Nonlinear energy transfer is represented through eddy viscosity and stochastic forcing within the framework of resolvent analysis.Previous investigations estimate the contribution of eddy-viscosity-enhanced resolvent ...Nonlinear energy transfer is represented through eddy viscosity and stochastic forcing within the framework of resolvent analysis.Previous investigations estimate the contribution of eddy-viscosity-enhanced resolvent opera-tor to nonlinear energy transfer.The present article estimates the contribution of stochastic forcing to nonlinear energy transfer and demonstrates that the contribution of stochastic forcing cannot be ignored.These results are achieved by numerically comparing the eddy-viscosity-enhanced resolvent operator and stochastic forcing with nonlinear energy transfer in turbulent channel flows.Furthermore,the numerical results indicate that composite resolvent operators can improve the prediction of nonlinear energy transfer.展开更多
This paper presents two new theorems for multiplicative perturbations of C-regularized resolvent families, which generalize the previous related ones for the resolvent families.
This paper is concerned with the convergence rates of ergodic limits and approximation for regularized resolvent families for a linear Volterra integral equation. The results contain C 0-semigroups, cosine operator fu...This paper is concerned with the convergence rates of ergodic limits and approximation for regularized resolvent families for a linear Volterra integral equation. The results contain C 0-semigroups, cosine operator functions and α-times integrated resolvent family as special cases.展开更多
Let and A be the generator of an -times resolvent family on a Banach space X. It is shown that the fractional Cauchy problem has maximal regularity on if and only if is of bounded semivariation on .
A new class of g-η-monotone mappings and a class of generalized implicit variational-like inclusions involving g-η-monotone mappings are introduced. The resolvent operator of g-η-monotone mappings is defined and it...A new class of g-η-monotone mappings and a class of generalized implicit variational-like inclusions involving g-η-monotone mappings are introduced. The resolvent operator of g-η-monotone mappings is defined and its Lipschitz continuity is presented, An iterative algorithm for approximating the solutions of generalized implicit wriational- like inclusions is suggested and analyzed. The convergence of iterative sequences generated by the algorithm is also proved,展开更多
. Utilizing the stability characterizations of generalized inverses of linear operator, we investigate the existence of generalized resolvent of linear pencils in Banach spaces. Some practical criterions for the exist.... Utilizing the stability characterizations of generalized inverses of linear operator, we investigate the existence of generalized resolvent of linear pencils in Banach spaces. Some practical criterions for the existence of generalized resolvents of the linear pencil λ→ T - λS are provided and an explicit expression of the generalized resolvent is also given. As applications, the characterization for the Moore-Penrose inverse of the linear pencil to be its generalized resolvent and the existence of the generalized resolvents of linear pencils of finite rank operators, Fredholm operators and semi-Fredholm operators are also considered. The results obtained in this paper extend and improve many results in this area.展开更多
Resolvent operator has been increasingly used to investigate turbulent flows and develop control strategies.Recently,Towne et al.(J Fluid Mech 883:A17,2020)proposed a resolvent-based estimation(RBE)method for predicti...Resolvent operator has been increasingly used to investigate turbulent flows and develop control strategies.Recently,Towne et al.(J Fluid Mech 883:A17,2020)proposed a resolvent-based estimation(RBE)method for predicting turbulent statistics in a channel flow.In this paper,we utilize the RBE method to predict the root-mean-square(RMS)and space-time energy spectra of streamwise velocity fluctuation,where the input is the space-time energy spectra at a reference horizontal plane located in the logarithmic layer and the output is the space-time energy spectra in the buffer layer.The explicit formulas for the RBE method are given in detail for numerical implementation.The results show the capability of the RBE method in the prediction of the convection velocity and bandwidth of the space-time energy spectra.Furthermore,we make a systematic evaluation of the performance of the RBE method by varying the input configurations,including the wall-normal location of the reference plane,the inclusion or exclusion of the pressure as an input variable,the implementation approach of the pressure boundary condition,and the choice of the window function.It is found that the results of both RMS velocity and space-time energy spectra obtained from the RBE method are sensitive to the location of the reference plane.However,the pressure boundary conditions and inclusion of pressure as an input do not cause significant change in the RMS velocity and space-time energy spectra.Although it does not influence the prediction of the RMS velocity,a window function is found crucial in the RBE method for the prediction of the space-time energy spectra.展开更多
