Home/fluid flow operations
  1. Asked: 2 months agoIn:

    Define Mach Number. Explain and give its significance.

    Satyam Kumar
    Satyam Kumar Teacher Chemical Engineering Expert

    Mach Number:- The Mach number (M) is a dimensionless quantity that represents the ratio of the speed of a fluid (usually air or any gas) to the speed of sound in that same fluid. Significance of Mach Number: Characterization of Flow Regimes: Mach number helps in determining the flow regime, which diRead more

    Mach Number:-

    The Mach number (M) is a dimensionless quantity that represents the ratio of the speed of a fluid (usually air or any gas) to the speed of sound in that same fluid.

    Significance of Mach Number:

    1. Characterization of Flow Regimes:
      Mach number helps in determining the flow regime, which dictates how the fluid will behave. For example:

      • Subsonic flows: The flow is usually smooth, and pressure and density variations are minor.
      • Supersonic flows: The flow becomes more complicated with the formation of shock waves, and properties such as pressure and temperature vary drastically in short distances.
    2. Shock Waves and Wave Formation:
      When an object or fluid flows at a Mach number greater than 1 (supersonic flow), shock waves form. These are abrupt changes in pressure, temperature, and density that can have significant effects on the object’s design, performance, and stability (e.g., in aircraft or rockets). For example, as the Mach number increases, the shock waves become stronger and can cause a dramatic rise in drag.
    3. Aerodynamic Design:
      In aerodynamics, Mach number is used to design vehicles like airplanes, missiles, and rockets. The flow characteristics around the vehicle will differ greatly depending on whether it is subsonic, transonic, supersonic, or hypersonic.

      • Subsonic aircraft: Designed with curved, smooth shapes to maintain steady airflow at low speeds.
      • Supersonic aircraft: Require sharp nosecones and delta wings to minimize drag and manage shockwaves at high speeds.
      • Hypersonic vehicles: Require special designs to handle extremely high temperatures and pressures due to the high-speed flow.
    4. Compressibility Effects:
      At higher Mach numbers, the fluid (especially gases) becomes compressible, meaning that changes in pressure and temperature can cause significant variations in density. For example, in supersonic and hypersonic flows, the density of the fluid may not be constant, unlike in subsonic flows where density changes are relatively negligible.
    5. Efficiency of Propulsion Systems:
      In jet engines and rocket propulsion, the Mach number affects the performance and efficiency of engines. For instance:

      • In subsonic jet engines, the engine works efficiently at lower Mach numbers.
      • Supersonic and hypersonic aircraft require engines designed for high-speed intake and exhaust systems, such as ramjets or scramjets.
    6. Weather and Meteorology:
      In meteorology, the Mach number is used to analyze winds at different altitudes and understand the formation of sonic booms or atmospheric shock waves. For example, the flow of winds around mountain ranges or large atmospheric disturbances can sometimes reach supersonic speeds, influencing the weather patterns.
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  3. Asked: 2 months agoIn:

    Describe different properties of fluids.

    Satyam Kumar
    Best Answer
    Satyam Kumar Teacher Chemical Engineering Expert

    Different properties of fluids are as follows:- 1. Density (ρ) Definition: Density is the mass per unit volume of a fluid. Formula: ρ=mV\rho = \frac{m}{V}ρ=Vm​ Where mmm is mass and VVV is volume. Units: kg/m³ (in SI units). Importance: Density determines the buoyancy of a fluid and affects the flowRead more

    Different properties of fluids are as follows:-

    1. Density (ρ)

    • Definition: Density is the mass per unit volume of a fluid.
    • Formula: ρ=mV\rho = \frac{m}{V}ρ=Vm​ Where mmm is mass and VVV is volume.
    • Units: kg/m³ (in SI units).
    • Importance: Density determines the buoyancy of a fluid and affects the flow rate. For example, fluids with higher density are harder to compress and usually flow slower under the same conditions.

