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WorksheetsFluids Mechanics CH 1_Game with Me, Dr Izzatul :)
Total questions: 20
Worksheet time: 20mins
What does mechanics means?
Skilled people who use hardware to repair and maintain machinery or machines
Physical science that deals with both stationary and moving bodies under the influences of forces.
Physical science that deals with both stationary and moving bodies under the influences of pressures.
A branch of classical mechanics that concerned with the study of forces and their effects on motion
Fluids Mechanics is divided into several categories. What are they?
Hydrodynamics
Gas Dynamics
Aerodynamics
Naturally occurring flows
Define Gas Dynamics.
Motion of incompressible fluids
Motion of compressible fluids
Flow of gases (especially air) over bodies at high or low speeds
Fluids flow that going on significant density changes
Naturally occurring flows consist of:
meteorology
hydrology
oceanography
theology
What are fluid characteristics?
Molecules move about at random
Strongest inter-molecular bonds
Molecules move about each other, but the volume remains constant due to strong cohesive forces between molecules
Expands until it encounters the wall of the container and fills the entire space available
Define pressure.
Normal component of a force acting on a surface per unit area
Tangential component of a force acting on a surface per unit area
Normal stress in a fluid at rest (= zero shear stress)
Force per unit area
What are the characteristics of fluid when shear force is applied?
Never stops deforming and approaches a constant rate of strain.
Deforms continuously under the influence of shear stress.
Stress is proportional to strain.
Stress is proportional to strain rate.
Define no slip condition.
A fluid in rest increase at the surface and assumes a maximum velocity relative to the surface.
A fluid in motion increase at the surface and assumes a maximum velocity relative to the surface.
A fluid in rest comes to a complete stop at the surface and assumes a zero velocity relative to the surface.
A fluid in motion comes to a complete stop at the surface and assumes a zero velocity relative to the surface.
A fluid property, viscosity responsible ?? to happen?
No slip condition
No slip condition and the development of boundary layer
The development of boundary layer
Drag force
Define the development of boundary layer.
When a fluid is forced to flow over a curved surface, the boundary layer may no longer remain attached to the surface, and separates from the surface
All velocity profiles must have zero values with respect to the surface at the points of contact between a fluid and a solid surface
The force a fluid exerts on a surface in the flow direction
The flow region adjacent to the wall in which the viscous effects (thus, the velocity gradients) are significant
Describe viscosity.
No fluid with zero viscosity
When 2 fluid layers move relative to each other, a friction force develops between them and the slower layer tries to slow down the faster layer
Cause by cohesive forces between the molecules in liquids and by molecular collisions in gases
Flows where the frictional effects are significant is called inviscid flow regions
Internal flow VS External flow
The flow where the fluid is completely bounded by solid surfaces
The flow of an unbounded fluid over a surface (plate, wire, pipe)
The viscous effects are limited to boundary layers near solid surfaces and to wake regions downstream of bodies
Dominated by the influence of viscosity throughout the flow field
Incompressible flow defined as
If the viscosity remains nearly constant throughout
If the density remains nearly constant throughout
The volume of every portion of fluids remains unchanged over the course of its motion
The densities of liquids are essentially constant, thus the flow of liquids is typically compressible
Describe laminar flow.
A flow that alternates between laminar and turbulent
The highly ordered fluid motion characterized by smooth layers of fluid
The flow of high-viscosity fluids (e.g. oil) at low velocities
The highly disordered fluid motion that typically occurs at high velocities and is characterized by velocity fluctuations
Define turbulent flow.
The highly disordered fluid motion that typically occurs at high velocities and is characterized by velocity fluctuations
The highly ordered fluid motion characterized by smooth layers of fluid
The flow of high-viscosity fluids (e.g. oil) at low velocities
The flow of low-viscosity fluids (e.g. air) at high velocities
Select the correct answer.
Key parameter to determine the flow regime is by Reynolds number
Reynolds number for laminar flow is larger than 2300
Reynolds number for turbulent flow is smaller than 4000
Reynolds number for transition flow is 2300>Re>4000
Natural flow is ...
a fluid motion
due to natural means such as the buoyancy effect, which manifests itself as the rise of cooler (and denser) fluid and the fall of warmer (and lighter) fluid.
is due to natural means such as the buoyancy effect, which manifests itself as the rise of warmer (and lighter) fluid and the fall of cooler (and denser) fluid.
a fluid that is forced to flow over a surface or in a pipe by external means such as pump or fan.
Please choose the correct statement.
Flow is steady when there is no change of fluid properties at a point with time
Example of steady flow is flowing river, waves
Example of steady flow is turbines, pumps, boilers, and condensers
Flow is unsteady when fluid properties change at a point with time
Which statement on Close and Open systems are wrong?
Close system is a system of a fixed mass (no mass transfer across the system boundary)
Matter and energy can crosses the boundary of a control mass (system)
Open system usually encloses a device that involves mass flow such as compressor, turbine and nozzle
Energy transfer (in the form of heat and work) into or out of the close system may happen, and the volume does not have to be fixed
Which statement is wrong?
A property that represents this internal resistance of a fluid to motion is viscosity
The force a flowing fluid exerts on a body in the flow direction is called the drag force
The force a flowing fluid exerts on a body in the flow direction is called the tangential component of force
For liquids, both the dynamic and kinematic viscosities are practically independent of pressure
