Fluid Mechanics Flashcards
Discuss the conditions necessary for a fluid to be at rest in a container.
For a fluid to be at rest in a container, it must be in a state of hydrostatic equilibrium, with the pressure increasing uniformly with depth, and the net force on any fluid element being zero.
Define buoyant force and describe how it is related to Archimedes’ principle.
Buoyant force is the upward force exerted by a fluid on an immersed or submerged object, and it is equal to the weight of the displaced fluid, as described by Archimedes’ principle.
Discuss how the buoyant force affects floating and submerged bodies.
The buoyant force causes a floating body to experience an upward force equal to the weight of the fluid it displaces, enabling flotation, while a submerged body experiences an upward buoyant force that reduces its effective weight in the fluid.
Define streamline, pathline, and streakline and explain the differences between them.
Streamline is an instantaneous line representing the direction of fluid flow at a given point; pathline is the actual trajectory followed by a fluid particle over time; and streakline is the continuous curve formed by connecting fluid particles that have passed through a specific point, with streamlines changing over time, pathlines following individual fluid particles, and streaklines showing the history of fluid motion.
Discuss the concept of velocity field and how it represents fluid motion.
The velocity field is a spatial distribution of instantaneous velocity vectors at different points in a fluid, providing a comprehensive representation of fluid motion and direction throughout the entire domain.
Discuss the differences between laminar and turbulent flow and the factors influencing the transition.
Laminar flow is characterized by smooth, orderly fluid motion, while turbulent flow involves chaotic and irregular fluid motion; the transition between them is influenced by factors such as flow velocity, viscosity, and the size and shape of the conduit.
Discuss the assumptions and limitations of Bernoulli’s equation.
Assumptions of Bernoulli’s equation include steady, incompressible, and irrotational flow with negligible viscous effects and external work, limiting its application to idealized fluid situations and excluding conditions involving high speeds, compressibility, and viscous or rotational effects.
Explain the principle of conservation of mass for fluid flow.
The principle of conservation of mass for fluid flow states that, in a steady flow, the mass entering a control volume must equal the mass leaving, ensuring the continuity of mass within the system.
Explain the concept of specific energy and how it relates to open channel flow.
Specific energy in open channel flow is the sum of the velocity head and the elevation head, and it is constant along a given flow streamline, influencing the depth and velocity of the flow at any point.
Discuss the major and minor losses in pipe flow.
Major losses in pipe flow result from friction and are proportional to the length and velocity of the pipe, while minor losses occur at fittings and valves, contributing to the total head loss in a fluid system.
Explain the concept of head loss and its calculation in pipe systems.
Head loss in pipe systems is the reduction in pressure energy due to friction and minor losses, and it is calculated using empirical formulas such as the Darcy-Weisbach equation or the Hazen-Williams equation.
Define specific energy in open channel flow and discuss its significance.
Specific energy in open channel flow is the total energy per unit weight of fluid, equal to the sum of velocity head and elevation head, and its significance lies in determining the stable and unstable flow conditions in an open channel.
Explain how critical flow conditions are determined in open channels.
Critical flow conditions in open channels are determined by comparing the actual specific energy to the critical specific energy, with subcritical flow occurring when actual specific energy is greater and supercritical flow when it is less, influencing the stability and behavior of the flow.
Discuss the operating principles of pumps and turbines.
Pumps operate by imparting energy to fluids, increasing their pressure and facilitating flow, while turbines extract energy from fluid flow, converting it into mechanical work, both functioning based on principles of fluid dynamics and thermodynamics.
Explain the relationship between pump and turbine performance and system curves.
The relationship between pump and turbine performance and system curves is crucial in determining the stable operating point, with the intersection point representing the equilibrium where the pump’s head-capacity curve matches the system curve for pumping, and the turbine’s head-capacity curve intersects the system curve for power generation.
