A new silicon micro flow sensor with multiple temperature sensing elements was proposed and numerically simulated in considering wide range flow measuring properties.The micro flow sensor has three pairs of temperatur...A new silicon micro flow sensor with multiple temperature sensing elements was proposed and numerically simulated in considering wide range flow measuring properties.The micro flow sensor has three pairs of temperature sensing elements with a central heater compared with typical sensor which has only a temperature sensing element on each side of a central heater.A numerical analysis of the micro flow sensor by Finite Difference Formulation for Heat Transfer Equation was performed.The nearest pair of temperature sensor showed very good linear sensitivity between 0 to 0.4m/s flow and saturated from 0.75m/s flow.However the furthest pair of temperature sensor showed some flow sensitivity even though the flow rate of 2.0m/s.Thus,this suggested new micro flow meter with multiple temperature sensing elements could be used as a thermal mass flow sensor which has accuracy sensitivity for very wide flow range.展开更多
The explicit solution to Cauchy problem for linearized system of two-dimensional isentropic flow with axisymmetrical initial data in gas dynamics is given.
An extensive set of measurements in 2-D turbulent mixing layer, wake and jet flow by the hot-wire technique and data sampling are presented. The measured quantities, i. e. the mean velocity, the turbulence intensity, ...An extensive set of measurements in 2-D turbulent mixing layer, wake and jet flow by the hot-wire technique and data sampling are presented. The measured quantities, i. e. the mean velocity, the turbulence intensity, the Reynolds stress and higher-order correlations of the fluctuating velocity in the self-preserving region of the above free shear flows are compared with the computational results based on Zhou's theory for the shear turbulence of in- compressible fluid. The experimental and computational results are in good agreement.展开更多
1-D and 2-D mathematical models for dam break flow were established and verified with the measured data in laboratory. The 1-D and 2-D models were then coupled, and used to simulate the dam break flow from the reservo...1-D and 2-D mathematical models for dam break flow were established and verified with the measured data in laboratory. The 1-D and 2-D models were then coupled, and used to simulate the dam break flow from the reservoir tail to the dam site, the propagation of dam break waves in the downstream channel, and the submergence of dam break flow in the downstream town with the hydrodynamics method. As a numerical example, the presented model was employed to simulate dam break flow of a hydropower station under construction. In simulation, different dam-break durations, upstream flows and water levels in front of dam were considered, and these influencing factors of dam break flow were analyzed, which could be referenced in planning and designing hydropower stations.展开更多
In this paper, the erosion-resisting coefficient was introduced to computebed deformation in a crush bedrock river. In the case of crush bedrock, there has been no propercontrol equation to describe bed stability, whi...In this paper, the erosion-resisting coefficient was introduced to computebed deformation in a crush bedrock river. In the case of crush bedrock, there has been no propercontrol equation to describe bed stability, which leads to difficulty in calculation of the beddeformation with conventional methods. The data from field survey were used to give thee-rosion-resisting capability with an appropriate coefficient. After the determination oflongitudinal distribution expressed by polynomial regression and transversal distribution expressedby normal distribution function, the plane distribution of erosion-resisting coefficient in a crushbedrock river was obtained. With the computational results from a 2-D horizontal flow mathematicalmodel, the erosion-resisting coefficient and controlling condition of local stability were employedto compute the values of bed deformation when riverbed is stable. The above method was applied in acase study, and the computational results of flow and bed deformations are in good a-greement withphysical model test data.展开更多
Navigable flow condition simulations can provide detailed information on water depth and velocity distribution, simulation speed is one of the key factors which influence real-time navigation. In this paper, a navigab...Navigable flow condition simulations can provide detailed information on water depth and velocity distribution, simulation speed is one of the key factors which influence real-time navigation. In this paper, a navigable flow condition simulation system is developed to provide useful information for waterway management and shipping safety. To improve the simulation speed of 2-D hydrodynamic model, an explicit finite volume method and Open MP are used to realize parallel computing. Two mesh schemes and two computing platforms are adopted to study the parallel model＇s performance in the Yangtze River, China. The results show that the parallel model achieves dramatic acceleration, with a maximum speedup ratio of 34.94？. The parallel model can determine the flow state of the navigable channel in about 4 min, efficiency is further improved by a flow simulation scheme database. The developed system can provide early warning information for shipping safety, allowing ships to choose better routes and navigation areas according to real-time navigable flow conditions.展开更多
