Fluid Mechanics Units and Properties
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Questions and Answers

What defines a dimension in measurement?

  • The standard level of measurement
  • A quantity with a specific description (correct)
  • A characteristic representing a measurement unit (correct)
  • The numerical value of mass

    • What is the SI unit for density?

  • kg/m
  • N/m2
  • kg/m3 (correct)
  • J/m3

    • According to Newton's second law, what unit measures force?

  • Joule
  • Newton (correct)
  • Watt
  • Pascal

    • What is the formula for specific weight of a fluid?

    <p>Weight of fluid / Volume of fluid</p> Signup and view all the answers

    What does specific gravity compare?

    <p>Density of a fluid to its density of a standard fluid</p> Signup and view all the answers

    What is the unit of pressure defined as a Newton per square meter?

    <p>Pascal</p> Signup and view all the answers

    Which physical quantity is measured in Watts?

    <p>Work done per second</p> Signup and view all the answers

    What is the relationship between mass and specific volume?

    <p>Volume per unit mass of fluid</p> Signup and view all the answers

    What phenomenon occurs when the pressure in a flowing liquid drops below its vapor pressure?

    <p>Cavitation</p> Signup and view all the answers

    What type of pressure is measured with reference to absolute zero or complete vacuum?

    <p>Absolute Pressure</p> Signup and view all the answers

    What is the main function of a manometer?

    <p>To measure pressure at a point in a fluid</p> Signup and view all the answers

    When the boiling point of a liquid can occur at a temperature lower than its normal boiling point, what condition must exist?

    <p>Reduced pressure above the liquid</p> Signup and view all the answers

    Which of the following devices is NOT a type of mechanical gauge for measuring pressure?

    <p>Simple Manometer</p> Signup and view all the answers

    What effect does the collapse of vapor bubbles during cavitation have on adjacent surfaces?

    <p>Results in surface erosion</p> Signup and view all the answers

    Which of the following statements regarding gauge pressure is true?

    <p>It includes atmospheric pressure in its measurement.</p> Signup and view all the answers

    Which pressure is defined as the difference between atmospheric pressure and absolute pressure?

    <p>Vacuum Pressure</p> Signup and view all the answers

    What causes vapor bubbles to be formed in a moving liquid?

    <p>Reduced pressure in the liquid</p> Signup and view all the answers

    What is a common type of simple manometer used for measuring pressure?

    <p>U-tube manometer</p> Signup and view all the answers

    What is the definition of viscosity?

    <p>The resistance to the movement of one layer of fluid over another.</p> Signup and view all the answers

    How is kinematic viscosity defined?

    <p>The ratio between dynamic viscosity and density of fluid.</p> Signup and view all the answers

    Which of these fluids is classified as a Newtonian fluid?

    <p>Fluid with a constant viscosity and proportional shear stress.</p> Signup and view all the answers

    What is the expression for the pressure inside a hollow bubble?

    <p>P = 8σ/d</p> Signup and view all the answers

    What happens during capillary rise in a glass tube?

    <p>The liquid rises above the level of the surrounding liquid.</p> Signup and view all the answers

    In which type of fluid is shear stress not proportional to shear strain?

    <p>Non-Newtonian fluid</p> Signup and view all the answers

    What is surface tension in liquids defined as?

    <p>The tensile force acting on the surface of a liquid in contact with another liquid.</p> Signup and view all the answers

    The formula for capillary rise is based on which parameters?

    <p>Surface tension, density of the liquid, and diameter of the tube.</p> Signup and view all the answers

    In terms of weight density, how is the weight density of a liquid calculated?

    <p>Weight density of liquid = S × weight density of water.</p> Signup and view all the answers

    What denotes a perfect fluid according to its properties?

    <p>Compressible and having no viscosity.</p> Signup and view all the answers

    What happens to the pressure intensity inside a liquid jet as per the equilibrium condition?

    <p>Pressure intensity is inversely proportional to the diameter of the jet.</p> Signup and view all the answers

    What is the relationship between the angle of contact and capillary fall in a liquid?

