Answer:
A fluid is a material that maintains continuous and permanent deformity when a shearing stress is applied.
• The pressure at a given point in a fluid remains unaffected by the direction of the surface that intersects this point; this pressure is isotropic.
• The force generated by pressure p acting on one side of a minimal surface area dA defined by a unit normal vector n can be expressed as −pndA.
• The speed at which pressure is conveyed through a fluid matches the speed of sound.
• The units employed vary based on the selected system, incorporating measures such as feet, seconds, newtons, and pascals. On the other hand, a dimension refers to a more abstract idea, encompassing terms like mass, length, and time.
• The specific gravity (SG) of a solid or liquid is the proportion of its density compared to that of water at the identical temperature.
• A Newtonian fluid is characterized by the viscous stress being directly proportional to the strain rate (velocity gradient). The viscosity, µ, is a property of the fluid that varies with temperature.
• At the boundary between solid and fluid, the velocities of both the fluid and solid coincide; this situation is referred to as the “no-slip condition.” Consequently, with high Reynolds numbers (>> 1), boundary layers develop near the solid surface. In those layers, significant velocity gradients occur, resulting in crucial viscous influences.
• At the junction of two distinct fluids, surface tension may play a significant role. Surface tension leads to the emergence of phenomena like meniscus, drops, bubbles, and capillary rise seen in narrow tubes since it can counterbalance pressure variations across the interface.