A 2-D Lattice Boltzmann Method（LBM） coupled with a Sub-Grid Stress（SGS） model is proposed and validated by flows around a non-submerged spur dike in a channel.And then the LBM-SGS model is further applied to flows...A 2-D Lattice Boltzmann Method（LBM） coupled with a Sub-Grid Stress（SGS） model is proposed and validated by flows around a non-submerged spur dike in a channel.And then the LBM-SGS model is further applied to flows in a pumping-station forebay.Shallow water equations are numerically solved by the LBM and the turbulence can be taken into account and modeled efficiently by the Large Eddy Simulation（LES） model.The bounce-back scheme of the non-equilibrium part of the distribution function is used at the inlet boundary,the normal gradient of the distribution function is set as zero at the outlet boundary and the bounce-back scheme is applied to the solid wall to ensure non-slip boundary conditions.Firstly,the model successfully predicts the flow characteristics around a spur dike,such as circulating flow,velocity and water depth distributions.The results are verified by the experimental data and compared to the results obtained by conventional Smagoringsky Model（SM） of LES.Finally,the LBM-SGS model is used to further predict the flow characteristics in a forebay,such as secondary flow and water level.The comparisons show that the model scheme has the capacity to simulate complex flows in shallow water with reasonable accuracy and reliability.展开更多
In order to explore the unforced unsteadiness of centrifugal pumps,a 2-D frequency domain imaging display technology was used to study the development of these unsteady flow structures at partial flow conditions.The r...In order to explore the unforced unsteadiness of centrifugal pumps,a 2-D frequency domain imaging display technology was used to study the development of these unsteady flow structures at partial flow conditions.The results showed that,the unsteady flow field was not only affected by rotor and stator interaction,but also appeared an unforced unsteadiness with fundamental frequency of St≈0.23 around the impeller throat area.Moreover,as the flow rates decreased,this unsteady flow structure gradually weakened and disappeared.When the flow rate was reduced to 0.6 times of design flow rate,another two unforced unsteady flow structures with characteristic frequencies of St≈0.0714 and St≈0.12 began to appear in the same area.Therefore,with the operating condition smaller than design flow rate,the internal flow became more and more complex.In addition to the forced unsteadiness,the unforced unsteadiness which is not connected with the blade passage frequency became more and more obvious.展开更多
The BEM combined with the time- st6pping scheme has been applied to the numerical calculation of fully nonlinear free surface flows generated by large amplitude forced transverse oscillation of two-dimensional body. P...The BEM combined with the time- st6pping scheme has been applied to the numerical calculation of fully nonlinear free surface flows generated by large amplitude forced transverse oscillation of two-dimensional body. Particular attention is paid on the compatibility of free surface and body surface conditions at the intersection point, and moving radiation boundary is adopted. A new calculating formula of the exact force on the body is also presented.The results demonstrate some nonlinear phenomena and indicate the stability and correctness of the numerical simulation.展开更多
In this paper, the self-organization process of the initially scattered 12 meso-β and -γ scale vortices evolving into a synoptic-scale typhoon-like vortex in the context of advection dynamics is numerically explored...In this paper, the self-organization process of the initially scattered 12 meso-β and -γ scale vortices evolving into a synoptic-scale typhoon-like vortex in the context of advection dynamics is numerically explored with an ）f-plane 2-D quasi-geostrophic vorticity equation model. The results show that the self-organization process was a step-by-step merging course, namely the two adjacent vortices first merged, then formed a tri-vortex flow pattern, and finally evolved into a resultant vortex of meso-α scale. Thus it can be seen as an interaction of binary vortices self-organization. Each initial vortex or vorticity lump confronted two ways out： it merged with an adjacent vortex, and thus became a source of the inner region vorticity of the new formed vortex; or it was stretched by the circulation of an adjacent vortex, and then became the vorticity source of the spiral band of new vortex. Similarly, each new formed vortex also confronted the two ways out, until the multi-vortex self-organized into a single vortex of lager scale. The representation precision of the initial vortex structure directly affected the speeds of the mutual rotation and merging of the resultant vortex. Therefore, it is important to provide an accurate description of initial vortex profiles. Finally, a property of the numerical solution of the self-organization for the 2-D quasi-geostrophic flow is that the total kinetic energy decays slowly, the total enstrophy decreases rapidly, and the circulation of the largest scale vortex grows quickly.展开更多
文摘A new silicon micro flow sensor with multiple temperature sensing elements was proposed and numerically simulated in considering wide range flow measuring properties.The micro flow sensor has three pairs of temperature sensing elements with a central heater compared with typical sensor which has only a temperature sensing element on each side of a central heater.A numerical analysis of the micro flow sensor by Finite Difference Formulation for Heat Transfer Equation was performed.The nearest pair of temperature sensor showed very good linear sensitivity between 0 to 0.4m/s flow and saturated from 0.75m/s flow.However the furthest pair of temperature sensor showed some flow sensitivity even though the flow rate of 2.0m/s.Thus,this suggested new micro flow meter with multiple temperature sensing elements could be used as a thermal mass flow sensor which has accuracy sensitivity for very wide flow range.
