can a rough surface reduce drag on an aircrafts wing?
338795
No. For airfoil shapes, drag is minimized by keeping the surface as smooth as possible (and as a result the airflow over the wing smooth as well). \nThis is not necessarily true for other shapes. For a sphere, drag can be less when the airflow is turbulent instead of smooth. As a result, the dimples on a golf ball (a rough surface) reduce the drag on the ball.
923752
Uh, let me see.....aerodynamics? lol.  To improve how stream-lined a product is so that the wind travels around, through, or under it in such away that it causes the least amount of friction. This helps improve speed, fuel efficiency, and reduces stress on the product.
416972
As the plane's engines provide thrust, there is a certain amount of force countering it in the form of drag.  So if the thrust from the engines were to drop off, the drag force would be greater than the forward force.  (Eventually, the drag force will also be reduced so that the two opposing forces will be in balance again.)  Because of this, the plane will immediately start to decelerate.
501575
the dimpling creates an aerodynamic effect that allows them to stay aloft longer.  \n\ninterestingly, the same effect occurs on the Mig29.  although, there it is an accident.  poor manufacture, not design causes the dimpling.
84077
It actually makes them less aerodynamic, not more, for the reasons listed above.
867227
An airplane wing is designed so that air travels slower under the wing. This increases, the pressure under the wing, giving the plane lift.\n\nReally it should be that the air travels *faster over* the wing, which*decreases* the *pressure above* the wing, giving the plane lift.
157431
They may call it friction but it's a misnomer.  There is skin friction, of course, which dissipates energy as heat, but much of the drag force is caused by imparting kinetic energy to the air mass, i.e., shoving it out of the way.  If you were shoving all the air downward that force would be called lift.  That energy may eventually be dissipated but it is theoretically recoverable. Friction dissipates energy as heat immediately.
193979
Airplane wings use a combination of Bernoulli's principle (the faster air flows over a surface the lower its pressure) and "Reaction" or Newtonian lift, the force produced by the downward acceleration of an air mass by a plane surface that is tilted with respect to the velocity. (See 1st & 2nd references). The upper surface of the wing is curved and the lower surface is relatively straight. Thus air passing over the wing has farther to travel before it rejoins the air that went under the wing, and must move faster. The lower pressure over the wing creates a Bernoulli lift force. The wing also has a positive "angle of attack" (basically the tilt angle of the wing's lower surface) producing Newtonian lift. Ref. 1 estimates that airliners have more Newtonian than Bernoullian lift. The wing transfers the sum of these lift forces to the airplane. And of course the thrust needed to reach the speed necessary for the wings to provide adequate lift comes from a motor-driven propellor or a jet engine. \nBirds, having movable wings, fly in two basic modes, gliding and flapping. These modes also use a mix of Bernoulli's principle and Newtonian momentum exchange to achieve lift. When gliding, the curved wing surface operates similarly to that of an airplane. More momentum exchange occurs when the wings are flapped; each downstroke pushes air downward and backward which provides an upward and forward force to the wing and through the wing to the bird's body. Feathers play a vital and mechanically complex role in flight, especially in flapping. The 3rd reference discusses this in some detail. I can't put pictures in this answer but the 4th reference provides a diagram of gliding lift, and you can find much more by googling "aerodynamic lift birds".
615749
the shape of the fuselage tends not to reflect a large amount of radar waves.  i think the B-2 has the radar image the same size as that of a bird.\n\nalso, the fuselage is coated with a substance that absorbs radar waves.  so the shape of the fuselage and the texture of the skin of the fuselage work together to lower the amount of radar waves that are reflected off its surface and 'seen' by the enemy.
38489
On an airplanes wing, the top is curved in shape, and the bottom is straight.  When the plane gains speed, the air will be forced to move faster over the curved portion.  The faster moving air applies less pressure than over the straight portion therefore creating "lift"
1175019
In general resistance increases.If there is no turbulence then it can be shown that viscous drag on a spherical moving body of radius r and velocity v is \n6*pi*(eta)*r*v\nwhere eta is coefficient of viscosity.\nTherefore air resistance is usually taken as directly proportional to velocity.\nHowever in real life things are not that simple.With turbulence various other forces come in play.Surprisingly it can reduce the air drag too.Though it may cause deviations in path as forces are no longer just opposite to velocity .
140128
the are trying to reduce wind drag
476031
Well, yes, neglecting any energy loss to friction (e.g. air resistance)
1110236
Airflow over the lifting surfaces creates pressure differences between top and bottom sides, which gives you the lifting force.  You have to shove the lifting surfaces through the air in order for them to generate the lift, though, hence why true aeroplanes must have engines to push them along.   If you don't have an engine then you are a glider, and barring thermal upcurrents you will be perpetually falling.   Until...\n\nI think passenger jets can glide at about a 1:20 downward slope with no engine power.
