Boeing 727 FedEx starboard, aft, fuselage, from engines to top-of-fin tail fairing : 無料・フリー素材/写真
Boeing 727 FedEx starboard, aft, fuselage, from engines to top-of-fin tail fairing / wbaiv
| ライセンス | クリエイティブ・コモンズ 表示-継承 2.1 |
|---|---|
| 説明 | Here are all you can see of engines #2 and #3 from the outside. the rudder and fin, the inboard half of one horizontal stabilizer. Lots of aerodynamic and structural details are visible here. From left to right:- the engine exhaust goes through an additional 'can' between the thrust-reverser cascade and the actual nozzle. Crafty engineering will absorb some noise directly, and mix the hot, high-speed flow from the core of the engine with the slower, cold, bypass air that goes around the engine (but inside the nacelle fairing), further reduces sound. (Turning the acoustic energy into a modest amount of heat that the cans just radiate away. So some efficiency is lost, but better mixing may scavenge and energize the bypass flow. Might be a net negative, might be a net positive. at the cost of weight, complexity and retail price.)- The rudder is split into top and bottom halves, and forward and aft sections, probably indicating something about powered controls with manual back-up, capable of keeping the airplane in control and flying even with one engine (left or right, worst case) turned off.- Then there's a line of vortex generators, the little tabs about halfway along the fin+rudder shape. Alternately aligned with the direction of travel and diagonal to it. These will create specific turbulence in a specific location, and are usually added to keep the airflow across the surface attached to that surface, not ready to peel off in big, chaotic, whirlwinds. Sometimes this is called 'energizing' the flow across the surface. You can appreciate that some distance, say 100 meters, from the fin, the air is just sitting there, and might get agitated by flow off the airplane after the plane is gone. Closer, say, 100mm from the side of the fin, the air next to the fin is going to be compressed by trans-sonic shock waves, if they're present, pushing at an angle to the plane's path, and also by the passage of a large object near by, pushing straight out sideways. And some of that air, that was 100mm from the side of the fin, when it arrived, will get attached to the airflow around the fin and accelerated to some fraction of the speed of the plane and travel with the plane for some distance. Finally, right at the edge of the fin, there are air molecules that will be trapped right next to the fin, accllerated to the speed of the plane, and leave with it. So there are a series of 'laminations' in the flow, from undisturbed air at some distance away, to air that will leave with the airplane, for the moment, at the speed the airplane is flying. One gets the least drag and simplest case to calculate and understand when the speeds of the air around the airframe decrease smoothly by distance. Closer = faster, further away = slower, and no abrupt changes. Such flow is said to be "Laminar". The line where the vortex generators are is the widest point in the fin - it tapers up to that size, then tapers back down to nothing at the trailing edge of the rudder. So after that mid-point, the metal skin of the plane is actually curved away from the airflow, so the air has to expand to fill the increased volume, just like it compressed along the part of the fin with increasing thickness.By making a little turbulence right next to the skin of the fin, the vortex generators are intended to keep the speed of the airflow smoothly decreasing with distance from the plane, and therefore no big eddies. Because the rudder doesn't work if there are big eddies on one side then the other. The oscillations can create a buzzing sound that's annoying to people in the plane and may shake things loose inside. It also fatigues the metal structure. If a buzz can't be cured, by aerodynamics, that part of the plane that's affected may have to be stiffened, trying to change the frequency of the buzz, and the frame beefed-up DSC_0705 |
| 撮影日 | 2014-01-04 16:34:10 |
| 撮影者 | wbaiv |
| タグ | |
| 撮影地 | North Highlands, California, United States 地図 |
| カメラ | NIKON D40X , NIKON CORPORATION |
| 露出 | 0.01 sec (1/100) |
| 開放F値 | f/5.0 |
| 焦点距離 | 19 mm |