Fluid Mechanics — Flow & Pressure
Hydrostatic pressure, buoyancy, continuity, Bernoulli, the Reynolds number, and pump power — the physics of anything that flows, every term unit-checked.
Fluid mechanics governs everything that flows — water in pipes, air over a wing, blood in arteries, oil through a refinery. A handful of relations carry most of the engineering: pressure with depth, conservation of mass and energy along a streamline, and one dimensionless number that predicts smooth versus chaotic flow.
- 01 Hydrostatic pressure — deeper means harder ELI5: every metre of water above you adds weight, so pressure grows with depth: P = ρ·g·h. It depends only on depth and density, not on the shape of the…
- 02 Buoyancy — why steel ships float ELI5: a submerged object is pushed up by the weight of the fluid it displaces: F = ρ·g·V. Displace more water-weight than you weigh, and you float — which is…
- 03 Continuity — squeeze the pipe, speed the flow ELI5: what goes in must come out, so when a pipe narrows the fluid speeds up: A₁·v₁ = A₂·v₂. Halve the diameter (quarter the area) and the speed quadruples.…
- 04 Bernoulli — fast flow means low pressure ELI5: along a streamline, pressure + motion energy stays constant, so where the fluid speeds up the pressure drops: ΔP = ½·ρ·(v₂² − v₁²). That trade is the…
- 05 The Reynolds number — smooth or turbulent? ELI5: one dimensionless number, Re = ρ·v·D / μ, predicts whether flow is smooth (laminar) or chaotic (turbulent). Below ~2300 it's orderly; above ~4000 it…
- 06 Pump power — the cost of pushing fluid uphill ELI5: to lift a flow Q to a height H you must supply power P = ρ·g·Q·H. It's just "weight lifted per second" — the same energy bookkeeping as…