Bernoulli

r1 = 5e-3;%m
v1 = 250e-3;%m/s
r2 = 3e-3;%m
rhoB = 1.03e3;%kg/m^3
v2 = v1*(r1^2)/(r2^2) %m/s
v2 = 0.6944
dP = rhoB/2 *(v2^2 - v1^2)
dP = 216.1728
verengung = r1^4/r2^4
verengung = 7.7160