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The fort.13 file contains nodal attributes, which can vary spatially. For each attribute, one or more values are specified at each node. The number of values and their meaning(s) varies by attribute.
Note that units for nodal attributes are specified by the user in the fort.13 file, though ADCIRC may require that attributes be supplied in certain units.
Primitive Weighting in Continuity Equation
Nodal attribute name: primitive_weighting_in_continuity_equation
Description: Related to TAU0, affects numerical damping and stability.
Values: Information and suggested range supplied in description of TAU0.
ADCIRC Variable: Tau0Var
Surface Submergence State
Nodal attribute name: surface_submergence_state
Description: This attribute can force a node to be categorized as dry at the start of the simulation, even if it is below the geoid. This is important for simulating places like New Orleans that are below sea level but are not underwater.
Values: If set to 1, the node is categorized as dry at the cold start of the simulation. If set to zero, the node is categorized as wet or dry depending on whether its depth is below or above the geoid.
ADCIRC Variable: StartDry
Quadratic Friction coefficient
Nodal attribute name: quadratic_friction_coefficient_at_sea_floor
Description: See the description of CF in the Model Parameter and Periodic Boundary Condition File. If the user elects to load this from the fort.13 file, NOLIBF must be set to 1 or the run will terminate.
Values: Same as CF.
ADCIRC Variable: Fric
Nodal attribute name: surface_directional_effective_roughness_length
Description: A measure of the “roughness” of the land that can impede wind flow and reduce the surface stress that the wind applies. The ocean would be considered very smooth, and skyscrapers would be considered very rough. This attribute is directional, and the twelve values represent the roughness lengths “seen” by winds blowing from twelve different compass directions at each node. The orientation of the twelve values follows the trigonometric convention, that is, zero degrees represents due east, and the values proceed counter clockwise. In other words, the first value at a node is applied to winds blowing from west to east, the second value applies to winds blowing East-Northeast, etc.
Units: Specified by the user, as is the case for all nodal attributes. The data we use is provided in meters.
Values: Greater than or equal to zero.
ADCIRC Variable: z0Land
Surface Canopy coefficient
Nodal attribute name: surface_canopy_coefficient
Description: This attribute allows the user to turn off wind stress in heavily forested areas that have been flooded, like a swamp. The canopy shields the water from the effect of the wind.
Values: Zero if the wind stress should be zero because of a canopy. One otherwise.
ADCIRC Variable: VCanopy
Bridge Pilings Friction Parameters
Nodal attribute name: bridge_pilings_friction_parameters
Description: Extra friction from bridge pilings. See Note below.
Requirement: Very optional.
Units: Vary, see note below and BK, BALPHA, BDELX and POAN.
Values: Vary, see note below and BK, BALPHA, BDELX and POAN.
ADCIRC Variable: BK, BAlpha, BDelX, POAN
Note: Special considerations must be used when designing a grid for an ADCIRC application that includes the effects of bridge pilings. Specifically, it is necessary to build the grid to provide at least three rows of nodes that parallel the bridge span. One row of nodes (centerline nodes) should lie along the approximate centerline of the bridge while the second and third rows of nodes (adjacent nodes) should lie on either side of the centerline nodes in the along steam direction. An initial implementation of obstruction drag in ADCIRC placed this drag entirely at the row of centerline nodes. However, tests showed that this arrangement led to significant oscillations in the numerical solution. The oscillations abated when the obstruction drag was distributed in the along stream direction so that 25 percent was located at each row of adjacent nodes and 50 percent was located at the row of centerline nodes. Node numbers and coefficient values at all nodes on the centerline and two adjacent rows must be entered in this input file. It is not necessary for centerline nodes to correspond to actual piling positions, (i.e., in the cross stream direction), since the overall effect of the pilings on the large scale circulation is all that is being represented. It is important, however, to construct a grid that is as uniform as possible in the vicinity of the bridge.
