We propose a hybrid quantum-classical method,the quantum-enriched large eddy simulation(QELES),for simulating turbulence.The QELES combines the large-scale motion of the large eddy simulation(LES)and the subgrid motio...We propose a hybrid quantum-classical method,the quantum-enriched large eddy simulation(QELES),for simulating turbulence.The QELES combines the large-scale motion of the large eddy simulation(LES)and the subgrid motion of the incompressible Schrodinger flow(ISF).The ISF is a possible way to be simulated on a quantum computer,and it generates subgrid scale turbu-lent structures to enrich the LES field.The enriched LES field can be further used in turbulent combustion and multi-phase flows in which the subgrid scale motion plays an important role.As a conceptual study,we perform the simulations of ISF and LES separately on a classical computer to simulate decaying homogeneous isotropic turbulence.Then,the QEI ES velocity is obtained by the time matching and the spectral blending methods.The QEL ES achieves significant improvement in predicting the energy spectrum,probaility density functions of velocity and vorticity components,and velocity structure functions,and reconstructs coherent small-scales vortices in the direct numerical simulation(DNS).On the other hand,the vortices in the QELES are less elongated and tangled than those in the DNS,and the magnitude of the third-order structure function in the QELES is less than that in the DNS,due to the diferent constitutive relations in the viscous flow and ISE.展开更多
The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transp...The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transported Probability Density Function(TPDF) turbulence combustion model is promising in engineering applications. In flame region, the impact of chemical reaction should be considered in TPDF molecular mixing model. Based on pioneer research, three new TPDF turbulence-chemistry dual time scale molecular mixing models were proposed tentatively by adding the chemistry time scale in molecular mixing model for nonpremixed flame. The Aero-Engine Combustor Simulation Code(AECSC) which is based on LES-TPDF method was combined with the three new models. Then the Sandia laboratory's methane-air jet flames: Flame D and Flame E were simulated. Transient simulation results show that all the three new models can predict the instantaneous combustion flow pattern of the jet flames. Furthermore,the average scalar statistical results were compared with the experimental data. The simulation result of the new TPDF arithmetic mean modification model is the closest to the experimental data:the average error in Flame D is 7.6% and 6.6% in Flame E. The extinction and re-ignition phenomena of the jet flames especially Flame E were captured. The turbulence time scale and the chemistry time scale are in different order in the whole flow field. The dual time scale TPDF combustion model has ability to deal with both the turbulence effect and the chemistry reaction effect, as well as their interaction more accurately for nonpremixed flames.展开更多
Cloud manufacturing is a specific implementation form of the "Internet + manufacturing" strategy. Why and how to develop cloud manufacturing platform(CMP), however, remains the key concern of both platform o...Cloud manufacturing is a specific implementation form of the "Internet + manufacturing" strategy. Why and how to develop cloud manufacturing platform(CMP), however, remains the key concern of both platform operators and users. A microscopic model is proposed to investigate advantages and diffusion forces of CMP through exploration of its diffusion process and mechanism. Specifically, a three-stage basic evolution process of CMP is innovatively proposed. Then, based on this basic process, a more complex CMP evolution model has been established in virtue of complex network theory, with five diffusion forces identified. Thereafter, simulations on CMP diffusion have been conducted. The results indicate that, CMP possesses better resource utilization,user satisfaction, and enterprise utility. Results of simulation on impacts of different diffusion forces show that both the time required for CMP to reach an equilibrium state and the final network size are affected simultaneously by the five diffusion forces. All these analyses indicate that CMP could create an open online cooperation environment and turns out to be an effective implementation of the "Internet + manufacturing" strategy.展开更多
Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by...Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by Jones-Launder was employed. The numerical results were compared with the experimental data in the literature. It is found that the calculated results are in good agreement with the experimental data.展开更多
AIM To investigate the use of a multidisciplinary,longitudinal simulation to educate pediatric residents and nurses on management of pediatric diabetic ketoacidosis.METHODS A multidisciplinary,multiple step simulation...AIM To investigate the use of a multidisciplinary,longitudinal simulation to educate pediatric residents and nurses on management of pediatric diabetic ketoacidosis.METHODS A multidisciplinary,multiple step simulation course was developed by faculty and staff using a modified Delphi method from the Pediatric Simulation Center and pediatric endocrinology department.Effectiveness of the simulation for the residents was measured with a pre-and post-test and a reference group not exposed to simulation.A follow up post-test was completed 3-6 mo after the simulation.Nurses completed a survey regarding the education activity.RESULTS Pediatric and medicine-pediatric residents(n=20)and pediatric nurses(n=25)completed the simulation course.Graduating residents(n=16)were used as reference group.Pretest results were similar in the control and intervention group(74%±10%vs 76%±15%,P=0.658).After completing the intervention,participants improved in the immediate post-test in comparison to themselves and the control group(84%±12%post study;P<0.05).The 3-6 mo follow up post-test results demonstrated knowledge decay when compared to their immediate post-test results(78%±14%,P=0.761).Residents and nurses felt the interdisciplinary and longitudinal nature of the simulation helped with learning.CONCLUSION Results suggest a multidisciplinary,longitudinal simulation improves immediate post-intervention knowledge but important knowledge decay occurs,future studies are needed to determine ways to decrease this decay.展开更多