    2. Viscosity (μ)

    • Definition: Viscosity is the measure of a fluid’s resistance to flow or deformation. It can be thought of as the “thickness” or “stickiness” of a fluid.
    • Formula: For Newtonian fluids: τ=μ(dudy)\tau = \mu \left(\frac{du}{dy}\right)τ=μ(dydu​) Where τ\tauτ is the shear stress, μ\muμ is the dynamic viscosity, and dudy\frac{du}{dy}dydu​ is the velocity gradient.
    • Units: Pa·s (Pascal-seconds) or N·s/m².
    • Types:
      • Dynamic Viscosity (μ\muμ): Measures internal friction within a fluid.
      • Kinematic Viscosity (ν\nuν): It is the ratio of dynamic viscosity to the density of the fluid.
    • Importance: Viscosity affects how easily a fluid can flow. Higher viscosity fluids (like honey or oil) flow slower, while lower viscosity fluids (like water or air) flow more easily.

    3. Surface Tension (σ)

    • Definition: Surface tension is the force that causes the surface of a liquid to behave like a stretched elastic membrane. It is due to the cohesive forces between liquid molecules at the surface.
    • Units: N/m (Newton per meter).
    • Importance: Surface tension is responsible for phenomena like water droplets forming beads, the rise of liquids in capillaries, and the ability of small objects (e.g., insects) to “float” on water.

    4. Compressibility (β)

    • Definition: Compressibility refers to the ability of a fluid to change its volume under pressure. It is the inverse of bulk modulus.
    • Formula: β=−1V(∂V∂P)\beta = -\frac{1}{V} \left(\frac{\partial V}{\partial P}\right)β=−V1​(∂P∂V​) Where VVV is volume and PPP is pressure.
    • Units: 1/Pa (inverse Pascals).
    • Importance: Gases are highly compressible, while liquids are relatively incompressible. Compressibility affects the behavior of fluids in high-pressure environments.

    5. Specific Volume (v)

    • Definition: Specific volume is the volume occupied by a unit mass of a fluid. It is the inverse of density.
    • Formula: v=1ρv = \frac{1}{\rho}v=ρ1​
    • Units: m³/kg.
    • Importance: Specific volume is used in thermodynamics, especially when analyzing the behavior of gases under different pressures and temperatures.

    6. Pressure (P)

    • Definition: Pressure is the force exerted per unit area by the fluid molecules on the surface they are in contact with.
    • Formula: P=FAP = \frac{F}{A}P=AF​ Where FFF is the force applied, and AAA is the area over which the force is distributed.
    • Units: Pascal (Pa) or N/m².
    • Importance: Pressure influences fluid flow, particularly in confined systems like pipes or tanks. In fluids at rest, pressure increases with depth due to the weight of the fluid above.

    7. Temperature (T)

    • Definition: Temperature is a measure of the thermal energy of a fluid. It affects many properties of fluids, including density, viscosity, and specific heat capacity.
    • Units: Kelvin (K) or degrees Celsius (°C).
    • Importance: As temperature increases, the density of most fluids decreases (except water near 4°C), and viscosity decreases in liquids and increases in gases. Temperature also influences the rate of fluid flow, with higher temperatures generally reducing viscosity and allowing easier flow.

    8. Specific Gravity (SG)

    • Definition: Specific gravity is the ratio of the density of a fluid to the density of water at a specified temperature (usually 4°C for water).
    • Formula: SG=ρfluidρwater​​
    • Importance: Specific gravity provides a quick comparison of fluid densities and is often used to determine whether a fluid will float or sink in water.
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  5. Asked: 2 months agoIn:

    Explain the construction and working of Orifice meter and Venturi meter.