Deals with the application of Kreiss resolvent condition in the error growth analysis of numerical methods, and studies the stability of Runge Kutta method in respect of Kreiss resolvent condition with emphasis on the...Deals with the application of Kreiss resolvent condition in the error growth analysis of numerical methods, and studies the stability of Runge Kutta method in respect of Kreiss resolvent condition with emphasis on the study on the subclass of collocation methods with abscissas in [0,1] by applying the methods to the test equation U′(t)=λU(t)+μU(t-τ)τ>0 with complex constraints μ and λ, and proves under some assumptions on the R K methods that the error growth is uniformly bounded in the stability region.展开更多
This paper deals with the stability analysis of the linear multistep (LM) methods in the numerical solution of delay differential equations. Here we provide a qualitative stability estimates, pertiment to the classica...This paper deals with the stability analysis of the linear multistep (LM) methods in the numerical solution of delay differential equations. Here we provide a qualitative stability estimates, pertiment to the classical scalar test problem of the form y′(t)=λy(t)+μy(t-τ) with τ>0 and λ,μ are complex, by using (vartiant to) the resolvent condition of Kreiss. We prove that for A stable LM methods the upper bound for the norm of the n th power of square matrix grows linearly with the order of the matrix.展开更多
In this paper, the heat, resolvent and wave kernels associated to the Schr?dinger operator with multi-inverse square potential on the Euclidian space Rn are given in explicit forms.
Resolvent methods are presented for generating systematically iterative numerical algorithms for constrained problems in mechanics.The abstract framework corresponds to a general mixed finite element subdif-ferential ...Resolvent methods are presented for generating systematically iterative numerical algorithms for constrained problems in mechanics.The abstract framework corresponds to a general mixed finite element subdif-ferential model,with dual and primal evolution versions,which is shown to apply to problems of fluid dynamics,transport phenomena and solid mechanics,among others.In this manner,Uzawa's type methods and penalization-duality schemes,as well as macro-hybrid formulations,are generalized to non necessarily potential nanlinear mechanical problems.展开更多
An equation concerning with the subdifferential of convex functionals defined in real Banach spaces and the metric projections to level sets is shown. The equation is compared with the resolvents of general monotone o...An equation concerning with the subdifferential of convex functionals defined in real Banach spaces and the metric projections to level sets is shown. The equation is compared with the resolvents of general monotone operators, and makes the geometric properties of differential equations expressed by subdifferentials clear. Hence, it can be expected to be useful in obtaining the steepest descents defined by the convex functionals in Banach spaces. Also, it gives a similar result to the Lagrange multiplier method under certain conditions.展开更多
We calculate in a numerically friendly way the Fourier transform of a non-integrable function, such as , by replacing F with R-1FR, where R represents the resolvent for harmonic oscillator Hamiltonian. As contrasted w...We calculate in a numerically friendly way the Fourier transform of a non-integrable function, such as , by replacing F with R-1FR, where R represents the resolvent for harmonic oscillator Hamiltonian. As contrasted with the non-analyticity of at in the case of a simple replacement of F by , where and represent the momentum and position operators, respectively, the turns out to be an entire function. In calculating the resolvent kernel, the sampling theorem is of great use. The resolvent based Fourier transform can be made supersymmetric (SUSY), which not only makes manifest the usefulness of the even-odd decomposition ofin a more natural way, but also leads to a natural definition of SUSY Fourier transform through the commutativity with the SUSY resolvent.展开更多
