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Linear wave propagation

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Problem definition

 \frac{\partial u}{\partial t}+ c \frac{\partial u}{\partial x}=0



Initial Condition


Boundary condition


Exact solution


Numerical method

 \mbox{Long wave  :}\frac{r}{dx}=20
 \mbox{Medium wave: }\frac{r}{dx}=6
 \mbox{Short wave : } \frac{r}{dx}=3


Explicit Scheme (DRP)

 {(\frac{\partial u}{\partial x})}_i=\frac{1.0}{dx}\sum_{k=-3}^3 a_k u_{i+k}

The coefficients can be found in Tam(1993).At the right boundaries use fourth order central difference and fourth backward difference.At left boundaries use second order central difference for i=2 and fourth order central difference for i=3.The Dispersion relation preserving (DRP) finite volume scheme can be found in Popescu (2005).

Implicit Scheme(Compact)

Domain: \alpha v_{i-1} + v_i + \alpha v_{i+1}=\frac{a}{2h}(u_{i+1}-u_{i-1})
Boundaries:  v_1+\alpha v_2=\frac{1}{h}(au_1+bu_2+cu_3+du_4)

where v refers to the first derivative.For a general treatment of compact scheme refer to Lele (1992).In this test case the following values are used

 \mbox{Domain:} \alpha=0.25 , a=\frac{2}{3}(\alpha+2)
 \mbox{Boundary:} \alpha=2 ,a=-(\frac{11+2\alpha}{6}),b=\frac{6-\alpha}{2},c=\frac{2\alpha-3}{2},d=\frac{2-\alpha}{6}

Both the schemes are 4th order accurate in the domain.The compact scheme has third order accuracy at the boundary.

Time (4th Order Runga-Kutta)

\frac{\partial u}{\partial t}=f
u^{M+1} =u^M + b^{M+1}dtH^M

,M=1,2..5 .The coefficients a and b can be found in Williamson(1980)


Initial condition.png Result wave.png


Mihaela Popescu, Wei Shyy , Marc Garbey (2005), "Finite volume treatment of dispersion-relation-preserving and optimized prefactored compact schemes for wave propagation", Journal of Computational Physics, Vol. 210, pp. 705-729.

Tam and Webb (1993), "Dispersion-relation-preserving finite difference schemes for computational acoustics", Journal of Computational Physics, Vol. 107, pp. 262-281.

SK Lele (1992), "Compact finite difference schemes with spectrum-like resolution", Journal of Computational Physics, Vol.103, pp.16-42.

Williamson (1980), "Low Storage Runge-Kutta Schemes", Journal of Computational Physics, Vol.35, pp.48–56.

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