How to provide axis direction for tilted impeller in ANSYS Fluent 2024 R2 Part 2

Summary

This video builds upon a previous tutorial, focusing on defining the origin point and rotation axis in a CFD simulation. The speaker explains how to place the origin point, calculate the position vector, and determine the rotation axis by aligning the vector with the direction of rotation. The importance of checking the motion and ensuring the impeller aligns correctly with the shaft in the simulation is emphasized. The tutorial simplifies the process by showing that the raw differences in coordinates can be used instead of calculating unit vectors. The speaker also demonstrates the process using specific examples in simulation software like Fluent.

Takeaways

• 😀 The origin point of the impeller's rotation can be placed at any point on the bottom side of the impeller's hub.
• 😀 The second point (point B) can be placed anywhere along the axis, and the position vector is defined as the vector from point A to point B.
• 😀 The rotation axis direction is determined by the vector from point A to point B using the thumb rule: thumb points upward for positive rotation and downward for negative rotation.
• 😀 Anticlockwise rotation around the axis is considered positive, while clockwise rotation is negative in this context.
• 😀 The position vector's direction can be represented directly without calculating the unit vector, simplifying the input process.
• 😀 To calculate the vector, subtract the coordinates of point A from those of point B (X2 - X1, Y2 - Y1, Z2 - Z1).
• 😀 The vector components (X2 - X1, Y2 - Y1, Z2 - Z1) are enough to define the direction and magnitude of the rotation axis in Fluent.
• 😀 In ANSYS Fluent, the rotation axis and origin coordinates are entered as (X1, Y1, Z1) for point A and (X2, Y2, Z2) for point B.
• 😀 It is not necessary to calculate the unit vector if only the direction of the rotation axis is required for simulation purposes.
• 😀 A preview animation in Fluent helps validate whether the impeller and shaft are properly aligned and rotating as expected.
• 😀 Ensuring proper alignment through the preview check confirms the correctness of the rotation axis direction and origin for the simulation.

Q & A

What is the focus of the video discussed in the transcript?

The video focuses on explaining how to determine the origin point and the rotation axis vector for an impeller system, along with how to calculate and input these values into the simulation software.

What is the significance of the 'origin point' in the context of the impeller system?

The origin point is crucial for defining the starting position of the impeller's hub, which is used as a reference point for calculating the position vector and the direction of rotation.

Can the origin point be placed anywhere on the impeller?

Yes, the origin point does not have to be at the coordinate (0, 0, 0). It can be placed anywhere on the impeller as long as the correct coordinates are input into the simulation.

What is the role of the position vector from point A to point B?

The position vector from point A to point B represents the direction and distance between these two points. This vector is crucial for defining the rotation axis in the system.

How is the rotation axis direction determined?

The rotation axis direction is determined by pointing the thumb of your right hand along the vector from point A to point B. The direction of the fingers (anticlockwise or clockwise) will define the rotation direction.

What is the difference between positive and negative rotation in this context?

Positive rotation corresponds to an anticlockwise direction when viewed along the rotation axis. A negative value indicates the opposite direction (clockwise). This is reflected in the RPM (revolutions per minute) value as either positive or negative.

Is it necessary to calculate the unit vector in this case?

No, it is not strictly necessary to calculate the unit vector. You can directly use the difference between the coordinates of points A and B (X2-X1, Y2-Y1, Z2-Z1) to define the rotation axis, which will yield similar results.

What are the advantages of using the direct difference method for calculating the position vector?

Using the direct difference method simplifies the calculations, as it avoids the need to compute the unit vector. The values will still be accurate for determining the direction of the rotation axis.

What is the purpose of previewing the motion in the simulation?

Previewing the motion helps verify that the impeller's rotation aligns correctly with the shaft and the output domain, ensuring that the rotation axis and origin point are properly defined and the simulation behaves as expected.

What should be observed during the preview of the impeller's motion?

During the preview, it is essential to ensure that the impeller (green part) and the shaft (yellow part) remain aligned and rotate together. Any misalignment could indicate an error in the setup of the origin point or rotation axis direction.