What is the physical definition of turbulence?
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Turbulence is merely the measure of Reynolds number of a fluid at rest or motion ( (turbulence occurs when fluid is in motion) let's say you light up a cigarette and when the smoke is at the tip of cigarette you see it flows upwards uniformly and this is because the fluid is in laminar flow and as it expands into its vicinity it becomes turbulent. so what is the physics here? basically, reynolds number defines if a fluid is laminar or turbulent. Reynolds number is defined as the ratio of inertial to viscous forces experienced on a body. when divided it gives a number without any units. If the Reynolds number is less than 2100 then the flow is laminar and greater than 4000 it's turbulent and if it's between 2100 and 4000 its transitional flow (which is rare and instantaneous)