To investigate the influence of operation parameters of abrasive water jet on surface roughness of carbon fiber reinforced plastic(CFRP),experimental studies were conducted.The three-dimensional landscape of cutting f...To investigate the influence of operation parameters of abrasive water jet on surface roughness of carbon fiber reinforced plastic(CFRP),experimental studies were conducted.The three-dimensional landscape of cutting front was reconstructed according to the measured data byμscan laser confocal microscopy.Fourier spectral analysis was also adopted to study surface structure in detail.It is found that the morphology of cutting front is similar to that of other materials.In the smooth cutting zone,the fluctuation of amplitudes of surface profile is gentler,compared with that in the rough cutting zone.The lower part of the rough cutting zone was characterized by the periodical appearance of peaks and valleys.The roughness of surface increases with the increase of depth.While in the smooth cutting zone and part of rough cutting zone,roughness increases with the increase of traverse speed.For the thickness of samples,in the smooth cutting zone,the roughness increases with the increase of depth.The dominant harmonic component in the surface profile is concentrated in a narrow range from 0 to 10 Hz,and the relatively higher density of frequency from 10 to 50 Hz is shown in the rough cutting zone,which is caused by the interaction between perpendicular abrasive water jet and reflect jet.展开更多
Based on the virial theory, we proposed VLW equation of state of detonation products (VLW EOS). Its basic theory and applications were described. The distinct features of the VLW EOS were:First, the detonation perform...Based on the virial theory, we proposed VLW equation of state of detonation products (VLW EOS). Its basic theory and applications were described. The distinct features of the VLW EOS were:First, the detonation performance of the new high energy density materials could be predicted more reliably. Second, it had extensive application. The detonation parameters of both the condensed high energy density materials and the gaseous fuel air explosives could be calculated. Moreover, combustion performance of propellants could also be precisely calculated. The calculation results were satisfactory.展开更多
Annular jet pumps that are used in hydraulic machinery have a very simple structure but very complex internal flow fields. Large eddy simulations were used to study the coherent structures in the turbulent flows in an...Annular jet pumps that are used in hydraulic machinery have a very simple structure but very complex internal flow fields. Large eddy simulations were used to study the coherent structures in the turbulent flows in annular jet pumps with various area ratios,m. The distribution, movement and evolution of the coherent structure in the annular jet pumps are described based on vorticity,pressure and Q criteria. All the criteria demonstrate that the vortexes are mainly distributed in the recirculation region and in the mixing and the boundary layers, which have large velocity gradients. The various characteristics of the coherent structures are shown by the different criteria with the vorticity criterion describing the distribution, movement and evolution of the vortexes,the pressure criterion describing the movement and the Q criterion describing the vortex movement and evolution. The vorticity variation in the spanwise direction is larger than the variation in the streamwise direction; however, the streamwise vortex is the main mechanism driving the entrainment of the secondary flow and the mixing. The annular jet pump with m=3.33 had a higher vortex shedding frequency(about 1000 Hz) than that with m=1.72(313–417 Hz). The azimuthal instability is the main reason for the generation of the streamwise vortex from the spanwise vortex. The vortex structures in the recirculation region are very strong,but small and disordered with no periodic vortex rings.展开更多
The large eddy simulation(LES) method is used to simulate cavitating flow in a venturi tube. The simulated results agree fairly well with the experimental data. To quantitatively describe the relationship between cavi...The large eddy simulation(LES) method is used to simulate cavitating flow in a venturi tube. The simulated results agree fairly well with the experimental data. To quantitatively describe the relationship between cavitation evolution and excited pressure fluctuation in the venturi tube, a modified prediction model is proposed and its accuracy is verified by the LES results. Based on the original one-dimensional model for the external cavitating flow around a hydrofoil, this model is corrected according to the internal cavitating flow characteristics in the venturi tube. The results show that the original one-dimensional model ignores the choking effect of cavitating flow, which is obvious in a venturi tube with a narrow flow channel, thus leading to an inaccurate prediction of pressure fluctuation in the venturi tube. The modified model can significantly overcome its deficiencies and improve the accuracy of the pressure fluctuation prediction, providing a theoretical basis and guidance for engineering application to controlling the pressure fluctuation in a venturi tube or for other internal flows.展开更多