    <p>Smaller angle results in lower capillary rise.</p> Signup and view all the answers

    Which equation represents Newton's law of viscosity?

    <p>τ = μ (du/dy)</p> Signup and view all the answers

    What characterizes a fluid's density?

    <p>Mass per unit volume</p> Signup and view all the answers

    Which unit is used to measure pressure?

    <p>Newton per square meter</p> Signup and view all the answers

    What is the unit for specific weight or specific density?

    <p>N/m3</p> Signup and view all the answers

    Which of these represents the correct formula for calculating work done?

    <p>Force x Distance</p> Signup and view all the answers

    What is the characteristic of a specific volume?

    <p>Volume of fluid per unit mass</p> Signup and view all the answers

    What does a Joule measure in terms of work done?

    <p>Force multiplied by distance</p> Signup and view all the answers

    What aspect of a fluid does the term 'weight density' refer to?

    <p>Weight per unit volume of a fluid</p> Signup and view all the answers

    What is the phenomenon where vapor bubbles form in a flowing liquid due to pressure dropping below the vapor pressure?

    <p>Cavitation</p> Signup and view all the answers

    Which pressure is measured with reference to atmospheric pressure?

    <p>Gauge pressure</p> Signup and view all the answers

    What type of manometer uses a U-shaped tube to measure pressure differences?

    <p>Differential manometer</p> Signup and view all the answers

    At what condition can a liquid start boiling at a temperature lower than its normal boiling point?

    <p>When the pressure is reduced to its vapor pressure</p> Signup and view all the answers

    What is the primary cause of pitting and erosion on metallic surfaces in cavitation?

    <p>Collapse of vapor bubbles</p> Signup and view all the answers

    Which device is used to balance a column of fluid for pressure measurement?

    <p>Manometer</p> Signup and view all the answers

    Which of the following statements about absolute pressure is correct?

    <p>It is the pressure measured with respect to a complete vacuum.</p> Signup and view all the answers

    What occurs when the vapor pressure of a liquid equals the surrounding pressure in a closed vessel?

    <p>Boiling of the liquid</p> Signup and view all the answers

    What defines vacuum pressure?

    <p>Pressure below atmospheric pressure</p> Signup and view all the answers

    Which type of mechanical pressure gauge relies on the expansion and compression of a spring?

    <p>Bourdon tube pressure gauge</p> Signup and view all the answers

    How is the density of a fluid calculated when its specific gravity is known?

    <p>By multiplying specific gravity with the density of water.</p> Signup and view all the answers

    Which statement accurately describes Newtonian fluids?

    <p>They have a constant viscosity at all shear rates.</p> Signup and view all the answers

    What is the expression for pressure inside a liquid jet derived from equilibrium conditions?

    <p>p = 2σ / d</p> Signup and view all the answers

    What phenomenon describes the rise or fall of a liquid in a tube due to surface tension?

    <p>Capillary action</p> Signup and view all the answers

    What is the relationship between shear stress and the rate of shear strain for Non-Newtonian fluids?

    <p>Not proportional at all.</p> Signup and view all the answers

    In the equation for capillary rise, what does the symbol 'σ' represent?

    <p>Surface tension of the liquid</p> Signup and view all the answers

    Which type of fluid is defined as having no viscosity?

    <p>Ideal fluid</p> Signup and view all the answers

    What force balances the weight of liquid in the capillary rise phenomenon?

    <p>Surface tension force</p> Signup and view all the answers

    What is the relationship between pressure intensity inside a hollow bubble and surface tension?

    <p>P = 8σ / d</p> Signup and view all the answers

    What does kinematic viscosity measure?

    <p>The ratio of dynamic viscosity to density of fluid.</p> Signup and view all the answers

    What equation represents the balance of forces in a capillary rise scenario?

    <p>h = 4σ / ρg</p> Signup and view all the answers

    How does pressure intensity behave inside a liquid droplet relative to outside pressure?

    <p>It is greater than the outside pressure.</p> Signup and view all the answers

    Which of the following is a property of a real fluid?

    <p>It possesses viscosity.</p> Signup and view all the answers

    What causes a capillary rise to occur in a small-diameter tube?

