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Fluid Mechanics Question and Answers

Fluid Mechanics questions and answers include topics such as fluid mechanics fundamentals and properties, viscosity, vapour pressure, compressibility, bulk modulus, and fluid types. These articles are taken from some of the most reputable and leading books on fluid mechanics. To understand and interpret Fluid Mechanics fully, one can allocate one hour a day for two to three months. Anybody could conveniently practice for Fluid Mechanics interviews, online exams, assessments, and certifications using this method of formal learning.

What is a radial-flow turbine? | Fluid Mechanics Question and Answers

In a radial-flow turbine, steam flows outward from the shaft to the casing. The unit is usually a reaction unit, having both fixed and moving blades.

Why is it easier to compress gases than liquids or solids?

Answer 1: Since gases have more space between their molecules, they are highly compressible and can be easily compressed by applying pressure. However, there are more enticing forces between the molecules in solids and liquids. As a result of the compact packing of molecules, liquids and solids may not compressed as easily as gases.

Answer 2: Since the molecular distance between gas particles is greater than the size of atoms of liquid and solids, there is a lot of space between them, and the coherent forces between them are weak, while solid particles do not have a gap, and liquid particles have a smaller gap than gas particles.

What are four types of turbine seals? | Fluid Mechanics Question and Answers

• Carbon rings fitted in segments around the shaft and held together by garter or retainer springs.
• Labyrinth mated with shaft serration’s or shaft seal strips.
• Water seals where a shaft runner acts as a pump to create a ring of water around the shaft. Use only treated water to avoid shaft pitting.
• Stuffing box using woven or soft packing rings that are compressed with a gland to prevent leakage along the shaft.

By partially covering the gap with your thumb, you can squirt water from a garden hose a much longer distance. Could you please explain how this works?

The water that emerges from the hose travels a greater distance for two reasons.
1. By putting your thumb over the end, you are expanding the water pressure and hence the kinetic energy conveyed to the water at just the time of exit, which is dissipated over the distance covered.
2. Water is inherently incompressible, meaning it does not contract when the pressure is increased. As a result, rather than providing a complete seal, restricting the water flow with your thumb will enable the same amount of water to flow out, even at a faster linear velocity through the restricted area. The result is similar to the effect of changing the depth of water flowing down a river: when the water is deep, it tends to be almost stagnant, but when it is narrow, it obtains a high linear velocity. In both sections of the river, the overall flow is the same.

The  relation between Mass flow rate of water, ‘Q’ and Fluid Velocity, ‘V’ is

Q = A x V

where, ‘A’ is the area of the cross section of the passage through which the fluid is passing.

What are two types of clearance in a turbine? | Fluid Mechanics Question and Answers

• Radial – clearance at the tips of the rotor and casing.
• Axial – the fore-and-aft clearance, at the sides of the rotor and the casing.

What is the function of a thrust bearing? | Fluid Mechanics Question and Answers

Thrust bearings keep the rotor in its correct axial position.

A table tennis ball may be suspended in mid-air if air from a hair dryer is blown over it. What makes you think this suspension is possible?

Since the air flowing quickly over the top exerts very little downward pressure on the ball, the upward pressure from the air below (which is not moving) becomes intense enough to suspend the light table-tennis ball in midair.
Since the pressure is lower above the ball, the table tennis ball can be suspended on air.

What are some conditions that may prevent a turbine from developing full power? | Fluid Mechanics Question and Answers

• The machine is overloaded.
• The initial steam pressure and temperature are not up to design conditions.
• The exhaust pressure is too high.
• The governor is set too low.
• The steam strainer is clogged.
• Turbine nozzles are clogged with deposits.
• Internal wear on nozzles and blades.

What is a stage in a steam turbine? | Fluid Mechanics Question and Answers

In an impulse turbine, the stage is a set of moving blades behind the nozzle. In a reaction turbine, each row of blades is called a “stage.” A single Curtis stage may consist of two or more rows of moving blades.

What is a diaphragm? | Fluid Mechanics Question and Answers

Partitions between pressure stages in a turbine’s casing are called diaphragms. They hold the vane-shaped nozzles and seals between the stages. Usually labyrinth-type seals are used. One-half of the diaphragm is fitted into the top of the casing, the other half into the bottom.

What are the two basic types of steam turbines? | Fluid Mechanics Question and Answers

• Impulse type.
• Reaction type.

What are topping and superposed turbines? | Fluid Mechanics Question and Answers

Topping and superposed turbines arc high-pressure, non-condensing units that can be added to an older, moderate-pressure plant. Topping turbines receive high-pressure steam from new high-pressure boilers. The exhaust steam of the new turbine has the same pressure as the old boilers and is used to supply the old turbines.

When an inflated beach ball is held under a water pool and the ball is released upwards. Why does this happen?

Because of its air, the beach ball has a very low mass and low density. The amount of water displacing the ball is thus much heavier than the ball itself. The floating force on the ball is thus much higher than its weight and the ball speeds up easily. The buoyant force is much higher than the ball weight.

In a glass of water, an ice cube is submerged. When the ice melts, what happens to the water level?

Ice is less compact than water, meaning it takes less space to dissolve into liquid. So the water level falls.

What is a combination thrust and radial bearing? | Fluid Mechanics Question and Answers

This unit has the ends of the Babbitt bearing extended radically over the end of the shell. Collars on the rotor face these thrust pads, and the journal is supported in the bearing between the thrust collars.