Inverse cascade via Burgers equation

Burgers equation is employed as a pedagogical device for analytically demonstrating the emergence of a form of inverse cascade to the lowest wavenumber in a flow. The transition from highly nonlinear mode-mode coupling to an ordered preference for large scale structure is shown, both analytically (revealing the presence of a global attractor) and via a numerical example. (c) 2000 American Institute of Physics.     

Direct perturbation method for perturbed complex Burgers equation

So far, Lou's direct perturbation method has been applied successfully to solve the nonlinear Schr?dinger equation(NLSE) hierarchy, such as the NLSE, the coupled NLSE, the critical NLSE, and the derivative NLSE. But to our knowledge, this method for other types of perturbed nonlinear evolution equations has still been lacking. In this paper, Lou's direct perturbation method is applied to the study of perturbed complex Burgers equation. By this method, we calculate not only the zero-order adiabatic solution, but also the first order modification.     

Exact solutions of the forced Burgers equation

Two new methods for obtaining exact solutions of the initial-value problem on an unbounded straight line (the Cauchy problem) for the inhomogeneous Burgers equation are considered. They are applied to the cases of a stationary and a transient external force. A self-similar solution and a solution which describes the localization (blocking) of solitary traveling waves are obtained as examples. Zh. Tekh. Fiz. 69, 10–14 (August 1999)     

Asymptotic solutions of the inhomogeneous Burgers equation

The method of the active second harmonic suppression in resonators is investigated in this paper both analytically and numerically. The resonator is driven by a piston which vibrates with two frequencies. The first one agrees with an eigenfrequency and the second one is equal to the two times higher eigenfrequency. The phase shift of the second piston motion is 180 deg. It is known that for this case it is possible to describe generation of the higher harmonics by means of the inhomogeneous Burgers equation. This model equation was solved for stationary state analytically by a number of authors but only for ideal fluids. Unlike their solutions, new asymptotic solutions are presented here which take into account dissipative effects. The asymptotic solutions are compared with numerical ones. For study of generation higher harmonics the solutions are developed in a spectral form.     

Integrability of fermionic extensions of the Burgers equation

Using the prolongation structure technique, we investigate the fermionic extensions of the Burgers equation suggested by Hlavaty. Besides those which pass the Painlevé test, some new integrable cases are found. Through the representations of the Lie superalgebras, the Lax pairs for these integrable cases are constructed.     

Baicklund transformations for the Burgers equation via localization of residual symmetries

We obtain the non-local residual symmetry related to truncated Painlev~ expansion of Burgers equation. In order to localize the residual symmetry, we introduce new variables to prolong the original Burgers equation into a new system. By using Lie＇s first theorem, we obtain the finite transformation for the localized residual symmetry. More importantly, we also Iocalize the linear superposition of multiple residual symmetries to find the corresponding finite transformations. It is interesting to find that the n-th B~icklund transformation for Burgers equation can be expressed by determinants in a compact way.     

Approximate analytical solution of the inhomogeneous Burgers equation

The method of the active second harmonic suppression in resonators is investigated in this paper both analytically and numerically. The resonator is driven by a piston which vibrates with two frequencies. The first one agrees with an eigenfrequency and the second one is equal to the two times higher eigenfrequency. The phase shift of the second piston motion is 180 degrees. It is known that for this case it is possible to describe generation of the higher harmonics by means of the inhomogeneous Burgers equation. The new approximate solution of inhomogeneous Burgers equation for real fluid is presented here. This work was supported by the grant GACR No. 202/01/1372 and the CTU research program J04/98:2123000016.     

Mach reflection and KP solitons in shallow water

Reflection of an obliquely incident solitary wave onto a vertical wall is studied analytically and experimentally. We use the Kadomtsev-Petviashivili (KP) equation to analyze the evolution and its asymptotic state. Laboratory experiments are performed using the laser induced fluorescent (LIF) technique, and detailed features and amplifications at the wall are measured. Due to the lack of physical interpretation of the theory, the numerical results were previously thought not in good agreement with the theory. With proper treatment, we demonstrate that the KP theory provides an excellent model to predict the present laboratory results as well as the previous numerical results. The KP theory also indicates that the present laboratory apparatus is too short to achieve the asymptotic state. The laboratory and numerical results suggest that the maximum of the predicted four-fold amplification would be difficult to be realized in the real-fluid environment. The reality of this amplification remains obscure.     