    Satyam Kumar
    Best Answer
    Satyam Kumar Teacher Chemical Engineering Expert

    Orifice Meter Construction: An Orifice Meter is a device used to measure the flow rate of a fluid in a pipe. It consists of the following components: Orifice Plate: A thin plate with a precisely sized hole (orifice) in the center, which is installed perpendicular to the flow direction of the fluid.Read more

    Orifice Meter

    Construction:
    An Orifice Meter is a device used to measure the flow rate of a fluid in a pipe. It consists of the following components:

    1. Orifice Plate: A thin plate with a precisely sized hole (orifice) in the center, which is installed perpendicular to the flow direction of the fluid. The orifice plate is typically made of stainless steel or other durable materials to resist wear and corrosion.
    2. Flanges: These are used to mount the orifice plate within the pipe, forming a secure seal around the edges of the orifice plate. The flanges also allow for pressure taps (inlet and outlet) to be connected to a differential pressure gauge.
    3. Pressure Taps: Located at the upstream and downstream of the orifice plate. These taps measure the pressure difference across the orifice, which is related to the flow rate.
    4. Differential Pressure Transmitter/Gauge: A device that measures the pressure difference between the two pressure taps. The pressure drop across the orifice is proportional to the flow rate.

    Working:
    When a fluid flows through the pipe, it is forced through the small hole in the orifice plate. According to Bernoulli’s principle, the velocity of the fluid increases as it passes through the orifice, causing a drop in pressure. This pressure drop can be measured by the differential pressure gauge. The relationship between the flow rate and the pressure drop is given by the continuity equation and Bernoulli’s equation

    Venturi Meter

    Construction:
    A Venturi Meter is another device used for measuring fluid flow, but it operates on the principle of gradual changes in pipe diameter. Its key components include:

    1. Converging Section: This is the section of the pipe where the diameter gradually decreases. As the fluid enters this section, its velocity increases and pressure decreases.
    2. Throat: The narrowest part of the Venturi meter, where the fluid velocity reaches its maximum and the pressure is at its minimum.
    3. Diverging Section: After the throat, the pipe diameter increases again, causing the fluid’s velocity to decrease and its pressure to recover.
    4. Pressure Taps: Located at the inlet (upstream of the converging section) and at the throat (the narrowest part of the Venturi). These taps measure the pressure at these two locations.
    5. Differential Pressure Gauge: Measures the pressure difference between the inlet and the throat. The difference in pressure is used to determine the flow rate.

    Working:
    The fluid flows into the converging section of the Venturi meter, where its velocity increases and pressure decreases due to the reduced cross-sectional area. At the throat, the velocity is at a maximum, and pressure is at a minimum. As the fluid exits the throat into the diverging section, the velocity decreases and pressure increases.

    The flow rate is determined by measuring the pressure difference between the inlet and the throat.

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  7. Asked: 2 months agoIn:

    Explain Priming and Cavitation.

    Satyam Kumar
    Best Answer
    Satyam Kumar Teacher Chemical Engineering Expert

    Priming: Priming refers to the process of filling a pump or pumping system with liquid to remove air or vapor before the pump can operate effectively. Priming is necessary for certain types of pumps, especially positive displacement pumps or centrifugal pumps, which rely on the fluid to create suctiRead more

    Priming:

    Priming refers to the process of filling a pump or pumping system with liquid to remove air or vapor before the pump can operate effectively. Priming is necessary for certain types of pumps, especially positive displacement pumps or centrifugal pumps, which rely on the fluid to create suction and generate flow. If a pump is not primed properly, it cannot generate the required suction, leading to failure in operation.

    How Priming Works:

    • Before Starting the Pump: The pump casing, suction pipe, and sometimes the inlet pipe need to be filled with liquid to ensure that the pump can create a vacuum and start moving fluid.
    • Importance: Pumps are typically designed to move liquids, not air. If there is air in the pump, it can prevent the creation of suction, leading to pump failure. Priming helps eliminate air or vapor from the system, ensuring proper fluid movement.

    Cavitation:

    Cavitation is a phenomenon that occurs when the local pressure in a fluid falls below its vapor pressure, leading to the formation of vapor bubbles. These bubbles then collapse violently when they encounter higher pressure areas, causing damage to the surface of pump components, pipes, or other parts of the system.

