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annotate +rv/+time/RungekuttaExteriorRv.m @ 1156:8c0e2b50f018 feature/rv

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Attempt to fix oscilations when not using bdfs by adding lower-order 2nd derivative correction term to the Residual
author Vidar Stiernström <vidar.stiernstrom@it.uu.se>
date Tue, 25 Jun 2019 13:06:42 +0200
parents 3108963cc42c
children
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78c75c95b7dd Rename Rungekutta-Rv classes according to naming convention
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1 classdef RungekuttaExteriorRv < time.Timestepper
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2 properties
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3 F % RHS of the ODE
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4 k % Time step
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5 t % Time point
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6 v % Solution vector
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7 n % Time level
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8 rkScheme % The particular RK scheme used for time integration
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9 RV % Residual Viscosity operator
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10 DvDt % Function for computing the time deriative used for the RV evaluation
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11 end
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12 methods
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13
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14 function obj = RungekuttaExteriorRv(F, k, t0, v0, RV, DvDt, order)
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15 obj.F = F;
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16 obj.k = k;
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17 obj.t = t0;
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18 obj.v = v0;
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19 obj.n = 0;
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21 if (order == 4) % Use specialized RK4 scheme
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22 obj.rkScheme = @time.rk.rungekutta_4;
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23 else
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24 % Extract the coefficients for the specified order
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25 % used for the RK updates from the Butcher tableua.
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26 [s,a,b,c] = time.rk.butcherTableau(order);
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27 coeffs = struct('s',s,'a',a,'b',b,'c',c);
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28 obj.rkScheme = @(v,t,dt,F) time.rk.rungekutta(v, t , dt, F, coeffs);
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29 end
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31 obj.RV = RV;
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32 obj.DvDt = DvDt;
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33 end
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35 function [v, t] = getV(obj)
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36 v = obj.v;
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37 t = obj.t;
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38 end
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40 function state = getState(obj)
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41 dvdt = obj.DvDt(obj.v);
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42 [viscosity, Df, firstOrderViscosity, residualViscosity] = obj.RV.evaluate(obj.v, dvdt);
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43 state = struct('v', obj.v, 'dvdt', dvdt, 'Df', Df, 'viscosity', viscosity, 'residualViscosity', residualViscosity, 'firstOrderViscosity', firstOrderViscosity, 't', obj.t);
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44 end
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45
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46 % Advances the solution vector one time step using the Runge-Kutta method given by
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47 % obj.coeffs, using a fixed residual viscosity for the Runge-Kutta substeps
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dce08a74e0ad Create a separate class of RungekuttaExteriorRV which uses BDFs for computing the time derivative. Remove BDFs from RungekuttaExteriorRV
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48 function obj = step(obj)
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49 % Fix the viscosity of the RHS function F
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50 viscosity = obj.RV.evaluateViscosity(obj.v, obj.DvDt(obj.v));
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51 m = length(viscosity);
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52 F_visc = @(v,t) obj.F(v,t,spdiags(viscosity,0,m,m));
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53 obj.v = obj.rkScheme(obj.v, obj.t, obj.k, F_visc);
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54 obj.t = obj.t + obj.k;
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55 obj.n = obj.n + 1;
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56 end
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57 end
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58 end