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The CORRECT option is (a) True

Best explanation: The upper and LOWER curvature are EQUAL in the symmetric AIRFOIL because there is no maximum camber in the symmetric airfoil when compare to cambered airfoil it does not produce high lift, so these are used in the subsonic flights.

The correct ANSWER is (a) True

To explain: The kelvin circulation theorem does not require the FLUID region to be simply connected, it does not require the dyed circuit C to be placed by a SURFACE Slying wholly in the fluid, this CONDITION is only applied to the vortex shedding off an airfoil.

Correct CHOICE is (a) Frozen VORTEX Lines

To explain: Kelvin’s theorem can be used to prove Helmholtz theorems, one of which SAYS ‘vortex lines MOVE with the fluid’ which is what is known as “frozen vortex lines”.

The CORRECT answer is (b) True

To elaborate: A vortex sheet is a term used in fluid mechanics for a surface ACROSS, which there is a DISCONTINUITY in fluid velocity. Such as in slippage of one layer of fluid over another .which the tangential components of the flow velocity are discontinuous across the vortex sheet, the normal components of the flow velocity is CONTINUOUS.

Correct option is (a) True

For explanation: In fluid FLOW AROUND a BODY with a sharp corner, the kutta condition refers to the flow pattern in which fluid approaches the corner from both DIRECTIONS, meets at the corner, and then flows away from the body. None of the fluid flows around the corner attached to the body.

Right choice is (a) True

The EXPLANATION is: The skin- FRICTION coefficient CF, has been defined for the skin-friction drag over one SURFACE only. So in order to calculate total drag, we need to multiply the result by 2.

Correct option is (b) True

The BEST explanation: Turbulent FLOW is a less orderly flow regime that is characterized by eddies, SMALL packets of fluid particles, which results in LATERAL mixing. In non-scientific terms, laminar flow is smooth, when turbulent flow is ROUGH.

Correct option is (d) STALL

Best explanation: Stall is characterized by a REDUCTION in the lift at HIGH angles of attack, i.e. when the angle of attack increases more than the critical angle of attack. The flow is no more attached and flow SEPARATION OCCURS.

The correct option is (a) True

The best EXPLANATION: Some shapes have less DRAG than others. The drag coefficient is seen to the FIRST drop with lift, then rise. These PHENOMENA cannot be explained on the basis of inviscid potential flow theory which will cause the viscous EFFECT.

Correct CHOICE is (b) False

Easiest explanation: The AERODYNAMIC center is always NEAR the quarter-chord for airfoils with LINEAR lift and moments but it is not exactly the quarter-chord always.

Correct choice is (a) Camber line curves BACKUP near the trailing edge

For explanation I would say: An airfoil where the camber line curves BACK up near the trailing edge is called a reflexed camber airfoil. Such an airfoil is USEFUL in certain SITUATIONS, such as with tailless AIRCRAFT, because the moment about the aerodynamic center of the airfoil is zero.

Correct ANSWER is (b) Barotropic Flow

To EXPLAIN I would say: A barotropic flow is a fluid where density is a function of pressure only, i.e. ρ = ρ(p). BAROCLINIC flow is the fluid which is not only dependent on the pressure but on other factors also. Viscous and INVISCID flows are not necessarily dependent on pressure only.

Correct choice is (B) True

To elaborate: A BODY with sharp trailing EDGE which is moving through a fluid will create about itself a circulation of sufficient strength to hold the rear stagnation POINT at the trailing edge when the fluid is moved over the airfoil decrease in the crossectional AREA will create the circulation.

Right answer is (a) Flow over the topside

Easiest explanation: As the vorticity INCREASES the BOUND vortex and also PROGRESSIVELY increases and causes the flow over the topside of the airfoil to increase in speed. The starting vortex is SOON cast-off the airfoil and is left behind, SPINNING in the air, where the airfoil left it.

The correct option is (a) True

The best explanation: POINT vortices are INHERENTLY chaotic, a FOURIER FILTER is necessary to control the growth of round-off errors. Continuous approximation of a vortex sheet by vortex panels with are wise diffusion of circulation density also SHOWS that the sheet rolls-up into a double branched spiral.

