The tilting of sunlight rays in your FLUENT solar load model, despite specifying the sun vector direction as (0, 0, 1), could be due to one or more of the following reasons:

1. Coordinate System Misalignment

• Global vs Local Coordinate System: Verify whether the sun vector direction is defined relative to the global coordinate system or a local coordinate system.In FLUENT, solar vectors are typically specified in the global coordinate system. Ensure that your geometry is oriented correctly within this global system.
• Orientation of Geometry: If your geometry (or domain) has been rotated or imported in a different orientation, the direction (0, 0, 1) may not be aligned with the actual vertical axis in your model.Fix: Check the orientation of your geometry in the pre-processor (e.g., ANSYS DesignModeler or SpaceClaim) and confirm that the Z-axis points vertically upward.

2. Solar Tracking Settings

• Solar Position Settings: If you are using solar calculator or solar tracking options, FLUENT may be automatically adjusting the incident angle based on geographical location, date, and time.Fix:Disable solar tracking if it's not needed. Set the Solar Load Model → Directional Specification Method to Manual Input instead of Solar Calculator.

3. Mesh Transformations

• Mesh Rotation or Scaling: Check if any mesh transformation (rotation or scaling) was applied after importing the geometry. Such transformations may alter the orientation of your domain relative to the global coordinates.Fix: Reorient the mesh to align with the global Z-axis properly.

4. Solar Beam Radiation Settings

• Beam Radiation Model: The beam radiation direction may appear tilted if the scattering effects or reflections from walls are dominating the visualization.Fix: Examine whether the tilting effect is due to reflections rather than direct beam direction. Disable reflections temporarily and focus on direct beam visualization to isolate the issue.

5. Visualization Artifacts

• Post-Processing Settings: Sometimes, the display of rays in the post-processing visualization tools can be misleading due to interpolation or scaling effects.Fix: Verify the ray trajectories by plotting solar flux contours or incident radiation intensity to confirm the true ray direction instead of relying solely on graphical visualization.

Steps to Debug