Applications of computational fluid dynamic(CFD) to the maritime industry continue to grow with the increasing development of computers.Numerical approaches have evolved to a level of accuracy which allows them to be ...Applications of computational fluid dynamic(CFD) to the maritime industry continue to grow with the increasing development of computers.Numerical approaches have evolved to a level of accuracy which allows them to be applied for hydrodynamic computations in industry areas.Hydrodynamic tests,especially planar-motion-mechanism(PMM) tests are simulated by CFD software-FLUENT,and all of the corresponding hydrodynamic coefficients are obtained,which satisfy the need of establishing the simulation system to evaluate maneuverability of vehicles during the autonomous underwater vehicle scheme design stage.The established simulation system performed well in tests.展开更多
A computational study of soot formation in ethylene/air coflow jet diffusion flame at atmospheric pres-sure was conducted using a reduced mechanism and soot formation model. A 20-step mechanism was derived from the fu...A computational study of soot formation in ethylene/air coflow jet diffusion flame at atmospheric pres-sure was conducted using a reduced mechanism and soot formation model. A 20-step mechanism was derived from the full mechanism using sensitivity analysis,reaction path analysis and quasi steady state(QSS) approximation. The model in premixed flame was validated and with computing savings in diffusion flame was applied by incor-porating into a CFD code. Simulations were performed to explore the effect of coflow air on flame structure and soot formation. Thermal radiation was calculated by a discrete-ordinates method,and soot formation was predicted by a simple two-equation soot model. Model results are in good agreement with those from experiment data and detailed mechanism at atmospheric conditions. The soot nucleation,growth,and oxidation by OH are all enhanced by decrease in coflow air velocity. The peak soot volume fraction region appears in the lower annular region be-tween the peak flame temperature and peak acetylene concentration locations,and the high soot oxidation rate due to the OH attack occurs in the middle annular region because of high temperature.展开更多
Heat exchangers are extensively utilized for waste heat recovery,oil refining,chemical processing,and steam generation.In this study,velocity profiles are measured using a 3D particle image velocimetry(PIV)system betw...Heat exchangers are extensively utilized for waste heat recovery,oil refining,chemical processing,and steam generation.In this study,velocity profiles are measured using a 3D particle image velocimetry(PIV)system between two baffles in a shell and tube heat exchanger for parallel and counter flows.The PIV and computational fluid dynamics results show the occurrence of some strong vectors near the bottom.These vectors are assumed due to the clearance between the inner tubes and the front baffle.Therefore,the major parts of the vectors are moved out through the bottom opening of the rear baffle,and other vectors produce a large circle between the two baffles.Numerical simulations are conducted to investigate the effects of the baffle on the heat exchanger using the Fluent software.The k-εturbulence model is employed to calculate the flows along the heat exchanger.展开更多
基金Supported by the Open Research Foundation of SKLabAUV,HEU under Grant No.2008003
文摘Applications of computational fluid dynamic(CFD) to the maritime industry continue to grow with the increasing development of computers.Numerical approaches have evolved to a level of accuracy which allows them to be applied for hydrodynamic computations in industry areas.Hydrodynamic tests,especially planar-motion-mechanism(PMM) tests are simulated by CFD software-FLUENT,and all of the corresponding hydrodynamic coefficients are obtained,which satisfy the need of establishing the simulation system to evaluate maneuverability of vehicles during the autonomous underwater vehicle scheme design stage.The established simulation system performed well in tests.
基金Supported by the National Natural Science Foundation of China（50806023 50721005 50806024） Program of Introducing Talents of Discipline to Universities of China（“111” Project B06019）
文摘A computational study of soot formation in ethylene/air coflow jet diffusion flame at atmospheric pres-sure was conducted using a reduced mechanism and soot formation model. A 20-step mechanism was derived from the full mechanism using sensitivity analysis,reaction path analysis and quasi steady state(QSS) approximation. The model in premixed flame was validated and with computing savings in diffusion flame was applied by incor-porating into a CFD code. Simulations were performed to explore the effect of coflow air on flame structure and soot formation. Thermal radiation was calculated by a discrete-ordinates method,and soot formation was predicted by a simple two-equation soot model. Model results are in good agreement with those from experiment data and detailed mechanism at atmospheric conditions. The soot nucleation,growth,and oxidation by OH are all enhanced by decrease in coflow air velocity. The peak soot volume fraction region appears in the lower annular region be-tween the peak flame temperature and peak acetylene concentration locations,and the high soot oxidation rate due to the OH attack occurs in the middle annular region because of high temperature.
基金supported by the RESEAT program funded by the Ministry of Science,ICT and Future Planningthe National Research Foundation of Koreathe Korea Lottery Commission grants
文摘Heat exchangers are extensively utilized for waste heat recovery,oil refining,chemical processing,and steam generation.In this study,velocity profiles are measured using a 3D particle image velocimetry(PIV)system between two baffles in a shell and tube heat exchanger for parallel and counter flows.The PIV and computational fluid dynamics results show the occurrence of some strong vectors near the bottom.These vectors are assumed due to the clearance between the inner tubes and the front baffle.Therefore,the major parts of the vectors are moved out through the bottom opening of the rear baffle,and other vectors produce a large circle between the two baffles.Numerical simulations are conducted to investigate the effects of the baffle on the heat exchanger using the Fluent software.The k-εturbulence model is employed to calculate the flows along the heat exchanger.
