过滤器过滤效率。