In this paper,we study the nonlinear stability problem for the two-dimensional Boussinesq system around the Couette flow in a finite channel with Navier-slip boundary condition for the velocity and Dirichlet boundary ...In this paper,we study the nonlinear stability problem for the two-dimensional Boussinesq system around the Couette flow in a finite channel with Navier-slip boundary condition for the velocity and Dirichlet boundary condition for the temperature with small viscosityνand small thermal diffusionμ.We establish that if the initial perturbation velocity and initial perturbation temperature satisfy ||u_(0)||H^(2)≤ε_(0) min{μ,ν}1/2, and ||θ_(0)||H^(1)+|||D_(x)|^(1/3)θ_(0)||H^(1)+|||D_(x)|^(1/3)θ_(0)||_(H^(1))≤εi min{μ,ν}^(5/6),for some smallε0 andε1 independent ofμ,ν,then the solution of the two-dimensional NavierStokes Boussinesq system does not transition away from the Couette flow for any time.展开更多
In hypersonic boundary layers,the optimal disturbance is notably caused by normalmode instabilities,such as Mack second mode.However,recent experimental and numerical efforts have demonstrated the dominance of nonmoda...In hypersonic boundary layers,the optimal disturbance is notably caused by normalmode instabilities,such as Mack second mode.However,recent experimental and numerical efforts have demonstrated the dominance of nonmodal growth in hypersonic flows with the presence of moderate nose bluntness.In this study,resolvent analysis and parabolized stability equation analysis are performed to investigate the instabilities over a blunt-tip wedge.Main parameters include Mach number 5.9,unit Reynolds number 91.5×10~6/m,half wedge angle 5°,and nose radii ranging from 2.54 mm to 15.24 mm.Two novel growth patterns of travelling waves are identified to compete,whose nature is the intersection of the energy gain of optimal and sub-optimal disturbances.Pattern A with large spanwise wavelengths has the signature of slow energy amplification over a long distance which concentrates in the entropy layer.By contrast,pattern B with relatively small spanwise wavelengths presents rapid transient growth inside the boundary layer.A systematic study is performed on the growth/attenuation mechanism of disturbance patterns and the effects of wall temperature and nose radius.Wall cooling is found to be an alternative control strategy aimed at nonmodal instabilities.The receptivity to slow acoustic waves is considered when the effect of bluntness is studied.An estimated amplitude response favorably reproduces the reversal-like phenomenon.The lift-up/Orr mechanism analysis provides an explanation of energy growth for nonmodal responses.展开更多
In this article,we study the approximate controllability of neutral partial differential equations with Hilfer fractional derivative and not instantaneous impulses effects.By using the Sadovskii's fixed point theo...In this article,we study the approximate controllability of neutral partial differential equations with Hilfer fractional derivative and not instantaneous impulses effects.By using the Sadovskii's fixed point theorem,fractional calculus and resolvent operator functions,we prove the approximate controllability of the considered system.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)Basic Science Center Program for Multiscale Problems in Nonlinear Mechanics(Grant No.11988102).
文摘Nonlinear energy transfer is represented through eddy viscosity and stochastic forcing within the framework of resolvent analysis.Previous investigations estimate the contribution of eddy-viscosity-enhanced resolvent opera-tor to nonlinear energy transfer.The present article estimates the contribution of stochastic forcing to nonlinear energy transfer and demonstrates that the contribution of stochastic forcing cannot be ignored.These results are achieved by numerically comparing the eddy-viscosity-enhanced resolvent operator and stochastic forcing with nonlinear energy transfer in turbulent channel flows.Furthermore,the numerical results indicate that composite resolvent operators can improve the prediction of nonlinear energy transfer.
文摘This paper presents two new theorems for multiplicative perturbations of C-regularized resolvent families, which generalize the previous related ones for the resolvent families.
基金This project is supported by the Special Funds for Major Specialties of Shanghai Education Committee and the Natural Foundation ofShanghai City.
文摘This paper is concerned with the convergence rates of ergodic limits and approximation for regularized resolvent families for a linear Volterra integral equation. The results contain C 0-semigroups, cosine operator functions and α-times integrated resolvent family as special cases.
文摘Let and A be the generator of an -times resolvent family on a Banach space X. It is shown that the fractional Cauchy problem has maximal regularity on if and only if is of bounded semivariation on .
