AEROFORUM

                                                                       Form Drag Form drag is experienced in the surface of the aircraft when the streamlined airflow separates and becomes turbulent. To experiment form drag keep a flat plate on the streamlined airflow, now the pressure before the plate is atmospheric and the pressure after it is below the atmospheric which results in sucking effect behind the plate and vortices are formed. It is mandatory to delay the separation point of airflow and this is achieved by altering the shape or streamline of the given object. When the airflow changes its direction rapidly form drag experienced is higher. A fairing is fitted around the fixed undercarriage leg to reduce form drag to consi...

                                                                                                    Drag When an aircraft or any other body moves in atmosphere it experiences air resistance which retards its forward motion. This force is called drag. Drag occurs when an aircraft or any other object moves in air and it depends on the shape of the flying object.   Aircrafts and other flying objects are designed in such a manner to reduce the drag, which increases the efficiency of the aircraft. Drag is experienced parallel to relative airflow. Drag is directly balanced by thrust produced by a propeller or an engine. Amount of thrust required to balance the drag depends of amount of dra...

Aerodynamics is field science of that studies about an object moving in air or behaviour of air inside a system. It is applied in various fields such as aeronautics, automotive, architecture etc.  Generally Aerodynamic design of vehicles is used to reduce drag coefficient which is a major factor that affects fuel efficiency. Since low cost bikes are  designed and developed for a budget market. Aerodynamics is used to improve fuel efficiency which reduces fuel consumption, which in turn improves the operating efficiency of the vehicle. In case of high cost bikes, performance of the vehicle plays a major role in design. Here aerodynamics is used to improve overall vehicle performance. On high speeds reducing the drag increases the vehicle movement in air. Most of the aerodynamically designed vehicles adopt tear drop model, which allows the air to pass through smooth surface of the design. In this type of design drag is considerably reduced which improves faster movement of the v...

                                        WING SHAPE AND ITS EFFECT ON LIFT The total Lift generated by an aircraft wing depends on three factors 1.        Degree of Induced Downwash( Caused by wing tip vortices) 2.        Chord wise Pressure Distribution 3.        Plan form Shape of the wing Since the aircraft wing is similar on both sides it is appropriate to consider only the semi span of the wing to study about the effect of lift on wing shape. Let us consider three types of wings and its lifting ability, which depends on the angle of attack also. 1.        Rectangular 2.        Elliptical 3.        Tapered   The above figure illustrates the picture of how effective...

                                                    Angle of Induced downwash Downwash generated through vortex deflects the airflow from horizontal through an angle called as the angle of induced Downwash. This effect not only occurs behind the wing but also impacts the airflow approaching the wing by deflecting in upward from the horizontal through the same angle ( ʠ ). The resulting airflow is called effective relative airflow and the angle between effective relative airflow and the horizontal is called Ineffective angle of attack. The resultant lift force which acts perpendicular to the relative airflow is also deflected rear ward through the same angle ( ʠ i ). The angle of attack producing this Lift force is called effective angle of attack ( ʠ e ) which is the angle between chord line and effective relative airflow. A portion...

  Three dimensional flow around Airfoil When an aircraft is in flight, pressure is not only distributed in chord wise direction but also in span wise direction. Due to span wise distribution of pressure wingtip vortices are created. In atmospheric flight it is the tendency of fluid to move from high pressure area to low pressure area. The same scenario happens when an aircraft is in levelled flight. Pressure of air is lower than atmospheric pressure at upper surface of the wing and higher than atmospheric pressure at the lower surface of the wing. Beyond the wing tips the pressure is normal. This causes the span wise flow of air away from the fuselage on lower surface and an inward flow towards fuselage on upper surface. Now the airflow is on both chord wise and span wise direction. Both meet at trailing edge of the wing, which imparts a twisting motion to the air and series of vortices are formed on the trailing edge. These are known as trailing edge vortices. As the aircraft ...

