Wind Tunnel Wall Interference Of VTOL Aircraft in Hover Flight - Computational Airflow Modeling
Although the phenomena of wind tunnel wall airflow interference is well known, especially when the size of the model is large, the speeds are slow, and the tunnel is small most mathematical computational models deal with these challenges as they relate to VTOL (vertical take-off and landing) aircraft as a function of pressure change as the airflow comes back to interfere with the relative wind flow in the wind tunnel itself.
As these new changes effect the air pressure on various parts of the aircraft and control surfaces in a chaotic and not always predictable set of new vortex flows we must realize that real VTOL aircraft do not operate in a tunnel, nor should a young aerospace designer completely rely on wind tested models for accurate results.
Of course, whereas, generally speaking if the model is small enough and the wind tunnel large enough, the changes become less relevant.
Now then, let's not forget that aircraft in the real world do operate with issues such as ground effect, vortex flows, and objects such as trees, ground equipment, barriers, buildings, and what have you around them as they do their prescribed activities, missions, or assignments.
There was an interesting report put out by NASA many years back titled; "The Effect of Wind Tunnel Wall Interference on the Performance of a Fan-in-Wing VTOL Model," by Harry H.
Heyson, NASA - Langley Research Center, Hampton, Va.
23665, February 1974, report # TN D-7518, which stated in the conclusion; "1.
Extreme caution must be used in interpreting uncorrected wind-tunnel data obtained at low speeds.
Unless the model is extremely small in relation to the test section size, the wall interference can be so large that even the trends in the data may be opposite to those which would be obtained in flight.
2.
Wall-induced interference is particularly large at the model tail.
" It was later noted that indeed, the size of the model and size of the actual wind tunnel in comparison was more important, read; "Comparison of Wind Tunnel and Flight Test Aerodynamic Data in Transition Flight Speed Range for 5 VTOL and STOL Aircraft," by Woodrow L.
Cook and David H.
Hickey of NASA's Ames Research Center.
In this paper the research shows that actual flight tests and wind tunnel modeling data was extremely close, enough to warrant throwing away and wind tunnel wall interference mathematical calculations.
Due to the incredible computing power of today's hardware and software, it is possible that a hovering aircraft prior to landing or rescue could 3-D map the environment prior to getting down within 19-feet of an object, and have the advanced calculations for functions of change pre-configured into the aircraft's control system.
This would allow the VTOL aircraft (or UAV) to land unassisted and without accident.
I am not suggesting that we use super computer processing and artificial intelligence to take the place of piss-poor engineering, rather that we consider utilizing all the current tools at our disposal for safety of our operations preventing loss of equipment or life.
Please consider all this and think on it.
If you have need to contact me on this or similar topics, look up my email online.
As these new changes effect the air pressure on various parts of the aircraft and control surfaces in a chaotic and not always predictable set of new vortex flows we must realize that real VTOL aircraft do not operate in a tunnel, nor should a young aerospace designer completely rely on wind tested models for accurate results.
Of course, whereas, generally speaking if the model is small enough and the wind tunnel large enough, the changes become less relevant.
Now then, let's not forget that aircraft in the real world do operate with issues such as ground effect, vortex flows, and objects such as trees, ground equipment, barriers, buildings, and what have you around them as they do their prescribed activities, missions, or assignments.
There was an interesting report put out by NASA many years back titled; "The Effect of Wind Tunnel Wall Interference on the Performance of a Fan-in-Wing VTOL Model," by Harry H.
Heyson, NASA - Langley Research Center, Hampton, Va.
23665, February 1974, report # TN D-7518, which stated in the conclusion; "1.
Extreme caution must be used in interpreting uncorrected wind-tunnel data obtained at low speeds.
Unless the model is extremely small in relation to the test section size, the wall interference can be so large that even the trends in the data may be opposite to those which would be obtained in flight.
2.
Wall-induced interference is particularly large at the model tail.
" It was later noted that indeed, the size of the model and size of the actual wind tunnel in comparison was more important, read; "Comparison of Wind Tunnel and Flight Test Aerodynamic Data in Transition Flight Speed Range for 5 VTOL and STOL Aircraft," by Woodrow L.
Cook and David H.
Hickey of NASA's Ames Research Center.
In this paper the research shows that actual flight tests and wind tunnel modeling data was extremely close, enough to warrant throwing away and wind tunnel wall interference mathematical calculations.
Due to the incredible computing power of today's hardware and software, it is possible that a hovering aircraft prior to landing or rescue could 3-D map the environment prior to getting down within 19-feet of an object, and have the advanced calculations for functions of change pre-configured into the aircraft's control system.
This would allow the VTOL aircraft (or UAV) to land unassisted and without accident.
I am not suggesting that we use super computer processing and artificial intelligence to take the place of piss-poor engineering, rather that we consider utilizing all the current tools at our disposal for safety of our operations preventing loss of equipment or life.
Please consider all this and think on it.
If you have need to contact me on this or similar topics, look up my email online.
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