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annotate four.m @ 1012:1e437c9e5132 feature/advectionRV

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Create residual viscosity package +rv and generalize the ResidualViscosity class - Generalize residual viscosity, by passing user-defined flux and calculating the time derivative outside of the update. - Create separate RungekuttaRV specifically using interior RV updates - Separate the artifical dissipation operator from the scheme AdvectionRV1D so that the same scheme can be reused for creating the diff op used by the ResidualViscosity class
author Vidar Stiernström <vidar.stiernstrom@it.uu.se>
date Wed, 05 Dec 2018 13:44:10 +0100
parents f6ada1719420
children
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f6ada1719420 Add functions for calculating fourier transforms
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1 % four returns the fourier transform u_hat of the function u and the frequencies w
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2 function [w, u_hat] = four(x, u)
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3 u_hat = fft(u);
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4
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5 N = length(x);
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6 L = x(end) - x(1);
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7
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8 k = shift_k(0:N-1);
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10 u_hat = fftshift(u_hat);
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12 dw = 2*pi/L;
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13 w = dw*k;
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14 end
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16 function k_shifted = shift_k(k)
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17 N = length(k);
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18 k_shifted = [-floor(N/2):-1, 0, 1:ceil(N/2)-1];
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19 end