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84 lines
2.9 KiB
Python
84 lines
2.9 KiB
Python
import os
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import struct
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import numpy as np
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def write_fortran_record(f, data_bytes):
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length = len(data_bytes)
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f.write(struct.pack('i', length))
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f.write(data_bytes)
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f.write(struct.pack('i', length))
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def generate_synthetic_grid(output_path, nx=16, ny=16, nz=16):
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"""Generates a 16x16x16 synthetic flow field binary file matching Fortran unformatted record format.
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Variables:
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u(x,y,z) = sin(x) * cos(y) * sin(z)
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v(x,y,z) = cos(x) * sin(y) * cos(z)
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w(x,y,z) = sin(x) * sin(y) * cos(z)
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c(x,y,z) = cos(x) * cos(y) * cos(z) (Stored in new_scalar(:,:,:,2))
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"""
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lx = 2.0 * np.pi
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ly = 2.0 * np.pi
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lz = 2.0 * np.pi
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hx = lx / nx
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hy = ly / ny
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hz = lz / nz
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# 1-based indexing coordinates for Fortran mesh mapping
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x = np.arange(1, nx + 1) * hx
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y = np.arange(1, ny + 1) * hy
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z = np.arange(1, nz + 1) * hz
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# Meshgrid with Fortran-contiguous indexing (x, y, z)
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X, Y, Z = np.meshgrid(x, y, z, indexing='ij')
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# Analytical functions
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u_field = np.sin(X) * np.cos(Y) * np.sin(Z)
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v_field = np.cos(X) * np.sin(Y) * np.cos(Z)
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w_field = np.sin(X) * np.sin(Y) * np.cos(Z)
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c_field = np.cos(X) * np.cos(Y) * np.cos(Z)
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# Convert fields to double precision (Fortran real*8)
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u_data = u_field.astype(np.float64)
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v_data = v_field.astype(np.float64)
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w_data = w_field.astype(np.float64)
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# new_scalar is shaped (nx, ny, nz, 2) in Fortran.
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# new_scalar(:,:,:,1) = 0.0
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# new_scalar(:,:,:,2) = c_field
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new_scalar = np.zeros((nx, ny, nz, 2), dtype=np.float64)
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new_scalar[:, :, :, 1] = c_field + 2.0
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# Serialize arrays in Fortran order (Column-major)
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u_bytes = u_data.tobytes(order='F')
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v_bytes = v_data.tobytes(order='F')
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w_bytes = w_data.tobytes(order='F')
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new_scalar_bytes = new_scalar.tobytes(order='F')
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# Combined data block record
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data_block_bytes = u_bytes + v_bytes + w_bytes + new_scalar_bytes
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# Write to Fortran unformatted file
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with open(output_path, 'wb') as f:
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# Record 1: tnow (double), nx (int64), ny (int64), nz (int64), tmp1 (double), tmp2 (double)
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rec1 = struct.pack('dqqqdd', 0.0, nx, ny, nz, 0.0, 0.0)
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write_fortran_record(f, rec1)
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# Record 2: ncyc (int64), dt (double), dummyu (double)
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rec2 = struct.pack('qdd', 1, 0.01, 0.0)
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write_fortran_record(f, rec2)
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# Record 3, 4, 5: tmpr(1:2) (double * 2)
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rec3 = struct.pack('dd', 0.0, 0.0)
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write_fortran_record(f, rec3)
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write_fortran_record(f, rec3)
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write_fortran_record(f, rec3)
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# Record 6: data arrays (u, v, w, new_scalar)
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write_fortran_record(f, data_block_bytes)
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print(f"Successfully generated synthetic grid data file at {output_path}")
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if __name__ == '__main__':
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generate_synthetic_grid("fort.1000")
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