Can someone tell how to use state.time, state.u simultaneously?

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Dhanush Bejjarapu 2020-6-9

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回答： Jorge Garcia Garcia 2023-7-10

I have a heat generation function of temperature and time. I'm confused how state.u gets translated to final temperature.

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Dhanush Bejjarapu 2020-6-9

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I'm attaching my heat source function which involves many constants so please ignore them.

The issue is: My state.u matrix is 1x2500 but it is constant and its values are all initial temperature values (303 K). I want state.u to get updated after each iteration so that I can use the updated state.u temperature in my heat generation.

Please help me with this! Thanks in advance!

function q = myfun(~, state) 
if any(isnan(state.u))
    q = NaN(size(state.u));
    return;
end
if any(isnan(state.time))
    q = NaN(size(state.u));
    return;
end
%% Ignore these Parameters
Rho_ce = 3.15; %g/cm3 == density of cement
Rho_w = 1; %g/cm3 == density of water
v_cbw = 0.25; %gmass of chemically bound water/gcement
wg = 0.15; %gmass of physically bound water/gcement
r0 = 9*10^-4;%cm
T_initial = 303;
wc_ratio = 0.303;% Water to cement ration
k_3 = (0.4/wc_ratio);
C3S = 54;C2S = 19;
C3A = 11;C4AF = 10;
Gypsum = 6;
beta_1 = 1000;beta_2 = 1000;
E_R = 5400;beta_3 = 7500;
Cem = 565*10^-9;
He = 5.9444*10^5;
tstep = 100;
%% Initialization
M = length(state.u);
alpha = zeros(1, M);
dalphadt = zeros(1, M);
R3 = zeros(1, M);S3 = zeros(1, M);
T3 = zeros(1, M);U3 = zeros(1, M);
q = real(zeros(1, M));
R3(:,1) = (((6*10^-12)*(C3S + C3A)) + (4*10^-10))*exp(-beta_1*((1/T_initial)-(1/293)));
S3(:,1) = (0.0003*C3S + 0.0186)*exp(-beta_2*((1/T_initial)-(1/293)));
T3(:,1) = r0./((7*10^-10 - (8*10^-12)*C2S)*(exp(-beta_3*((1/T_initial)-(1/293)))));
U3(:,1) = 1./(((8*10^-8)*C3S + (10^-6))*exp(-E_R*((1/T_initial)-(1/293))));
for i = 2:M %assuming M is the final time
        alpha(1, i) = alpha(1, i-1) + dalphadt(1, i-1).*(tstep/3600);
        
        R3(1,i) = (((6*10^-12)*(C3S + C3A)) + (4*10^-10))*exp(-beta_1.*((1./state.u(1, i))-(1/293)));%temp. dependent
        
        S3(1,i) = (0.0003*C3S + 0.0186)*exp(-beta_2.*((1./state.u(1, i))-(1/293)));%temp. dependent
        
        T3(1,i) = r0./((7*10^-10 - (8*10^-12)*C2S)*(exp(-beta_3.*((1./state.u(1, i))-(1/293)))));%temp. dependent
        
        U3(1,i) = 1./(((8*10^-8)*C3S + (10^-6))*exp(-E_R.*((1./state.u(1, i))-(1/293))));%temp. dependent
        
        dalphadt(1, i) = ((3*Rho_w/(r0*Rho_ce*(v_cbw+wg))) .* power(1 - k_3 .* alpha(1, i), (2.6-4*wc_ratio))) ./ ((1 ./ ((R3(1, i) .* power(alpha(1, i), -1.5)) + S3(1, i) .* power(alpha(1, i), 3))) + T3(1, i) ./ log(alpha(1, i)) + U3(1, i) .* power(1 - alpha(1, i), -2/3) - T3(1, i) .* power(1 - alpha(1, i), -1/3) ./ log(alpha(1, i)));    
        
        q(1, i) = (Cem*He).*dalphadt(1, i)./3600;%depends on alpha and temperature
        
end
end

Ravi Kumar 2020-6-9

Hi Dhanush,

I see that the temperature is changing, but by very small amount from its initial temperature. What version of matlab are you using?

Regards,

Ravi

Dhanush Bejjarapu 2020-6-10

Hello,

I'm using the latest R2020a version and I don't think that this version has the issues.

When I've changed the initial conditions, state.u is changing accordingly while state.time is remaining at 0, so maybe I need to make state.time to become functional to have the change in state.u but unable to figure out how to do this...

Regards,

Dhanush

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Answer 1

Jorge Garcia Garcia 2023-7-10

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I am also having some issues with state.time. I have 5 time instances and it seems just to read 0 and a randon number.. then it just generates NAN values

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Can someone tell how to use state.time, state.u simultaneously?

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