For the numerical simulation of flow systems with various complex components, the traditional one-dimensional （1D） network method has its comparative advantage in time consuming and the CFD method has its absolute a...For the numerical simulation of flow systems with various complex components, the traditional one-dimensional （1D） network method has its comparative advantage in time consuming and the CFD method has its absolute advantage in the detailed flow capturing. The proper coupling of the advantages of different dimensional methods can strike balance well between time cost and accuracy and then significantly decrease the whole design cycle for the flow systems in modern machines. A novel multi-fidelity coupled simulation method with numerical zooming is developed for flow systems. This method focuses on the integration of one-, two-and three-dimensional codes for various components. Coupled iterative process for the different dimensional simulation cycles of sub-systems is performed until the concerned flow variables of the whole system achieve convergence. Numerical zooming is employed to update boundary data of components with different dimen-sionalities. Based on this method, a highly automatic, multi-discipline computing environment with integrated zooming is developed. The numerical results of Y-Junction and the air system of a jet engine are presented to verify the solution method. They indicate that this type of multi-fidelity simulationmethod can greatly improve the prediction capability for the flow systems.展开更多
Cross iteration often exists in the computational process of the simulation models, especially for control models. There is a credibility defect tracing problem in the validation of models with cross iteration. In ord...Cross iteration often exists in the computational process of the simulation models, especially for control models. There is a credibility defect tracing problem in the validation of models with cross iteration. In order to resolve this problem, after the problem formulation, a validation theorem on the cross iteration is proposed, and the proof of the theorem is given under the cross iteration circumstance. Meanwhile, applying the proposed theorem, the credibility calculation algorithm is provided, and the solvent of the defect tracing is explained. Further, based on the validation theorem on the cross iteration, a validation method for simulation models with the cross iteration is proposed, which is illustrated by a flowchart step by step. Finally, a validation example of a sixdegree of freedom (DOF) flight vehicle model is provided, and the validation process is performed by using the validation method. The result analysis shows that the method is effective to obtain the credibility of the model and accomplish the defect tracing of the validation.展开更多
In order to deal with aliasing distortions of Doppler frequencies shown in time-frequency representation（ TFR） with aspect undersampling,an approach using adaptive segmental compressive sampling according to the asp...In order to deal with aliasing distortions of Doppler frequencies shown in time-frequency representation（ TFR） with aspect undersampling,an approach using adaptive segmental compressive sampling according to the aspect dependencies of the scattering centers is proposed. The random noise problem induced by compressive sampling is solved by employing a series of signal processing techniques of filtering,image transformation and Hough Transform. Three examples are presented to verify the effectiveness of this approach. The comparisons between the built models and the precise scattered fields computed by a well-validated full-wave numerical method are investigated,and the results showgood agreements between each other.展开更多
This paper discusses a float-coded genetic algorithm and its application to the optimization of the power plant operation concerning the simulation problem of economical operation for power plant systems. The method p...This paper discusses a float-coded genetic algorithm and its application to the optimization of the power plant operation concerning the simulation problem of economical operation for power plant systems. The method proposed realizes the load optimization between generating units of power plants and their loads, solves the problem of influence of a unit plant pause spoilage and load variance on the optimal plant combination and load, and finally establishes a simulation platform for the power plant economical operation.展开更多
Different paradigms that relate verification and validation to the simulation model have different development process. A simulation model developing process based on Five-Object Framework (FOF) is discussed in this p...Different paradigms that relate verification and validation to the simulation model have different development process. A simulation model developing process based on Five-Object Framework (FOF) is discussed in this paper. An example is given to demonstrate the applications of the proposed method.展开更多
