Turbulent Mixing Quiz: Test Your Knowledge Of Fluid Motion

Concept: enhanced heat transfer. Turbulent motion continually brings fresh fluid into contact with the wall. This increases the temperature gradient and boosts heat exchange.

Concept: cost of turbulence. Turbulence increases frictional losses in pipes and around vehicles. More energy is then required to maintain the same flow speed.

Concept: dominant transport mechanism. In large-scale flows, diffusion alone is too slow. Turbulence is the main reason substances spread quickly.

Concept: turbulent dispersion. Eddies spread pollutants sideways and vertically, not just downwind. This increases dispersion compared with smooth laminar motion.

Concept: dissipation at small scales. Turbulence transfers energy from large eddies to smaller ones. At the smallest scales, viscosity converts motion into heat and removes kinetic energy.

Concept: turbulent mixing. Turbulent eddies move fluid parcels across streamlines, greatly increasing mixing. Laminar flow relies more on molecular diffusion, which is slower.

Concept: stretching and folding. Turbulent eddies create complex motion that spreads dye rapidly. This increases contact area between dyed and clear water, speeding mixing.

Concept: turbulence and aeration. Turbulence increases surface renewal and mixing, helping gases like oxygen enter water. This supports aquatic life in fast-flowing streams.

Concept: convection strength. Turbulence enhances mixing near the surface, increasing heat transfer. Laminar flow tends to form smoother layers that insulate more.

Concept: mixing equalises properties. Turbulence moves air parcels around, blending warm and cool regions. This reduces temperature differences over time.

Concept: turbulent momentum mixing. Turbulent eddies mix momentum across the pipe, reducing the centre-to-wall speed difference. This often makes the profile flatter than laminar flow.

Concept: parcel transport. Turbulence moves chunks of fluid around, carrying heat, momentum, and dissolved substances. This is far more efficient than diffusion alone.

Concept: trade-offs. Turbulence can improve mixing and heat transfer, but it also increases drag and energy losses. Engineers choose when turbulence is worth the cost.

Concept: environmental transport. Turbulence lifts and moves sediment and mixes dissolved materials. It also helps exchange gases at the water surface.

Concept: visible turbulence. Turbulence can entrain air and create froth, especially in rapids. It also creates swirls and irregular surface patterns.

Concept: diffusion in laminar flow. Without cross-stream eddies, molecules must move by random motion to mix. This is typically much slower than turbulent mixing.

Concept: eddy diffusivity (qualitative). Turbulent motion can be treated as adding a mixing effect beyond molecular diffusion. Eddy diffusivity is a way to describe that stronger transport.

Concept: shear-driven turbulence. Large velocity gradients provide energy to disturbances. This can generate and sustain turbulent eddies.

Concept: forced turbulence. Stirring creates eddies and chaotic motion. This distributes ingredients faster than diffusion can.

Concept: gradient smoothing. By moving fluid parcels around, turbulence reduces sharp differences in concentration or temperature. This tends to smooth gradients over time.