Mid Term Chapter 1 Flashcards
What is a fluid? How does it differ from a solid? How does it differ from a liquid?
A substance in the liquid or gas phase is referred to as a fluid. A fluid differs from a solid, and that a solid can resist and applied your stressed by deforming, whereas a fluid to force continuously under the influence of stress no matter how small. A liquid takes the shape of the container it’s in, and a liquid forms of free surface in a larger container in a gravitational field. A gas on the other hand expanse until it encounters the walls of the container and fill the entire available space
Consider the flow of air over the wings of an aircraft. Is this flow internal or external? How about the flows if gasses through a jet engine
The flow of air over the wings of an aircraft is external, since this is an unbounded fluid flow over our surface. The flow of gases through a jet engine is internal flow since the flow is completely bounded by the solid surface of the engine.
Define incompressible flow and incompressible fluid. Must the flow of a compressible fluid necessarily be treated as compressible?
A fluid flow during which the density of the fluid remains nearly constant is called incompressible flow. A flow in which density very significantly is called compressible flow. Fluid density is practically independent of pressure such as a liquid is commonly referred to as an incompressible fluid, although it is more proper to refer to incompressible flow.the flow is of compressible fluid such as air does not necessarily need to be treated as impressible since the density of compressible fluid may still remain nearly constant during flow, especially flow at low speeds
Define internal external and open channel flows
External flow is the flow of an unbounded fluid over a surface such as a plate, a wire or a pipe. The flow in a pipe or duct is internal flow if the fluid is completely bound by solid surfaces. The flow of liquid in a pipe is called open flow if the pipe is partially filled with the liquid, and there is every surface such as the flow of water in rivers and irrigation ditches.
How is the mach number of a flow defined? What does a mach number of two indicate
The Mac number of a flow is defined as the ratio of the speed of flow to the speed of sound in the flowing fluid. A mock number of two indicates a flow speed that is twice the speed of sound in that fluid mark is a dimension less parameter.
When an airplane is flying at a constant speed relative to the ground, is it correct to say that the mock number of the airplane is also constant?
No, the speed of sound unless the mock number changes with temperature which may change considerably from point to point in the atmosphere
Consider the flow of error at mock number 0.12. Should this flow be approximated as being incompressible?
Gas flows can often be approximated as incompressible if the density change are under about 5%, which is usually the case when Ma < 0.3. Therefore airflow with a mock number of 0.12 may be approximated as being incompressible.
What is the no slip condition? What causes it?
A fluid indirect contact with a solid surface sticks to the surface, and there is no slip. This is known as the no slip condition and it is due to the viscosity of the fluid.
What is force flow? How does it differ from natural flow? Is flow caused by wind forced or natural flow
Enforced flow, the fluid is forced to flow over surface or in a tube by external means such as a pump or a fan in natural flow, any fluid motion is caused by natural means such as the war and effect that manifest itself in the rise of warmer fluids and the cooler fluids. The flow caused by wind is natural flow for earth, but it is forest flow for bodies subjected to the wind since the body. It makes no difference whether the air motion is caused by a fan or by the wind.
What is a boundary layer? What causes a boundary layer to develop?
A boundary layer is the region of flow, usually near a wall in which the velocity ingredients are significant and functional effects are important. When a fluid stream encounters a solid surface at rest, the fluid velocity assumes a value of zero at that surface. The velocity varies from zero at that surface to some larger value sufficiently far from the surface. The development of a boundary layer is caused by the no slip condition.
What is the difference between the classical and statistical approaches?
The classical approaches of microscopic approach based on experiments or analysis of the gross behavior of fluids without knowledge of of individual molecules, where statistical approach is a microscopic approach based on the average behavior of large groups of individual molecules
What is a steady flow process?
The process is said to be steady if it involves no change with time anywhere within the system or at the system boundaries.
Define stress, normal stress, sheer stress, and pressure
Stress is defined as force per unit area and is determined by dividing the force by the area upon which it acts. The normal component of a force acting on a surface per unit area is called the normal stress, and the tangential component of force acting on the surface per unit area is called sheer stress. In a fluid at rest, the normal stress is called pressure.
When analyzing the acceleration of gases as their flow through a nozzle, what would you choose as your system? What type of system is this?
When analyzing acceleration of gases as they flow through a nozzle, a wise choice for the system is the volume within the nozzle, bound by the entire inner surface of the nozzle and the inlet and outlet cross-sections. This is a control volume or open system since the mass crosses the boundary.
When is a system closed system and when is it a control volume?
Systems may be considered to be closed or open, depending on whether a fixed mass or a volume in space is chosen for study. A closed system, also known as a control mass or simply a system consists of a fixed amount of mass and no mask can cross its boundary. An open system, or a control volume is a selected region and space. Mass may cross the boundary of a control volume or open system.
You were trying to understand how a reciprocating air compressor a piston slender device works. What system would you use? What type of system is this?
We would most likely take the system as the air contained in the piston cylinder device. The system is closed or fixed mass system when it is compressing and no mass enters or leaves it. However, it is an open system during intake or exhaust.
What are system, surroundings, and boundary?
A system is defined as a quantity of matter or a region in space chosen for study. The mass or region outside the system is called the surroundings. The real or imaginary surface that separates the system from its surroundings is called the boundary.
Explain why light-year has the dimensions of length
In this unit, the word light refers to the speed of light. The light-year unit is then the product of a velocity and time hence this produces a distance dimension, and unit
What is the difference difference between kilograms mass and kilograms force?
The unit kilogram is the mass unit in the SI system. And it is sometimes called kilogram mass where is kilograms force is a force unit. 1 kg force is the force to accelerate a 1 kg mass by 9.81 m/s squared in other words, the weight of 1 kg mass at sea level on earth is 1 kg force.
What is the difference between pound mass and pound force?
A pound mass is the mass unit in the English system. Where is pound force is the force unit in the English system. 1 pound mass is forest required to accelerate a mass of 32.2 pounds mass by 1 ft./s squared. In other words the weight of a 1 pound mass at sea level on earth is 1 pound for force.
In a news article, it is stated that a recently developed cured turbo fan engine produces 15,000 pounds of thrust to propel and aircraft forward. Is pound mentioned here pounds mass or pounds force?
The pound of mentioned here must be pound force since the rest is a force. And pound force is that force unit in the English system.
What is the net force acting on a car cruising at a constant velocity of 70 km/h on a level road and on an uphill road
There is no acceleration because the car is moving out of constant velocity. Thus the net force is zero in both cases.
