PBL Velocity Profile: Sinusoidal Variation w/ Height

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Discussion Overview

The discussion revolves around the characteristics of the planetary boundary layer velocity profile, specifically addressing the sinusoidal variation with height as depicted in a referenced figure from a fluid mechanics textbook. Participants explore the implications of this profile and seek clarification on its representation and underlying principles.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the existence of a sinusoidal variation in the velocity profile, suggesting a possible misinterpretation of the referenced figure.
  • Another participant acknowledges the general explanation provided in the text but highlights the lack of detail regarding the undulation of the velocity profile with height.
  • Some participants express uncertainty about the specific figure being discussed and request clarification or additional context from the original poster.
  • There is mention of the Ekman boundary layer profile and a question about whether the discussion pertains to the "Ekman spiral" phenomenon.
  • Participants reference external resources, including a Wikipedia article, to provide additional context and visuals related to the planetary boundary layer.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus regarding the sinusoidal variation in the velocity profile, with multiple competing views and interpretations present in the discussion.

Contextual Notes

Some participants express limitations in accessing the referenced textbook, which may affect their understanding and contributions to the discussion. There is also ambiguity regarding the specific figures and concepts being referenced, leading to potential miscommunication.

Who May Find This Useful

This discussion may be of interest to students and professionals in fluid dynamics, meteorology, and related fields who are exploring the characteristics of boundary layer profiles and their implications in various contexts.

MOHAMMAD UMAIR
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Why does the planetary boundary layer velocity profile shows a sinusoidal variation with height?
Reference: Fig:14.10 Page 576 Fluid Mechanics - Kundu and Cohen 2nd edition
 
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I don't see any mention of sinusoidal variation with height in the text ? Perhaps you have misinterpreted what is shown in fig 4.10 (b) ?

I think that the general topic is explained quite well by the author .

Please post new questions if you have any specific problems .
 
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Nidum said:
I don't see any mention of sinusoidal variation with height in the text ? Perhaps you have misinterpreted what is shown in fig 4.10 (b) ?

I think that the general topic is explained quite well by the author .

Please post new questions if you have any specific problems .
Thanks Nidum for your reply. I know that the general topic is explained quite well in the text but the author has presented the boundary layer velocity profile in the figure without explaining why there is an undulation of the velocity profile with height. You won't find such undulations in the general boundary layer velocity profiles on a flat plate.
 
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jim mcnamara said:
My apologies if I am making a mess of this question. But. Is Figure 1 in the linked pdf file what you are talking about?

people.atmos.ucla.edu/jcm/turbulence_course_notes/planetary_boundary_layers.pdf

interesting article, thanks :smile:
MOHAMMAD UMAIR said:
Why does the planetary boundary layer velocity profile shows a sinusoidal variation with height?
Reference: Fig:14.10 Page 576 Fluid Mechanics - Kundu and Cohen 2nd edition
I don't have access to that article/book ... it would be good for you to copy and paste the section or if you cannot, scan it or at bare minimum type out the paragraph or two that you are referring to, so that we are all on the same page

As a result, I have no idea which boundary you are referring to ??
Moho ?, upper/lower mantle ?, mantle/outer core ?
MOHAMMAD UMAIR said:
I know that the general topic is explained quite well in the text but the author has presented the boundary layer velocity profile in the figure without explaining why there is an undulation of the velocity profile with height. You won't find such undulations in the general boundary layer velocity profiles on a flat plate.

assuming you are referring to one of my listed ones, and probably the Moho boundary,

Why would you expect to ? the Earth isn't flat and nor are the layers and their boundariesDave
 
Thank you all for showing your keen interest in answering the question I've posed. Davenn I am referring to the Ekman boundary layer profile that you have in your lecture notes on page number 24 figure15 a.
 
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jim mcnamara said:
I believe he is talking about this, which is why I am cautious, cannot see the book he referenced. (meteorology, laminar flow (fluid dynamics) and more intricacies):
https://en.wikipedia.org/wiki/Planetary_boundary_layer

There is a really great graphic there.

ohhh, we are going up, not down, I guessed that wrong ... will do some reading :smile:
 
MOHAMMAD UMAIR said:
Thank you all for showing your keen interest in answering the question I've posed. Davenn I am referring to the Ekman boundary layer profile that you have in your lecture notes on page number 24 figure15 a.
Are you asking why the "Ekman spiral" spirals?
 

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