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Mixing and Transport Processes > Bildschirmfoto > Flashcards

Bildschirmfoto Flashcards

1
Q

Which of the processe is relevant for oil couds regrading mixing and tansport?

A

Advection
Buoyancy

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2
Q

We have considered the transport and mixing of physical quantities. Which quantities were considered?

A

Matter
Heat

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3
Q

Passive and (re)active physical quantities - which of the following statements are true?

The fate of the passive physical quantities is only determined by processes induced by the flow.
The fate of the (re)active physical quantity is inter alia determined by processes induced by the flow.
Chemical, physical and/or biological transformations determine the fate of the (re)active physical quantitiy.
Chemical, physical and/or biological transformations determine the fate of the passive and (re)active physiacl quantiy.
The fate of the passive physical quantitiy is determinded by passive reaction processes.

A

1.
2.
3.

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4
Q

Which of the following statements are true?

Advection is the transport of a subsatnce by the motion of that fluid.
Advection is the mixing of a substance by bulk motion.
Advevtion is driven by a gradient in concentration.
Advection is a process which only occours in stagnant substances.

A

1.

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5
Q

Which of the following statements are true?

Diffusion is the net movement drom a region of higher concentration to a region of lower concentration.
Diffsuision is the mixing of a substance by bulk motion.
Diffsuision is driven by a gradient in concentration.
Diffsuision is a process which only occours in stagnant substances.

A

1.
3.

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6
Q

Why is transport and mixing of sediments important for the water quality?

Sediment increases the oxygen level.
Sediment decreases the oxygen level.
Sediment can act as a vector for pollutants.
Pollutanta can adsorb to sediment.

A

3.
4.

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7
Q

Reynolds-averaging…

means a decomposition into time-averaging and fluctuating parts.
leads to a loss of information of turbulent fluctuations
means a decompostition into time-averaged and fluctuatuing parts
meand a decompostition into depth-averaged and fluctuationg parts
is done in order to simplify the Navier-Stokes equation and to increase computational costs

A

1.
2.

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8
Q

Dispersion is…

enhanced mixing induced by the temporal structure of the flow.
negligible as compared ti turbulent diffusion (in river flows)
enhanced mixing induced by the spatial structure of the flow.

A

3.

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9
Q

The transverse velocity didtribution contibutes more to mixing than the vertical one in shallow rivers. True or False?

A

True

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10
Q

Dispersion is a process that needs ti be modelled in a Reynold’s-averages 3D approach. True or False?

A

False

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11
Q

A depth-averaged 2D model resolves transverse dispersion. True or False?

A

False

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12
Q

The 1D modelling approach with reaction in rivers is….

only valid downstrams of the location where the substande is completels mixed in the creoo section
only valid if the distance required for complete mixing

A

1.
2.

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13
Q

The maximum concentration of oxygen that can be dissolved in the water…

depens on the temperature and the salinity
depens on the temperature only
increases with temperature and salinity

A

1.

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14
Q

A sufficiently hgigh concentration of dissolved oxygen is a guarentee of good water quality. True or False?

A

False

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15
Q

Which of the following processses are considered in the Streeter-Phelps model?

Advection
Biomechanical oxygenation
Re-oxygenation by transfer across the water surface
Turbulent diffusion
Molecular diffusion
Photosynthesis
Langitudional disperion
Lateral diserion

A

Advection
Biomechanical oxygenation
Re-oxygenation by transfer across the water surface

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16
Q

Which of the following statements are true for determining the total sediment transport rate?

devisions by factor 10 ore not exceptional
you can expect uncertainties of at least 100 % in sediment transport
you can expect uncertainties of max 100 % in sediment transport
careful choice of appropriate formulae is important

A

1.
2.
4.

17
Q

Which of the following forces play a role in the suspended sediment transport?

the force induced by the laminar flow on the particle
the submerged weight of the particles
the archmiedes force
the shear force on the bottom
the force induced by the turbulent flow on the particle

A

2.
3.
5.

18
Q

The settling velocity if a particle of a certain density in water with a certain temperature can e estimated from the particle diameter. True or False?

A

True

19
Q

There is considerable scatter in the data of the Shields diagramm. True or False?

A

True

20
Q

What is the physical interpreation of the Shield’s number?

the ration of the destabilizing force induced na the flow to the stabilizing force due to the particle weight
a characteristic of the flow
a characteristic of the sediment
the density ratio is p_s/p

A

1.

21
Q

Which of the following statesman are true for dimensional analysis in connection with sediment transport?

the Buckingham-PI theorem is used for this
the reduction to 4 dimensional variables is the goal
theroticalls, an infinite number of fimensionless variables can be generated
the objective is to choose physically meaningful variables
it is assumed that there are 7 variable descirbing sediment transport in the simplified system

A

1.
3.
4.
5.

22
Q

As soon as sediment transport occurs and bedforms develop, the friction coefficient (Darcy-Weisbach, Chezcy, Manning-Strickler, etc. ) will change. True r False?

A

True

23
Q

The inition of motion of sediment transport (in a simplified system) depends on the following dominant variables:

Shields number
particle Reynolds number
flow depth
dansitiy ratio

A

1.
2.

24
Q

Which of the following parameters are dominant in the theory of suspended sediment transport?

Shields number
particle Reynolds number
setting velocity
shear velocity

A

3.
4.

25
Q

There is no suspended sedimant transport in a laminar flow. True or False?

A

True

26
Q

Mixing an transport processes only occur in river flows. True or False?

A

False

Mixing and Transport Processes (2 decks)

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