function handle as boundary condition

Question

Jorge Garcia Garcia 2023-4-19

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1949718-function-handle-as-boundary-condition

回答： Avni Agrawal 2023-11-16

sorry if this is a very silly question as I am quite new using matlab. So I apologise in advance.

I have a vector with accelerations corresponding to time intances. I need to use a interpolation function to interpolate values of accelerations at different times, and I need to pass this function as boundary condition in specific edges.

len=length(accel_filt);
%Create a time vector with the total length of the vector of acceleration
%measure every time instance
tlist=linspace(0,len,len);
%Create the interpolation function to use as boundary condition
bc = griddedInterpolant(tlist,accel_filt',"linear","nearest");
%--APPLY BOUNDARY CONDITION TO INNER EDGES-- 19/04/23----------------------
for j = 1:numel(edges)                                %for every value store in perimeter
    edge=edges(j);
    
    applyBoundaryCondition(modelTwoDomain,"dirichlet","Edge",edge,"u",@bcfundcD);
end
function defined at the end of code: 
    function bc=bcfundcD(location,bc)
        state.u = bc(location.x);
    end

What am I doing wrong?

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Jorge Garcia Garcia 2023-4-19

yes, I forgot to post it. the Error:

Index exceeds the number of array elements. Index must not exceed 1.

Error in DomainsharedEdge_WorkingVersion>bcfundcD (line 269)

state.u = bc(location.x);

Error in pde.internal.pde3DBCImpl/callValueFuncOnFace (line 37)

bci = func(appRegion, state);

Error in pde.internal.pde3DBCImpl/setValueBCOnFace (line 79)

uVec = self.callValueFuncOnFace(bci, bci.nodes, bci.term1, faceNormals);

Error in pde.internal.pde3DBCImpl/getBCMatrices (line 56)

self.setValueBCOnFace(bcsi, dirBoundaryConditions);

Error in pde.EquationModel/assembleBoundary (line 74)

bcmat = bcImpl.getBCMatrices(u,time,gmat);

Error in pde.EquationModel/assembleSelectedFEMatrices (line 30)

bmat = self.assembleBoundary(u,time,gmatrix);

Error in pde.DiscretizedPDEModel/initialDiscretization (line 50)

femat0 = self.thePde.assembleSelectedFEMatrices(self.p, self.t, self.coefstruct, u0, tdummy, requiredMats, false);

Error in pde.DiscretizedPDEModel (line 33)

obj = obj.initialDiscretization(u0,tdummy);

Error in pde.DynamicDiscretizedPDEModel (line 32)

obj=obj@pde.DiscretizedPDEModel(thePde,p,e,t,coefstruct,u0,false);

Error in pde.EquationModel/solveTimeDependent (line 27)

femodel=pde.DynamicDiscretizedPDEModel(self,p,e,t,coefstruct,u0,tlist,tsecondOrder);

Error in pde.PDEModel/solvepde (line 57)

[u,dudt] = self.solveTimeDependent(coefstruct, u0, ut0, tlist, ...

Error in DomainsharedEdge_WorkingVersion (line 249)

res=solvepde(modelTwoDomain,tlist);

Jorge Garcia Garcia 2023-4-21

Thanks!! will check it out. And thanks for all your guidance! Will let you know what happens :D

Jorge Garcia Garcia 2023-4-26

编辑：Jorge Garcia Garcia 2023-4-26

Hello again

I have been some days trying the following:

tshort= tlist(1:2); %reduce the selection to 2 secs

tshort=tshort'; %transforms tlist into column vector to be like accel

ashort=accel_filt(1:2); %reduce acceleration to short time of test

%bcfund = @(location,state) [bc(state.time); 0];

bc = griddedInterpolant(tshort,ashort,"linear","nearest");

% Define the time at which to evaluate the boundary condition

t = 0.05;

% Evaluate the acceleration at time t

accel_bc = bc(t);

bcfund = @(location,state) [0;accel_bc];

% Apply the modified boundary condition to the PDE model

for j = 1:numel(edges)

edge = edges(j);

applyBoundaryCondition(modelTwoDomain, "dirichlet", "Edge", edge, "u", bcfund)

end

I think it kills matlab and it keeps executing but does not solve the system

res=solvepde(modelTwoDomain,tshort);

I am useless. Any clues?

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Answer 1

Avni Agrawal 2023-11-16

0
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https://ww2.mathworks.cn/matlabcentral/answers/1949718-function-handle-as-boundary-condition#answer_1353747

在 MATLAB Online 中打开

Hi,

I understand that you are trying to pass function handle as an argument to the ‘applyBoundaryCondition’ function in MATLAB. Here is an example of how you can achieve this:

Method 1:

bcfundcD = @(location, state) yourCustomBoundaryCondition(region, state);
% Apply the boundary condition using the function handle
applyBoundaryCondition(model, 'face', 1:4, 'u', bcfundcD);

‘yourCustomBoundaryCondition’ is a function that you have defined to implement your specific boundary condition logic. The ‘bcfoundcD’ function handle is created using an anonymous function that calls ‘yourCustomBoundaryCondition’ with the appropriate arguments. i.e location, state.

Method 2:

% Define the named function
function bcfundcD = yourCustomBoundaryCondition(region, state)
% Implement your boundary condition logic here
% ...
end
% Apply the boundary condition using the function handle
applyBoundaryCondition(model, 'face', 1:4, 'u', @yourCustomBoundaryCondition);