What Do You Know About Aerodynamics?

Explanation
The motion of air around an object is called a flow field.

Explanation
Drag is not a characteristic of a continuum flow field. Drag is a force that acts opposite to the direction of motion and is typically experienced by objects moving through a fluid. It is caused by the interaction between the object and the fluid, and is not a property of the flow field itself. The other options, flow velocity, pressure, and density, are all characteristics that describe the properties of the flow field.

Explanation
Thrust is not used to classify flow fields. Density, viscosity, and flow velocity are all important factors in determining the behavior and characteristics of a flow field. Density refers to the mass per unit volume of a fluid and affects its compressibility and buoyancy. Viscosity is the measure of a fluid's resistance to flow and determines its ability to transmit shear stress. Flow velocity is the speed at which the fluid is moving and influences the overall dynamics of the flow. Thrust, on the other hand, is a force that propels an object forward and is not directly related to the classification of flow fields.

Explanation
Flow velocity is related to the speed regime when it comes to the classification of flows. The speed regime of a flow refers to the range of velocities at which the flow occurs. Different flow regimes have different characteristics and behaviors. Flow velocity, which measures the speed at which the fluid is moving, is a crucial factor in determining the flow regime. It helps in categorizing flows as laminar or turbulent, as well as in understanding other flow properties such as pressure drop and flow rate.

Explanation
The question asks for a classification of flows that is not included in the given options. The options provided are hyposonic flow, supersonic flow, subsonic flow, and hypersonic flow. Therefore, the correct answer is "Hyposonic flow" because it is not a recognized classification of flows.

Explanation
Supersonic flow is characterized by a flow speed greater than the speed of sound. In supersonic flow, the flow velocity exceeds the local speed of sound, resulting in shock waves and a change in the flow behavior. This type of flow is commonly observed in high-speed aircraft, missiles, and other objects that travel at speeds faster than the speed of sound.

Explanation
Subsonic flow is incompressible because it occurs at speeds below the speed of sound. In this type of flow, the fluid velocity is much lower than the speed of sound, resulting in a low level of compression. The density of the fluid remains relatively constant throughout the flow, and the flow can be considered incompressible for practical purposes.

Explanation
External aerodynamics is the study of flow around solid objects of various shapes. It focuses on the interaction between the object and the surrounding air, considering factors such as drag, lift, and turbulence. This field of study is particularly important in industries such as automotive and aerospace, where understanding and optimizing the aerodynamic performance of vehicles and aircraft is crucial.

Explanation
The study of flow through passages inside solid objects is called internal aerodynamics. External aerodynamics, on the other hand, is the study of flow around solid objects. Flow aerodynamics and total aerodynamics are not specific terms used in the study of fluid dynamics.

Explanation
The conservation principles of fluid mechanics refer to the principles of mass conservation, momentum conservation, and energy conservation. These principles state that mass, momentum, and energy cannot be created or destroyed, but can only be transferred or transformed. Therefore, the correct answer is "Three principles".