PDE Toolbox - Convection in Diffusion Equation

Question

Andrew Ferguson 2020-1-21

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/501285-pde-toolbox-convection-in-diffusion-equation

评论： Gobinda Debnath 2023-7-23

采纳的回答： Ravi Kumar

在 MATLAB Online 中打开

I'm trying to add a convection term to solve a diffusion PDE using the PDE Toolbox. I'm defining the PDE as:

specifyCoefficients(model,'Face',2,'m',0,'d',1,'c',Da,'a',0,'f',@fcoeff);

and have the following at the end of my code:

function f = fcoeff(location,state)
y = location.y./h;
x = location.x./L;
v = va;
f = -(v.*state.ux.*state.time + v.*state.uy.*state.time);
end

However, whenever I try to run the code I get the following error:

Error using pde.CoefficientAssignment/checkCoefFcnHdlArgCounts (line 499)
Function specifying a coefficient must accept two
input arguments and return one output argument.
Error in pde.CoefficientAssignment/checkFcnHdlArgCounts (line 272)
            self.checkCoefFcnHdlArgCounts(self.f, systemsize, ndims);
Error in pde.CoefficientAssignment (line 104)
      obj.checkFcnHdlArgCounts(systemsize, numdims);
Error in pde.PDEModel/specifyCoefficients (line 143)
        coef = pde.CoefficientAssignment(self.EquationCoefficients,argsToPass{:});
Error in Dry_Air (line 49)
specifyCoefficients(model,'Face',2,'m',0,'d',1,'c',Da,'a',0,'f',@fcoeff);

I don't understand the error because as I see it I am ipnuting two arguments and am returning one output. Whenever I take away the function for 'f' on the RHS of the PDE my code works perfectly. Any help would be much appreciated!

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Answer 1

Ravi Kumar 2020-1-21

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/501285-pde-toolbox-convection-in-diffusion-equation#answer_411253

It looks like your function errored without returning one onput. Most likely the error could have been due to 'va' being out of scope for the function fcoeff.

Regards,

Ravi

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Andrew Ferguson 2020-1-21

Thanks! Adding in h and L worked!

Gobinda Debnath 2023-7-23

Hello Andrew ferguson and ravi sir, i am new to matlab, can i get a sample code for convection-diffusion term equation, in matlab how to handle convection term, please help me on this, thank you

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