    How Cavitation Occurs:

    • Pressure Drop: Cavitation typically happens when the pressure in the pump inlet drops too low, causing the fluid to vaporize and form bubbles.
    • Vapor Bubble Formation: When the pressure falls below the vapor pressure of the fluid (the pressure at which the fluid turns into vapor), small vapor bubbles form.
    • Bubble Collapse: As the fluid moves into regions of higher pressure, the vapor bubbles collapse or implode. The rapid collapse generates shock waves, which can cause pitting, erosion, and vibration, ultimately damaging the pump or other components.
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  9. Asked: 2 months agoIn:

    Explain the different types of flows in detail.

    Satyam Kumar
    Best Answer
    Satyam Kumar Teacher Chemical Engineering Expert

    Types of flows:- 1. Laminar Flow: Definition: In laminar flow, fluid particles move in parallel layers or streamlines with minimal mixing between the layers. The flow is smooth and orderly. Characteristics: The fluid velocity is low, and the Reynolds number (Re) is less than 2000. The flow is typicaRead more

    Types of flows:-

    1. Laminar Flow:

    • Definition: In laminar flow, fluid particles move in parallel layers or streamlines with minimal mixing between the layers. The flow is smooth and orderly.
    • Characteristics:
      • The fluid velocity is low, and the Reynolds number (Re) is less than 2000.
      • The flow is typically seen in narrow pipes or when the fluid viscosity is high.
      • Flow follows a predictable, steady pattern with minimal turbulence.
    • Example: Flow of oil through a narrow pipe or blood flow in small capillaries.

    2. Turbulent Flow:

    • Definition: In turbulent flow, the fluid experiences chaotic and irregular motion with eddies and vortices, leading to significant mixing between fluid layers.
    • Characteristics:
      • The Reynolds number is greater than 4000, indicating high velocity and/or low viscosity.
      • Flow is characterized by rapid fluctuations in velocity and pressure.
      • Energy dissipation due to friction is higher than in laminar flow.
    • Example: Flow of water through large pipes, airflow around aircraft wings at high speed, or river flow.

    3. Transitional Flow:

    • Definition: Transitional flow occurs between laminar and turbulent flow, where the flow is unstable and fluctuates between both types.
    • Characteristics:
      • The Reynolds number ranges between 2000 and 4000.
      • The flow may switch from laminar to turbulent depending on small disturbances or changes in the system.
    • Example: Flow in a pipe where the velocity is increased gradually, potentially causing laminar to transition into turbulent flow.

    4. Steady Flow:

    • Definition: In steady flow, the fluid’s velocity at any given point does not change over time. The flow pattern remains constant.
    • Characteristics:
      • There are no fluctuations in velocity or pressure at any point in the fluid at any moment.
      • Can occur in both laminar or turbulent conditions, provided the flow remains unchanged over time.
    • Example: Steady flow of water in a pipe at a constant rate.

    5. Unsteady Flow:

    • Definition: In unsteady flow, the velocity and/or pressure of the fluid changes over time at any given point.
    • Characteristics:
      • The velocity of the fluid fluctuates at different points in space or over time.
      • Common in dynamic systems where flow conditions (like pump operation or valve opening) change with time.
    • Example: Flow in a pipe where the flow rate changes due to varying pump speeds or fluctuating pressures.

    6. Uniform Flow:

    • Definition: In uniform flow, the fluid velocity at every point in the fluid is constant, even if time is considered.
    • Characteristics:
      • The velocity at each point does not vary in space; it remains the same along the flow direction.
      • This type of flow is often an idealization, and is rarely seen in practice for real fluids.
    • Example: Idealized flow of a fluid in a straight, wide pipe where the velocity is constant along the length.

    7. Non-Uniform Flow:

    • Definition: In non-uniform flow, the velocity of the fluid varies from point to point, even along the same streamline.
    • Characteristics:
      • The velocity changes along the length of the flow path, and the flow may be faster in some areas and slower in others.
    • Example: Flow through a pipe with varying cross-sectional area or due to changes in pipe roughness.

