This is not directly answering your query about which data set to use but rather querying the validity of all 3 and consideration of wind impact altogether.
I have experience of wind tunnel testing but not in the field of cycling. Perhaps this has all been well discussed and there are generally accepted test practices I'm not aware of. However, since I don't know that to be the case, and I'm pretty skeptical of cycling aerodynamic testing robustness in general, I think it's worth questioning.
As I'm sure everyone's already aware, wind has an airspeed gradient such that airflow in contact with the ground is zero and it increases as you rise above it. However, the bike moves forward as one object so the speed and yaw of airflow impinging on the bike will NOT be uniform except in static air.
Let me give some examples to illustrate this....
(I'm ignoring the fact that rotating/reciprocating parts, i.e. wheels, cranks and legs don't have a constant airspeed)
Case 1: Still air
The bike and rider encounters an impinging airflow with a constant velocity from ground level all the way up to the top of the riders head. A wind tunnel test for this case would require a uniform airflow across the tunnel cross section or, if a significant gradient exists in the tunnel, compensation would be required.
Case 2: Headwind
The impinging airflow velocity at the base of the bike will be in the same direction but lower speed than the top of the bike/rider. In this case the rider position, helmet and aerobars will be of greater significance than in the still air case but the wheels and frame will be comparatively less relevant. An accurate wind tunnel test for this case would require a representative airspeed gradient across the tunnel section such that airspeed increases as you move higher in the tunnel.
Case 3: Tailwind
The impinging airflow velocity at the base of the bike will be higher than the top of the bike. Like the headwind case, the entire bike is not effected equally. The lower part of the bike will experience higher airspeeds than the upper parts of the bike and the rider. So, for example, the helmet and aerobars will be less relevant while the frame and wheels would be more relevant compared to the still air case. An accurate wind tunnel test for this case would require a representative airspeed gradient across the tunnel section such that airspeed is higher at the floor of the tunnel and decreases as you move higher in the tunnel. I've never seen this configuration.
Case 4: Crosswind (at right angles to direction of travel)
The lateral component of the airflow velocity will be lower at the base of the bike than the top of the bike/rider while the component in the direction of travel will be constant. Thus, the bottom of the bike will be at zero yaw and this angle will increase higher on the bike/rider as the lateral component becomes more significant. Bike yaw, as measured at handlebar level will not be representative of the yaw at the height of most parts of the frame or wheels for example. An accurate wind tunnel test for this case would be very difficult, probably impossible, to produce. A truly representative test would require a complex impinging flow, not only that but it would have to be adjustable to mimic different wind/speed permutations, which makes an accurate static test utterly unfeasible.
Case 5: Everything else (there is some wind, direction not exactly in line with or perpendicular to direction of travel)
There are infinite combinations of the above cases and the overall airspeed/yaw profile will vary widely depending on wind speed, wind direction and bike speed. As with Case 4, anything involving a crosswind is likely untestable in a static wind tunnel.
Question 1 - What is the airspeed velocity profile of the wind tunnel used for testing? This is a basic wind tunnel characteristic.
Question 2 - Does this allow useful/accurate analysis for a bike in still air?
Question 3 - How useful is this data once wind enters the equation (in axis of travel)?
Question 4 - How useful is this data once wind enters the equation (off axis of travel)?
I have experience of wind tunnel testing but not in the field of cycling. Perhaps this has all been well discussed and there are generally accepted test practices I'm not aware of. However, since I don't know that to be the case, and I'm pretty skeptical of cycling aerodynamic testing robustness in general, I think it's worth questioning.
As I'm sure everyone's already aware, wind has an airspeed gradient such that airflow in contact with the ground is zero and it increases as you rise above it. However, the bike moves forward as one object so the speed and yaw of airflow impinging on the bike will NOT be uniform except in static air.
Let me give some examples to illustrate this....
(I'm ignoring the fact that rotating/reciprocating parts, i.e. wheels, cranks and legs don't have a constant airspeed)
Case 1: Still air
The bike and rider encounters an impinging airflow with a constant velocity from ground level all the way up to the top of the riders head. A wind tunnel test for this case would require a uniform airflow across the tunnel cross section or, if a significant gradient exists in the tunnel, compensation would be required.
Case 2: Headwind
The impinging airflow velocity at the base of the bike will be in the same direction but lower speed than the top of the bike/rider. In this case the rider position, helmet and aerobars will be of greater significance than in the still air case but the wheels and frame will be comparatively less relevant. An accurate wind tunnel test for this case would require a representative airspeed gradient across the tunnel section such that airspeed increases as you move higher in the tunnel.
Case 3: Tailwind
The impinging airflow velocity at the base of the bike will be higher than the top of the bike. Like the headwind case, the entire bike is not effected equally. The lower part of the bike will experience higher airspeeds than the upper parts of the bike and the rider. So, for example, the helmet and aerobars will be less relevant while the frame and wheels would be more relevant compared to the still air case. An accurate wind tunnel test for this case would require a representative airspeed gradient across the tunnel section such that airspeed is higher at the floor of the tunnel and decreases as you move higher in the tunnel. I've never seen this configuration.
Case 4: Crosswind (at right angles to direction of travel)
The lateral component of the airflow velocity will be lower at the base of the bike than the top of the bike/rider while the component in the direction of travel will be constant. Thus, the bottom of the bike will be at zero yaw and this angle will increase higher on the bike/rider as the lateral component becomes more significant. Bike yaw, as measured at handlebar level will not be representative of the yaw at the height of most parts of the frame or wheels for example. An accurate wind tunnel test for this case would be very difficult, probably impossible, to produce. A truly representative test would require a complex impinging flow, not only that but it would have to be adjustable to mimic different wind/speed permutations, which makes an accurate static test utterly unfeasible.
Case 5: Everything else (there is some wind, direction not exactly in line with or perpendicular to direction of travel)
There are infinite combinations of the above cases and the overall airspeed/yaw profile will vary widely depending on wind speed, wind direction and bike speed. As with Case 4, anything involving a crosswind is likely untestable in a static wind tunnel.
Question 1 - What is the airspeed velocity profile of the wind tunnel used for testing? This is a basic wind tunnel characteristic.
Question 2 - Does this allow useful/accurate analysis for a bike in still air?
Question 3 - How useful is this data once wind enters the equation (in axis of travel)?
Question 4 - How useful is this data once wind enters the equation (off axis of travel)?