Tidal Characteristic Numbers of Current: Difference between revisions
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Timespan between slack water time of flood current and the next slack water time of ebb current | Timespan between slack water time of flood current and the next slack water time of ebb current | ||
[[Example: Flood Current Duration for the Inner Außenweser ]] | [[Example: Flood Current Duration for the Inner Außenweser]] | ||
====Slack Water Time of Flood Current==== | ====Slack Water Time of Flood Current==== | ||
Official time of slack water occurrence at the end of a flood current duration | Official time of slack water occurrence at the end of a flood current duration | ||
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Timespan between high water occurrence and slack water time of flood current | Timespan between high water occurrence and slack water time of flood current | ||
[[Example: Slack Water Dislocation of Flood Current for the Inner Außenweser ]] | [[Example: Slack Water Dislocation of Flood Current for the Inner Außenweser]] | ||
====Differences of Time of Maximum Flood Current between Different Locations==== | ====Differences of Time of Maximum Flood Current between Different Locations==== | ||
Differences of time of maximum flood current occurrence between different locations within the area of data analysis | Differences of time of maximum flood current occurrence between different locations within the area of data analysis | ||
[[Example: Time of Maximum Flood Current for the Inner Außenweser]] | [[Example: Time of Maximum Flood Current for the Inner Außenweser]] | ||
====Flood Path==== | |||
Vectorial summation of the path length for a certain location during the flood current duration | |||
[[Example: Flood Path for the Inner Außenweser]] | |||
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back to [[Analysis of Calculated Results]] | back to [[Analysis of Calculated Results]] | ||
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[[Overview]] | [[Overview]] | ||
Revision as of 10:50, 8 June 2010
Graphical representation of characteristic numbers of current velocity (with German text only). This graphical representation is also available in Encapsulated PostScript format.
Graphical representation of characteristic numbers of volume fluxes (with German text only). This graphical representation is also available in Encapsulated PostScript format.
Graphical representation of eulerian residual current and residual path (with German text only). This graphical representation is also available in Encapsulated PostScript format.
Motivation
Computation as well as graphical display of several tidal characteristic numbers of current add aditional insight into tidally induced dynamic processes which are reflected in the current velocity and its related derived quantities. This type of tidal analysis should therefore go hand in hand with the calculation of tidal characteristic numbers of water level.
- The computation is carried out separately for the periods of flood and ebb current duration. Therefore it yields information about the asymmetry of the tide-induced currents. An asymmetry can result in different durations of ebb and flood currents on the one hand side and on the other hand side in different maximum flood and ebb current velocities. This imbalance might be a result of different speeds for the fall and rise of the water level which causes a distinguished acceleration of the flow. Different values of the maximum flood and ebb current velocities may be a main cause for residual transport (up- or down-estuary) of bedload material or suspended sediments.
- Unequal slack water times of flood or ebb current are mainly due to the varying significance of the various dynamic driving forces (e.g. batropic and baroclinic pressure gradient as well as bottom friction versus inertia forces). They mainly depend on water depth as well as on the precise location of the water volume in the water column.
- Different times of slack water dislocation are related to the character of the tidal wave. In a purely propagating deep water wave there exists a phase shift of approximately 90 ° between current and water level elevation. Whereas in shallow water, bottom friction and reflexion of the tidal wave causes a much smaller phase shift. Remember: for a purely standing wave the phase shift is zero.
- The periods of slack water are good indicators for the times of mild current climate. During these periods suspended sediments may settle to the bottom and become deposited. Unsymmetrical periods of slack water can result in net up- or down-estuary transport of suspended sediments.
- Tidal characteristic numbers of current which are representative for the whole tidal cycle may give some insight into the residual transport paths for the water masses travelling along an estuary. For example the Eulerian residual current is a first order approximation to the respective Lagrangian one. It should be therefore interpreted with some care.
Automatic analyses for all of the above mentioned tidal characteristic numbers of current are carried out for 2D- as well as for 3D-data by the program TDKVF.
Definition of Tidal Characteristic Numbers of Current
Flood Current
Maximum Flood Current Velocity
Maximum value of the flood current velocity during the flood current duration
Example: Maximum Flood Current Velocity for the Inner Außenweser
Mean Flood Current Velocity
Mean value of the flood current velocity during the flood current duration
Example: Mean Flood Current Velocity for the Inner Außenweser
Flood Volume
Volume of water, which flows through a certain cross section during the flood current duration
Example: Flood Volume for the Inner Außenweser
Flood Current Duration
Timespan between slack water time of flood current and the next slack water time of ebb current
Example: Flood Current Duration for the Inner Außenweser
Slack Water Time of Flood Current
Official time of slack water occurrence at the end of a flood current duration
Example: Slack Water Time of Flood Current for the Inner Außenweser
Slack Water Duration around Slack Water Time of Flood Current
Timespan around slack water time of flood current for which the flow velocity does not exceed a certain value
Example: Slack Water Duration of Flood Current for the Inner Außenweser
Slack Water Dislocation of Flood Current
Timespan between high water occurrence and slack water time of flood current
Example: Slack Water Dislocation of Flood Current for the Inner Außenweser
Differences of Time of Maximum Flood Current between Different Locations
Differences of time of maximum flood current occurrence between different locations within the area of data analysis
Example: Time of Maximum Flood Current for the Inner Außenweser
Flood Path
Vectorial summation of the path length for a certain location during the flood current duration
Example: Flood Path for the Inner Außenweser
back to Analysis of Calculated Results