    8. Compressible Flow:

    • Definition: Compressible flow occurs when the fluid’s density changes significantly due to variations in pressure and temperature, typically in gases.
    • Characteristics:
      • Changes in pressure and temperature lead to significant changes in fluid density.
      • Requires accounting for the variation in density in the flow equations (e.g., the ideal gas law).
    • Example: Flow of air through nozzles, jet engines, or gas pipelines at high speeds.

    9. Incompressible Flow:

    • Definition: Incompressible flow refers to flow where the fluid density remains nearly constant, even with changes in pressure. This is typically true for liquids, which are relatively incompressible.
    • Characteristics:
      • Density changes are negligible (density is constant).
      • Simplifies flow analysis, as density can be treated as a constant.
    • Example: Flow of water or oil through a pipe, where the pressure and temperature changes are too small to affect density significantly.

    10. Rotational Flow:

    • Definition: In rotational flow, the fluid particles exhibit a rotational motion, meaning they have angular momentum about an axis.
    • Characteristics:
      • Fluid elements rotate as they move along the flow path.
      • This is typically seen in vortex flows or when the flow is influenced by centrifugal forces.
    • Example: Flow in a rotating pump or the formation of whirlpools.

    11. Irrotational Flow:

    • Definition: In irrotational flow, the fluid particles do not exhibit any rotational motion, meaning the vorticity (rate of rotation) is zero at every point.
    • Characteristics:
      • Fluid elements move without any spinning around their axes.
      • Often used in idealized conditions to simplify calculations, especially in potential flow theory.
    • Example: Idealized flow in a frictionless fluid, such as airflow around a streamlined object in aerodynamics.
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  11. Asked: 2 months agoIn:

    Write the difference between Orifice meter and Venturi meter?

    Satyam Kumar
    Best Answer
    Satyam Kumar Teacher Chemical Engineering Expert

    Difference between orificemeter and venturimeter:- 1. Design and Construction:- Orifice Meter: Consists of a flat plate with a hole (orifice) in the center, installed perpendicular to the flow. The pressure difference is measured across the orifice. Venturi Meter: Has a gradually narrowing section (Read more

    Difference between orificemeter and venturimeter:-

    1. Design and Construction:-

    • Orifice Meter: Consists of a flat plate with a hole (orifice) in the center, installed perpendicular to the flow. The pressure difference is measured across the orifice.
    • Venturi Meter: Has a gradually narrowing section (converging cone), followed by a gradually widening section (diverging cone), designed to create a smooth acceleration and deceleration of the flow.

    2. Flow Characteristics:

    • Orifice Meter: Causes a more abrupt change in the flow, leading to greater turbulence and energy loss.
    • Venturi Meter: Provides a smoother flow transition with less turbulence and energy loss, making it more efficient.

    3. Pressure Drop:

    • Orifice Meter: Typically produces a higher pressure drop due to sharp edges of the orifice.
    • Venturi Meter: Generates a lower pressure drop, as the flow is more gradual.

    4. Accuracy:

    • Orifice Meter: Generally less accurate due to higher energy losses, friction, and turbulence.
    • Venturi Meter: More accurate because of its smooth and gradual shape, which minimizes flow disturbances.

    5. Cost:

    • Orifice Meter: Relatively cheaper and easier to install, but more prone to wear and maintenance.
    • Venturi Meter: More expensive due to its complex design and larger size, but requires less maintenance.

    6. Applications:

    • Orifice Meter: Common in low-cost, less critical applications where precision is less important.
    • Venturi Meter: Preferred in high-accuracy applications, such as large-scale flow measurements in pipes, where energy loss and flow disturbance need to be minimized.

    7. Maintenance:

    • Orifice Meter: May require more frequent cleaning and maintenance due to erosion and fouling at the orifice.
    • Venturi Meter: Requires less frequent maintenance as the design is less prone to clogging or erosion.
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  13. Asked: 2 months agoIn:

    Explain the limitations of Bernoulli’s equation.

