Fluids Exam One Theory

false

(T/F) A body immersed in a fluid will experience a force only if there is a relative motion between the body and the fluid

false

(T/F) A control volume has to be fixed in space with the fluid moving through it and it may not move with the fluid such that the same fluid particles are always inside it

true

(T/F) Flows at high Reynolds numbers are often studied by dividing the flow into two regions, where the influence of friction, thermal conduction and diffusion is limited to a very thin region adjacent to the surface and the remainder of the flow is treated as an inviscid flow

finite, infinitesimally small, or infinitely large

A control volume is a ______________________________________________________ region of the flow.

M < 0.3

A flow can be treated as an incompressible flow when ...

inviscid flow

A flow that is assumed to involve no friction, thermal conductivity or diffusion is called ...

unsteady flow

A flow where the flow-field variables at any given point are changing with time is called ...

Three

Assume the number of variables required to describe a particular physical process is 7, and that the number of fundamental dimensions needed to describe those variables is 4. From the Buckingham Pi Theorem, what is the number of dimensionless products (Π products) needed to re-express the physical relation?

Supersonic flow

Consider a vehicle flying through the atmosphere. If the flow over the vehicle is characterized by the presence of shock waves at the nose of the vehicle, across which the flow properties change discontinuously, as what type of flow would the freestream be classified?

pressure drag

For a blunt body, most of the drag is due to ....

heating the body and heating the airflow around the body

For a body in reentry, the large kinetic and potential energy near the outer edge of the atmosphere reduces to virtually zero kinetic and potential energy as the body reaches the surface of the earth. All this energy goes into...

continuity and momentum equations

For incompressible flow with constant viscosity, the ______ ______ _________ ___________are necessary and sufficient tools to solve for the primary flow-field variables.

Hypersonic flow

For which type of flow is the temperature in the shock layer high enough for chemical reactions to occur in the air?

liquids

Hydrodynamics refers to the flow of _____

stalled

If an airfoil is inclined at a high incidence angle to the flow, then the boundary layer will tend to separate from the top surface and a large wake is formed downstream. Such a separated flow is a characteristic of a flow-field over a ______ airfoil.

continuum flow

If the mean free path, λ is orders of magnitude smaller than the scale of the body measured by d, then the flow is called ...

kg/(m*s)

SI units for the absolute viscosity coefficient (mu)

kg/(s*m^2)

SI units of mass flux

N/m^2

SI units of shear stress

Euler

The momentum equations for inviscid flows are called the _________ equations

no slip condition

The phenomenon where friction causes the infinitesimally thin layer of air molecules immediately adjacent to the body surface to stick to the surface is called the ...

boundary layer

The thin viscous region adjacent to a body in a flow field where dissipative effects are included is called ...

force

The time rate of change of momentum is called ...

divergence

The time rate of change of the volume of a moving fluid element, per unit volume represents the ________________ of the velocity field

thermal conduction

The transfer of heat from a hotter region to a colder region by random molecular motion is called ...

buoyancy

The weight of fluid displaced by an object that is immersed in the fluid is equal to the force of ...

blunt

To minimize aerodynamic heating, we need a ____body

velocity distribution

We need to measure the ______ _________ using a Pitot rake in order to calculate the drag of a two dimensional body in a wind tunnel.

solid

When a force is applied tangential to the surface of a _____, it will experience a finite deformation and the shear stress will usually be proportional to the amount of the deformation.

the streamline patterns are geometrically similar; the nondimensional pressure, temperature, density, velocity, etc. distributions are the same; the drag coefficients are the same; lift on cylinders are the same

consequences of two flows being dynamically similar

Mass conservation - Scalar equation, Momentum conservation - Vector equation, Energy conservation - Scalar equation

scalar or vector equation? mass conservation momentum conservation energy conservation

Pressure - scalar, Velocity - vector, Temperature - scalar, Density - scalar

scalar or vector? pressure velocity temperature density

geometrically similar as well as the similarity parameters are the same

two flows will be dynamically similar if the bodies and any other solid boundaries are ...