                                                                                     Lift Coefficient: Coefficient of lift C L is defined as the lifting ability of the wing which depends on geometry of the airfoil. Coefficient of Lift Changes with change in angle of attack and it differs for symmetric and Assymetric airfoils. To Know about Coefficient of lift C L we plot the variation of lift with change in angle of attack. For asymmetric airfoil at 0 degree of angle of attack the lift generated is minimum and at 15-16 degrees its maximum which is called C L max . Angle of attack remains a straight line between 0 -12 Degrees. Above 12 Degrees rate of increase in lift reduces and forms a peak. The Peak formed denotes the maximum A...

Lift Lift is a force generated by the airfoil when the airfoil moves in a streamlined airflow at aerodynamic speeds (above 80 Km/h) with increasing angle of attack. Amount of lift generated by the wing depends on the following parameters. Wing shape Angle of attack Density of Air Wing Plan form surface area Square of free stream air velocity Lifting efficiency of wing A fast moving fluid creates a dynamic pressure with the airfoil, which is half times the density multiplied by velocity squared. Lifting efficiency of wing depends on wing shape and angle of attack which is usually expressed as Coefficient of lift.                          Lift = Co efficient of Lift X Pressure X Area Lift varies for different type of airfoils with change in angle of attack, Lift is expressed in Newton (N) and the general lift formula is                ...

          AERODYNAMIC CENTER IN ASYMMETRICAL AIRFOILS THE CENTER OF PRESSURE MOVES ALONG THE CHORD LINE WITH CHANGES IN ANGLE OF ATTACK. AS THE ANGLE OF ATTACK INCREASES THE CENTER OF PRESSURE MOVES TOWARDS THE LEADING EDGE AND WHEN IT DECREASES IT MOVES TOWARDS THE TRAILING EDGE. A NOSE DOWN PITCHING MOMENT IS ALWAYS PRESENT AND INCREASES IN INTENSITY WITH INCREASING ANGLES OF ATTACK. HOWEVER THERE IS A POINT ON THE CHORD LINE ABOUT WHICH THE PITCHING MOMENT REMAINS CONSTANT,REGARDLESS OF ANY CHANGE IN ANGLE OF ATTACK. THIS POINT IS CALLED AERODYNAMIC CENTER. IN SUBSONIC AIRFLOW IT IS LOCATED AT A DISTANCE 25% FROM LEADING EDGE ON THE CHORD LINE. HOWEVER IN SUPERSONIC AIRFLOW IT IS CONSIDERED TO BE LOCATED ON 50 % FROM LEADING EDGE ON THE CHORD LINE. FOR DESIGN PURPOSES IT IS CONSIDERED TO BE OVERALL LIFT FORCE TO ACT ON THAT POINT COMBINED WITH A PITCHING MOMENT OF CONSTANT STRENGTH.

                                   PITCHING MOMENTS PITCHING MOMENTS HAPPEN WHEN TWO EQUAL PRESSURE FORCES ACT IN DIFFERENT DIRECTION FROM THE SAME CENTER. PRESSURE DISTRIBUTION AROUND AN ASYMMETRICAL AIRFOIL IN NEGATIVE ANGLE OF ATTACK GIVES ZERO LIFT AND PRODUCES A PITCHING MOMENT WHICH IS NOSE DOWN. IN NEGATIVE  ANGLE OF ATTACKS THERE ARE TWO PRESSURE VECTORS WHICH CONSTITUTE A COUPLE, HENCE NO LIFT IS CREATED AND THE AIRFOIL IS PITCHED NOSE DOWN. WHEN THE SAME AIRFOIL IS PLACED AT ZERO DEGREES OR POSITIVE ANGLE OF ATTACKS THE PRESSURE DISTRIBUTION VARIES IN WHICH UPPER SURFACE OF THE AIRFOIL  CREATES MORE LIFT THAN THE LOWER SURFACE . THUS THE AIRFOIL CREATES LIFT EVEN AT ZERO DEGREES OF ANGLE OF ATTACK AND DUE TO THIS AN INCREASED NOSE DOWN PITCHING MOMENT ALSO OCCURS.  PITCHING MOMENT TAKES...

