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annotate +rv/+time/RungekuttaExteriorRV.m @ 1014:e547794a9407 feature/advectionRV

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Add boot-strapping to RungeKuttaExteriorRV - Higher order BDF approximations are successively used as increasing number of time levels are obtained.
author Vidar Stiernström <vidar.stiernstrom@it.uu.se>
date Thu, 06 Dec 2018 11:30:47 +0100
parents eb441fbdf379
children 9b7fcd5e4480
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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 coeffs % The coefficents used for the RK time integration
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9 RV % Residual Viscosity
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10 bdfOrder
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11 v_prev % Solution vector at previous time levels, used for the RV update
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12 DvDt % Function for computing the time deriative used for the RV update
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13 end
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14 methods
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15
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16 function obj = RungekuttaExteriorRV(F, k, t0, v0, RV, rkOrder, bdfOrder)
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17 obj.F = F;
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18 obj.k = k;
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19 obj.t = t0;
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20 obj.v = v0;
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21 obj.n = 0;
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22 % Extract the coefficients for the specified rkOrder
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23 % used for the RK updates from the Butcher tableua.
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24 [s,a,b,c] = time.rk.butcherTableau(rkOrder);
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25 obj.coeffs = struct('s',s,'a',a,'b',b,'c',c);
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27 obj.RV = RV;
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28 % TBD: For cases where h~k we could probably use rkOrder-2 here.
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29 % TBD: Decide on if the initialization of the previous stages used by
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30 % the BDF should be done here, or if it should be checked for each
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31 % step taken.
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32 assert(bdfOrder >= 2);
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33 obj.bdfOrder = bdfOrder;
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34 obj.v_prev = [];
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35 obj.DvDt = rv.time.BDFDerivative();
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36 end
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38 function [v, t] = getV(obj)
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39 v = obj.v;
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40 t = obj.t;
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41 end
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43 function state = getState(obj)
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44 [residual, u_t, grad_f] = obj.RV.getResidual();
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45 state = struct('v', obj.v, 'residual', residual, 'u_t', u_t, 'grad_f', grad_f, 'viscosity', obj.RV.getViscosity(), 't', obj.t);
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46 end
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48 function obj = step(obj)
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49 % Store current time level
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50 if (size(obj.v_prev,2) < obj.bdfOrder)
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51 obj.v_prev = [obj.v, obj.v_prev];
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52 else
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53 obj.v_prev(:,2:end) = obj.v_prev(:,1:end-1);
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54 obj.v_prev(:,1) = obj.v;
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55 end
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56 % Fix the viscosity of the RHS function F
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57 F_visc = @(v,t) obj.F(v,t,obj.RV.getViscosity()); %TBD: Remove state in RV?
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58 obj.v = time.rk.rungekutta(obj.v, obj.t, obj.k, F_visc, obj.coeffs);
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59 % Calculate dvdt and update RV
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60 dvdt = obj.DvDt.evaluate(obj.v, obj.v_prev, obj.k);
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61 obj.RV.update(obj.v,dvdt);
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62 obj.t = obj.t + obj.k;
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63 obj.n = obj.n + 1;
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64 end
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65 end
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66 end