Current transient analysis predominantly relies on zero-dimensional/one-dimensional tools,proficient at capturing aerothermodynamic variations across critical engine stations but insufficient for analyzing the interna...Current transient analysis predominantly relies on zero-dimensional/one-dimensional tools,proficient at capturing aerothermodynamic variations across critical engine stations but insufficient for analyzing the internal flow field evolution during transients.Addressing this gap,the study presents an enhanced quasi-three dimensional(quasi-3D)transient simulation technique that integrates component volume effects,offering a significant leap from the preceding quasi-3D transient simulation method based on quasi-steady assumption.By embedding the component volume effects on density,momentum,and energy within the physical temporal dimension of the Navier-Stokes equations,the refined quasi-3D transient model achieves a closer representation of physical phenomena.Validation against a single-shaft turbofan engine’s experimental data confirms the model’s accuracy.Average errors for key performance indicators,including shaft speed,thrust,mass flow rate,and critical component exit temperature and pressure,remain below 0.41%,5.69%,2.55%,3.18%and 0.67%,respectively.Crucially,the model exposes a discernible temporal lag in the compressor outlet pressure and temperature response due to volume effects—previously unquantified in quasi-3D transient simulations.And further exploration of the meridional flow field emphasizes the consequential role of volumes in transient flow field evolution.Incorporating volume effects within quasi-3D transient simulations enhances engine modeling and is pivotal for precise transient analysis in engine design and optimization.展开更多
Global linear gyrokinetic simulations using realistic DIII-D tokamak geometry and plasma profiles find co-existence of unstable reversed shear Alfvén eigenmodes(RSAE)with low toroidal mode number n and electromag...Global linear gyrokinetic simulations using realistic DIII-D tokamak geometry and plasma profiles find co-existence of unstable reversed shear Alfvén eigenmodes(RSAE)with low toroidal mode number n and electromagnetic ion temperature gradient(ITG)instabilities with higher toroidal mode number n.For intermediate n?=?[10,12],RSAE and ITG co-exist and overlap weakly in the radial domain with similar growth rates but different real frequencies.Both RSAE and ITG growth rates decrease less than 5%when compressible magnetic perturbations are neglected in the simulations.The ITG growth rates increase less than 7%when fast ions are not included in the simulations.Finally,the effects of trapped electrons on the RSAE are negligible.展开更多
It is difficult or even impossible for a pure mathematical model to represent a complex giant system because of the complexity, activity, uncertainty in such a system. The meta-synthesis methodology and the generalize...It is difficult or even impossible for a pure mathematical model to represent a complex giant system because of the complexity, activity, uncertainty in such a system. The meta-synthesis methodology and the generalized modelling method are used to model a complex giant system. This paper has an in-depth study on the confidence assessment of a complex giant system simulation model that is built based on the meta-synthesis methodology and the generalized modelling method. A new definition of VV&A for complex system is given, on which is based a 12-step reference model and proposed for VV&A purpose. Furthermore, the principle and method of intelligent boundary interval intermediate assessment is proposed for the harmonization of modelling and model-validation.展开更多
This conference report summarizes recent progress in plasma theory and simulation that was presented in contributed papers and discussions at the 11th Conference on Magnetic Confined Fusion Theory and Simulation(CMCFT...This conference report summarizes recent progress in plasma theory and simulation that was presented in contributed papers and discussions at the 11th Conference on Magnetic Confined Fusion Theory and Simulation(CMCFTS)held in Chengdu,China,27–30 October,2023.Progress in various fields has been achieved.For example,results on zonal flow generation by mode coupling,simulations of the key physics of divertor detachment,energetic particle effects on magnetohydrodynamic(MHD)modes in addition to ion-and electron-scale turbulence,physics of edge coherent modes and edge-localized modes,and the optimization of ion heating schemes as well as confinement scenarios using advanced integrated modeling are presented at the conference.In this conference,the scientific research groups were organized into six categories:(a)edge and divertor physics;(b)impurity,heating,and current drive;(c)energetic particle physics;(d)turbulent transport;(e)MHD instability;and(f)integrated modeling and code development.A summary of the highlighted progress in these working groups is presented.展开更多
A conservative scheme of kinetic electrons for gyrokinetic simulations in the presence of magnetic islands has been implemented and verified in the gyrokinetic toroidal code, where zonal and nonzonal components of all...A conservative scheme of kinetic electrons for gyrokinetic simulations in the presence of magnetic islands has been implemented and verified in the gyrokinetic toroidal code, where zonal and nonzonal components of all perturbed quantities are solved together. Using this new conservative scheme, linear simulation of kinetic ballooning mode has been successfully benchmarked with the electromagnetic hybrid model. Simulations of nonlinear interactions between magnetic islands and the ion temperature gradient(ITG) mode in a tokamak show that the islands rotate at the electron diamagnetic drift velocity. The linear ITG structure shifts from the island O-point toward the X-point due to the pressure flattening effect inside the islands, and the nonlinear ITG structure peaks along the magnetic island separatrix because of the increased pressure gradient there.展开更多
