Aerodynamics Mcqs - Set 1

ANSWER: fluids

Explanation:
Because fluid (liquid and gas) is a “squishy” substance. While the solid body is geometrically well defined and hence its motion can be defined easily. Whereas, in fluids, it is difficult to decide the qualitatively model the motion of the fluid.

ANSWER: True

Explanation:
During re-entry, near the outer edge of the atmosphere, the vehicle has a large amount of kinetic energy due to its high velocity and a large amount of potential energy due to its altitude but as it reaches the surface of earth it becomes zero because the kinetic and potential energy is utilized in heating the body and heating the airflow around the body.

ANSWER: liquid and gas

Explanation:
When force is applied to liquid and gas, there will be an increasing deformation, proportional to the rate of change of deformation. Also, the molecules in liquid and gas are loosely packed. When filled in a container, they take the shape of that container.

ANSWER: Pressure and density

Explanation:
Both pressure and density vary from one point to another. Pressure and density vary with the altitude and are directly proportional to each other. Pressure and density does depend on a path as they change from one point to other. If one parameter is changed, it affects pressure and density.

ANSWER: free molecular flow

Explanation:
In free molecular flow, the gas molecules are spaced so far apart that collisions with the body surface occur only infrequently and the body surface can feel distinctly each molecular impact which reduces the vibration in the space vehicle.

ANSWER: inviscid flow

Explanation:
The flow without friction, thermal conduction, or diffusion is practically impossible. During any process or flow, the energy losses take place which leads to frictional losses, thermal losses, diffusion and various other losses.

ANSWER: supersonic flow

Explanation:
Supersonic flows are characterized by the presence of shock waves across which the flow properties and streamlines change discontinuously. In supersonic flow, the gas can be compressed using shock waves.

ANSWER: True

Explanation:
Continuity equation relates aerodynamic phenomena over a finite region of space without being concerned about the details of precisely what is happening at a given distinct point in the flow.

ANSWER: pressure and shear stress

Explanation:
Pressure force and shear stress acts on the complete surface of the body which means that the surface force acts on the surface and not on a point or the body. Surface forces may act either on external or on an internal surface of the body.

ANSWER: True

Explanation:
Heat and work are forms of energy. During the transfer of heat and work, the system and surrounding lose its energy. Boundary separates system and surrounding. A system is included in the surrounding.

ANSWER: All the three models can be used based on the need

Explanation:
The finite control volume considers a finite volume which may be either fixed in space or moving along a fluid. The infinitesimal small element considers a finite element which may be either fixed or moving along with the flow. The molecular approach is a microscopic approach and can be applied to atoms and molecules.

ANSWER: Geometric Similarity

Explanation:
Geometric similarity occurs when the model and prototype have same dimensional ratio in each direction. These ratios are called as scale ratio. For ex, Length scale ratio Lr = Lm/Lp where, m and p represent model and prototype.

ANSWER: Dynamic Similarity

Explanation:
For a dynamic similarity, the model and prototype must be geometrically and kinematically similar along with the condition of total sum of forces acting at a point on model and prototype must be equal. Inertia force satisfies the condition and hence it falls under dynamic similarity.

ANSWER: Surface tension

Explanation:
In a jet of oil, the molecules at the surface and the free layer differs because of which the oil resists the external force. The cohesive nature of the oil molecules helps to increase the surface area of the oil.

ANSWER: Water

Explanation:
The fluids which obey Newton’s law of viscosity are Newtonian fluids. It states that the applied shear stress is directly proportional to the amount of deformation.
τ = μdv/dy
Where, μ—–viscosity of the fluid
τ—-shear stress
dv/dy -velocity gradient.

ANSWER: Inertia force to viscous force

Explanation:
Reynold’s number is given by Re = VL ρ / μ, which signifies the inertia to viscous force occurring in a flow. ρ / μ is called as kinematic viscosity of the fluid. Larger Reynold’s number, greater will be the inertial effects.

ANSWER: True

Explanation:
Pressure force acts on various parts of an aircraft. When these forces are resolved into a single component they act at a point and that a point is center of pressure. Also, it is a point where all the hydrostatic forces (forces due to fluids) act.

ANSWER: Bernoulli’s principle

Explanation:
Bernoulli’s principle states that the sum of all the forms of energy (potential energy, kinetic energy, internal energy) remains constant. Only the weight of the body and the pressure forces act on the body.

ANSWER: Mass conservation

Explanation:
Continuity equation is related to mass conservation. It states that the total mass entering a body is equal to the total mass leaving a body.
Mass entering the body = mass leaving the body.

ANSWER: Flux

Explanation:
Flux is also referred to as flux density. It is the amount of quantity (q) which is flowing per unit volume(v). The quantity should have the ability to move or flow.