文摘The explicit solution to Cauchy problem for linearized system of two-dimensional isentropic flow with axisymmetrical initial data in gas dynamics is given.
文摘An extensive set of measurements in 2-D turbulent mixing layer, wake and jet flow by the hot-wire technique and data sampling are presented. The measured quantities, i. e. the mean velocity, the turbulence intensity, the Reynolds stress and higher-order correlations of the fluctuating velocity in the self-preserving region of the above free shear flows are compared with the computational results based on Zhou's theory for the shear turbulence of in- compressible fluid. The experimental and computational results are in good agreement.
基金the National Basic Research Program of China(973 Program, Grant No. 2003CB415203)the National Natural Science Foundation of China (Grant No.50579054).
文摘1-D and 2-D mathematical models for dam break flow were established and verified with the measured data in laboratory. The 1-D and 2-D models were then coupled, and used to simulate the dam break flow from the reservoir tail to the dam site, the propagation of dam break waves in the downstream channel, and the submergence of dam break flow in the downstream town with the hydrodynamics method. As a numerical example, the presented model was employed to simulate dam break flow of a hydropower station under construction. In simulation, different dam-break durations, upstream flows and water levels in front of dam were considered, and these influencing factors of dam break flow were analyzed, which could be referenced in planning and designing hydropower stations.
文摘In this paper, the erosion-resisting coefficient was introduced to computebed deformation in a crush bedrock river. In the case of crush bedrock, there has been no propercontrol equation to describe bed stability, which leads to difficulty in calculation of the beddeformation with conventional methods. The data from field survey were used to give thee-rosion-resisting capability with an appropriate coefficient. After the determination oflongitudinal distribution expressed by polynomial regression and transversal distribution expressedby normal distribution function, the plane distribution of erosion-resisting coefficient in a crushbedrock river was obtained. With the computational results from a 2-D horizontal flow mathematicalmodel, the erosion-resisting coefficient and controlling condition of local stability were employedto compute the values of bed deformation when riverbed is stable. The above method was applied in acase study, and the computational results of flow and bed deformations are in good a-greement withphysical model test data.
基金Project supported by the 13th Five-Year National Key Research and Development Program of China(Grant No.2016YFC0401407)the 12th Five-Year National Key Tech-nology R&D Program(Grant No.2012BAB05B05)the National Natural Science Foundation of China(Grant No.51722901)
文摘Navigable flow condition simulations can provide detailed information on water depth and velocity distribution, simulation speed is one of the key factors which influence real-time navigation. In this paper, a navigable flow condition simulation system is developed to provide useful information for waterway management and shipping safety. To improve the simulation speed of 2-D hydrodynamic model, an explicit finite volume method and Open MP are used to realize parallel computing. Two mesh schemes and two computing platforms are adopted to study the parallel model＇s performance in the Yangtze River, China. The results show that the parallel model achieves dramatic acceleration, with a maximum speedup ratio of 34.94？. The parallel model can determine the flow state of the navigable channel in about 4 min, efficiency is further improved by a flow simulation scheme database. The developed system can provide early warning information for shipping safety, allowing ships to choose better routes and navigation areas according to real-time navigable flow conditions.