In the present paper,we first derive the eigenmode equation of the ideal ballooning mode in tokamak plasmas using a gyrokinetic equation.It is shown that the gyrokinetic eigenmode equation can be reduced to the magnet...In the present paper,we first derive the eigenmode equation of the ideal ballooning mode in tokamak plasmas using a gyrokinetic equation.It is shown that the gyrokinetic eigenmode equation can be reduced to the magnetohydrodynamic（MHD） form in the long wavelength limit when kinetic effects are ignored.Then,the global gyrokinetic toroidal code（GTC） is applied for simulations of the edge-localized ideal ballooning modes.The obtained mode structures are compared with the results of ideal MHD simulations.The observed scaling of the linear growth rate with the toroidal mode number is consistent with the ideal MHD theory.The simulation results verify the GTC capability of simulating MHD processes in toroidal plasmas.展开更多
In this study,a code,named Peking University Helicon Discharge(PHD),which can simulate helicon discharge processes under both a background magnetic field greater than 500 G and a pressure less than 1 Pa,is developed.I...In this study,a code,named Peking University Helicon Discharge(PHD),which can simulate helicon discharge processes under both a background magnetic field greater than 500 G and a pressure less than 1 Pa,is developed.In the code,two fluid equations are used.The PHD simulations led to two important findings:(1)the temporal evolution of plasma density with the background magnetic field exhibits a second rapid increase(termed as the second density jump),similar to the transition of modes in helicon plasmas;(2)in the presence of a magnetic field,the peak positions of electron power absorption appeared near the central axis,unlike in the case of no magnetic field.These results may lead to an enhanced understanding of the discharge mechanism.展开更多
A cooperative guidance law is proposed in a two-ontwo engagement scenario with large-heading-errors by choosing zero-effort miss distance as a sliding surface,which consists of an attacker,a protector,a defender,and a...A cooperative guidance law is proposed in a two-ontwo engagement scenario with large-heading-errors by choosing zero-effort miss distance as a sliding surface,which consists of an attacker,a protector,a defender,and a target,based on fixed-time sliding mode control theory.Based on the nonlinear method of fixed-time sliding mode control,the performance of the cooperative guidance law remains satisfactory even with large-heading-errors scenarios where the linearization-based approaches might be invalid.By virtue of this law,the attacker pursues the target with the assistance of the protector,which can intercept the defender in the engagement scenario.Furthermore,if the attacker is intercepted by the defender,the guidance law of the protector could guarantee that the protector attacks the target.A robust adaptive term is included in the guidance law to deal with the case of the unknown disturbance upper bound of the defender-target team.Finally,the feasibility of the guidance law is verified by nonlinear numerical simulations,and the superiority of it is illustrated by comparing with the linearization guidance law.展开更多
Single-and dual-atom catalysts(SACs and DACs)on single-layer graphene are widely investigated for a wide range of electrochemical reactions.However,the effect of van der Waals interactions on the activity of these cat...Single-and dual-atom catalysts(SACs and DACs)on single-layer graphene are widely investigated for a wide range of electrochemical reactions.However,the effect of van der Waals interactions on the activity of these catalysts has not been investigated through systematic high-throughput screening.Here we introduce the concept of van der Waals interactions through a double-layer DAC structure which has axial d orbital modification towards enhanced CO_(2) reduction reaction(CO_(2)RR),hydrogen evolution reaction(HER),oxygen reduction reaction(ORR),and oxygen evolution reaction(OER).We applied density functional theory(DFT)to screen 3d,4d,and 5d transition metals supported by double-layer nitrogen-doped graphene,denoted as M2N8.We sought catalysts with high thermodynamic and electrochemical stabilities along with low overpotentials for CO_(2)RR,ORR,OER,or HER.We find that HER can take place inside the van der Waals gap of V2N8 and Co2N8 leading to overpotentials of 0.10 and 0.16 V.Moreover,ORR and OER can take place on the surface of Fe2N8 and Ir2N8,respectively,leading to overpotentials of 0.39 and 0.37 V.DFT predicts a CO_(2)RR overpotential of 0.85 V towards CO on the surface of Co2N8 along with the HER overpotential of 0.16 V inside the van der Waals gap of Co2N8 towards the production of syngas(CO+H_(2)).This paper provides fundamental insights into the design of advanced multi-layer catalysts by applying the concept of van der Waals interactions for electrochemistry at room temperature.展开更多
Aimed at the guidance requirements of some missiles which attack targets with terminal impact angle at the terminal point,a new integrated guidance and control design scheme based on variable structure control approac...Aimed at the guidance requirements of some missiles which attack targets with terminal impact angle at the terminal point,a new integrated guidance and control design scheme based on variable structure control approach for missile with terminal impact angle constraint is proposed.First,a mathematical model of an integrated guidance and control model in pitch plane is established,and then nonlinear transformation is employed to transform the mathematical model into a standard form suitable for sliding mode control method design.A sufficient condition for the existence of linear sliding surface is given in terms of linear matrix inequalities（LMIs）,based on which the corresponding reaching motion controller is also developed.To verify the effectiveness of the proposed integrated design scheme,the numerical simulation of missile is made.The simulation results demonstrate that the proposed guidance and control law can guide missile to hit the target with desired impact angle and desired flight attitude angle simultaneously.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.11925201,and 11988102)the National Key R&D Program of China (Grant No.2020YFE0204200)the Xplore Prize.Numerical simulations were carried out on the TH-2A supercomputer in Guangzhou,China.
