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python
21 days ago
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```import numpy as np
from scipy.linalg import solve_banded

def implicitsolver(D, upsilon, theta_end, d_theta, dy, U_x, delta_x, isturbulent):
R = D / 2

x_num = int(np.ceil(theta_end / d_theta))
y_max = max(delta_x)
y_num = int(np.ceil(y_max / dy))

u = np.zeros((x_num + 1, y_num + 1))
v = np.zeros((x_num + 1, y_num + 1))

for i in range(x_num - 1):
i_i = i + 1
j_max = int(np.ceil(delta_x[i_i + 1] / dy)) - 1

A = np.zeros((3, j_max))  # Adjusted for use with solve_banded
B = np.zeros(j_max)

for j in range(j_max):
j_i = j
r = R + dy * j

# Similar turbulent viscosity calculation as MATLAB, adapt as needed
y = dy * j
# Example calculation for y_plus and upsilon_t, adapt as needed
y_plus = np.sqrt(upsilon * (u[i_i, j_i + 1] - u[i_i, j_i]) / dy) * y / upsilon
if 60 < y_plus < 300:
upsilon_t_p = (1 + 0.4 * y_plus) * upsilon
upsilon_t_n = (1 + 0.4 * y_plus) * upsilon
else:
l = min(0.4 * (j + 1) * dy, 0.09 * delta_x[i_i + 1])
upsilon_t_p = upsilon + isturbulent * l ** 2 * abs((u[i_i, j_i + 2] - u[i_i, j_i + 1]) / dy)
upsilon_t_n = upsilon + isturbulent * l ** 2 * abs((u[i_i, j_i + 1] - u[i_i, j_i]) / dy)

# Example calculation for B, adapt as needed
# Example calculations for A matrix elements, adapt as needed

# Solve tridiagonal system using solve_banded
# You need to adjust A and B accordingly to match solve_banded's expected input format
# u_t = solve_banded((1, 1), A, B)

# Update u and v fields
# Remember to adapt indexing and operations to match Python's zero-based indexing

return u, v

# Note: This code will not run as-is due to placeholders and simplifications.
# It's meant to provide a structural template for converting the MATLAB function to Python.
```