196 lines
9.4 KiB
Python
196 lines
9.4 KiB
Python
import numpy as np
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#importing pressure conversion function
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import sys
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import os
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from pyparsing import alphanums
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current = os.path.dirname(os.path.realpath(__file__))
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parent = os.path.dirname(current)
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sys.path.append(parent)
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from functions.pressure_conversion import pressure_conversion
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class Francis_Turbine:
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# units
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# make sure that units and display units are the same
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# units are used to label graphs and disp units are used to have a bearable format when using pythons print()
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density_unit = r'$\mathrm{kg}/\mathrm{m}^3$'
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flux_unit = r'$\mathrm{m}^3/\mathrm{s}$'
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LA_unit = '%'
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pressure_unit = 'Pa'
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time_unit = 's'
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velocity_unit = r'$\mathrm{m}/\mathrm{s}$'
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volume_unit = r'$\mathrm{m}^3$'
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density_unit_disp = 'kg/m³'
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flux_unit_disp = 'm³/s'
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LA_unit_disp = '%'
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time_unit_disp = 's'
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velocity_unit_disp = 'm/s'
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volume_unit_disp = 'm³'
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g = 9.81 # m/s² gravitational acceleration
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# init
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def __init__(self,Q_nenn,p_nenn,t_closing,timestep,pressure_unit_disp):
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"""
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Creates a turbine with given attributes in this order: \n
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Nominal flux [m³/s] \n
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Nominal pressure [Pa] \n
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Closing time [s] \n
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Simulation timestep [s] \n
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Pressure unit for displaying [string] \n
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"""
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self.Q_n = Q_nenn # nominal flux
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self.p_n = p_nenn # nominal pressure
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self.LA_n = 1. # 100% # nominal Leitapparatöffnung
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self.dt = timestep # simulation timestep
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self.t_c = t_closing # closing time
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self.d_LA_max_dt = 1/t_closing # maximal change of LA per second
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self.pressure_unit_disp = pressure_unit_disp
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# initialize for get_info()
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self.p = -np.inf
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self.Q = -np.inf
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self.LA = -np.inf
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# setter - set attributes
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def set_LA(self,LA,display_warning=True):
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# warn user, that the .set_LA() method should not be used ot set LA manually
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if display_warning == True:
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print('You are setting the guide vane opening of the turbine manually. \n \
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This is not an intended use of this method. \n \
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Refer to the .update_LA() method instead.')
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# set Leitapparatöffnung
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self.LA = LA
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def set_pressure(self,pressure):
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# set pressure in front of the turbine
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self.p = pressure
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def set_steady_state(self,ss_flux,ss_pressure):
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# calculate and set steady state LA, that allows the flow of ss_flux at ss_pressure through the
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# turbine at the steady state LA
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ss_LA = self.LA_n*ss_flux/self.Q_n*np.sqrt(self.p_n/ss_pressure)
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if ss_LA < 0 or ss_LA > 1:
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raise Exception('LA out of range [0;1]')
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self.set_LA(ss_LA,display_warning=False)
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self.set_pressure(ss_pressure)
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self.get_current_Q()
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#getter - get attributes
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def get_current_Q(self):
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# return the flux through the turbine, based on the current pressure in front
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# of the turbine and the Leitapparatöffnung
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if self.p < 0:
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self.Q = 0
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else:
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self.Q = self.Q_n*(self.LA/self.LA_n)*np.sqrt(self.p/self.p_n)
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return self.Q
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def get_current_LA(self):
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return self.LA
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def get_current_pressure(self,disp_flag=True):
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if disp_flag == True:
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return pressure_conversion(self.p,self.pressure_unit,self.pressure_unit_disp)
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else:
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return self.p
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def get_info(self, full = False):
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new_line = '\n'
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p = pressure_conversion(self.p,self.pressure_unit,self.pressure_unit_disp)
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p_n = pressure_conversion(self.p_n,self.pressure_unit,self.pressure_unit_disp)
