Georg_Brantegger/Python-DT_Slot_3
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fix for numerical runaway of rounding errors

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due to turbine-pipeline interatction
via a convergence method in the turbine
and a "damping" trick on the reservoir velocity
plus: code cleanup with consistent naming of variables
This commit is contained in:
Brantegger Georg
2022-08-03 15:56:56 +02:00
parent 84631ee4cc
commit ba696444bb
13 changed files with 1257 additions and 1198 deletions
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131
Turbinen/Turbinen_class_file.py
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@@ -1,8 +1,10 @@
from time import time
import numpy as np
#importing pressure conversion function
import sys
import os
from pyparsing import alphanums
current = os.path.dirname(os.path.realpath(__file__))
parent = os.path.dirname(current)
sys.path.append(parent)
@@ -11,7 +13,7 @@ from functions.pressure_conversion import pressure_conversion
class Francis_Turbine:
# units
# make sure that units and print units are the same
# units are used to label graphs and print units are used to have a bearable format when using pythons print()
# units are used to label graphs and disp units are used to have a bearable format when using pythons print()
density_unit = r'$\mathrm{kg}/\mathrm{m}^3$'
flux_unit = r'$\mathrm{m}^3/\mathrm{s}$'
LA_unit = '%'
@@ -20,30 +22,28 @@ class Francis_Turbine:
velocity_unit = r'$\mathrm{m}/\mathrm{s}$'
volume_unit = r'$\mathrm{m}^3$'
density_unit_print = 'kg/m³'
flux_unit_print = 'm³/s'
LA_unit_print = '%'
pressure_unit_print = 'mWS'
time_unit_print = 's'
velocity_unit_print = 'm/s'
volume_unit_print = 'm³'
density_unit_disp = 'kg/m³'
flux_unit_disp = 'm³/s'
LA_unit_disp = '%'
time_unit_disp = 's'
velocity_unit_disp = 'm/s'
volume_unit_disp = 'm³'
g = 9.81 # m/s² gravitational acceleration
# init
def __init__(self, Q_nenn,p_nenn,t_closing=-1.,timestep=-1.):
def __init__(self, Q_nenn,p_nenn,t_closing,timestep,pressure_unit_disp):
self.Q_n = Q_nenn # nominal flux
self.p_n = p_nenn # nominal pressure
self.LA_n = 1. # 100% # nominal Leitapparatöffnung
h = pressure_conversion(p_nenn,'Pa','MWs') # nominal pressure in terms of hydraulic head
self.A = Q_nenn/(np.sqrt(2*self.g*h)*0.98) # Ersatzfläche
self.dt = timestep # simulation timestep
self.t_c = t_closing # closing time
self.t_c = t_closing # closing time
self.d_LA_max_dt = 1/t_closing # maximal change of LA per second
self.pressure_unit_disp = pressure_unit_disp
# initialize for get_info() - parameters will be converted to display -1 if not overwritten
self.p = pressure_conversion(-1,self.pressure_unit_print,self.pressure_unit)
self.p = pressure_conversion(-1,self.pressure_unit_disp,self.pressure_unit)
self.Q = -1.
self.LA = -0.01
@@ -54,19 +54,22 @@ class Francis_Turbine:
self.LA = LA
# warn user, that the .set_LA() method should not be used ot set LA manually
if display_warning == True:
print('Consider using the .update_LA() method instead of setting LA manually')
def set_timestep(self,timestep,display_warning=True):
# set Leitapparatöffnung
self.dt = time
# warn user, that the .set_LA() method should not be used ot set LA manually
if display_warning == True:
print('WARNING: You are changing the timestep of the turbine simulation. This has implications on the simulated closing speed!')
print('You are setting the guide vane opening of the turbine manually. \n \
This is not an intended use of this method. \n \
Refer to the .update_LA() method instead.')