基金Project supported by the Key Science Foundation of Sichuan Education Department of China (No.2003A081)
文摘A new class of g-η-monotone mappings and a class of generalized implicit variational-like inclusions involving g-η-monotone mappings are introduced. The resolvent operator of g-η-monotone mappings is defined and its Lipschitz continuity is presented, An iterative algorithm for approximating the solutions of generalized implicit wriational- like inclusions is suggested and analyzed. The convergence of iterative sequences generated by the algorithm is also proved,
基金Supported by the Natural Science Foundation of China (10971182)the Natural Science Foundation of Jiangsu Province (BK2010309)+1 种基金the Jiangsu Government Scholarship for Overseas Studies, the Natural Science Foundation of Jiangsu Education Committee (10KJB110012 and 11KJB110018)the Natural Science Foundation of Yangzhou University
文摘. Utilizing the stability characterizations of generalized inverses of linear operator, we investigate the existence of generalized resolvent of linear pencils in Banach spaces. Some practical criterions for the existence of generalized resolvents of the linear pencil λ→ T - λS are provided and an explicit expression of the generalized resolvent is also given. As applications, the characterization for the Moore-Penrose inverse of the linear pencil to be its generalized resolvent and the existence of the generalized resolvents of linear pencils of finite rank operators, Fredholm operators and semi-Fredholm operators are also considered. The results obtained in this paper extend and improve many results in this area.
基金supported by the National Natural Science Foundation of China(Basic Science Center Program for“Multiscale Problems in Nonlinear Mechanics”)(Grant 11988102)The authors would like to thank the support from the Strategic Priority Research Program(Grant XDB22040104)。
文摘Resolvent operator has been increasingly used to investigate turbulent flows and develop control strategies.Recently,Towne et al.(J Fluid Mech 883:A17,2020)proposed a resolvent-based estimation(RBE)method for predicting turbulent statistics in a channel flow.In this paper,we utilize the RBE method to predict the root-mean-square(RMS)and space-time energy spectra of streamwise velocity fluctuation,where the input is the space-time energy spectra at a reference horizontal plane located in the logarithmic layer and the output is the space-time energy spectra in the buffer layer.The explicit formulas for the RBE method are given in detail for numerical implementation.The results show the capability of the RBE method in the prediction of the convection velocity and bandwidth of the space-time energy spectra.Furthermore,we make a systematic evaluation of the performance of the RBE method by varying the input configurations,including the wall-normal location of the reference plane,the inclusion or exclusion of the pressure as an input variable,the implementation approach of the pressure boundary condition,and the choice of the window function.It is found that the results of both RMS velocity and space-time energy spectra obtained from the RBE method are sensitive to the location of the reference plane.However,the pressure boundary conditions and inclusion of pressure as an input do not cause significant change in the RMS velocity and space-time energy spectra.Although it does not influence the prediction of the RMS velocity,a window function is found crucial in the RBE method for the prediction of the space-time energy spectra.
文摘Deals with the application of Kreiss resolvent condition in the error growth analysis of numerical methods, and studies the stability of Runge Kutta method in respect of Kreiss resolvent condition with emphasis on the study on the subclass of collocation methods with abscissas in [0,1] by applying the methods to the test equation U′(t)=λU(t)+μU(t-τ)τ>0 with complex constraints μ and λ, and proves under some assumptions on the R K methods that the error growth is uniformly bounded in the stability region.
文摘This paper deals with the stability analysis of the linear multistep (LM) methods in the numerical solution of delay differential equations. Here we provide a qualitative stability estimates, pertiment to the classical scalar test problem of the form y′(t)=λy(t)+μy(t-τ) with τ>0 and λ,μ are complex, by using (vartiant to) the resolvent condition of Kreiss. We prove that for A stable LM methods the upper bound for the norm of the n th power of square matrix grows linearly with the order of the matrix.
文摘In this paper, the heat, resolvent and wave kernels associated to the Schr?dinger operator with multi-inverse square potential on the Euclidian space Rn are given in explicit forms.
