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Correct answer is (B) Coefficient of PRESSURE

To elaborate: In fluid dynamics, the coefficient of pressure is used to find the relative pressure at each and every point in a fluid flow. Coefficient of pressure is different at every point in fluid flow and HENCE has a WIDE APPLICATION in aerodynamics and hydrodynamics.

Right option is (a) lower than ambient pressure

To explain: It is the characteristics of the venturi duct that the pressure at the throat is lower than the pressure at the INLET (ambient pressure). Because of this characteristic, it has MANY APPLICATIONS in the AERODYNAMICS.

Correct OPTION is (c) Pitot static probe

Explanation: A pitot static probe is to combine the measurement of static and total PRESSURE. It measures P0 at the nose of the probe and p1 at a SUITABLY placed static pressure tap on the probe surface DOWNSTREAM of the nose.

Correct answer is (c) Bernoulli’s principle

The explanation: An AIRCRAFT fly BASED on Bernoulli’s principle. As the air SPEED increases, the pressure decreases which results in HIGH lift generation. ACCORDING to this principle, the pressure is inversely proportional to velocity.

Correct option is (B) Static and dynamic pressure

The explanation is: The total pressure or STAGNATION pressure is the sum of static and dynamic pressure. Let P0 be the total pressure, ps be the static pressure and PD be the dynamic pressure.

Therefore, p0 = ps + pd.

The CORRECT option is (a) 0.5ρ*V^2

Explanation: The DYNAMIC pressure is not ACTUALLY a pressure. It simply JUSTIFIES the decrease in pressure due to the increase in the velocity. It simply justifies that when the DENSITY is half and the velocity is squared, the pressure decreases.

The CORRECT option is (a) True

Easiest explanation: The difference between total pressure (p0) and static pressure (p1) gives DYNAMIC pressure holds true only for incompressible FLOW. The BERNOULLI’s equation cannot be SOLVED for compressible flow and also the pressure difference is not equal to dynamic pressure (q).

Right OPTION is (b) p + 0.5ρ*V^2 = constant

The explanation is: The relation between pressure and velocity can be given by p+0.5ρ*V^2 = constant which is called as Bernoulli’s equation. In the above equation, p is the pressure and V is the velocity which IMPLIES that as the pressure increases, velocity decreases and VICE VERSA.

The correct CHOICE is (a) INVERSELY

The explanation is: PRESSURE is inversely proportional to altitude. As altitude increases, pressure decreases and vice versa because the air molecules are pulled DOWNWARDS due to the gravitational force of the earth and hence, all the molecules are close at lower altitude thus generating higher pressure at lower altitudes.

Right answer is (a) POSITION errors

To EXPLAIN I would SAY: The errors that OCCUR due to the location of pitot tube on an aircraft and also due to the effect of localized airflow over the pitot tube are called as position errors. These errors are needed to be considered while calculations.

Right option is (b) EQUIVALENT airspeed

Explanation: Equivalent airspeed refers to the speed of an AIRCRAFT at which it should fly so as to maintain the same DYNAMIC pressure. In the above EXAMPLE, 65m/s is the equivalent airspeed at an ALTITUDE of 10km flying with a true airspeed of 110 m/s.

The correct CHOICE is (C) Inviscid, incompressible flow

For explanation I would say: Bernoulli’s equation is applicable only for inviscid and incompressible flow because in inviscid flow, the viscosity is zero and hence no viscous forces acts on the body also incompressible flow means the density remains constant. The inviscid and incompressible flow REDUCES MANY FLUID problems.

The correct choice is (c) AIRFOIL

To ELABORATE: The SHAPE of the wing is called airfoil. When the flow passes over an airfoil, it produces aerodynamic forces. Instead of ANALYZING the complete wing, the analysis is done on an airfoil which gives similar characteristics LIKE a wing.

Right answer is (d) pitot TUBE

For explanation I would say: Pitot tube is a tube bent in L shaped. The ONE END of the pitot tube is exposed to air so that it can DIRECTLY come in contact with the flow VELOCITY. The pressure inside this tube is used to measure the velocity.

Correct ANSWER is (a) difference of TOTAL and static pressure

The best explanation: In incompressible flow, the dynamic pressure has a special MEANING, it is a difference between the total pressure and the static pressure. LET P0 be the total pressure and p1 be the static pressure.

