Which partial differential equation is used to define the characteristic at sonic condition?

Elliptic partial differential equation

Circular partial differential equation

Parabolic partial differential equation

Hyperbolic partial differential equation

Correct Answer : Parabolic partial differential equation

Explanation : At sonic condition, when Mach number is equal to 1, there is only one characteristic that passes through the flow field point. This is defined by the parabolic partial differential equation.

Recently Updated in Aerodynamics Questions

What is the region of influence?

Area outside right running wave

Area outside the left running wave

Area within the upstream characteristics

Area within the downstream characteristics

Correct Answer : Option (D) : Area within the downstream characteristics

Explanation : For a point A which is present in a flow field with incoming steady supersonic flow, there will be two characteristic lines passing through them. The area formed between these two characteristics in the downstream region is known as region of influence.

For a point in the supersonic flow lying at the intersection of the characteristics, its flow field properties depend on change in which of these regions?

Region of influence

Domain of dependence

Region outside the characteristics

Intersection points of the characteristics

Correct Answer : Option (B) : Domain of dependence

Explaination : If a point P lies at the intersection of the left and right running waves, the flow field properties at point P is dependent on the flow field information in the region upstream i.e. domain of dependence.

On which of these points does the properties of flow field at point A depend?

Point B

Point C

Point D

Point P

Correct Answer : Option (D) : Point P

Explaination : Point P lies at the intersection of the two characteristic lines. Point A lies in the region of influence thus its flow properties depend on the properties generated due to disturbances at point P which is the intersection point.