    Satyam Kumar
    Best Answer
    Satyam Kumar Teacher Chemical Engineering Expert

    The limitations of Bernoulli’s equation are as:- 1. Incompressible Fluids Only:- Bernoulli's equation assumes that the fluid is incompressible, meaning its density remains constant throughout the flow. This is generally valid for liquids like water but not for gases, especially at high velocities orRead more

    The limitations of Bernoulli’s equation are as:-

    1. Incompressible Fluids Only:-

    • Bernoulli’s equation assumes that the fluid is incompressible, meaning its density remains constant throughout the flow. This is generally valid for liquids like water but not for gases, especially at high velocities or under significant pressure changes where compressibility effects become important.

    2. Non-Viscous Fluid:-

    • The equation assumes that the fluid has no viscosity (i.e., there is no internal friction between fluid layers). This means that the effects of viscous forces, which are significant in real-world fluid flow (like in pipes with high resistance or turbulent flows), are neglected. In practical applications where viscosity plays a role, Bernoulli’s equation cannot be directly applied without adjustments.

    3. Steady Flow:-

    • Bernoulli’s equation assumes that the flow is steady, meaning the velocity of the fluid at any given point does not change with time. In unsteady flows, where fluid velocity fluctuates over time, Bernoulli’s principle no longer holds.

    4. Flow Along a Streamline:-

    • The equation applies to flow along a single streamline, meaning it assumes that the fluid particles are moving along a specific path without crossing into other streamlines. If the flow is turbulent or involves significant mixing between streamlines, Bernoulli’s equation cannot be used.

    5. No Energy Losses:-

    • Bernoulli’s equation assumes that there are no energy losses due to friction or turbulence. In real-world systems, however, friction (especially in pipe flows or around rough surfaces) and turbulence cause energy dissipation, which reduces the total mechanical energy in the system, making the simple Bernoulli equation inaccurate.

    6. Neglecting Gravitational Effects in Some Cases:-

    • Bernoulli’s equation includes the gravitational potential energy term (ρgh), which is important when height differences are involved. However, in situations where gravitational effects are negligible (such as horizontal flow), this term can often be ignored, though it must be accounted for in vertical or inclined flow.

    7. Requires Ideal Flow Assumptions:-

    • Bernoulli’s equation assumes idealized conditions, such as no heat transfer and no external forces other than pressure and gravity. Real-world fluids often experience heat exchange, surface tension, and external forces (e.g., electromagnetic forces), which are not considered in Bernoulli’s principle.

    8. No Boundary Layer Considerations:-

    • The equation assumes no boundary layer effects, which are important near solid surfaces (e.g., walls of pipes or ducts). In real flow near boundaries, the velocity gradient due to viscous effects can be significant, and Bernoulli’s equation does not capture this effect.
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  15. Asked: 2 months agoIn:

    Give the classification of pressure measuring devices.

    Satyam Kumar
    Best Answer
    Satyam Kumar Teacher Chemical Engineering Expert

      Pressure measuring devices can be classified based on various factors such as their working principle, measurement range, accuracy, and the type of pressure they measure. But we are classified on the basis of mechanical pressure gauges:- 1) Bourdon Tube Pressure Gauges: Utilize a curved tubeRead more

     

    Pressure measuring devices can be classified based on various factors such as their working principle, measurement range, accuracy, and the type of pressure they measure. But we are classified on the basis of mechanical pressure gauges:-

    1) Bourdon Tube Pressure Gauges: Utilize a curved tube that straightens when pressure is applied.

    2) Diaphragm Pressure Gauges: Use a flexible diaphragm that deforms under pressure.

    3) Bellows Pressure Gauges: Utilize a metal bellows that expands or contracts with pressure changes.

    4) Manometer (U-Tube): A simple device that measures pressure by balancing a column of liquid (e.g., mercury or water) against the pressure.

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