Therefore, the dynamic pressure (q)= total pressure (p0)- static pressure (p1).

The correct OPTION is (d) USING the pressure difference

The best I can EXPLAIN: The pitot tube is closed at one end and is opened from other ends. When the air is filled inside the tube, the pressure at the open end equals to total pressure and it DIFFERS from the pressure outside the tube. Using this pressure difference and applying Bernoulli’s equation, the speed of air can be calculated.

Right OPTION is (c) 1

Easiest explanation: The coefficient of pressure is the dimensional LESS quantity and it DESCRIBES the RELATIVE pressure at each and every point in a FLOW field. At stagnation point, its value is maximum and it can change from point to point in a flow field.

Correct choice is (c) PRESSURE energy

To ELABORATE: When the VELOCITY of the flow becomes zero, the pressure is increased due to the conversion of kinetic energy into pressure energy which LEADS to the generation of the pressure difference.

The CORRECT choice is (d) Cp = 0.5*ρ*V1^2

For explanation: The pressure is given in terms of COEFFICIENT rather than the pressure itself. P2-P1 is the pressure DIFFERENCE at two different POINTS in the flow field. ‘q’ is the DYNAMIC pressure which is given by 0.5*ρ*V1^2 and Cp is the coefficient of pressure.

Right option is (b) dimensionless QUANTITY

Easy explanation: Although PRESSURE is dimensional quantity, Coefficient of pressure is DIMENSION less quantity. It is used THROUGHOUT the aerodynamics from incompressible flow to hypersonic flow. In aerodynamics, it is very easy to find coefficient of pressure rather than pressure.

The correct choice is (b) Divergent section

The best explanation: The purpose of the diffuser is to reduce the velocity. In order to DECREASE the velocity, the WIND tunnel is DESIGNED in such a way that the area in the divergent section decreases and the pressure in this section INCREASES further.

Right choice is (a) True

To EXPLAIN: In an open circuit wind tunnel, the AIR is directly drawn from the atmosphere, and again sent back to the atmosphere. Also, the VELOCITY at the INLET is greater than exhaust and the pressure is greater at the exhaust.

The correct option is (c) Convergent-divergent duct

Explanation: The VELOCITY increases in the convergent duct (V1) and the reaches V2 at the throat and the pressure BECOMES MINIMUM at the throat condition. In the divergent SECTION, the velocity decreases and the pressure begin to increases.

Right ANSWER is (B) Stagnation point

To ELABORATE: Stagnation point is the point where the FLOW slows down and come to rest. The STREAMLINE divides the flow into two parts- the upper flow and the lower flow. At a point, the flow cannot enter into an object so it has to stop and that point is called a stagnation point.

The correct choice is (B) constant

To explain I WOULD say: In incompressible flow, the density remains constant because of which the fluids cannot be compressed and are CALLED as incompressible fluids. Water is the best example of incompressible fluids. But still some extent we can COMPRESSIBLE water.

Correct choice is (c) b^2/s

To ELABORATE: ASPECT RATIO (AR) is the ratio of span to the mean chord. It is given by the square of WING span divided by wing area. A long and narrow wing has a HIGH aspect ratio and vice versa. It is given by:

AR = b^2/S where b is the wing span and S is the wing area.

Correct OPTION is (d) greater than 1

The explanation is: In the CASE of compressible flow, the value of VELOCITY at a STAGNATION point never equals to 0. The pressure and velocity DIFFER from one point to another. Hence, the Cp value is always greater than 1.

The correct option is (b) CONSERVATION of energy

To elaborate: It states that the sum of all the forms of energy in flow is the same at all the POINTS in that flow field. The energy here refers to KINETIC energy, potential energy and INTERNAL energy.

The CORRECT CHOICE is (b) False

For EXPLANATION I would say: No, the Bernoulli’s equation cannot be directly applied to viscous flow because in viscous flow, the motion of the fluid particle is CONSTANT. Hence, we need to convert the viscous flow into Navier-stoke equation and then Bernoulli’s equation can be applied to it.

Correct choice is (a) pV=nRT

The explanation is: In an ideal gas, molecules does not have volume and HENCE they do not interact with each other. For an ideal gas, the PRESSURE is DIRECTLY proportional to TEMPERATURE and is INVERSELY proportional to volume.