Lecture 10 Flashcards
Geophysical Fluid Dynamics
Are dynamic viscosities of liquids generally higher than dynamic viscosities in gases?
Yes, several orders of magnitude higher
Surface seawater is more viscous at the poles than it is at the equator. True or False
True, seawater is half as viscous at the equator than it is at the poles. Likely to do with the fact its colder there so the water is freezing causing it to move slower and by thicker/stickier.
Is surface seawater more or less viscous than it is below the thermocline?
It is less than half as viscous at the surface. So it is more viscous below the thermoline due to the cooler temperatures.
What does ice-loading do to the lithosphere?
it depresses it, the fluid asthenosphere is squeezed out. The melting of the ice causes isostatic rebound,
Navier-Stokes Equation is coupled to what other equation?
Maxwell’s Equation, as they can model magnetohydro-dynamics
What is the non-linearity caused by in the Navier-Stokes equation?
Convective acceleration, any convective flow whether turbulent or laminar will involve non-linearity.
Navier-Stokes Equations are to do with what type of movement>
Fluid Movement; motion of fluid substances
Laminar flow
Otherwise known as streamline flow.
When fluids flow in parallel layers, no cross-currents or disruption between layers.
All particles of fluid move in straight lines
Turbulent Flow
Chaotic motions, rapid variation of pressure and velocity in space and time.
Kinetic energy stored in Edies, very effective at mixing.
What does the transition from turbulent to laminar flow depend on? When does the transition occur?
Reynolds Number
Transition occurs when Re increases. So when size increases, density increases or viscosity decreases.
Stokes Law only works when Reynolds number is small. True or false?
True. It only works for small grains, where viscous affects dominate.
Reflects a transition from laminar to turbulent flow when grain size increases.
Describe the difference between a jet and a plume
Jets: Continuous source of momentum.
Plumes: Continuous source of buoyancy.
Explain and define the Richardsons Number
Buoyancy vs momentum of a system; the ratio of potential to kinetic energy.
When R>1 is buoyancy or momentum dominant?
Buoyancy
When R<1 is buoyancy or momentum dominant?
Momentum, it is driving the flow.