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if full == True:
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# :<10 pads the self.value to be 10 characters wide
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print_str = (f"Turbine has the following attributes: {new_line}"
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f"----------------------------- {new_line}"
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f"Type = Francis {new_line}"
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f"Nominal flux = {self.Q_n:<10} {self.flux_unit_disp} {new_line}"
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f"Nominal pressure = {round(p_n,3):<10} {self.pressure_unit_disp}{new_line}"
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f"Nominal LA = {self.LA_n*100:<10} {self.LA_unit_disp} {new_line}"
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f"Closing time = {self.t_c:<10} {self.time_unit_disp} {new_line}"
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f"Current flux = {round(self.Q,3):<10} {self.flux_unit_disp} {new_line}"
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f"Current pipe pressure = {round(p,3):<10} {self.pressure_unit_disp} {new_line}"
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f"Current LA = {round(self.LA,4)*100:<10} {self.LA_unit_disp} {new_line}"
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f"Simulation timestep = {self.dt:<10} {self.time_unit_disp} {new_line}"
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f"----------------------------- {new_line}")
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else:
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# :<10 pads the self.value to be 10 characters wide
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print_str = (f"The current attributes are: {new_line}"
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f"----------------------------- {new_line}"
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f"Current flux = {round(self.Q,3):<10} {self.flux_unit_disp} {new_line}"
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f"Current pipe pressure = {round(p,3):<10} {self.pressure_unit_disp} {new_line}"
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f"Current LA = {round(self.LA,4)*100:<10} {self.LA_unit_disp} {new_line}"
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f"----------------------------- {new_line}")
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print(print_str)
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def get_Q_n(self):
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# needed for Kraftwerk_class
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return self.Q_n
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# update methods
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def update_LA(self,LA_soll):
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# update the Leitappartöffnung and consider the restrictions of the closing time of the turbine
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LA_diff = self.LA-LA_soll # calculate the difference to the target LA
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LA_diff_max = self.d_LA_max_dt*self.dt # calculate the maximum possible change in LA based on the given timestep
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LA_diff = np.sign(LA_diff)*np.min(np.abs([LA_diff,LA_diff_max])) # calulate the correct change in LA
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# make sure that the LA is not out of the range [0;1]
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LA_new = self.LA-LA_diff
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if LA_new < 0.:
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LA_new = 0.
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elif LA_new > 1.:
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LA_new = 1.
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self.set_LA(LA_new,display_warning=False)
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# methods
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def converge(self,convergence_parameters):
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# 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
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# new pressure from the forward characteristic are not perfectly compatible.
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# Therefore, iterate the flux and the pressure so long, until they converge
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eps = 1e-12 # convergence criterion: iteration change < eps
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iteration_change = 1. # change in Q from one iteration to the next
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i = 0 # safety variable. break loop if it exceeds 1e6 iterations
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g = self.g # gravitational acceleration
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p = convergence_parameters[0] # pressure at second to last node (see method of characterisctics - boundary condidtions)
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v = convergence_parameters[1] # velocity at second to last node (see method of characterisctics - boundary condidtions)
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D = convergence_parameters[2] # diameter of the pipeline
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area_pipe = convergence_parameters[3] # area of the pipeline
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alpha = convergence_parameters[4] # elevation angle of the pipeline
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f_D = convergence_parameters[5] # Darcy friction coefficient
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c = convergence_parameters[6] # pressure wave propagtation velocity
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rho = convergence_parameters[7] # density of the liquid
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dt = convergence_parameters[8] # timestep of the characteristic method
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p_old = convergence_parameters[9] # pressure of previous timestep
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Q_old = self.get_current_Q()
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v_old = Q_old/area_pipe
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while iteration_change > eps:
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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
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# print(p_new)
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p_new = p_old+(p_new-p_old)/3
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# print(p_new)
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self.set_pressure(p_new)
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Q_new = self.get_current_Q()
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v_new = Q_new/area_pipe
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# print(Q_old,Q_new)
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iteration_change = abs(Q_old-Q_new)
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Q_old = Q_new.copy()
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v_old = v_new.copy()
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p_old = p_new.copy()
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i = i+1
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if i == 1e6:
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print('did not converge')
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break
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# print(i) |