If the frequency of the incident sound wave coincides with one of the eigenfrequencies of the underwater elastic cylinder, the corresponding eigenvibration will be excited by incident sound wave and strongly reradiate...If the frequency of the incident sound wave coincides with one of the eigenfrequencies of the underwater elastic cylinder, the corresponding eigenvibration will be excited by incident sound wave and strongly reradiate sound wave towards surronding water. It has been revealed by previous investigations that the amplitude of backscattering sound appears to be minimum at the eigenfrequencies of the underwater metallic cylinders because of the destructive interference between reradiated wave of the eigenvibration and the geometrical reflected wave from surface of the cylinders. In this paper, a new phenomenon has been revealed. The amplitude of backscattering sound appears to be maximum at the eigenfrequencies of a cylinder made from nonmetallic material in which the velocity of elastic transverse wave is less than the sound velocity in water.展开更多
The forced-vibration response of a simply-supported isotropic thick-walled hollow elastic circular cylinder subjected to two-dimensional harmonic standing-wave excitations on its curved surfaces is studied within the ...The forced-vibration response of a simply-supported isotropic thick-walled hollow elastic circular cylinder subjected to two-dimensional harmonic standing-wave excitations on its curved surfaces is studied within the framework of linear elastodynamics.Exact semi-analytical solutions for the steady-state displacement field of the cylinder are constructed using recently-published parametric solutions to the Navier-Lam´e equation.Formal application of the standing-wave boundary conditions generates three parameter-dependent 66 linear systems,each of which can be numerically solved in order to determine the parametric response of the cylinder’s displacement field under various conditions.The method of solution is direct and demonstrates a general approach that can be applied to solve many other elastodynamic forcedresponse problems involving isotropic elastic cylinders.As an application,and considering several examples,the obtained solution is used to compute the steady-state frequency response in a few specific low-order excitation cases.In each case,the solution generates a series of resonances that are in exact correspondence with a unique subset of the natural frequencies of the simply-supported cylinder.The considered problem is of general theoretical interest in structural mechanics and acoustics and more practically serves as a benchmark forced-vibration problem involving a thickwalled hollow elastic cylinder.展开更多
The steady state, two dimensional creeping flow of an upper convected Maxwell (UCM) fluid between two eccentric cylinders, with the inner one rotating,is computed by p version of EVSS/SUPG finite element method. T...The steady state, two dimensional creeping flow of an upper convected Maxwell (UCM) fluid between two eccentric cylinders, with the inner one rotating,is computed by p version of EVSS/SUPG finite element method. The solutions converge as the polynomial order of the approximation increases. An upper Deborah number (De) limit attains 30 (p≤5). With De increasing, The boundary layers form and develop in the stress, which match closely with those predicted by asymptotic analysis. The results show that numerical oscillations is caused by the boundary layers of stress and can be reduced by increasing the polynomial order of the approximation.展开更多
The objective of this study is to apply numerical methods to investigate the effects of the spacing on the vortex shedding of two elastically mounted cylinders in tandem arrangement. 2-D computational simulations are ...The objective of this study is to apply numerical methods to investigate the effects of the spacing on the vortex shedding of two elastically mounted cylinders in tandem arrangement. 2-D computational simulations are carried out at low Reynolds number of 100. The study utilized a commercial software ANSYS FLUENT to carry out the computational simulations. First, a number of test cases, including flows past one and two cylinders with predetermined motions, are simulated to evaluate the solver’s accuracy. The vortex shedding and hydrodynamic forces from the current findings and those from literature show good agreement, which supports the accuracy of the current solver. Multiple simulations were the performed for flow around two elastically mounted cylinders in tandem arrangement. The subsequent relative flow fields demonstrated that for a certain range of spacing, vortex shedding was completely eliminated while it remained completely unaffected or partially reduced for other ranges of spacing. This suggests that the spacing between the two cylinders can be utilized as a passive method of suppressing vortex shedding.展开更多
基金The project was supported by the National Science Foundation
文摘If the frequency of the incident sound wave coincides with one of the eigenfrequencies of the underwater elastic cylinder, the corresponding eigenvibration will be excited by incident sound wave and strongly reradiate sound wave towards surronding water. It has been revealed by previous investigations that the amplitude of backscattering sound appears to be minimum at the eigenfrequencies of the underwater metallic cylinders because of the destructive interference between reradiated wave of the eigenvibration and the geometrical reflected wave from surface of the cylinders. In this paper, a new phenomenon has been revealed. The amplitude of backscattering sound appears to be maximum at the eigenfrequencies of a cylinder made from nonmetallic material in which the velocity of elastic transverse wave is less than the sound velocity in water.
基金support from the Natural Sciences and Engineering Research Council(NSERC)of Canada and the Ontario Research Foundation(ORF).
文摘The forced-vibration response of a simply-supported isotropic thick-walled hollow elastic circular cylinder subjected to two-dimensional harmonic standing-wave excitations on its curved surfaces is studied within the framework of linear elastodynamics.Exact semi-analytical solutions for the steady-state displacement field of the cylinder are constructed using recently-published parametric solutions to the Navier-Lam´e equation.Formal application of the standing-wave boundary conditions generates three parameter-dependent 66 linear systems,each of which can be numerically solved in order to determine the parametric response of the cylinder’s displacement field under various conditions.The method of solution is direct and demonstrates a general approach that can be applied to solve many other elastodynamic forcedresponse problems involving isotropic elastic cylinders.As an application,and considering several examples,the obtained solution is used to compute the steady-state frequency response in a few specific low-order excitation cases.In each case,the solution generates a series of resonances that are in exact correspondence with a unique subset of the natural frequencies of the simply-supported cylinder.The considered problem is of general theoretical interest in structural mechanics and acoustics and more practically serves as a benchmark forced-vibration problem involving a thickwalled hollow elastic cylinder.
文摘The steady state, two dimensional creeping flow of an upper convected Maxwell (UCM) fluid between two eccentric cylinders, with the inner one rotating,is computed by p version of EVSS/SUPG finite element method. The solutions converge as the polynomial order of the approximation increases. An upper Deborah number (De) limit attains 30 (p≤5). With De increasing, The boundary layers form and develop in the stress, which match closely with those predicted by asymptotic analysis. The results show that numerical oscillations is caused by the boundary layers of stress and can be reduced by increasing the polynomial order of the approximation.
文摘The objective of this study is to apply numerical methods to investigate the effects of the spacing on the vortex shedding of two elastically mounted cylinders in tandem arrangement. 2-D computational simulations are carried out at low Reynolds number of 100. The study utilized a commercial software ANSYS FLUENT to carry out the computational simulations. First, a number of test cases, including flows past one and two cylinders with predetermined motions, are simulated to evaluate the solver’s accuracy. The vortex shedding and hydrodynamic forces from the current findings and those from literature show good agreement, which supports the accuracy of the current solver. Multiple simulations were the performed for flow around two elastically mounted cylinders in tandem arrangement. The subsequent relative flow fields demonstrated that for a certain range of spacing, vortex shedding was completely eliminated while it remained completely unaffected or partially reduced for other ranges of spacing. This suggests that the spacing between the two cylinders can be utilized as a passive method of suppressing vortex shedding.