Correct option is (a) True

Easiest explanation: The integral form the CAUCHY principal VALUE integral. The initial condition for a flat vortex SHEET with a constant strength is zero. The flat vortex sheet is an EQUILIBRIUM solution. However, it is unstable to infinitesimal periodic disturbance. Hence, with a constant strength flat vortex sheet is used.

Right answer is (b) True

The best explanation: The formulation of the VORTEX sheet equation of MOTION is given in terms of a complex COORDINATES z=x+iy. The sheet is described parametrically by z(s, t), where s is the arc length between coordinate z and a reference POINT and t is the time left. This equation will GIVE the vortex sheet for different complex coordinates.

Correct answer is (a) False

For explanation I would say: The TURBULENT FLOW analysis has no exact ANALYTICAL solutions. They require EMPIRICAL DATA to proceed and all the solutions obtained are approximate.

The correct OPTION is (a) True

For explanation: TURBULENCE is caused by excessive KINETIC energy in parts of a fluid flow, which overcomes the damping EFFECT of the fluid’s viscosity. For this reason, turbulence is easier to create in low viscosity fluids but more difficult in highly VISCOUS fluids.

Right CHOICE is (a) True

Explanation: When a fluid is FLOWING through a closed channel such as a pipe or between two flat plates, EITHER of two types of flow may occur depending on the VELOCITY and viscosity of the fluid, laminar flow tends to occur at lower velocities, below a threshold at which it BECOMES turbulent.

Correct OPTION is (a) True

For explanation I would SAY: The Reynolds number is the ratio of inertial force to the viscous force of the fluid, how FAST the fluid is moving relative to how viscous it is, irrespective of the scale of the fluid system. LAMINAR flow generally occurs when fluid is moving slowly or the fluid is very viscous.

Correct choice is (c) Drag being zero for non-zero LIFT

The explanation: The d’Alembert’s PARADOX arises due to the assumption of an inviscid FLUID. The lift predicted with this assumption is correct but the drag comes out zero. Which is not true as pointed out by EXPERIMENTS or general observation.

Correct CHOICE is (a) True

To EXPLAIN: The super critical airfoil was a major breakthrough in high SPEED AERODYNAMICS, the super critical airfoil is used to improve the drag at subsonic speeds. The LS-0417 LOW speed airfoil first introduced as the GA-1 airfoil.

Right choice is (a) True

To EXPLAIN: A 50 percent increase in the ratio of lift to drag at a lift coefficient of 0.1. This value of q=0.1 is typical of the climb lift coefficient for general AVIATION aircraft, and a high value of L/D GREATLY IMPROVES the climb.

Correct option is (b) True

The explanation: The new NASA AIRFOILS were DESIGNED on a computer using a NUMERICAL technique similar to the source and vortex panel methods discussed earlier, ALONG with numerical PREDICTIONS of the viscous flow behavior.

The correct choice is (a) 0.087

Explanation: For zero SLOPE of camber line, the airfoil is symmetrical and A0 is the same as that of the angle of attack. We can also GET the same VALUE from the CAMBERED airfoil solution since \(\frac {dz}{dx}\)=0.

Correct choice is (a) True

To explain: The CAMBER is the CURVE of the upper and lower SURFACES of an AIRFOIL. This curve is measured by how much it departs from the CHORD of the airfoil, the horizontal line joining the leading and trailing edges, some airfoil has a high degree of camber.

Right answer is (b) 15+4=0

To explain: In thin AIRFOIL theory, the CAMBER line has to be a streamline. Thus, the component of velocity in the normal DIRECTION to the camber line is zero at any given point. This means the sum of velocity COMPONENTS by the free stream velocity and the induced velocity is zero.

Right answer is (a) True

Explanation: The SYMMETRIC airfoil with good lift to drag ratio is used for an aircraft wing, this will be translated into lower FUEL CONSUMPTION, SHORTER take-off and landing times, and shorter runways. Airfoil With backward facing will get high lift coefficient.

