samiyare

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10 years, 24 days

 

Amir

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These are questions asked by samiyare

Hi,

i wrote the following code

restart:
zet:=0.5:
rhop:=3880;
rhobf:=998.2;
cp:=773;
cbf:=4182;

eq1 := diff(u(eta), eta, eta)+0.133762025280e-2/(0.993000000000e-3+0.388362300000e-1*phi(eta)+.530162700000*phi(eta)^2)+(1/(eta-1)+(0.388362300000e-1+1.06032540000*phi(eta))*(diff(phi(eta), eta))/(0.993000000000e-3+0.388362300000e-1*phi(eta)+.530162700000*phi(eta)^2))*(diff(u(eta), eta));
eq2 := diff(T(eta), eta, eta)+(.63267672*((2.66666666666*(-1.1752324*10^6*phi(eta)+4.1744724*10^6))*u(eta)/p2+7.04876575828*(diff(phi(eta), eta))-(1.58058605349*(.597+4.45959*phi(eta)))*(diff(T(eta), eta))/(1-eta)))/(.597+4.45959*phi(eta));
eq3 := diff(phi(eta), eta)-5.00000000000*phi(eta)*(diff(T(eta), eta));
p:=proc(pp2) if not type([pp2],list(numeric)) then return 'procname(_passed)' end if:

res := dsolve({eq1=0,subs(p2=pp2,eq2)=0,eq3=0,u(0)=0,u(1-zet)=0,phi(0)=0.008,T(0)=0,D(T)(0)=1}, numeric);
F0,F1,F2:=op(subs(res,[u(eta),phi(eta),T(eta)]));
res(parameters=[pp2]);
evalf(2/(1-zet^2)*Int((1-eta)*(F1(eta)*rhop+(1-F1(eta))*rhobf)*( F1(eta)*rhop*cp+(1-F1(eta))*rhobf*cbf )/(F1(eta)*rhop+(1-F1(eta))*rhobf)*F0(eta),eta=0..1-zet))-pp2
end proc;

fsolve(p(pp2)=0,pp2=(20000)..(8000000));

 

it has an error and i cannot find that. would you please help me?

 

thanks

hi,

 

how can i solve the following ode

u'' + 3.4/ (u(0.25)*2+u(0.16)+2) + uu'=0

boundary conditions   u(0)=a  , u(0.5)=b

a and b are constants. for example a=0.1 and b=1

 

hi

please help me to solve the following system of ODE

 

diff(u(eta), eta, eta)+.5699919300/(0.9930000000e-3+0.3883623000e-1*phi(eta)+.5301627000*phi(eta)^2)+1/(eta-1)+(0.3883623000e-1+1.060325400*phi(eta))*(diff(phi(eta), eta))*(diff(u(eta), eta))/(0.9930000000e-3+0.3883623000e-1*phi(eta)+.5301627000*phi(eta)^2) = 0;

 

diff(T(eta), eta, eta)+(5.05659*((-1.1752324*10^6*phi(eta)+4.1744724*10^6)*u(eta)/(int((1-eta)*(-1.1752324*10^6*phi(eta)+4.1744724*10^6)*u(eta), eta = 0 .. .5))+7.47*(diff(phi(eta), eta))/(1+7.47*phi[0])-(.1977617327*(.597+4.45959*phi(eta)))*(diff(T(eta), eta))/(1-eta)))/(.597+4.45959*phi(eta))=0;

 

diff(phi(eta), eta)-5.000000000*phi(eta)*(diff(T(eta), eta)) = 0;

 

with following boundary condition

u(0)=0,u(0.5)=0,phi(0)=1,T(0)=0,D(T)(0)=0

 

thanks for your attention in advance

Hi

i want to minimizez the "Eq1(h[1],h[2],...h[n])" for all the h[i] in the ranges of -1<h[i]<1.  "n" (number of unknown variables) can be determined during the code and was not know before. how can i do this?

It must be stated that when i have Eq1 and two unknown variables such as h[1] and h[2], i wrote the following code and it works good, but i dont know how can i write mentioned command for unknown number of variables.

NLPSolve(Eq1,h[1]=-1..1,h[2]=-1..1);

thanks for your attention in advance

hi,

i have one equation (like equ1) wich this equatioin is a function of x. i want to find x in such a way that the equ1 minimizes. unfortunetly the equ1 is large and when i want to use NLPsolve it takes several time. is there any quick method to find the minimum x?

thanks for your attention in advance

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