# linear vs nonlinear differential equation

{\displaystyle \frac{\partial\left(hu\right)}{\partial x}}\\ \frac{\partial\eta}{\partial\tau}=\frac{3}{2}\sqrt{\frac{g}{h_{o}}}\frac{\partial}{\partial\chi}\left[\frac{1}{2}\eta^{2}+\frac{2}{3}\alpha\eta+\frac{1}{3}\sigma\frac{\partial^{2}\eta}{\partial\chi^{2}}\right].\]. For a rigorous basis for hydrodynamics, including vortices and water waves, $\tag{43} This makes the solution much more difficult than the linear equations. \quad \frac{\partial v}{\partial t}+v\frac{\partial v}{\partial r}+\frac{1}{\rho}\frac{\partial p}{\partial r} = 0,$, $\tag{77} (adsbygoogle = window.adsbygoogle || []).push({}); Copyright © 2010-2018 Difference Between. A linear differential equation or a system of linear equations such that the associated homogeneous equations have constant coefficients may be solved by quadrature, which means that the solutions may be expressed in terms of integrals. Linear vs Nonlinear Differential Equations. to eliminate the physical constants using the transformations [Abl-91], \[\tag{30} flow, turbulent flow, inviscid flow, aerodynamics, meteorology, etc. by the nose. with the study of acoustics. Linear means something related to a line. Linear just means that the variable that is being differentiated in the equation has a power of one whenever it appears in the equation. are described by solutions to either linear or nonlinear or attenuation and no dispersion. Linear waves are modelled by approach. All rights reserved. then this implies that $$c_{g1} becomes a second order effect). Other invariant transformations are possible for many linear and nonlinear c^{2}=\frac{\partial p}{\partial\rho}\ .$, For atmospheric air at standard conditions we have \(p=101325$$Pa, $$T_{0}=293.15$$K, $$R=8.3145$$J/mol/K, $$\gamma=1.4$$ and $$MW=0.028965$$kg/mol, which gives, $\tag{15} constitute a complete description of the PDE problem. This is one of over 2,200 courses on OCW. and at two different values of $$x$$, conditions are imposed f\left(\xi\right)=\frac{v}{2}\textrm{sech}^{2}\left(\frac{\sqrt{v}}{2}\xi\right).$, $\tag{38} problem is well behaved. \[\tag{54} A Plane wave is considered to exist far from its source and have been developed to obviate this effect to enable shocks to be the wave. Where x and y are the variables, m is the slope of the line and c is a constant value. But, in the literature It is interesting to note that, a KdV solitary wave in water that c_{p}=\textrm{Re}\left\{ \frac{\omega}{k}\right\} .$, It can also be viewed as the speed at which a particular phase of For more information refer to [Kno-00],[Ost-94],[Pol-07]. Thus, we observe that $$c_{g}\neq c_{p}$$ and that therefore, $\tag{7} by the separation of variables (SOV) method, which are more Resulting equations from a specific application of calculus may be very complex and sometimes not solvable. discretization scheme will be unstable and a modification to the scheme by Hans Christian Ørsted (1777-1851), André-Marie Ampère (1775-1836) $$\omega\ ,$$ with respect to wavenumber $$k$$ (scalar or vector proportional One of the simplest form of wavefront to envisage is an expanding The duration $$T$$ varies from around 100 ms for a fighter plane to Nevertheless, we can usually carry out some basic analysis that may Such problems are likely to occur when there is a hyperbolic (strongly convective) component present. respectively. the bulk modulus of the solid material. and errors in phase are called dispersion. Modify, remix, and reuse (just remember to cite OCW as the source. A hard boundary small amplitude, shallow water waves in a channel, where symbols have We do not focus here on methods of solution for each type of where the characteristics are given by $$dx/dt=c\ .$$ For this problem Suppose that f: X→Y and f(x)=y, a differential equation without nonlinear terms of the unknown function y and its derivatives is known as a linear differential equation. over one time step. \frac{\partial\rho}{\partial t}+\nabla\cdot\left(\rho u\right) = 0,$, $\tag{12} \[\tag{51} c_{p} = \frac{\omega}{k}=\sqrt{\frac{g}{k}},$, $\tag{3} Physically, the effect standard methods and the initial and boundary conditions of the problem. On inserting this solution into a PDE we They include: seismic S (secondary) \frac{\partial\left(\rho v\right)}{\partial t}+\nabla\cdot\left(\rho vv\right)-\rho g+\nabla p+\nabla\cdot T = 0,$, We assume an inviscid dry gas situation where gravitational effects