![]() ![]() The designations span dominated and chord dominated are related to the the fact that the main parameter in the span dominated ground effect (reduces drag) is the height-to-span ratio ,whereas in the chord dominated ground effect (increases lift)it is the height-to-chord ratio. The former results mainly in the reduction of the induced drag (D) and the latter in the increase of the lift (L). These two phenomena are sometimes referred to as span dominated and chord dominated ground effect. The ground effect is a common name for both effects, which is sometimes confusing. When a wing approaches the ground two phenomena are actually involved in the increase of the lift force and reduction of the drag.Another important issue regarding ground effect is that the makeup of the surface directly affects the intensity this is to say that a concrete or other smooth hard surface will produce more effect than water or broken ground.Low winged aircraft are more affected by ground effect than high wing aircraft. Due to the change in up-wash, down-wash, and wingtip vortices there may be errors in the airspeed system while in ground effect due to changes in the local pressure at the static source.Ground effect will also alter thrust versus velocity, in that reducing induced drag will require less thrust to maintain the same velocity. If the angle of attack and velocity remain constant, an increase in the lift coefficient will result, which accounts for the “floating” effect. While in the ground effect, the wing will require a lower angle of attack to produce the same amount of lift. As the wing gets lower, the ground effect becomes more pronounced. Flying close to a surface increases air pressure on the lower wing surface, known as the “ram” or “cushion” effect, and thereby improves the aircraft lift-to-drag ratio. These air pressure differences also accelerate the mass of air downwards. During normal flight, the upper wing surface experiences reduced static air pressure and the lower surface comparatively higher static air pressure. A wing generates lift, in part, due to the difference in air pressure gradients between the upper and lower wing surfaces.The result is lower induced drag, which increases the speed and lift of the aircraft. When a wing is flown very close to the ground, wingtip vortices are unable to form effectively due to the obstruction of the ground. This is caused primarily by the ground interrupting the wing tip vortices and downwash behind the wing. When an aircraft is flying at an altitude that is approximately at or below the same distance as the aircraft’s wingspan or helicopter’s rotor diameter, there is, depending on airfoil and aircraft design, an often noticeable ground effect.In practice, the boundary is the earth’s surface, whether it is terrain or water. ![]() This results in an effective increase in the static pressure below the wing and increases the lift to drag ratio. Ground effect is the common name for the phenomenon where a boundary is placed below (and near) the lower surface of the wing. WIG(wing in ground effect) craft make use of a phenomenon known as ‘ground effect’. The pressure differential equates to a resultant force upward which supports the weight of the aircraft.Īircraft normally fly in a freestream, that is the air around the wing is not bounded in any way. In very broad terms, aircraft fly because the movement of the wing through the air produces a greater static pressure on the lower surface of the wing than on the upper surface of the wing. The conventional practical use of lifting bodies, are wings on aircraft. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |