# Aerodynamics Questions and Answers – Pressure Coefficient

This set of Aerodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Pressure Coefficient”.

**1. Generally, the gliders have C _{p} as ________**

a) 1

**b) -1**

c) 0

d) infinity

**Explanation:**The pressure coefficient of -1 is common for gliders because it indicates the position of total energy, which is employed by a variometer (a vertical speed indicator) that reacts to all vertical movements of the atmosphere.

**2. Which of the following is an example of hydrostatic manometer?**

a) pressure gauge

b) piston type gauge

**c) mercury column manometer**

d) spring manometer

**Explanation**: This sort of manometer is used to measure pressure and compare it to the hydrostatic force per unit area at the column’s base. They don’t respond dynamically well.

**3. In a wing, the coefficient of pressure at the upper surface is greater than the lower surface.**

a) true

**b) false**

**Explanation**: The lower surface of the wing is under more pressure than the upper surface. The amount of lift generated grows as the pressure on the lower surface increases, and we receive more lift. The pressure at the lower surface determines the amount of lift.

**4. The shape of the wing is called as ____________**

a) geometry

b) wing

**c) airfoil**

d) wing box

**Explanation:** The wing’s shape is known as an airfoil. Aerodynamic forces are created when a flow passes over an airfoil. Rather of studying the entire wing, the analysis is carried out on an airfoil that has similar characteristics to a wing.

**5. Cl vs Cd is called as _______________**

**a) drag polar**

b) parasitic drag

c) total drag

d) no significance

**Explanation:** It’s known as drag polar, and it describes the relationship between an aircraft’s lift and drag. It refers to the amount of lift created per unit of drag. The Cl/Cd ratio needs to be high. With less drag, the quantity of lift generated should be greater.

**6. The aspect ratio (AR) is given by __________**

a) b/s

b) s/b

**c) b ^{2}/s**

d) s

^{3}/b

**Explanation:**The span to mean chord ratio is known as the aspect ratio (AR). It’s calculated by dividing the square of the wing span by the wing area. The aspect ratio of a long and narrow wing is high, and vice versa. AR = b2/S, where b is the wing span and S is the wing area, is the formula.

**7. Pressure is _____ proportional to altitude.**

**a) inversely**

b) directly

c) no relation

d) equal

**Explanation**: The relationship between pressure and altitude is inverse. Because the air molecules are forced downwards by the earth’s gravitational force, all of the molecules are close at lower altitudes, resulting in increased pressure at lower altitudes.

**8. The pressure and temperature are ________**

**a) directly proportional to each other**

b) inversely proportional to each other

c) equal

d) independent of each other

**Explanation**: The link between temperature and pressure is stated by Gay-law. Lussac’s They have a direct proportional relationship. As the temperature rises, so does the pressure, and vice versa. As the temperature rises, the gas molecules move quicker, increasing the pressure.

**9. Coefficient of pressure is a ________**

a) dimensional quantity

**b) dimensionless quantity**

c) negligible value

d) cannot be determined

**Explanation:** Despite the fact that pressure is a dimensional quantity, the pressure coefficient is a dimensionless quantity. From incompressible to hypersonic flow, it is applied throughout aerodynamics. It is much easier to find coefficient of pressure rather than pressure in aerodynamics.

**10. For incompressible flow, C _{p} is expressed only in terms of ____________**

a) pressure

b) density

c) temperature

**d) velocity**

**Explanation:**In incompressible flow, the pressure and velocity at two different points can be given by-

P

_{1}+0.5*ρ*V

_{1}

^{2}= P

_{2}+0.5*ρ*V

_{2}

^{2}

From here we get, P

_{2}-P

_{1}= 0.5*ρ (V

_{1}

^{2}– V

_{2}

^{2})

Hence, Cp = (P

_{2}-P

_{1})/q

Where q-dynamic pressure

On solving the above equation we get, C

_{p}= 1 – (V

_{2}/ V

_{1})

^{2}.

**11. The highest value of C _{p} is given at ________**

a) end points

**b) stagnation point**

c) everywhere in the flow field

d) at boundaries

**Explanation:**Because the value of velocity is 1 at the point of stagnation, Cp = 1 – (V2/ V1)2 gives the value of the coefficient of pressure as 1. This only applies to incompressible flow. The largest value of the coefficient of pressure is found at the point of stagnation.

**12. For compressible flow, the value of C _{p} at stagnation point is __________**

a) 0

b) negative

c) infinity

**d) greater than 1**

**Explanation:**The value of velocity at a stagnation point in compressible flow is never equal to 0. The pressure and velocity vary from one location to the next. As a result, the Cp value is never less than 1.

**13. The value of C _{p} for compressible flow can be given as ___________**

a) C

_{p}= P

_{2}-P

_{1}

b) C

_{p}= 0

c) C

_{p}= (P

_{2}-P

_{1}) /q

**d) C**

_{p}= 0.5*ρ*V_{1}^{2}**Explanation:**The pressure is expressed as a coefficient rather than as a number. The pressure differential between two places in the flow field is P2-P1. The dynamic pressure is given by 0.5**V12, and the coefficient of pressure is given by Cp.

**14. If the value of C _{p}=1, then the local pressure can be given as ___________**

**a) P = P**

_{freestream}+ qb) P = 0.5*ρ*V

_{1}

^{2}

c) P = P

_{freestream}

d) P = 0

**Explanation:**When Cp=1, the flow becomes incompressible, and Cp tells us how much p differs from Pfreestream in dynamic pressure multiples. When Cp=1, the local pressure is equal to the dynamic pressure plus the freestream static pressure.

**15. Ram is working on an experiment. He has a beaker in which fluid is moving at a very high velocity. He wants to calculate the relative pressure at each and every point of the flow. Which of the following will help him to do so?**

a) Coefficient of lift

**b) Coefficient of pressure**

c) Drag polar

d) Velocity

**Explanation:** The coefficient of pressure is used in fluid dynamics to determine the relative pressure at each and every point in a fluid flow. Because the coefficient of pressure varies at each location in a fluid flow, it has a wide range of applications in aerodynamics and hydrodynamics.

The increase in pressure of a gas per degree rise in temperature divided by its pressure at 0C is known as the pressure coefficient of the gas at constant volume. The lift coefficient Cl is calculated by dividing the lift L by the following formula: density r divided by half the velocity V squared times the wing area A. The lift coefficient is the ratio of the lift force to the force generated by the dynamic pressure multiplied by the area. Furthermore, the well-known relationship that stagnation pressure equals total pressure is not always accurate. As a result, pressure coefficients in compressible flow can be more than one.