文摘We propose a hybrid quantum-classical method,the quantum-enriched large eddy simulation(QELES),for simulating turbulence.The QELES combines the large-scale motion of the large eddy simulation(LES)and the subgrid motion of the incompressible Schrodinger flow(ISF).The ISF is a possible way to be simulated on a quantum computer,and it generates subgrid scale turbu-lent structures to enrich the LES field.The enriched LES field can be further used in turbulent combustion and multi-phase flows in which the subgrid scale motion plays an important role.As a conceptual study,we perform the simulations of ISF and LES separately on a classical computer to simulate decaying homogeneous isotropic turbulence.Then,the QEI ES velocity is obtained by the time matching and the spectral blending methods.The QEL ES achieves significant improvement in predicting the energy spectrum,probaility density functions of velocity and vorticity components,and velocity structure functions,and reconstructs coherent small-scales vortices in the direct numerical simulation(DNS).On the other hand,the vortices in the QELES are less elongated and tangled than those in the DNS,and the magnitude of the third-order structure function in the QELES is less than that in the DNS,due to the diferent constitutive relations in the viscous flow and ISE.
基金co-supported by the National Key R&D Program of China(Nos.2017YFB0202400 and 2017YFB0202402)the National Natural Science Foundation of China(No.91741125)the Project of Newton International Fellowship Alumnus from Royal Society(No.AL120003)
文摘The numerical simulation of modern aero-engine combustion chamber needs accurate description of the interaction between turbulence and chemical reaction mechanism. The Large Eddy Simulation(LES) method with the Transported Probability Density Function(TPDF) turbulence combustion model is promising in engineering applications. In flame region, the impact of chemical reaction should be considered in TPDF molecular mixing model. Based on pioneer research, three new TPDF turbulence-chemistry dual time scale molecular mixing models were proposed tentatively by adding the chemistry time scale in molecular mixing model for nonpremixed flame. The Aero-Engine Combustor Simulation Code(AECSC) which is based on LES-TPDF method was combined with the three new models. Then the Sandia laboratory's methane-air jet flames: Flame D and Flame E were simulated. Transient simulation results show that all the three new models can predict the instantaneous combustion flow pattern of the jet flames. Furthermore,the average scalar statistical results were compared with the experimental data. The simulation result of the new TPDF arithmetic mean modification model is the closest to the experimental data:the average error in Flame D is 7.6% and 6.6% in Flame E. The extinction and re-ignition phenomena of the jet flames especially Flame E were captured. The turbulence time scale and the chemistry time scale are in different order in the whole flow field. The dual time scale TPDF combustion model has ability to deal with both the turbulence effect and the chemistry reaction effect, as well as their interaction more accurately for nonpremixed flames.
基金supported by the National High-Tech R&D Program,China(2015AA042101)
文摘Cloud manufacturing is a specific implementation form of the "Internet + manufacturing" strategy. Why and how to develop cloud manufacturing platform(CMP), however, remains the key concern of both platform operators and users. A microscopic model is proposed to investigate advantages and diffusion forces of CMP through exploration of its diffusion process and mechanism. Specifically, a three-stage basic evolution process of CMP is innovatively proposed. Then, based on this basic process, a more complex CMP evolution model has been established in virtue of complex network theory, with five diffusion forces identified. Thereafter, simulations on CMP diffusion have been conducted. The results indicate that, CMP possesses better resource utilization,user satisfaction, and enterprise utility. Results of simulation on impacts of different diffusion forces show that both the time required for CMP to reach an equilibrium state and the final network size are affected simultaneously by the five diffusion forces. All these analyses indicate that CMP could create an open online cooperation environment and turns out to be an effective implementation of the "Internet + manufacturing" strategy.
基金Supported by the Ph.D. Start-up Fund of Beijing University of Technology (No.127-00227).
文摘Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by Jones-Launder was employed. The numerical results were compared with the experimental data in the literature. It is found that the calculated results are in good agreement with the experimental data.