       CENTRE OF PRESSURE When an aircraft is in flight it experiences several loads across its structure which is defined as pressure distribution in technical terms. The pressure varies across the fuselage and the wing structure and it is impossible to analyse it. Hence the overall pressure distribution is represented by a single aerodynamic force called  center  of pressure or total reaction force which lies on the chord line of the aerofoil. The  center  of pressure moves along the chord line when the angle of attack is altered. At normal cruising speeds and low positive angles of attack the  center  of pressure is positioned on the chord line near the  center  of an aerofoil. With increasing angles of attack the  center  of pressure moves forward towards the leading edge and the magnitude of the total reaction force increases. When the aircraft reaches the stalling angle of atta...

                       Air foil Terminology What is an airfoil? How an air foil is described in modern science, what are the parameters that determines its shape? An Air foil is primary building block of an aircraft which has two edges namely leading edge and trailing edge, the straight line connecting the leading and trailing edge of the air foil is called as chord line. The line which is drawn equidistant from the upper and lower surfaces of the air foil and connecting the leading and trailing edge is called as mean camber line.The distance between the leading and trailing edge is called chord of an air foil.   The maximum distance between the mean camber line and chord line is referred as maximum camber. This is one of the variables that determine the aerodynamic characteristics of the wings. Maximum thickness to chord ratio is expressed in terms of percentage. For subsonic wings the ratio is normally 12-14%...

                   Wing  components Wing is the main source of lift and stability of an aircraft in flight. Our doubt is how this structure controls the motion of the aircraft? These are the scientific facts behind that; first of all an aircraft wing resembles an air foil which creates lift when it is in moving air. Normally the wing is constructed with many components and they have their own characteristics. They are Spars Ribs Stringers or Longerons Skin Spars are the main structural members that bear the loads acting on the wing; they are extended from fuselage and are in right angles to the fuselage. Ribs provide shape and rigidity to wing, which resemble the shape of an air foil. They are arranges in chord wise manner from wing root to wing tip. Stringers or longerons are thin long materials usually fastened with the skin of the wing. The primary function of the stringers is to transfer the aero...

HOW DOES AN AIRCRAFT FLY??? The question arises in our mind from our childhood days. We have seen aircraft flying in the sky and many of us have experienced the flight, but still we have the doubt that how does the aircraft flies? Here is the answer for the question. An aircraft flies in the air due to the forces (air) acting on it. The aircraft’s body and structure is designed in a manner to produce a difference in pressure which creates lift. So what is there in the design of aircraft? Why other objects can’t fly in the air? What is the science behind the flight of the aircraft? Many people would not have noticed the shape of the aircraft. The truth lies behind the aircraft’s shape. The body, wing, tail and other components are designed in a way to accelerate the moving air, which does not create any disturbance to the aircraft in motion. When the aircraft flies the air passes smoothly over the surface of the aircraft. Most of the aircraft ...

                        Albatross Albatross are Pacific Ocean seabirds of biological family Diomedeidae and they weigh up to 10kgs. They are highly efficient in flying because of their aerodynamic techniques such as dynamic soaring and slope soaring. They travel from one country to another country during climate change. They travel from southern to northern hemisphere in clockwise direction and in reverse as in anti clockwise direction. They belong to Carnivores clan of species. They are the largest among the flying birds and the procellaniformes. When discovering the structure of this bird it resembles an aircraft with high aspect ratio wings. These high aspect ratio wings are suitable for long flight distances. Albatross lives in North and South Pacific Ocean. Discovery of albatross Albatross has a long, strong and sharp edged bill. The bill is composed of ...