Contents

function [UserVar,LSF,c]=DefineCalving(UserVar,CtrlVar,MUA,LSF,c,F,BCs)

[UserVar,LSF,c]=DefineCalving(UserVar,CtrlVar,MUA,LSF,c,F,BCs)

Define calving the Level-Set Field (LSF) and the Calving Rate Field (c)

Both the Level-Set Field (LSF) and the Calving-Rate Field (c) must be defined over the whole computational domain.

The level-set option must be activated by setting

CtrlVar.LevelSetMethod=1;

in DefineInitialInputs.m

The LSF should, in general, only be defined in the beginning of the run and set the initial value for the LSF. However, if required, the user can change LSF at any time step. The LSF is evolved by solving the Level-Set equation, so any changes done to LSF in this m-file will overwrite/replace the previously calculated values for LSF.

The calving-rate field, c, is an input field to the Level-Set equation and needs to be defined in this m-file in each call.

The variable F has F.LSF and F.c as subfields. In a transient run, these will be the corresponding values from the previous time step.

In contrast to LSF, c is never evolved by Úa. (Think of c as an input variable similar to the input as and ab for upper and lower surface balance, etc.)

If c is returned as a NaN, ie

     c=NaN;

then the level-set is NOT evolved in time using by solving the level-set equation. This can be usefull if, for example, the user simply wants to manually prescribe the calving front position at each time step.

See more information in Ua2D_DefaultParameters.

initialize LSF

if isempty(F.LSF)   % Do I need to initialize the level set function?

    if contains(UserVar.RunType,"-c0isGL0-")  % -> Initial calving front (c0) is set a initial grounding line position (GL0)

        LSF=-ones(MUA.Nnodes,1) ;
        LSF(F.GF.node>0.5)=+1;
        Xc=[] ;  % If Xc and Yc are left empty, the Xc and Yc will be calculated as the zero contorl of the LSF field
        Yc=[] ;

    else

        Xc=UserVar.CalvingFront0.Xc;
        Yc=UserVar.CalvingFront0.Yc;

        % A rough sign-correct initialisation for the LSF
        io=inpoly2([F.x F.y],[Xc(:) Yc(:)]);
        LSF=-ones(MUA.Nnodes,1) ;
        LSF(io)=+1;
    end

    % figure ; PlotMuaMesh(CtrlVar,MUA);   hold on ; plot(F.x(io)/1000,F.y(io)/1000,'or')

    [xc,yc,LSF]=CalvingFrontLevelSetGeometricalInitialisation(CtrlVar,MUA,Xc,Yc,LSF,plot=true,ResampleCalvingFront=true);


end

Define calving rate (if needed)

if  CtrlVar.LevelSetEvolution=="-Prescribed-"

    c=nan;   % setting the calving rate to nan implies that the level set is not evolved

elseif  CtrlVar.CalvingLaw.Evaluation=="-int-"

    % c=0; % Must not be nan or otherwise the LSF will not be evolved.
    % But otherwise these c values are of no importance and the c defined at int points is the one used

    % This value for the calving rate will actually not be used directly by the code
    % because the calving rate is here defined at integration points.
    % But for plotting purposes it is good to define the calving at nodal points as well
    % so here a call is made to define c at the nodes.
    % c=DefineCalvingAtIntegrationPoints(UserVar,CtrlVar,nan,nan,F.ub,F.vb,F.h,F.s,F.S,F.x,F.y) ;
    c=DefineCalvingAtIntegrationPoints(UserVar,CtrlVar,nan,nan,F) ;

else

    % It's assumed that the calving is defined at integration points only, or prescribed directly.
    % Anything else is deemed an error.
    error("Define calving rate at integration points")

end

Published with MATLAB® R2023b