基金Supported by A University of Alabama at Birmingham Department of Pediatrics Founders Fund Grant
文摘AIM To investigate the use of a multidisciplinary,longitudinal simulation to educate pediatric residents and nurses on management of pediatric diabetic ketoacidosis.METHODS A multidisciplinary,multiple step simulation course was developed by faculty and staff using a modified Delphi method from the Pediatric Simulation Center and pediatric endocrinology department.Effectiveness of the simulation for the residents was measured with a pre-and post-test and a reference group not exposed to simulation.A follow up post-test was completed 3-6 mo after the simulation.Nurses completed a survey regarding the education activity.RESULTS Pediatric and medicine-pediatric residents(n=20)and pediatric nurses(n=25)completed the simulation course.Graduating residents(n=16)were used as reference group.Pretest results were similar in the control and intervention group(74%±10%vs 76%±15%,P=0.658).After completing the intervention,participants improved in the immediate post-test in comparison to themselves and the control group(84%±12%post study;P<0.05).The 3-6 mo follow up post-test results demonstrated knowledge decay when compared to their immediate post-test results(78%±14%,P=0.761).Residents and nurses felt the interdisciplinary and longitudinal nature of the simulation helped with learning.CONCLUSION Results suggest a multidisciplinary,longitudinal simulation improves immediate post-intervention knowledge but important knowledge decay occurs,future studies are needed to determine ways to decrease this decay.
基金National Weapon Equipment Pre-research Foundation of China(0C410101110C4101)Innovation Foundation of BUAA for PhD Graduates(YWF-13-A01-15)for funding this work
文摘For the numerical simulation of flow systems with various complex components, the traditional one-dimensional （1D） network method has its comparative advantage in time consuming and the CFD method has its absolute advantage in the detailed flow capturing. The proper coupling of the advantages of different dimensional methods can strike balance well between time cost and accuracy and then significantly decrease the whole design cycle for the flow systems in modern machines. A novel multi-fidelity coupled simulation method with numerical zooming is developed for flow systems. This method focuses on the integration of one-, two-and three-dimensional codes for various components. Coupled iterative process for the different dimensional simulation cycles of sub-systems is performed until the concerned flow variables of the whole system achieve convergence. Numerical zooming is employed to update boundary data of components with different dimen-sionalities. Based on this method, a highly automatic, multi-discipline computing environment with integrated zooming is developed. The numerical results of Y-Junction and the air system of a jet engine are presented to verify the solution method. They indicate that this type of multi-fidelity simulationmethod can greatly improve the prediction capability for the flow systems.
基金supported by the National Natural Science Foundation of China(61374164)
文摘Cross iteration often exists in the computational process of the simulation models, especially for control models. There is a credibility defect tracing problem in the validation of models with cross iteration. In order to resolve this problem, after the problem formulation, a validation theorem on the cross iteration is proposed, and the proof of the theorem is given under the cross iteration circumstance. Meanwhile, applying the proposed theorem, the credibility calculation algorithm is provided, and the solvent of the defect tracing is explained. Further, based on the validation theorem on the cross iteration, a validation method for simulation models with the cross iteration is proposed, which is illustrated by a flowchart step by step. Finally, a validation example of a sixdegree of freedom (DOF) flight vehicle model is provided, and the validation process is performed by using the validation method. The result analysis shows that the method is effective to obtain the credibility of the model and accomplish the defect tracing of the validation.
基金Supported by the National Natural Science Foundation of China(61421001,61471041,61671059)
文摘In order to deal with aliasing distortions of Doppler frequencies shown in time-frequency representation（ TFR） with aspect undersampling,an approach using adaptive segmental compressive sampling according to the aspect dependencies of the scattering centers is proposed. The random noise problem induced by compressive sampling is solved by employing a series of signal processing techniques of filtering,image transformation and Hough Transform. Three examples are presented to verify the effectiveness of this approach. The comparisons between the built models and the precise scattered fields computed by a well-validated full-wave numerical method are investigated,and the results showgood agreements between each other.
文摘This paper discusses a float-coded genetic algorithm and its application to the optimization of the power plant operation concerning the simulation problem of economical operation for power plant systems. The method proposed realizes the load optimization between generating units of power plants and their loads, solves the problem of influence of a unit plant pause spoilage and load variance on the optimal plant combination and load, and finally establishes a simulation platform for the power plant economical operation.
文摘Different paradigms that relate verification and validation to the simulation model have different development process. A simulation model developing process based on Five-Object Framework (FOF) is discussed in this paper. An example is given to demonstrate the applications of the proposed method.
基金supported by the National Natural Science Foundation of China(No.52376021).
文摘Current transient analysis predominantly relies on zero-dimensional/one-dimensional tools,proficient at capturing aerothermodynamic variations across critical engine stations but insufficient for analyzing the internal flow field evolution during transients.Addressing this gap,the study presents an enhanced quasi-three dimensional(quasi-3D)transient simulation technique that integrates component volume effects,offering a significant leap from the preceding quasi-3D transient simulation method based on quasi-steady assumption.By embedding the component volume effects on density,momentum,and energy within the physical temporal dimension of the Navier-Stokes equations,the refined quasi-3D transient model achieves a closer representation of physical phenomena.Validation against a single-shaft turbofan engine’s experimental data confirms the model’s accuracy.Average errors for key performance indicators,including shaft speed,thrust,mass flow rate,and critical component exit temperature and pressure,remain below 0.41%,5.69%,2.55%,3.18%and 0.67%,respectively.Crucially,the model exposes a discernible temporal lag in the compressor outlet pressure and temperature response due to volume effects—previously unquantified in quasi-3D transient simulations.And further exploration of the meridional flow field emphasizes the consequential role of volumes in transient flow field evolution.Incorporating volume effects within quasi-3D transient simulations enhances engine modeling and is pivotal for precise transient analysis in engine design and optimization.
