Cheap Wind Tunnel?
02-22-10, 06:21 PM
#28
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I'd say getting the air to stay attatched (laminar is not the correct term, that's something completely different) as far as possible on the back is going to be a big trick. The longer it stays attached, the less of a separation bubble you're going to have and the less pressure drag you're going to have.
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02-26-10, 09:04 AM
#29
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Laminar describes the condition of the boundary layer - the airflow region next to and near the rider and bike (or any object moving through a "fluid"). Laminar = smooth - the classic textbook illustration of streamlines of airflow over a wing show laminar flow. Laminar = lowest drag.
Turbulent flow is not smooth - it moves around, changes rapidly. A turbulent boundary layer has > drag than laminar. Aerodynamicists strive mightily to maintain laminar flow and delay transition to turbulent. Both laminar and turbulent flow are still following the surface of the object (rider in this case).
Detached (or separated) boundary layer has much much greater drag. The flow stops following the object surface, you get large vortexes and eddies and bubbles in the airflow. You want to avoid or delay it as long as possible. One technique is to "trip" the flow from laminar to turbulent as turbulent flow will stay attached better than laminar. Remember the spat at the Olympics over the small ridges in the helmet of the British woman in skeleton (she won the gold medal) - I'm confident they are intended to trip the boundary layer so it stays attached to her helmet better, reduces drag, makes her faster (or helps her believe she's faster and her competitors worry she has an "edge" on them).
Turbulent flow is not smooth - it moves around, changes rapidly. A turbulent boundary layer has > drag than laminar. Aerodynamicists strive mightily to maintain laminar flow and delay transition to turbulent. Both laminar and turbulent flow are still following the surface of the object (rider in this case).
Detached (or separated) boundary layer has much much greater drag. The flow stops following the object surface, you get large vortexes and eddies and bubbles in the airflow. You want to avoid or delay it as long as possible. One technique is to "trip" the flow from laminar to turbulent as turbulent flow will stay attached better than laminar. Remember the spat at the Olympics over the small ridges in the helmet of the British woman in skeleton (she won the gold medal) - I'm confident they are intended to trip the boundary layer so it stays attached to her helmet better, reduces drag, makes her faster (or helps her believe she's faster and her competitors worry she has an "edge" on them).
02-26-10, 09:07 AM
#30
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Laminar describes the condition of the boundary layer - the airflow region next to and near the rider and bike (or any object moving through a "fluid"). Laminar = smooth - the classic textbook illustration of streamlines of airflow over a wing show laminar flow. Laminar = lowest drag.
Turbulent flow is not smooth - it moves around, changes rapidly. A turbulent boundary layer has > drag than laminar. Aerodynamicists strive mightily to maintain laminar flow and delay transition to turbulent. Both laminar and turbulent flow are still following the surface of the object (rider in this case).
Detached (or separated) boundary layer has much much greater drag. The flow stops following the object surface, you get large vortexes and eddies and bubbles in the airflow. You want to avoid or delay it as long as possible. One technique is to "trip" the flow from laminar to turbulent as turbulent flow will stay attached better than laminar. Remember the spat at the Olympics over the small ridges in the helmet of the British woman in skeleton (she won the gold medal) - I'm confident they are intended to trip the boundary layer so it stays attached to her helmet better, reduces drag, makes her faster (or helps her believe she's faster and her competitors worry she has an "edge" on them).
Turbulent flow is not smooth - it moves around, changes rapidly. A turbulent boundary layer has > drag than laminar. Aerodynamicists strive mightily to maintain laminar flow and delay transition to turbulent. Both laminar and turbulent flow are still following the surface of the object (rider in this case).
Detached (or separated) boundary layer has much much greater drag. The flow stops following the object surface, you get large vortexes and eddies and bubbles in the airflow. You want to avoid or delay it as long as possible. One technique is to "trip" the flow from laminar to turbulent as turbulent flow will stay attached better than laminar. Remember the spat at the Olympics over the small ridges in the helmet of the British woman in skeleton (she won the gold medal) - I'm confident they are intended to trip the boundary layer so it stays attached to her helmet better, reduces drag, makes her faster (or helps her believe she's faster and her competitors worry she has an "edge" on them).
02-26-10, 09:31 AM
#31
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