On the phase manifold geometry of the two-dimensional Burgers equations

A two space dimensional Burgers hierarchy is constructed and analyzed in terms of an invariant, Nijenhuis mixed tensor field on the phase manifold. The analysis extends to Burgers equations in higher dimension as well.     

Nonlinear stability of an undercompressive shock for complex Burgers equation

Though there is strong numerical evidence for the stability of undercompressive shocks, their stability has not been verified analytically. In particular, the energy methods used to analyze stability of standard shocks do not apply. Here, we present the first proof of stability for a particular undercompresive shock, the real Burgers shock considered as a solution of the complex Burgers equation. Our analysis is by direct calculation of the Green's function for the linearized equations, combined with pointwise estimates of nonlinear effects. A benefit of this method is to obtain fairly detailed information about the solution, includingL ¹ behavior, and rates of decay in different regions of space.     

Galerkin modelling of the Burgers equation using harmonic wavelets

In this paper we present a wavelet Galerkin approximation of the one-dimensional Burgers equation using complex harmonic wavelets. We derive exact expressions for the connection coefficients for the linear dissipation and nonlinear advection terms. A large reduction in the number of space-scale nonlinear modes is obtained by exploiting the band-limited spectra and localisation properties of harmonic wavelets. We discuss the advantages and disadvantages of implementing harmonic wavelets as opposed to the more standard choice of wavelets basis, highlighting the relevance to shell models of turbulence.     

Solution and transcritical bifurcation of Burgers equation

Burgers equation is reduced into a first-order ordinary differential equation by using travelling wave transformation and it has typical bifurcation characteristics.We can obtain many exact solutions of the Burgers equation,discuss its transcritical bifurcation and control dynamical behaviours by extending the stable region.The transcritical bifurcation exists in the (2 + 1)-dimensional Burgers equation.     

耦合Burgers方程的对称性及对称约化

对称性分析是自然科学研究中的重要方法之一. 利用对称性分析研究了一个描述两层流体体系的模型即耦合Burgers方程的对称性. 利用对称性给出了这个模型的四种对称性约化并给出了这些约化方程的一些特殊的严格解,如有理解、行波孤立子解和非行波孤立子解. 关键词： 对称性约化 耦合Burgers方程 孤立子     

Intermittence phenomena in the Burgers equation involving thermal noise

Leading terms of the asymptotic behavior of the pair and higher order correlation functions for finite times and large distances have been calculated for the Burgers equation involving thermal noise. It is shown that an intermittence phenomenon occurs, whereby certain correlation functions are much greater than their reducible parts.     

Solutions of the reflection equation for the vertex model

We investigate the possible regular solutions of the boundary Yang–Baxter equation for the fundamental U_q[G₂] vertex model. We find four distinct classes of reflection matrices such that half of them are diagonal while the other half are non-diagonal. The latter are parameterized by two continuous parameters but only one solution has all entries non-null. The non-diagonal solutions do not reduce to diagonal ones at any special limit of the free-parameters.     

Random solution of the Burgers equation in the inviscid case

The structure of solutions of the Burgers equation in the inviscid case is investigated numerically by computing the space-time behavior of the asymptotic solutions expressed as sequences of triangular shock waves. They are sensitively dependent on initial conditions and can display intrinsic randomness, depending on the number of zeros of the initial velocity fields.     

Detonation re-initiation mechanism following the Mach reflection of a quenched detonation

This experimental study addresses the re-initiation mechanism of detonation waves following the Mach reflection of a shock–flame complex. The detonation diffraction around a cylinder is used to reproducibly generate the shock–flame complex of interest. The experiments are performed in methane–oxygen. We use a novel experimental technique of coupling a two-in-line-spark flash system with a double-frame camera in order to obtain microsecond time resolution permitting accurate schlieren velocimetry. The first series of experiments compares the non-reactive sequence of shock reflections with the reflection over a rough wall under identical conditions. It was found that the hot reaction products generated along the rough wall are entrained by the wall jet into a large vortex structure behind the Mach stem. The second series of experiments performed in more sensitive mixtures addressed the sequence of events leading to the detonation establishment along the Mach and transverse waves. Following ignition and jet entrainment, a detonation first appears along the Mach stem while the transverse wave remains non-reactive. The structure of the unburned tongue however indicates local instabilities and hot spot formation, leading to the rapid reaction of this gas. Numerical simulations are also reported, confirming the sequence of ignition events obtained experimentally.