基金supported by the China National Magnetic Confinement Fusion Science Program(Grant No.2018YFE0304100)the US Department of Energy,Office of Science,Office of Advanced Scientific Computing Research and Office of Fusion Energy Sciences,and the Scientific Discovery through Advanced Computing(Sci DAC)program under Award No.DE-SC0018270(Sci DAC ISEP Center)+2 种基金the China Scholarship Council(Grant No.201806010067)used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory(DOE Contract No.DEAC05-00OR22725)the National Energy Research Scientific Computing Center(DOE Contract No.DE-AC02-05CH11231)
文摘Global linear gyrokinetic simulations using realistic DIII-D tokamak geometry and plasma profiles find co-existence of unstable reversed shear Alfvén eigenmodes(RSAE)with low toroidal mode number n and electromagnetic ion temperature gradient(ITG)instabilities with higher toroidal mode number n.For intermediate n?=?[10,12],RSAE and ITG co-exist and overlap weakly in the radial domain with similar growth rates but different real frequencies.Both RSAE and ITG growth rates decrease less than 5%when compressible magnetic perturbations are neglected in the simulations.The ITG growth rates increase less than 7%when fast ions are not included in the simulations.Finally,the effects of trapped electrons on the RSAE are negligible.
文摘It is difficult or even impossible for a pure mathematical model to represent a complex giant system because of the complexity, activity, uncertainty in such a system. The meta-synthesis methodology and the generalized modelling method are used to model a complex giant system. This paper has an in-depth study on the confidence assessment of a complex giant system simulation model that is built based on the meta-synthesis methodology and the generalized modelling method. A new definition of VV&A for complex system is given, on which is based a 12-step reference model and proposed for VV&A purpose. Furthermore, the principle and method of intelligent boundary interval intermediate assessment is proposed for the harmonization of modelling and model-validation.
文摘This conference report summarizes recent progress in plasma theory and simulation that was presented in contributed papers and discussions at the 11th Conference on Magnetic Confined Fusion Theory and Simulation(CMCFTS)held in Chengdu,China,27–30 October,2023.Progress in various fields has been achieved.For example,results on zonal flow generation by mode coupling,simulations of the key physics of divertor detachment,energetic particle effects on magnetohydrodynamic(MHD)modes in addition to ion-and electron-scale turbulence,physics of edge coherent modes and edge-localized modes,and the optimization of ion heating schemes as well as confinement scenarios using advanced integrated modeling are presented at the conference.In this conference,the scientific research groups were organized into six categories:(a)edge and divertor physics;(b)impurity,heating,and current drive;(c)energetic particle physics;(d)turbulent transport;(e)MHD instability;and(f)integrated modeling and code development.A summary of the highlighted progress in these working groups is presented.
基金supported by the China National Magnetic Confinement Fusion Science Program (Grant No. 2018YFE0304100)the US Department of Energy, Office of Science, Office of Advanced Scientific Computing Research and Office of Fusion Energy Sciences, Scientific Discovery through Advanced Computing (Sci DAC) program under Award Number DE-SC0018270 (Sci DAC ISEP Center)+2 种基金the China Scholarship Council (Grant No. 201306010032)resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory (DOE Contract No. DE-AC05-00OR22725)the National Energy Research Scientific Computing Center (DOE Contract No. DE-AC02-05CH11231)
文摘A conservative scheme of kinetic electrons for gyrokinetic simulations in the presence of magnetic islands has been implemented and verified in the gyrokinetic toroidal code, where zonal and nonzonal components of all perturbed quantities are solved together. Using this new conservative scheme, linear simulation of kinetic ballooning mode has been successfully benchmarked with the electromagnetic hybrid model. Simulations of nonlinear interactions between magnetic islands and the ion temperature gradient(ITG) mode in a tokamak show that the islands rotate at the electron diamagnetic drift velocity. The linear ITG structure shifts from the island O-point toward the X-point due to the pressure flattening effect inside the islands, and the nonlinear ITG structure peaks along the magnetic island separatrix because of the increased pressure gradient there.