51813
Your question is too wide to be answered easily in one sitting.  So I'll look at how and why of aerodynamics (simply) and then answer the speed bit.\n\nThis a bit of material I wrote for flight cabin staff to help them understand these principles.\n\nLift is the aerodynamic force that counteracts gravity and holds an airplane in the air. Most of the lift required by an airplane is created by its wings, but a certain portion is also generated by other parts of the aircraft, such as the fuselage. But what actually causes the lift to be created?\nAir is a fluid, just like water. Lift can only be generated when a fluid is in motion. For example, a wing must be passing through the air or the air must be moving around a stationary wing, one or the other. (The way it usually happens is that the wing is doing most of the moving, although the air may be moving, at the same time.)  The wing is moved through the air by the thrust generated by the aircraft’s engines.\n\nMost aircraft wings have a special, basic shape as viewed edge-on: The upper surfaces are curved and their lower surfaces are flatter. This shape is what works with the fluid motion of the air to create lift. As air moves around a wing, some goes over the top and some goes underneath. The air that goes over the curved upper surface undergoes two important changes: it is reduced in pressure and it is accelerated downward (as it leaves the trailing edge of the wing). The wing is forced up into the region of reduced air pressure above the upper surface of the wing by the higher air pressure beneath the wing. Also, the downward acceleration of the air (downwash) at the trailing edge forces the wing upward.\n\nSo this is the basis of aerodynamics.  Roraty wing aircraft (helicopters) work on the same basis, the aerofoil is rotated and lift created by the rotors (moving aerofoils). The thrust to move the aircraft forward is produced by tilting the rotor head, in the direction required.  Hence it can move forwards, sideways and backwards.  But the explanation would take a separate large answer.\n\nAs for speed, the maximum forward speed of the aircraft is determined by the thrust available, but the aircraft is limited by the design of the wing, the wing shape for a low speed high lift glider is very different to that of a supersonic aircraft.  The lowest speed is really controlled by the wing.  As the aircraft sppeed reduces so does the speed of the flow over the wing, surface friction slows it down further until the air refuses to flow over the aerofoil and it breaks up into turbulence and all lift is lost.  A number of things can be done to get this point at which the lift is lost (stall) at the lowest speed possible - such as flaps, slats etc (but this is another long answer).  On helicopters there is no slowest speed as the aircraft will just hover when it stops moving forward, but its maximum forward sppeed is limited by the air over the blades going sonic and loosing lift, and problems with the trailing blade (the one that is heading towards the back of the helicopter in forward flight.) Again another long answer.\n\nHope that helps.  The book below is the RAF's bible on aerodynamics.
236113
Aerodynamics\n\nWhen a golf ball is hit, the impact, which lasts less than a millisecond, determines the ball’s velocity, launch angle and spin rate, all of which influence its trajectory (and its behavior when it hits the ground).\n\nA ball moving through air experiences two major forces: lift and drag. Drag slows the forward motion, whereas lift acts in a direction perpendicular to it. The magnitude of these forces depends on the behavior of the boundary layer of air moving with the ball surface.\n\nEvery modern golf ball has dimples; their purpose is to increase and shape the lift and drag forces by modifying the behavior of the boundary layer. It should be noted that drag and lift forces exist also on smooth balls: they are only modified, not created, by dimples.\n\nOne effect of dimples is a reduction of drag, contributing to the increased length of flight of dimpled balls compared with smooth ones.\n\nA spinning ball deforms the flow of air around it, thus acting similar to an airplane wing. Backspin is imparted in almost every shot due to the golf club's loft (i.e. angle between the clubface and a vertical plane). A backspinning ball experiences an upward lift force which makes it fly higher and longer than a ball without spin would. Sidespin occurs when the clubface is not aligned perpendicularly to the direction of swing, leading to a lift force that makes the ball curve to a side. These lift forces are further increased through the presence of dimples.\n\nIn order to keep the aerodynamics optimal, the ball needs to be clean. Golfers can wash their golf balls manually, but there are also mechanical ball washers available.\n[edit]\n\nDesign\nA two-piece golf ball with large and small dimples\nEnlarge\nA two-piece golf ball with large and small dimples\n\nMost balls on sale today have about 300 to 450 dimples. There were a few balls having over 500 dimples before. The record holder was a ball with 1,070 dimples -- 414 larger ones (in four different sizes) and 656 pinhead-sized ones. All brands of balls, except one, have even-numbered dimples. The only odd-numbered ball on market is a ball with 333 dimples.\n\nOfficially sanctioned balls are designed to be as symmetrical as possible. This symmetry is the result of a dispute that stemmed from the Polara, a ball sold in the late 1970s that had six rows of normal dimples on its equator but very shallow dimples elsewhere. This asymmetrical design helped the ball self-adjust its spin-axis during the flight. The USGA refused to sanction it for tournament play and, in 1981, changed the rules to ban aerodynamic asymmetrical balls. Polara's producer sued the USGA and the association paid US$1.375 million in a 1985 out-of-court settlement.\n\nThe United States Patent and Trademark Office's patent database is a good source of past dimple designs. Most designs are based on Platonic solids such as icosahedron.
387844
The top of an aircrafts wings are usually rounded to a certain extent, while the bottom of the wing is flat, this causes the air that flows over the top of the wing to speed up as the aircraft itself gains speed. the sped up air flow tries to catch up with the faster air flow at the bottom of the wing, causing lower air pressure at the top of the wing, and the higher air pressure on the bottom of the wing actually pushes the aircraft up.