The correct answer is (a) True

For explanation: The NACA 0012 is symmetric airfoil because the MEAN camber line and CHORD line intersect in the same line.so, there is no camber in the NACA 0012 airfoil. That the reason the first and second DIGITS are will become ZERO, and the THICKNESS of NACA 0012 airfoil is 12 percent.

Correct answer is (a) True

The best I can EXPLAIN: The time RATE of change of circulation around a CLOSED curve consisting of the same fluid elements is zero, change in circulation with respect to time is zero, along which its supporting discussion is called KELVIN’s circulation theorem.

The correct answer is (a) True

The best I can explain: The inviscid EQUATION of motion enter the proof only in helping to evaluate a line integral round C, so if VISCOUS FORCES happened to be important elsewhere in the flow that is off the CURVE C, this would not affect the CONCLUSION that the circulation remains constant round C.

Right answer is (c) generation of lift and circulation

To explain I would say: From Kelvin’s Theorem, circulation REMAINS constant with time. So for initial ZERO circulation, the FORMATION of starting VORTEX MEANS there has to be equal and opposite circulation in the form of lift.

Correct choice is (a) Because of no camber

Easy EXPLANATION: The NACA 0012 AIRFOIL indicates the symmetric airfoil, because an airfoil with no camber, that is with the camber line and CHORD line co-incident in an airfoil is called a symmetric airfoil. For the NACA 0012 airfoil is with a maximum thickness of 12%.

The correct option is (a) 15%

Easy explanation: In NACA 747A315 airfoil. The7 denotes the series, 4provides the LOCATION of minimum pressure on the UPPER surface in a tenth of chord, 7 provides the location of the minimum pressure on the lower surface in tenth of chord, the 4^th character i.e. A indicates the thickness distribution and MEAN line form used. Again 5^th digit 3 indicates the design lift coefficient in the tenth and the final two digits indicate the thickness of the chord 15%.

Correct option is (a) True

The explanation: Turbulent flow is a flow REGIME in fluid dynamics CHARACTERIZED by CHAOTIC CHANGES in pressure and flow velocity. It is in contrast to a laminar flow regime, which OCCURS when a fluid flows in parallel layers, with no disruption between those layers.

Right choice is (B) Higher symmetry

The BEST explanation: The larger leading EDGE radius gave a reduced peak in pressure coefficient at the leading edge. The trailing edge was cusped which INCREASED camber, thus decreasing symmetry. These FEATURES reduced flow separation and gave a higher value of maximum lift coefficient.

The correct option is (a) True

To explain I would say: In fluid DYNAMICS, laminar flow OCCURS when fluid FLOWS I parallel layers, with no disruption between the layers. At low velocities, the fluid tends to flow WITHOUT lateral mixing, and adjacent layers slide PAST one another like playing cards.

Right answer is (d) The SLOPE of the camber line is zero

Easiest explanation: Slope of the camber line \(\FRAC {dz}{dx}\) is not zero for a cambered AIRFOIL but is some FINITE value. All the other statements are valid assumptions of thin airfoil theory.

Right option is (b) True

The best explanation: Camber is usually DESIGNED into an airfoil is to INCREASE the maximum lift coefficient. This minimizes the stalling speed of aircraft using airfoil. Aircraft with wings based on cambered airfoils usually have low lower stalling speeds than similar aircraft with wings based on SYMMETRIC airfoils.

The CORRECT OPTION is (a) STREAMLINE

For EXPLANATION: For thin airfoils, camber and chord lines are very close and the vortex sheet can be assumed to be placed at the chord line. And the camber line becomes a streamline.

The correct option is (c) 5

Best explanation: The WAKE structure is CLASSIFIED into FIVE different modes ACCORDING to their pattern obtained from instantaneous and mean vorticity fields by also taking into ACCOUNT the amplitude spectrum of the lift coefficient.

Right choice is (b) False

To ELABORATE: According to Kelvin’s theorem vortex sheet cannot die since circulation has to REMAIN constant with time. It says a vortex sheet stays FOREVER, in the ideal CASE.