Based on the potential theory and perturbation techniques, the problem of second-order sloshing in a three-dimensional tank in combination with surge and sway motions is analyzed. When excitation is applied in both ho...Based on the potential theory and perturbation techniques, the problem of second-order sloshing in a three-dimensional tank in combination with surge and sway motions is analyzed. When excitation is applied in both horizontal directions, the second-order resonance can occur when the sum frequency or the difference frequency of any two excitation components is equal to one of the natural frequencies. The resonance can also occur when the sum or difference frequency of one of the excitation frequencies and one of the natural frequencies is equal to another natural frequency.展开更多
In this paper,a lattice Boltzmann method is developed to simulate the water displacement of oil in porous media at the macroscopic-scale,which is built upon the generalized Darcy’s law while incorporating cross terms...In this paper,a lattice Boltzmann method is developed to simulate the water displacement of oil in porous media at the macroscopic-scale,which is built upon the generalized Darcy’s law while incorporating cross terms to consider the viscous coupling between two phases.The Buckley-Leverett equation is applied to describe the saturation front advance,thus allowing the determination of water saturation at shock front by using the Welge’s graphic method.We explore the effect of viscous coupling on the displacement by comparing the positions of the shock front under the conditions with different degrees of coupling and without viscous coupling.Results show that the advancing speed of shock front increases with the degree of coupling when the viscosity ratio of oil to water remains at 5.We also find that the effect of viscous coupling on the displacement can be neglected when the tolerance quantifying the degree of coupling equals the reciprocal of viscosity ratio.In addition,the effect of viscous coupling on the displacement is very sensitive to the change of viscosity ratio,which decreases monotonously with the decrease of viscosity ratio under the same coupling degree.展开更多
The betatron matching of a rotationally asymmetric beam in space charge dominated low-energy beam transports （LEBTs） where solenoids are used for the transverse matching has been studied. For better understanding, t...The betatron matching of a rotationally asymmetric beam in space charge dominated low-energy beam transports （LEBTs） where solenoids are used for the transverse matching has been studied. For better understanding, the coupling elements of a beam matrix are interpreted in special forms that are products of a term defined by the Larmor rotation angle and another by the difference between the beam matrix elements in the two transverse planes. The coupling form originally derived from the rotationally symmetric field in solenoids still holds when taking into account the rotationally asymmetric space charge forces that are due to the unequal emittance in the two transverse planes. It is shown in this paper that when an LEBT mainly comprising solenoids transports a beam having unequal emittance in the two transverse planes and the linear space charge force is taken into account, the initial Twiss parameters can be modified to obtain the minimum and equal emittance at the LEBT exit. The TRACE3D calculations also prove the principle. However, when quadrupoles that are also rotationally asymmetric are involved in between solenoids, the coupling between the two transverse planes becomes more complicated and the emittance increase is usually unavoidable. A matching example using the CSNS （China Spallation Neutron Source） LEBT conditions is also presented.展开更多
基金supported by the National Science Foundation of China(Grant No.51079082)
文摘Based on the potential theory and perturbation techniques, the problem of second-order sloshing in a three-dimensional tank in combination with surge and sway motions is analyzed. When excitation is applied in both horizontal directions, the second-order resonance can occur when the sum frequency or the difference frequency of any two excitation components is equal to one of the natural frequencies. The resonance can also occur when the sum or difference frequency of one of the excitation frequencies and one of the natural frequencies is equal to another natural frequency.
基金supported by the National Natural Science Foundation of China(Nos.12072257,51876170)the National Key Project(No.GJXM92579)the Major Special Science and Technology Project of the Inner Mongolia Autonomous Region(No.2020ZD0022).
文摘In this paper,a lattice Boltzmann method is developed to simulate the water displacement of oil in porous media at the macroscopic-scale,which is built upon the generalized Darcy’s law while incorporating cross terms to consider the viscous coupling between two phases.The Buckley-Leverett equation is applied to describe the saturation front advance,thus allowing the determination of water saturation at shock front by using the Welge’s graphic method.We explore the effect of viscous coupling on the displacement by comparing the positions of the shock front under the conditions with different degrees of coupling and without viscous coupling.Results show that the advancing speed of shock front increases with the degree of coupling when the viscosity ratio of oil to water remains at 5.We also find that the effect of viscous coupling on the displacement can be neglected when the tolerance quantifying the degree of coupling equals the reciprocal of viscosity ratio.In addition,the effect of viscous coupling on the displacement is very sensitive to the change of viscosity ratio,which decreases monotonously with the decrease of viscosity ratio under the same coupling degree.
基金Supported by CAS Knowledge Innovation Program-'CSNS R&D Studies'National Natural Science Foundation of China(10775153)
文摘The betatron matching of a rotationally asymmetric beam in space charge dominated low-energy beam transports （LEBTs） where solenoids are used for the transverse matching has been studied. For better understanding, the coupling elements of a beam matrix are interpreted in special forms that are products of a term defined by the Larmor rotation angle and another by the difference between the beam matrix elements in the two transverse planes. The coupling form originally derived from the rotationally symmetric field in solenoids still holds when taking into account the rotationally asymmetric space charge forces that are due to the unequal emittance in the two transverse planes. It is shown in this paper that when an LEBT mainly comprising solenoids transports a beam having unequal emittance in the two transverse planes and the linear space charge force is taken into account, the initial Twiss parameters can be modified to obtain the minimum and equal emittance at the LEBT exit. The TRACE3D calculations also prove the principle. However, when quadrupoles that are also rotationally asymmetric are involved in between solenoids, the coupling between the two transverse planes becomes more complicated and the emittance increase is usually unavoidable. A matching example using the CSNS （China Spallation Neutron Source） LEBT conditions is also presented.
