What is span wise flow?
On a straight wing airplane, all of the airflow over the wing travels parallel to the aircraft’s chord line. But, on a swept wing, only some of the air flows parallel to the chord line. The other part flows perpendicular to the chord – this is called spanwise flow.
What is the spanwise direction?
The SPAN of an aircraft is the distance from wingtip to wingtip – but when we talk of spanwise, we would be referring to the distance from wingtip to the wing-root (where it is attached to the fuselage). The term “Spanwise” is used to describe the orientation of a measurement along a wing from the root to the tip.
What is spanwise and chordwise?
a) spanwise is from root to tip, generally following the quarter-chord line, and chordwise is the direction that gives the shortest distance from leading edge to trailing edge, very roughly perpendicular to the quarter-chord line.
Why does spanwise flow happen?
The lower the local pressure, the more the flow lines bend inward. Higher than ambient pressure at the trailing edge or on the lower side of the wing will bend the flow lines outward accordingly. Let the red color denote suction: It bends the flow lines (black) towards it, creating a spanwise flow component.
What is Spanwise velocity?
The spanwise velocity (v) variance is found to exhibit an Re invariant logarithmic slope in the log region, in a similar manner to the streamwise velocity (u), which is consistent with the existence of self-similar features within wall-bounded flows.
Where does the term spanwise flow come from?
But perhaps the word “spanwise” has more than one usage in the context of swept wings. Likewise, “chordwise” would normally mean parallel to the fuselage, not measured along the shortest dimension of the (swept) wing as shown in the diagrams.
Why does air flow in a spanwise direction?
This means that as the air starts to flow over the wing, it starts out with some spanwise momentum. The second reason is that on a swept wing, there is a pressure gradient that as a result of the sweep, tends to push the flow in the spanwise direction slightly.
What makes spanwise flow on a swept wing?
On a swept wing, you have two things that will help lead to spanwise flow. First, there is no leading edge stagnation point. Instead there is what is called an attachment line, which is essentially the linear analog.
How does deceleration affect the spanwise flow?
Now the deceleration in the area of pressure recovery will slow down the already decelerated air close to the wing, and again that slowing will happen in a direction perpendicular to the lines of equal chord. If this deceleration is sufficient, it will leave the boundary layer flow with an outward speed component.