Uneven Airflow of a Fan: Explained

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Discussion Overview

The discussion revolves around the uneven airflow produced by a house fan, specifically exploring the reasons behind stronger airflow on one side compared to the other. Participants examine the implications of fan design, measurement techniques, and airflow dynamics.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that the airflow may be related to vortex formation but seeks clarification on how this leads to uneven airflow.
  • Several participants express confusion regarding the initial question about the airflow being stronger on one side.
  • A participant describes a testing method involving an airflow meter placed at different angles and distances from the fan, noting significantly higher airflow from one side (A) compared to the other (C).
  • Another participant inquires about the direction of the fan's rotation and questions the symmetry of the airflow measurements, suggesting that the fan's rotational symmetry may affect the vortex and airflow distribution.
  • Concerns are raised about the measurement setup, including the height of the airflow meter and the physical positioning of the fan, which could influence the results.

Areas of Agreement / Disagreement

Participants show a lack of consensus on the initial question, with some expressing confusion and others providing insights into potential factors affecting airflow. The discussion remains unresolved regarding the specific causes of the observed uneven airflow.

Contextual Notes

Participants highlight potential limitations in measurement techniques, such as the height of the airflow meter and the fan's placement, which may affect the accuracy of the airflow readings.

jszuch
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Why is the airflow of a fan (a regular house fan for instance) stronger on one side than it is the other? I think it has something to do with the fact that the airflow is a vortex, but I don't understand how this creates uneven airflow.

Thanks
 
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I don't understand the question. How is it stronger on one side?
 
russ_watters said:
I don't understand the question. How is it stronger on one side?

Let's say you are looking at the fan. We initially tested the airflow meter about 6 inches away from the fan, and centered (B). Then we measured a 45 degree angle from the fan at the 6 inch distance again, and took measurements again, both to the right and to the left. This would put the air flow meter roughly perpendicular to the meat of the fan blades. The air flow readings indicated that there was significantly more airflow from the left side of the fan (A) than there was from the right side of the fan (C).

Fan
/ | \
/ | \
/ | \
A B C
 
More data. What direction is the fan rotating in? CW or CCW?

The fan is rotationally symmetrical, not reflection symmetrical, so its vortex will be too. Are your measurment points horizontally level with the centre of the fan? If you were measuring a little high, you'd get a different result for the 'up' side of the fan than the 'down' side.

Was the fan physically distant from whatever it was sitting on? I can imagine a loss in air flow on one side but not the other if you were using a small fan sitting on a desk.
 

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