文摘Resolvent methods are presented for generating systematically iterative numerical algorithms for constrained problems in mechanics.The abstract framework corresponds to a general mixed finite element subdif-ferential model,with dual and primal evolution versions,which is shown to apply to problems of fluid dynamics,transport phenomena and solid mechanics,among others.In this manner,Uzawa's type methods and penalization-duality schemes,as well as macro-hybrid formulations,are generalized to non necessarily potential nanlinear mechanical problems.
文摘An equation concerning with the subdifferential of convex functionals defined in real Banach spaces and the metric projections to level sets is shown. The equation is compared with the resolvents of general monotone operators, and makes the geometric properties of differential equations expressed by subdifferentials clear. Hence, it can be expected to be useful in obtaining the steepest descents defined by the convex functionals in Banach spaces. Also, it gives a similar result to the Lagrange multiplier method under certain conditions.
文摘We calculate in a numerically friendly way the Fourier transform of a non-integrable function, such as , by replacing F with R-1FR, where R represents the resolvent for harmonic oscillator Hamiltonian. As contrasted with the non-analyticity of at in the case of a simple replacement of F by , where and represent the momentum and position operators, respectively, the turns out to be an entire function. In calculating the resolvent kernel, the sampling theorem is of great use. The resolvent based Fourier transform can be made supersymmetric (SUSY), which not only makes manifest the usefulness of the even-odd decomposition ofin a more natural way, but also leads to a natural definition of SUSY Fourier transform through the commutativity with the SUSY resolvent.
文摘In this paper,we study the nonlinear stability problem for the two-dimensional Boussinesq system around the Couette flow in a finite channel with Navier-slip boundary condition for the velocity and Dirichlet boundary condition for the temperature with small viscosityνand small thermal diffusionμ.We establish that if the initial perturbation velocity and initial perturbation temperature satisfy ||u_(0)||H^(2)≤ε_(0) min{μ,ν}1/2, and ||θ_(0)||H^(1)+|||D_(x)|^(1/3)θ_(0)||H^(1)+|||D_(x)|^(1/3)θ_(0)||_(H^(1))≤εi min{μ,ν}^(5/6),for some smallε0 andε1 independent ofμ,ν,then the solution of the two-dimensional NavierStokes Boussinesq system does not transition away from the Couette flow for any time.
基金supported by the Hong Kong Research Grants Council(Nos.15216621,15204322,25203721)the National Natural Science Foundation of China(No.12102377)。
文摘In hypersonic boundary layers,the optimal disturbance is notably caused by normalmode instabilities,such as Mack second mode.However,recent experimental and numerical efforts have demonstrated the dominance of nonmodal growth in hypersonic flows with the presence of moderate nose bluntness.In this study,resolvent analysis and parabolized stability equation analysis are performed to investigate the instabilities over a blunt-tip wedge.Main parameters include Mach number 5.9,unit Reynolds number 91.5×10~6/m,half wedge angle 5°,and nose radii ranging from 2.54 mm to 15.24 mm.Two novel growth patterns of travelling waves are identified to compete,whose nature is the intersection of the energy gain of optimal and sub-optimal disturbances.Pattern A with large spanwise wavelengths has the signature of slow energy amplification over a long distance which concentrates in the entropy layer.By contrast,pattern B with relatively small spanwise wavelengths presents rapid transient growth inside the boundary layer.A systematic study is performed on the growth/attenuation mechanism of disturbance patterns and the effects of wall temperature and nose radius.Wall cooling is found to be an alternative control strategy aimed at nonmodal instabilities.The receptivity to slow acoustic waves is considered when the effect of bluntness is studied.An estimated amplitude response favorably reproduces the reversal-like phenomenon.The lift-up/Orr mechanism analysis provides an explanation of energy growth for nonmodal responses.
基金Supported by Shandong University of Finance and Economics 2023 International Collaborative Projectsthe National Natural Science Foundation of China(Grant No.62073190)。
文摘In this article,we study the approximate controllability of neutral partial differential equations with Hilfer fractional derivative and not instantaneous impulses effects.By using the Sadovskii's fixed point theorem,fractional calculus and resolvent operator functions,we prove the approximate controllability of the considered system.
