%Wesley N Donald

%Lab HMWK

%Moody Chart

clc

clear

j=[1 2 3 4 5 6 7 8 9 10];

A(1)=0;

i=3;

n=1;

for k= 1:10

while j(i)<9

A(k)=10^(j(i));

for l=1:9

Re(n)=A(k)*l;

n=n+1;

end

i=i+1;

end

end

Rr=[.00001,.00005,.0001,.0002,.0004,.0006,.0005,.001,.002,.004,.006,.008,.01,.015,.02,.03,.04,.05];

n=length (Re);

m=length(Rr);

for j=1:m

for i=1:n

f(i)=(1/(-1.8*log10(6.9/Re(i)+(Rr(j)/3.7)^1.11)))^2;

end

loglog(Re,f)

axis ([10^3 10^8 0.008 0.1])

hold on

grid on

xlabel('Reynolds number')

ylabel('Friction Factor')

end

%backsub

clc

clear

A=[8 4 -2;0 -4 2 ; 0 0 -1];

b=[1 2 3];

n = length(b);

x(n)=b(n)/A(n,n);

for i= n-1:-1:1

x(i)=(b(i)-sum(A(i,i+1:n).*x(i+1:n)))/A(i,i);

end

x

A=[8 4 -2;0 -4 2 ; 0 0 -1]

b=[1 2 3]'

x=inv(A)*b

b =

1

2

3

x =

0.3750

-2.0000

-3.0000

function x = GaussNaive(A,b)

[m,n] = size(A)

if m~=n, error('Matrix A must be square'); end

nb=n+1

Aug = [A b]

for k = 1:n-1

for i = k+1:n

factor = Aug(i,k)/Aug(k,k)

Aug(i,k:nb) = Aug(i,k:nb)-factor*Aug(k,k:nb)

end

end

x=zeros(n,1)

x(n)= Aug(n,nb)/Aug(n,n)

for i = n-1:-1:1

x(i)= (Aug(i,nb)-Aug(i,i+1:n)*x(i+1:n))/Aug(i,i)

end