Python Forum

I am working on a simple code, for calculating Re number. The problem is that I want to check every number in Re vector, although I do not know how to do it.
The error I am getting is: ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

The code:

import numpy as np
from CoolProp.CoolProp import PropsSI
from numpy import*

v = [1,2,3,4,5]
Tz = 42 + 273
v = 4e-2 # [m]
s = 2e-2 # [m]
#------------------------------------------------------------------------------------

npv = np.array(v)

A = v*s
ob = 2*(s + v)
Dh = (4*A)/ ob
roZ = PropsSI('D', 'P', 101325, 'T', Tz, 'Air')
din_vis= PropsSI('V', 'P', 101325, 'T', Tz, 'Air')
kin_vis = din_vis/roZ

Re= (npv *Dh )/ kin_vis
Pr = PropsSI('PRANDTL', 'P', 101325, 'T', Tz, 'Air')
print ('Re:',Re)
print ('Pr:',Pr)

if Re < 2300:
    print('Laminar flow, Re = ', Re)
elif Re > 10000 and Pr >= 0.6 and Pr <= 160:
    print('Turbolent flow, Re = ', Re)
    print('Pr = ', Pr)
else:
    print(' Re = ', Re)
    print('Pr = ', Pr)

Any help is much appreciated.

I am not a profi in hydrodynamics, but ... (hope that helps):

import numpy as np
from CoolProp.CoolProp import PropsSI
# from numpy import* # Remove this line, numpy is already imported as np!
 
v = [1, 2, 3, 4, 5] # be pep8 compliant
Tz = 42 + 273
v = 4e-2 # [m]
s = 2e-2 # [m]
#------------------------------------------------------------------------------------
 
npv = np.array(v, dtype=np.float64)  # don't forget to specify the type of your data; 
 
A = npv * s # pep8, use npv instead of v; npv is a numpy array, that could be multiplied on a constant
# A is an array now

ob = 2 * (s + npv) # don't forget spaces; v -> npv
Dh = (4 * A) / ob # elementwise division of vectors A and ob (hope `ob` doesn't not include zeros)

# Probably, roZ is a scalar value... 
roZ = PropsSI('D', 'P', 101325, 'T', Tz, 'Air') 

# Probably, din_vis is a scalar value... 
din_vis= PropsSI('V', 'P', 101325, 'T', Tz, 'Air')

kin_vis = din_vis / roZ #  kin_vis = a scalar
 
Re = (npv * Dh) / kin_vis # now Re is a numpy array (length(Re) = length(v))


Pr = PropsSI('PRANDTL', 'P', 101325, 'T', Tz, 'Air') # this is (probably) a scalar value

print ('Re:', Re)
print ('Pr:', Pr)
 

# You can use for loop  here:

for r in Re:
    if r < 2300:
        print('Laminar flow, Re = ', r)
    elif r > 10000 and Pr >= 0.6 and Pr <= 160:
        print('Turbolent flow, Re = ', r)
        print('Pr = ', Pr)
    else:
        print('Re = ', r)
        print('Pr = ', Pr)

# or use numpy vectorized notation:

print('Laminar flow, Re = ', Re[Re < 2300])

if Pr >= 0.6 and Pr <= 160:
    print('Turbolent flow, Re = ', Re[Re > 10000])

Eliza5

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