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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143
Druckrohrleitung/Druckrohrleitung_class_file.py
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@@ -1,5 +1,13 @@
import numpy as np
#importing pressure conversion function
import sys
import os
current = os.path.dirname(os.path.realpath(__file__))
parent = os.path.dirname(current)
sys.path.append(parent)
from functions.pressure_conversion import pressure_conversion
class Druckrohrleitung_class:
# units
acceleration_unit = r'$\mathrm{m}/\mathrm{s}^2$'
@@ -13,72 +21,66 @@ class Druckrohrleitung_class:
velocity_unit = r'$\mathrm{m}/\mathrm{s}$' # for flux and pressure propagation
volume_unit = r'$\mathrm{m}^3$'
acceleration_unit_print = 'm/s²'
angle_unit_print = 'rad'
area_unit_print = 'm²'
density_unit_print = 'kg/m³'
flux_unit_print = 'm³/s'
length_unit_print = 'm'
time_unit_print = 's'
velocity_unit_print = 'm/s' # for flux and pressure propagation
volume_unit_print = 'm³'
acceleration_unit_disp = 'm/s²'
angle_unit_disp = 'rad'
area_unit_disp = 'm²'
density_unit_disp = 'kg/m³'
flux_unit_disp = 'm³/s'
length_unit_disp = 'm'
time_unit_disp = 's'
velocity_unit_disp = 'm/s' # for flux and pressure propagation
volume_unit_disp = 'm³'
g = 9.81
# init
def __init__(self,total_length,diameter,number_segments,pipeline_angle,Darcy_friction_factor,rho=1000,g=9.81):
def __init__(self,total_length,diameter,number_segments,pipeline_angle,Darcy_friction_factor,pw_vel,timestep,pressure_unit_disp,rho=1000):
self.length = total_length # total length of the pipeline
self.dia = diameter # diameter of the pipeline
self.n_seg = number_segments # number of segments for the method of characteristics
self.angle = pipeline_angle # angle of the pipeline
self.f_D = Darcy_friction_factor # = Rohrreibungszahl oder flow coefficient
self.f_D = Darcy_friction_factor # = Rohrreibungszahl oder flow coefficient
self.c = pw_vel
self.dt = timestep
self.density = rho # density of the liquid in the pipeline
self.g = g # gravitational acceleration
self.A = (diameter/2)**2*np.pi
self.dx = total_length/number_segments # length of each segment
self.l_vec = np.arange(0,(number_segments+1),1)*self.dx # vector giving the distance from each node to the start of the pipeline
self.x_vec = np.arange(0,(number_segments+1),1)*self.dx # vector giving the distance from each node to the start of the pipeline
# initialize for get_info method
self.c = '--'
self.dt = '--'
self.pressure_unit_disp = pressure_unit_disp
# setter
def set_pressure_propagation_velocity(self,c):
self.c = c # propagation velocity of the pressure wave
self.dt = self.dx/c # timestep derived from c, demanded by the method of characteristics
def set_number_of_timesteps(self,number_timesteps):
self.nt = number_timesteps # number of timesteps
if self.c == '--':
raise Exception('Please set the pressure propagation velocity before setting the number of timesteps.')
else:
self.t_vec = np.arange(0,self.nt*self.dt,self.dt)
def set_initial_pressure(self,pressure):
# initialize the pressure distribution in the pipeline
if np.size(pressure) == 1:
self.p0 = np.full_like(self.l_vec,pressure)
elif np.size(pressure) == np.size(self.l_vec):
self.p0 = pressure
p0 = np.full_like(self.x_vec,pressure)
elif np.size(pressure) == np.size(self.x_vec):
p0 = pressure
else:
raise Exception('Unable to assign initial pressure. Input has to be of size 1 or' + np.size(self.l_vec))
raise Exception('Unable to assign initial pressure. Input has to be of size 1 or' + np.size(self.x_vec))
#initialize the vectors in which the old and new pressures are stored for the method of characteristics
self.p_old = self.p0.copy()
self.p = self.p0.copy()
self.p_old = p0.copy()
self.p = p0.copy()
self.p_min = p0.copy()
self.p_max = p0.copy()
def set_initial_flow_velocity(self,velocity):
# initialize the velocity distribution in the pipeline
if np.size(velocity) == 1:
self.v0 = np.full_like(self.l_vec,velocity)
elif np.size(velocity) == np.size(self.l_vec):
self.v0 = velocity
v0 = np.full_like(self.x_vec,velocity)
elif np.size(velocity) == np.size(self.x_vec):
v0 = velocity
else:
raise Exception('Unable to assign initial velocity. Input has to be of size 1 or' + np.size(self.l_vec))
raise Exception('Unable to assign initial velocity. Input has to be of size 1 or' + np.size(self.x_vec))
#initialize the vectors in which the old and new velocities are stored for the method of characteristics
self.v_old = self.v0.copy()
self.v = self.v0.copy()
self.v_old = v0.copy()
self.v = v0.copy()
self.v_min = v0.copy()
self.v_max = v0.copy()
def set_boundary_conditions_next_timestep(self,p_reservoir,v_turbine):
# derived from the method of characteristics, one can set the boundary conditions for the pressures and flow velocities at the reservoir and the turbine
@@ -112,16 +114,16 @@ class Druckrohrleitung_class:
self.p[0] = p_boundary_res
