Aerodynamics Mcqs - Set 5

ANSWER: lower than ambient pressure

Explanation:
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.

ANSWER: venturi duct

Explanation:
In venturi duct, the pressure at the throat(p2) is lower than the pressure at the inlet(p1). The pressure difference p2-p1 helps to force the fuel into the airstream and mix it with the airstream downstream of the throat.

ANSWER: temperature

Explanation:
Using venturi, velocity can be measured. We can calculate the pressure difference using venturi. In the duct, we can place pressure gauge which will directly give us the pressure difference (p2-p1). This pressure difference can be related to velocity using Bernoulli’s equation and hence, the velocity can be calculated.

ANSWER: Low speed wind tunnel

Explanation:
Low speed wind tunnel is a large venturi where the airfoil is driven by a fan connected to some type of motor drive. The wind tunnel fan is similar to the propeller of an aircraft and is designed to draw the airflow through the tunnel circuit.

ANSWER: True

Explanation:
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.

ANSWER: Divergent section

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.

ANSWER: pitot tube

Explanation:
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.

ANSWER: Absolute

Explanation:
Static pressure is the measure of purely random motion of the molecules of the gas. It is the pressure which we can feel when we ride along with the gas at the local flow velocity. For reference, we always consider pressure as static pressure.

ANSWER: Using the pressure difference

Explanation:
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.

ANSWER: 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.

ANSWER: True

Explanation:
The dynamic pressure can be used in all kinds of flow. It is denoted by ‘q’ and is the grouping of density and velocity in which the density is halfed and the velocity is squared.
q=0.5*ρ*V2.

ANSWER: difference of total and static pressure

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).

ANSWER: True

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).

ANSWER: total pressure is equal to static pressure

Explanation:
When the local flow velocity, the static pressure and the total pressure is the same. Consider the air flow in the room, assuming the air is motionless and the standard sea level pressure is 101314.1 pa or 1 atm.

ANSWER: 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.

ANSWER: False

Explanation:
Pitot tubes with flat faces are least sensitive. For these tubes, the total pressure measurement varies only 1 percent for misalignment as large as 20 degrees.

ANSWER: pressure energy

Explanation:
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.

ANSWER: 90 degrees

Explanation:
The lower end of the tube is bent at an angle of 90 degrees. The liquid rises up in the tube due to the conversion of kinetic energy into the pressure energy. The velocity is determined by measuring the rise of the liquid in the tube.

ANSWER: position errors

Explanation:
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.

ANSWER: True

Explanation:
In the grounded condition, the pitot static tubes are generally covered so as to prevent them from atmosphere effect. If the atmospheric air enters into it, it may show certain variations in the reading.