    <p>Adhesive forces between the liquid and tube walls.</p> Signup and view all the answers

    Study Notes

    Fluid Mechanics Units and Properties

    • Dimensions and Units: Dimensions describe measurable characteristics (mass, length, temperature). Units are standard measures for dimensions. Fundamental dimensions are mass (kg), length (m), time (s), and temperature (°C or K).

    • Density: Mass per unit volume (kg/m³). Fluid density (ρ) = mass of fluid / volume of fluid. Water density is 1000 kg/m³.

    • Specific Weight/Specific Density: Weight per unit volume (N/m³). Specific weight (w) = weight of fluid / volume of fluid.

    • Specific Volume: Volume per unit mass (m³/kg). Specific volume = volume of fluid / mass of fluid.

    • Specific Gravity (Relative Density): Ratio of fluid's weight density (or density) to a standard fluid's weight density (or density). For liquids, the standard is water; for gases, it's air. Specific gravity (S) is dimensionless.

      S (liquid) = weight density of liquid / weight density of water S (gas) = weight density of gas / weight density of air

    • Viscosity: Fluid's resistance to layers moving past each other. Shear stress (τ) is proportional to the rate of velocity change (du/dy) across the layers.
      Newtonian fluids obey this relationship (τ = μ (du/dy)); Non-Newtonian fluids do not.

    • Kinematic Viscosity: Ratio of dynamic viscosity to fluid density (ν).

    Fluid Types

    • Ideal Fluid: Imaginary fluid, incompressible and non-viscous.

    • Real Fluid: Possesses viscosity - all real-world fluids.

    • Newtonian Fluid: Shear stress is directly proportional to shear rate.

    • Non-Newtonian Fluid: Shear stress is not proportional to shear rate.

    • Ideal Plastic Fluid: Shear stress exceeds a yield value, and then is proportional to shear rate beyond that yield point.

    Surface Tension

    • Definition: Tensile force acting at a liquid-gas interface or liquid-solid interface. Measured in N/m.

    • Liquid Droplet: Pressure inside a droplet (excess over outside pressure) = 4σ/d (σ=surface tension, d=diameter).

    • Hollow Bubble: Pressure inside a hollow bubble = 8σ/d

    • Liquid Jet: Pressure inside a liquid jet = 2σ/d.

    Capillarity

    • Definition: Rise or fall of a liquid surface in a narrow tube. Capillary rise/depression determined by liquid specific weight, tube diameter, and surface tension.

    • Capillary Rise: Height (h) of liquid rise in a tube: h = 4σ cos θ/(ρgd) (σ = surface tension, θ = contact angle, ρ = density, g = acceleration due to gravity, d = tube diameter).

    • Capillary Fall: Similar formula to the capillary rise equation, showing the height below the liquid surface in a tube (e.g. mercury in a glass tube).

    Vapor Pressure and Cavitation

    • Vapor Pressure: Pressure exerted by a liquid's vapor when it's in equilibrium with its liquid phase.

    • Cavitation: Formation and collapse of vapor bubbles in a flowing liquid (when pressure drops below vapor pressure). Collapse creates high pressure, damaging nearby surfaces.

    Pressure Measurement

    • Absolute Pressure: Measured against a perfect vacuum.

    • Gauge Pressure: Measured relative to atmospheric pressure (atmospheric pressure is set to zero).

    • Vacuum Pressure: Measured below atmospheric pressure.

      Absolute pressure = Atmospheric pressure + Gauge pressure Vacuum pressure = Atmospheric pressure - Absolute pressure

    • Manometers: Devices balancing fluid columns to measure pressure (simple and differential types).

    • Mechanical Gauges: Devices balancing fluid column with springs or dead weights (diaphragm, Bourdon tube, dead-weight, bellows types). Simple manometers include Piezometers, and U-Tube manometers.

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    Description

    Explore the basics of fluid mechanics with this quiz focusing on dimensions, units, and various properties of fluids. Understand concepts such as density, specific weight, specific volume, and specific gravity. Test your knowledge and solidify your understanding of these essential fluid mechanics principles.

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