基金supported by the National Natural Science Foundation of China (Grant No. 50779069)the Beijing Natural Science Foundation (Grant No. 3083022)+3 种基金the Open Fund of Key Laboratory of Yellow River Sediment Research of the Ministry of Water Resources (Grant No. 200903)the National Science and Technology Supporting Programs in the 11th Five-Year Plan (Grant No. 2006BAB06B02)the Chinese Universities Scientific Fund (Grant Nos. 2009-1-90, 2009-2-12)the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. PCSIRT0657)
文摘A 2-D Lattice Boltzmann Method（LBM） coupled with a Sub-Grid Stress（SGS） model is proposed and validated by flows around a non-submerged spur dike in a channel.And then the LBM-SGS model is further applied to flows in a pumping-station forebay.Shallow water equations are numerically solved by the LBM and the turbulence can be taken into account and modeled efficiently by the Large Eddy Simulation（LES） model.The bounce-back scheme of the non-equilibrium part of the distribution function is used at the inlet boundary,the normal gradient of the distribution function is set as zero at the outlet boundary and the bounce-back scheme is applied to the solid wall to ensure non-slip boundary conditions.Firstly,the model successfully predicts the flow characteristics around a spur dike,such as circulating flow,velocity and water depth distributions.The results are verified by the experimental data and compared to the results obtained by conventional Smagoringsky Model（SM） of LES.Finally,the LBM-SGS model is used to further predict the flow characteristics in a forebay,such as secondary flow and water level.The comparisons show that the model scheme has the capacity to simulate complex flows in shallow water with reasonable accuracy and reliability.
基金supported by the National Natural Science Foundation of China(Grant No.51976125)Open Research Subject of Key Laboratory of Fluid and Power Machinery(Xihua University),Ministry of Education(Grant number zj2015-024)Natural Science Fund of Shanghai(Grant No.19ZR1425900)。
文摘In order to explore the unforced unsteadiness of centrifugal pumps,a 2-D frequency domain imaging display technology was used to study the development of these unsteady flow structures at partial flow conditions.The results showed that,the unsteady flow field was not only affected by rotor and stator interaction,but also appeared an unforced unsteadiness with fundamental frequency of St≈0.23 around the impeller throat area.Moreover,as the flow rates decreased,this unsteady flow structure gradually weakened and disappeared.When the flow rate was reduced to 0.6 times of design flow rate,another two unforced unsteady flow structures with characteristic frequencies of St≈0.0714 and St≈0.12 began to appear in the same area.Therefore,with the operating condition smaller than design flow rate,the internal flow became more and more complex.In addition to the forced unsteadiness,the unforced unsteadiness which is not connected with the blade passage frequency became more and more obvious.
文摘The BEM combined with the time- st6pping scheme has been applied to the numerical calculation of fully nonlinear free surface flows generated by large amplitude forced transverse oscillation of two-dimensional body. Particular attention is paid on the compatibility of free surface and body surface conditions at the intersection point, and moving radiation boundary is adopted. A new calculating formula of the exact force on the body is also presented.The results demonstrate some nonlinear phenomena and indicate the stability and correctness of the numerical simulation.
基金The present study was made possible by the financial sup-port of National Science Council of the Republic of China under the Grant NSC 95-2221-E-019-090.
基金Supported by the Key Project of National Natural Science Fbundation of China under Grant No. 40333028.
文摘In this paper, the self-organization process of the initially scattered 12 meso-β and -γ scale vortices evolving into a synoptic-scale typhoon-like vortex in the context of advection dynamics is numerically explored with an ）f-plane 2-D quasi-geostrophic vorticity equation model. The results show that the self-organization process was a step-by-step merging course, namely the two adjacent vortices first merged, then formed a tri-vortex flow pattern, and finally evolved into a resultant vortex of meso-α scale. Thus it can be seen as an interaction of binary vortices self-organization. Each initial vortex or vorticity lump confronted two ways out： it merged with an adjacent vortex, and thus became a source of the inner region vorticity of the new formed vortex; or it was stretched by the circulation of an adjacent vortex, and then became the vorticity source of the spiral band of new vortex. Similarly, each new formed vortex also confronted the two ways out, until the multi-vortex self-organized into a single vortex of lager scale. The representation precision of the initial vortex structure directly affected the speeds of the mutual rotation and merging of the resultant vortex. Therefore, it is important to provide an accurate description of initial vortex profiles. Finally, a property of the numerical solution of the self-organization for the 2-D quasi-geostrophic flow is that the total kinetic energy decays slowly, the total enstrophy decreases rapidly, and the circulation of the largest scale vortex grows quickly.
