Space Shuttle Reentry: Laminar to Turbulent Air Flow

[Q_Goest]

I would have never guessed that during reentry, and at very high mach number, the flow of air over the Shuttle’s wing is laminar! To make it even stranger, as velocity decreases, there is a transition to turbulent flow across the wing (I suspect this is also caused by an increase in air density as the Shuttle decends into the atmosphere).

The shuttle's transition from laminar to turbulent flow occurs naturally as the spacecraft slows down, typically at velocities around mach 8, or eight times the speed of sound, about 20 minutes after atmospheric entry begins.

Also very interesting is that this laminar flow actually provides some measure of insulation.

The goal of the research is to gain a better understanding of how smooth, laminar airflow, which provides a thin layer of insulation during peak heating, can change to the disturbed, turbulent flow that can cause downstream temperatures to climb, possibly affecting aerodynamics and causing damage.

And the affect is quite dramatic, causing up to a 500 degree F reduction in temperature for the laminar flow.

For Discovery's boundary layer transition - BLT - experiment, a single tile on the bottom of the shuttle's left wing, about 10 feet behind the leading edge, featured a 0.25-inch-high ridge that was expected to cause the insulating boundary layer downstream to go turbulent between mach 12 and 14. That, in turn, was expected to raise the temperatures of downstream tiles by 500 to 600 degrees Fahrenheit.

The tiles in that region of the wing normally experience maximum temperatures of 1,500 to 1,600 degrees when the re-entry airflow across the wing is smooth. Preliminary reports indicated the maximum temperature experienced by the "protuberance tile" was around 2,000 degrees, somewhat less than expected.

Ref: http://spaceflightnow.com/shuttle/sts119/090329blt/
Interesting article, well worth reading!

 

[Achy47]

Hello, thank you for sharing your thoughts on the shuttle's reentry and the role of laminar flow in its aerodynamics. I can confirm that the transition from laminar to turbulent flow is indeed a natural occurrence during reentry. This change is primarily driven by the increase in air density as the shuttle descends into the atmosphere, which in turn affects the boundary layer of air around the spacecraft.

The insulation provided by laminar flow is a fascinating aspect of this phenomenon. As you mentioned, the smooth airflow acts as a thin layer of protection against the intense heat generated during reentry. However, as the flow becomes turbulent, this insulation is disrupted, causing downstream temperatures to rise significantly. This can potentially lead to damage to the shuttle's exterior, which is why it is crucial for us to understand this transition and its effects.

The BLT experiment conducted on Discovery was a great opportunity for us to gather data and gain a better understanding of this transition. The results of this experiment will help us improve our models and predictions for future reentries, making them safer and more efficient. The fact that the maximum temperature experienced by the tile with the protuberance was lower than expected is promising and shows that our understanding of this phenomenon is continuously improving.

Thank you again for sharing this interesting article, and I hope we can continue to learn more about the fascinating world of aeronautics and space exploration.

 

[oswaler]

I find this information fascinating. The transition from laminar to turbulent flow during reentry is a natural occurrence caused by the decrease in velocity and increase in air density. This change in flow has a significant impact on the temperature experienced by the shuttle and its tiles, with the laminar flow providing insulation and the turbulent flow causing an increase in temperature. The BLT experiment conducted on the Discovery shuttle provides valuable data on this transition and its effects. It is important for us to continue studying and understanding these phenomena to ensure the safety and efficiency of future space missions. This information also has potential applications in other areas of aerodynamics and heat transfer. Overall, this is a very interesting and relevant topic in the field of aerospace engineering and I look forward to learning more about it.