## Ex3-pg184¶

In [1]:
import math
#calculate The total resistance of the prototype
u_p=10.; ## m/s
scale=1/25.;  ## l_m/l_p
L=125.; ## m
meu=1.235*10**(-6); ## m**2/s
meu_p=1.188*10**(-6); ## m**2/s
rho_p=1025.; ## kg/m**3
rho_m=1000.; ## kg/m**3
A=3500.; ## wetted surface in m**2

u_m=u_p*math.sqrt(scale);

d=L*scale;
Re=d*u_m/meu; ## Reynolds no.
C_F=0.075/(math.log10(Re)-2)**2; ## Skin friction coefficient

res_skin=rho_m/2*u_m**2*(A*scale**2)*C_F;

res_tot=54.2; ## N

F_resid_m=res_tot-res_skin;

F_resid_p=F_resid_m*rho_p/rho_m/scale**3;

Re_p=u_p*L/meu_p;

C_F_p=0.075/(math.log10(Re_p)-2)**2+0.0004;
C_F_pnew=1.45*C_F_p;

res_friction=rho_p/2*u_p**2*A*C_F_pnew;

Resistance=F_resid_p+res_friction;
print'%s %.1f %s'%("The total resistance of the prototype",Resistance,"N")
The total resistance of the prototype 809273.4 N

## Ex4-pg 184¶

In [2]:
import math
#calculate Maximum speed of the redesigned torpedo

A=0.88; ## ratio of A2 and A1
C_D=0.85; ## ratio of C_D2 to C_D1
P=1.20; ## ratio of P2 to P1
V1=11.; ## m/s

V2=V1*(P/A/C_D)**(1/3.);
print'%s %.2f %s'%("Maximum speed of the redesigned torpedo =",V2,"m/s")
Maximum speed of the redesigned torpedo = 12.88 m/s