self.p[-1] = p_boundary_tur
def set_steady_state(self,ss_flux,ss_level_reservoir,area_reservoir,pl_vec,h_vec):
def set_steady_state(self,ss_flux,ss_level_reservoir,area_reservoir,x_vec,h_vec):
# set the pressure and velocity distributions, that allow a constant flow of water from the (steady-state) reservoir to the (steady-state) turbine
# the flow velocity is given by the constant flow through the pipe
ss_v0 = np.full(self.n_seg+1,ss_flux/self.A)
ss_v0 = np.full_like(self.x_vec,ss_flux/self.A)
# the static pressure is given by static state pressure of the reservoir, corrected for the hydraulic head of the pipe and friction losses
ss_v_in_res = abs(ss_flux/area_reservoir)
ss_v_out_res = abs(ss_flux/self.A)
ss_pressure_res = self.density*self.g*(ss_level_reservoir)+self.density*ss_v_out_res*(ss_v_in_res-ss_v_out_res)
ss_pressure = ss_pressure_res+(self.density*self.g*h_vec)-(self.f_D*pl_vec/self.dia*self.density/2*ss_v0**2)
ss_pressure = ss_pressure_res+(self.density*self.g*h_vec)-(self.f_D*x_vec/self.dia*self.density/2*ss_v0**2)
self.set_initial_flow_velocity(ss_v0)
self.set_initial_pressure(ss_pressure)
@@ -135,30 +137,61 @@ class Druckrohrleitung_class:
# :<10 pads the self.value to be 10 characters wide
print_str = (f"The pipeline has the following attributes: {new_line}"
f"----------------------------- {new_line}"
f"Length = {self.length:<10} {self.length_unit_print} {new_line}"
f"Diameter = {self.dia:<10} {self.length_unit_print} {new_line}"
f"Length = {self.length:<10} {self.length_unit_disp} {new_line}"
f"Diameter = {self.dia:<10} {self.length_unit_disp} {new_line}"
f"Number of segments = {self.n_seg:<10} {new_line}"
f"Number of nodes = {self.n_seg+1:<10} {new_line}"
f"Length per segments = {self.dx:<10} {self.length_unit_print} {new_line}"
f"Pipeline angle = {round(self.angle,3):<10} {self.angle_unit_print} {new_line}"
f"Length per segments = {self.dx:<10} {self.length_unit_disp} {new_line}"
f"Pipeline angle = {round(self.angle,3):<10} {self.angle_unit_disp} {new_line}"
f"Pipeline angle = {angle_deg}° {new_line}"
f"Darcy friction factor = {self.f_D:<10} {new_line}"
f"Density of liquid = {self.density:<10} {self.density_unit_print} {new_line}"
f"Pressure wave vel. = {self.c:<10} {self.velocity_unit_print} {new_line}"
f"Simulation timestep = {self.dt:<10} {self.time_unit_print} {new_line}"
f"Density of liquid = {self.density:<10} {self.density_unit_disp} {new_line}"
f"Pressure wave vel. = {self.c:<10} {self.velocity_unit_disp} {new_line}"
f"Simulation timestep = {self.dt:<10} {self.time_unit_disp} {new_line}"
f"Number of timesteps = {self.nt:<10} {new_line}"
f"Total simulation time = {self.nt*self.dt:<10} {self.time_unit_print} {new_line}"
f"Total simulation time = {self.nt*self.dt:<10} {self.time_unit_disp} {new_line}"
f"----------------------------- {new_line}"
f"Velocity and pressure distribution are vectors and are accessible by the .v and .p attribute of the pipeline object")
print(print_str)
def get_current_pressure_distribution(self):
return self.p
def get_current_pressure_distribution(self,disp=False):
if disp == True:
return pressure_conversion(self.p,self.pressure_unit,self.pressure_unit_disp)
elif disp == False:
return self.p
def get_current_velocity_distribution(self):
return self.v
def get_current_flux_distribution(self):
return self.v*self.A
def get_lowest_pressure_per_node(self,disp=False):
if disp == True:
return pressure_conversion(self.p_min,self.pressure_unit,self.pressure_unit_disp)
elif disp == False:
return self.p_min
def get_highest_pressure_per_node(self,disp=False):
if disp == True:
return pressure_conversion(self.p_max,self.pressure_unit,self.pressure_unit_disp)
elif disp == False:
return self.p_max
def get_lowest_velocity_per_node(self):
return self.v_min
def get_highest_velocity_per_node(self):
return self.v_max
def get_lowest_flux_per_node(self):
return self.v_min*self.A
def get_highest_flux_per_node(self):
return self.v_max*self.A
def timestep_characteristic_method(self):
# use the method of characteristics to calculate the pressure and velocities at all nodes except the boundary ones
# they are set with the .set_boundary_conditions_next_timestep() method beforehand
@@ -180,6 +213,12 @@ class Druckrohrleitung_class:
self.p[i] = 0.5*(self.p_old[i+1]+self.p_old[i-1]) - 0.5*rho*c*(self.v_old[i+1]-self.v_old[i-1]) \
+f_D*rho*c*dt/(4*D)*(abs(self.v_old[i+1])*self.v_old[i+1]-abs(self.v_old[i-1])*self.v_old[i-1])
# update overall min and max values for pressure and velocity per node
self.p_min = np.minimum(self.p_min,self.p)
self.p_max = np.maximum(self.p_max,self.p)
self.v_min = np.minimum(self.v_min,self.v)
self.v_max = np.maximum(self.v_max,self.v)
# prepare for next call
# use .copy() to write data to another memory location and avoid the usual python reference pointer
# else one can overwrite data by accidient and change two variables at once without noticing