def set_pressure(self,pressure):
# set pressure in front of the turbine
self.p = pressure
def set_steady_state(self,ss_flux,ss_pressure):
# calculate and set steady state LA, that allows the flow of ss_flux at ss_pressure through the
# turbine at the steady state LA
ss_LA = self.LA_n*ss_flux/self.Q_n*np.sqrt(self.p_n/ss_pressure)
if ss_LA < 0 or ss_LA > 1:
raise Exception('LA out of range [0;1]')
self.set_LA(ss_LA,display_warning=False)
#getter
def get_current_Q(self):
# return the flux through the turbine, based on the current pressure in front
@@ -80,10 +83,13 @@ class Francis_Turbine:
def get_current_LA(self):
return self.LA
def get_current_pressure(self):
return pressure_conversion(self.p,self.pressure_unit,self.pressure_unit_disp)
def get_info(self, full = False):
new_line = '\n'
p = pressure_conversion(self.p,self.pressure_unit,self.pressure_unit_print)
p_n = pressure_conversion(self.p_n,self.pressure_unit,self.pressure_unit_print)
p = pressure_conversion(self.p,self.pressure_unit,self.pressure_unit_disp)
p_n = pressure_conversion(self.p_n,self.pressure_unit,self.pressure_unit_disp)
if full == True:
@@ -91,33 +97,34 @@ class Francis_Turbine:
print_str = (f"Turbine has the following attributes: {new_line}"
f"----------------------------- {new_line}"
f"Type = Francis {new_line}"
f"Nominal flux = {self.Q_n:<10} {self.flux_unit_print} {new_line}"
f"Nominal pressure = {round(p_n,3):<10} {self.pressure_unit_print}{new_line}"
f"Nominal LA = {self.LA_n*100:<10} {self.LA_unit_print} {new_line}"
f"Closing time = {self.t_c:<10} {self.time_unit_print} {new_line}"
f"Current flux = {self.Q:<10} {self.flux_unit_print} {new_line}"
f"Current pipe pressure = {round(p,3):<10} {self.pressure_unit_print} {new_line}"
f"Current LA = {self.LA*100:<10} {self.LA_unit_print} {new_line}"
f"Simulation timestep = {self.dt:<10} {self.time_unit_print} {new_line}"
f"Nominal flux = {self.Q_n:<10} {self.flux_unit_disp} {new_line}"
f"Nominal pressure = {round(p_n,3):<10} {self.pressure_unit_disp}{new_line}"
f"Nominal LA = {self.LA_n*100:<10} {self.LA_unit_disp} {new_line}"
f"Closing time = {self.t_c:<10} {self.time_unit_disp} {new_line}"
f"Current flux = {self.Q:<10} {self.flux_unit_disp} {new_line}"
f"Current pipe pressure = {round(p,3):<10} {self.pressure_unit_disp} {new_line}"
f"Current LA = {self.LA*100:<10} {self.LA_unit_disp} {new_line}"
f"Simulation timestep = {self.dt:<10} {self.time_unit_disp} {new_line}"
f"----------------------------- {new_line}")
else:
# :<10 pads the self.value to be 10 characters wide
print_str = (f"The current attributes are: {new_line}"
f"----------------------------- {new_line}"
f"Current flux = {self.Q:<10} {self.flux_unit_print} {new_line}"
f"Current pipe pressure = {round(p,3):<10} {self.pressure_unit_print} {new_line}"
f"Current LA = {self.LA*100:<10} {self.LA_unit_print} {new_line}"
f"Current flux = {self.Q:<10} {self.flux_unit_disp} {new_line}"
f"Current pipe pressure = {round(p,3):<10} {self.pressure_unit_disp} {new_line}"
f"Current LA = {self.LA*100:<10} {self.LA_unit_disp} {new_line}"
f"----------------------------- {new_line}")
print(print_str)
# methods
# update methods
def update_LA(self,LA_soll):
# update the Leitappartöffnung and consider the restrictions of the closing time of the turbine
LA_diff = self.LA-LA_soll # calculate the difference to the target LA
LA_diff_max = self.d_LA_max_dt*self.dt # calculate the maximum change in LA based on the given timestep
LA_diff = self.LA-LA_soll # calculate the difference to the target LA
LA_diff_max = self.d_LA_max_dt*self.dt # calculate the maximum possible change in LA based on the given timestep
LA_diff = np.sign(LA_diff)*np.min(np.abs([LA_diff,LA_diff_max])) # calulate the correct change in LA
# make sure that the LA is not out of the range [0;1]
LA_new = self.LA-LA_diff
if LA_new < 0.:
LA_new = 0.
@@ -125,10 +132,42 @@ class Francis_Turbine:
LA_new = 1.
self.set_LA(LA_new,display_warning=False)
def set_steady_state(self,ss_flux,ss_pressure):
# calculate and set steady state LA, that allows the flow of ss_flux at ss_pressure through the
# turbine at the steady state LA
ss_LA = self.LA_n*ss_flux/self.Q_n*np.sqrt(self.p_n/ss_pressure)
if ss_LA < 0 or ss_LA > 1:
raise Exception('LA out of range [0;1]')
self.set_LA(ss_LA,display_warning=False)
# methods
def converge(self,convergence_parameters):
# small numerical disturbances (~1e-12 m/s) in the velocity can get amplified at the turbine node, because the new velocity of the turbine and the
# new pressure from the forward characteristic are not compatible.
eps = 1e-12 # convergence criterion: iteration change < eps
iteration_change = 1. # change in Q from one iteration to the next
i = 0 # safety variable. break loop if it exceeds 1e6 iterations
g = self.g # gravitational acceleration
p = convergence_parameters[0] # pressure at second to last node (see method of characterisctics - boundary condidtions)
v = convergence_parameters[1] # velocity at second to last node (see method of characterisctics - boundary condidtions)
D = convergence_parameters[2] # diameter of the pipeline
area_pipe = convergence_parameters[3] # area of the pipeline
alpha = convergence_parameters[4] # elevation angle of the pipeline
f_D = convergence_parameters[5] # Darcy friction coefficient
c = convergence_parameters[6] # pressure wave propagtation velocity
rho = convergence_parameters[7] # density of the liquid
dt = convergence_parameters[8] # timestep of the characteristic method
p_old = self.get_current_pressure()
Q_old = self.get_current_Q()
v_old = Q_old/area_pipe
while iteration_change > eps:
self.set_pressure(p_old)
Q_new = self.get_current_Q()
v_new = Q_new/area_pipe
p_new = p-rho*c*(v_old-v)+rho*c*dt*g*np.sin(alpha)-f_D*rho*c*dt/(2*D)*abs(v)*v
iteration_change = abs(Q_old-Q_new)
Q_old = Q_new.copy()
p_old = p_new.copy()
v_old = v_new.copy()
i = i+1
if i == 1e6:
print('did not converge')
break
# print(i)
self.Q = Q_new