基金National High Technology Research and Development Program 863(2015AA043401)
文摘To investigate the influence of operation parameters of abrasive water jet on surface roughness of carbon fiber reinforced plastic(CFRP),experimental studies were conducted.The three-dimensional landscape of cutting front was reconstructed according to the measured data byμscan laser confocal microscopy.Fourier spectral analysis was also adopted to study surface structure in detail.It is found that the morphology of cutting front is similar to that of other materials.In the smooth cutting zone,the fluctuation of amplitudes of surface profile is gentler,compared with that in the rough cutting zone.The lower part of the rough cutting zone was characterized by the periodical appearance of peaks and valleys.The roughness of surface increases with the increase of depth.While in the smooth cutting zone and part of rough cutting zone,roughness increases with the increase of traverse speed.For the thickness of samples,in the smooth cutting zone,the roughness increases with the increase of depth.The dominant harmonic component in the surface profile is concentrated in a narrow range from 0 to 10 Hz,and the relatively higher density of frequency from 10 to 50 Hz is shown in the rough cutting zone,which is caused by the interaction between perpendicular abrasive water jet and reflect jet.
基金Supported by the National Natural Science Foundation of China (Grant No. 1860382)the Science Foundation of China Academy of Engineering Physics (Grant Nos. 920513, 9401009 & 960577)
文摘Based on the virial theory, we proposed VLW equation of state of detonation products (VLW EOS). Its basic theory and applications were described. The distinct features of the VLW EOS were:First, the detonation performance of the new high energy density materials could be predicted more reliably. Second, it had extensive application. The detonation parameters of both the condensed high energy density materials and the gaseous fuel air explosives could be calculated. Moreover, combustion performance of propellants could also be precisely calculated. The calculation results were satisfactory.
基金supported by the National Natural Science Foundation of China(Grant Nos.51179134&11472197)
文摘Annular jet pumps that are used in hydraulic machinery have a very simple structure but very complex internal flow fields. Large eddy simulations were used to study the coherent structures in the turbulent flows in annular jet pumps with various area ratios,m. The distribution, movement and evolution of the coherent structure in the annular jet pumps are described based on vorticity,pressure and Q criteria. All the criteria demonstrate that the vortexes are mainly distributed in the recirculation region and in the mixing and the boundary layers, which have large velocity gradients. The various characteristics of the coherent structures are shown by the different criteria with the vorticity criterion describing the distribution, movement and evolution of the vortexes,the pressure criterion describing the movement and the Q criterion describing the vortex movement and evolution. The vorticity variation in the spanwise direction is larger than the variation in the streamwise direction; however, the streamwise vortex is the main mechanism driving the entrainment of the secondary flow and the mixing. The annular jet pump with m=3.33 had a higher vortex shedding frequency(about 1000 Hz) than that with m=1.72(313–417 Hz). The azimuthal instability is the main reason for the generation of the streamwise vortex from the spanwise vortex. The vortex structures in the recirculation region are very strong,but small and disordered with no periodic vortex rings.
基金supported by the National Natural Science Foundation of China(Grant Nos.51679169,11472197)。
文摘The large eddy simulation(LES) method is used to simulate cavitating flow in a venturi tube. The simulated results agree fairly well with the experimental data. To quantitatively describe the relationship between cavitation evolution and excited pressure fluctuation in the venturi tube, a modified prediction model is proposed and its accuracy is verified by the LES results. Based on the original one-dimensional model for the external cavitating flow around a hydrofoil, this model is corrected according to the internal cavitating flow characteristics in the venturi tube. The results show that the original one-dimensional model ignores the choking effect of cavitating flow, which is obvious in a venturi tube with a narrow flow channel, thus leading to an inaccurate prediction of pressure fluctuation in the venturi tube. The modified model can significantly overcome its deficiencies and improve the accuracy of the pressure fluctuation prediction, providing a theoretical basis and guidance for engineering application to controlling the pressure fluctuation in a venturi tube or for other internal flows.