基金supported by U.S.Department of Energy(DOE) SciDAC GSEP Center and National Special Research Program of China for ITER
文摘In the present paper,we first derive the eigenmode equation of the ideal ballooning mode in tokamak plasmas using a gyrokinetic equation.It is shown that the gyrokinetic eigenmode equation can be reduced to the magnetohydrodynamic（MHD） form in the long wavelength limit when kinetic effects are ignored.Then,the global gyrokinetic toroidal code（GTC） is applied for simulations of the edge-localized ideal ballooning modes.The obtained mode structures are compared with the results of ideal MHD simulations.The observed scaling of the linear growth rate with the toroidal mode number is consistent with the ideal MHD theory.The simulation results verify the GTC capability of simulating MHD processes in toroidal plasmas.
基金supported by National Natural Science Foundation of China(No.11975038)。
文摘In this study,a code,named Peking University Helicon Discharge(PHD),which can simulate helicon discharge processes under both a background magnetic field greater than 500 G and a pressure less than 1 Pa,is developed.In the code,two fluid equations are used.The PHD simulations led to two important findings:(1)the temporal evolution of plasma density with the background magnetic field exhibits a second rapid increase(termed as the second density jump),similar to the transition of modes in helicon plasmas;(2)in the presence of a magnetic field,the peak positions of electron power absorption appeared near the central axis,unlike in the case of no magnetic field.These results may lead to an enhanced understanding of the discharge mechanism.
基金supported by the National Natural Science Foundation of China(62273119).
文摘A cooperative guidance law is proposed in a two-ontwo engagement scenario with large-heading-errors by choosing zero-effort miss distance as a sliding surface,which consists of an attacker,a protector,a defender,and a target,based on fixed-time sliding mode control theory.Based on the nonlinear method of fixed-time sliding mode control,the performance of the cooperative guidance law remains satisfactory even with large-heading-errors scenarios where the linearization-based approaches might be invalid.By virtue of this law,the attacker pursues the target with the assistance of the protector,which can intercept the defender in the engagement scenario.Furthermore,if the attacker is intercepted by the defender,the guidance law of the protector could guarantee that the protector attacks the target.A robust adaptive term is included in the guidance law to deal with the case of the unknown disturbance upper bound of the defender-target team.Finally,the feasibility of the guidance law is verified by nonlinear numerical simulations,and the superiority of it is illustrated by comparing with the linearization guidance law.
基金William A.Goddard III thanks the US National Science Foundation(No.CBET-2311117)for supportGuanHua Chen acknowledges financial support from the General Research Fund(Grant No.17309620)Research Grants Council(RGC:T23-713/22-R).
文摘Single-and dual-atom catalysts(SACs and DACs)on single-layer graphene are widely investigated for a wide range of electrochemical reactions.However,the effect of van der Waals interactions on the activity of these catalysts has not been investigated through systematic high-throughput screening.Here we introduce the concept of van der Waals interactions through a double-layer DAC structure which has axial d orbital modification towards enhanced CO_(2) reduction reaction(CO_(2)RR),hydrogen evolution reaction(HER),oxygen reduction reaction(ORR),and oxygen evolution reaction(OER).We applied density functional theory(DFT)to screen 3d,4d,and 5d transition metals supported by double-layer nitrogen-doped graphene,denoted as M2N8.We sought catalysts with high thermodynamic and electrochemical stabilities along with low overpotentials for CO_(2)RR,ORR,OER,or HER.We find that HER can take place inside the van der Waals gap of V2N8 and Co2N8 leading to overpotentials of 0.10 and 0.16 V.Moreover,ORR and OER can take place on the surface of Fe2N8 and Ir2N8,respectively,leading to overpotentials of 0.39 and 0.37 V.DFT predicts a CO_(2)RR overpotential of 0.85 V towards CO on the surface of Co2N8 along with the HER overpotential of 0.16 V inside the van der Waals gap of Co2N8 towards the production of syngas(CO+H_(2)).This paper provides fundamental insights into the design of advanced multi-layer catalysts by applying the concept of van der Waals interactions for electrochemistry at room temperature.
基金supported by the Nationa Natural Science Foundation of China(60434010)Outstanding Youth Fund of Heilongjiang Province(JC200606)
文摘Aimed at the guidance requirements of some missiles which attack targets with terminal impact angle at the terminal point,a new integrated guidance and control design scheme based on variable structure control approach for missile with terminal impact angle constraint is proposed.First,a mathematical model of an integrated guidance and control model in pitch plane is established,and then nonlinear transformation is employed to transform the mathematical model into a standard form suitable for sliding mode control method design.A sufficient condition for the existence of linear sliding surface is given in terms of linear matrix inequalities（LMIs）,based on which the corresponding reaching motion controller is also developed.To verify the effectiveness of the proposed integrated design scheme,the numerical simulation of missile is made.The simulation results demonstrate that the proposed guidance and control law can guide missile to hit the target with desired impact angle and desired flight attitude angle simultaneously.
