Shock Waves Water Waves Small amplitude waves Large
- Slides: 27
Shock Waves
Water Waves Small amplitude waves Large amplitude waves
Shock Development Wave front steepening • Transverse waves • Longitudinal waves
Jumps Discontinuous solutions obeying conservation laws Jumps in (P, Rho, V, T); Continuous (E, M)
Rankine-Hugoniot Equation 1 D Euler equations:
Rankine-Hugoniot Equation Jump conditions:
3 D Shocks 3 D Euler equation in the conservative form:
Shock Consequences Viscous Heating Bow shock produced by a neutron star Supernova envelope Supernova remnant
HD Linear Spectrum Fourier Analysis: ( V, P, r ) ~ exp(i k r – i w t) Dispersion Equation: w 2 (w 2 - Cs 2 k 2)=0 Solutions: Vortices: Sound waves: w 2 = 0 w 2 = Cs 2 k 2
HD Discontinuities Sound waves -> Shocks (P 1, r 1, Vn 1) -> (P 2, r 2, Vn 2) ; Vt 1=Vt 2 Vortex -> Contact Discontinuity Vt 1 -> Vt 2 ; (P 1, r 1, Vn 1)= (P 2, r 2, Vn 2) Vt Vn
MHD modes - Fast magnetosonic waves; - Slow magnetosonic waves; - Alfven waves; - Fast shocks; - Slow shocks; - Contact shocks;
MHD shocks
Riemann Shock Tube Problem 1 D: Shock tube problem Method of characteristics:
Riemann Shock Tube Problem Shock wave Rarefaction wave
Riemann Problem Shocks in Euler equations
Godunov Method Godunov 1959 Grid: Cell interface
Godunov scheme Find cell interface jumps ¯ Solve Riemann Problem (for every cell) ¯ Find cell center values (conservative interpolation) integration step
Riemann stepping
Interpolation
Conservative Interpolation Rho = Rho(P, S) Rho<0
Approximations Riemann Solver: - Linear Riemann solver (ROE) Fast, medium accuracy - Harten-Laxvan-Leer solver (HLL) Problems with contact discontinuities - Two-Shock Rieman Solver Problems with entropy waves Interpolation - Linear (numerical stability) - Parabolic (ppm) - High order
Riemann Solvers Linear Riemann solver (Roe, 1981) Formulate approximate linear problem d/dt Ut + A(UL, UR) d/dx U = 0
Interpolations - Linear (numerical stability) - Parabolic (ppm) - High order
+/+ Best accuracy + Shock capturing + study of the Heating, viscosity, … - Slow - Turbulence - Complicated
end www. tevza. org/home/course/modelling-II_2016/
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