Wind tunnel use Research Paper Example | Topics and Well Written Essays - 1500 words

Wind tunnel use - Research Paper Example An aerodynamic force is produced by any body which moves inside a fluid. The component of this force which is perpendicular to the direction of motion is called Lift.On the contrary, the force in the direction of motion is called the drag The Lift force is created according to the hydrostatical theorem of the Archimedes principle. According to this principle, the aircraft will be buoyed up by a force equal to the weight of the air displaced by the aircraft. (Milne-Thomson, 1966) An aerofoil is a perfect example to discuss the creation of the lift and the reasons associated with it. An aerofoil is a non-symmetric object and therefore a non-symmetric flow field is created around that object. This non-symmetric flow field also causes an uneven pressure distribution which would not have happened in case of a symmetric object. In the case of the aero foil, the differences in the length of the upper and the lower surfaces and the shape causes the creation of a pressure gradient which resul ts in the creation of the lift force. Source: www.tpub.com The creation of the lift can further be explained using Bernoulli's equation. In a typical aerofoil, the length at the bottom is shorter than the length at the top. Therefore air at the bottom travels slowly to ensure constant displacements of top and bottom. Bernoulli's equation predicts that higher pressure will develop where velocity is slow and therefore the pressure at the bottom will be higher. Thus the upward force will be greater than the downward thrust resulting in the generation of an upward lift. (Munson, 2008) The horizontal component is labeled induced drag. b)Describe how atmospheric parameters ( temperature, pressure, density) affect the generation of lift and drag as an aircraft gains altitude.? The calculation of the lift has a simple formula which is Where  is the lift coefficient, L is the lift force,  is the fluid density, U is the relative speed between the object and the fluid and A is the cross-se ctional area (Munson, Young and Okiishi). This means that the lift coefficient determines the lift force and this coefficient is directly dependent upon the shape of the foil, the fluid properties and the roughness of the surface. Fluid properties include fluid density, viscosity and temperature which contribute to the lift force. The general equation for this is Where Re is the Reynolds Number, Fr is the Froude number, Ma is the Mach number, and  is a measure of surface roughness (Munson, Young and Okiishi) Thus when these external parameters change, the lift coefficient is affected directly which consequentially affects the lift force. Taking temperature to be the first variable, we know that temperature is inversely proportional to density. The aircraft, when it gains altitude, flies at lower temperatures and thus faces an increase in the density of the surrounding air. An increase in air density results in the increase in the weight of the displaced air and thus an increase in the lift force. A contradiction however is the mass of air which is higher near the surface of the earth due to gravity. Thus the density which is dependent upon mass decreases with increasing altitude, resulting in a lower lift force at higher altitudes. When it comes to pressure, it also decreases as the aircraft gains altitude. This is so because the density lowers and the direct effect of this is the reduction in the pressure gradient between opposite surfaces. Again this decrease causes a reduction in the amount of lift force produced. Research a) Describe how drag varies with airspeed and the generation of lift. Drag will always be present on a moving body, even though lift is not produced. What do we call this type of drag and how does shape affect it? As mentioned before, the drag force is the force acting parallel to the direction of motion or the line of symmetry of the object. It normally opposes motion and slows down objects. it is