Airflow Across a Persistent Cold Air Pool in a Basin

In summary, the conversation discusses the topic of fluid dynamics involving warm air advection aloft a cold air pool in a small, recessed basin with a compound parabolic shape. The temperature inversion at the base of the basin and the potential impact of wind on mixing are also mentioned. The impact of a screen atop the basin on mixing is also considered, as well as the potential influence of the dynamic pressure of the advection on the volume of air in the basin. The type of flow (laminar, transitional, or turbulent) and its impact on mixing is also discussed.
  • #1
skyfridge
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This question is regarding the general fluid dynamics involving warm air advection aloft a persistent cold air pool in a small basin that is recessed in a horizontal planar surface. For scale, the basin has a compound parabolic shape, with a 30° viewing angle, a .146m radius at the base, a .292m radius at the aperture and a height of .759m. It has a temperature inversion at the base, with a temperature at the base that is up to 40°C below the ambient temperature aloft.

Angus[1] compares a simpler enclosure uncovered and covered with a polyethylene mesh, under mild winds.

In attempting to answer the questions, I have researched multiple disciplines, including general science, fluid dynamics, meteorology, greenhouse ventilation, building wind loads and agriculture, but I haven't found any specific information to answer the questions.

(1) How would airflow aloft the uncovered basin mix with the cold air pool in the basin under different wind speeds? Specifically, would the temperature inversion minimize mixing? What equations model this case?

(2) To what degree would a screen covering the aperture or recessed in the basin affect mixing of the advection with the cold air pool? What equations would model this case?

[1] Performance comparison of sky window spectral selective and high emittance radiant cooling systems under varying atmospheric conditions, Dr Angus Gentle, Prof Geoff Smith
 
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  • #2
Also, the dynamic pressure of the advection across the aperture would be

q=1/2*ρ*t^2

so the advection would be at a lower pressure than the volume in the basin. What does that do to the volume of air in the basin?

I'm picturing a vertical pipe filled with water with an inverted temperature gradient and water moving across the top of the pipe. Since the temperature decreases and thus the density increases from top to bottom in the vertical pipe, I might assume that would lessen the mixing. Does the volume of air act like a surface, preventing or minimizing the advection from circulating into the basin?

The flow across the horizontal surface would probably be laminar to transitional, but I'm guessing. How would that affect the mixing?

A screen atop the basin would probably make it turbulent. Would the advection across the uncovered (or basin with a recessed screen) basin also be laminar to transitional? How does that affect the mixing?
 

1. What is a persistent cold air pool?

A persistent cold air pool is a large body of cold air that forms in a low-lying area, such as a basin, due to temperature inversion. This means that the air near the ground is colder than the air above it, trapping the cold air in the basin and keeping it from dissipating.

2. How does airflow across a persistent cold air pool affect weather patterns?

The presence of a persistent cold air pool can significantly impact local weather patterns. As the cold air mass interacts with warmer air masses, it can cause changes in wind patterns, precipitation, and temperature. It can also lead to the formation of fog and low clouds in the basin.

3. What factors influence the strength of airflow across a persistent cold air pool?

The strength of airflow across a persistent cold air pool is influenced by several factors, including the size and depth of the basin, the strength of the temperature inversion, and the wind speed and direction. Topography and surrounding land features can also play a role in shaping the airflow patterns.

4. How is airflow across a persistent cold air pool measured?

Airflow across a persistent cold air pool can be measured using various instruments, such as anemometers, which measure wind speed and direction, and thermometers, which measure temperature. Remote sensing techniques, such as Doppler radar and satellite imagery, can also provide information on the movement and strength of air masses.

5. Can airflow across a persistent cold air pool impact air quality?

Yes, airflow across a persistent cold air pool can have a significant impact on air quality. As the cold air mass moves out of the basin, it can carry pollutants and particles with it, affecting the air quality in surrounding areas. This can be especially concerning in urban areas where air pollution is already a problem.

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