Nodal attribute name: mannings_n_at_sea_floor
Description: Manning's n. If the user elects to use this nodal attribute, NOLIBF must be set to 1 or the run will terminate. During execution, the Manning’s n value specified here is converted to an equivalent quadratic friction coefficient before the bottom stress is calculated. The equivalent quadratic friction coefficient is calculated according to the following formula at each node at each time step: Cd(t)=(g*n^2)/cuberoot(depth[+eta(t)]) where depth is the bathymetric depth and [eta(t)] is the water surface elevation. The addition of the water surface elevation is conditional upon the setting of NOLIFA: eta(t) is treated as zero if NOLIFA is set to zero in the fort.15 file. Finally, the value of CF in the fort.15 is used to set a lower limit on the resulting equivalent quadratic friction coefficient, since the Cd calculated from this formula tends to become small in deep water.
Units: Specified by user.
Values: Greater than zero.
ADCIRC Variable: ManningsN
Chezy Friction Coefficient
Nodal attribute name: chezy_friction_coefficient_at_sea_floor
Description: Chezy friction coefficient. If the user elects to use this nodal attribute, NOLIBF must be set to 1 or the run will terminate.
Units: Specified by user.
Values: Greater than zero.
ADCIRC Variable: ChezyFric
Sea Surface offset
Nodal attribute name: sea_surface_height_above_geoid
Description: Creates an initial offset of the sea surface from the geoid. If the offset is also specified at the boundaries, it will remain throughout the simulation. This has been used to simulate a steric effect, where water levels are higher in warm seasons because of thermal expansion.
Units: Specified by the user (length).
ADCIRC Variable: GeoidOffset
Wave Refraction in SWAN
Nodal attribute name: wave_refraction_in_swan
Description: to turn wave refraction on or off in the SWAN calculations during a coupled ADCIRC+SWAN run. In an ADCIRC-only run, this nodal attribute is ignored.
Values: If set to 1 at a node, wave refraction will be active at that node in the SWAN calculations during a coupled ADCIRC+SWAN run. If set to 0, wave refraction will be deactivated at that node in a coupled ADCIRC+SWAN run.
ADCIRC Variable: SwanWaveRefrac
Nodal attribute name: bottom_roughness_length
Description: Roughness length for 3D bottom friction calculations. Has no effect on a 2DDI ADCIRC run.
Units: Length (m)
Values: Greater than zero. A reasonable range for the bottom_roughness_length would be 0.001m -0.2m , (densely vegetated overland values would have an upper limit of about 0.2-0.5m and smooth muddy bottoms could have values as low as 0.0001 m).
ADCIRC Variable: Z0b_var
Nodal attribute name: average_horizontal_eddy_viscosity_in_sea_water_wrt_depth
Description: See description of ESLC in the Model Parameter and Periodic Boundary Condition File.
Units: Specified by the user. ((length**2)/time).
Values: Greater than or equal to zero.
ADCIRC Variable: EVC
Elemental Slope Limiter
Nodal attribute name: elemental_slope_limiter
Description: This nodal attribute is used to selectively limit the maximum elevation gradient that can occur across an element, thus improving numerical stability. Alternatively, it is also capable of merely logging individual elements where a specified elemental slope is exceeded at some point during the simulation. When this nodal attribute is loaded, warning messages will be written to the screen and to the fort.16 log file whenever the elevation gradient meets or exceeds the threshold value for the first time at a particular node. Once the elevation gradient is met or exceeded at a node, the elemental slope limiter remains active at that node for the remainder of the ADCIRC run. When the elemental slope limiter is active at a node, the water surface elevation at that node is reset to the average of the water surface elevations of the surrounding nodes. At the end of the run, a file called ESLNodes.63 will be written to indicate the nodes where the threshold elevation gradient was met or exceeded. Furthermore, If there is an ESLNodes.63 file in the input directory when ADCIRC starts, ADCIRC will load the existing ESLNodes.63 file along with the hotstart file so that the simulation can pick up where it left off, in terms of the elements where the slope is actively limited. When such a simulation finishes, it will overwrite the existing ESLNodes.63 file with a new one that reflects the updated state of limited elemental slopes.
Units: length/length or unitless.
Values: Zero indicates that slope limiting is always active at that node, because a zero elevation gradient will always be met or exceeded; a positive value indicates the maximum gradient to be allowed at that node, at or beyond which the slope limiter is activated; a negative number indicates that the elevation gradients should be compared to the absolute value of the nodal attribute at this node. In the case of a negative number, ADCIRC will log a warning to the screen and to the fort.16 file the first time the elemental slope is exceeded, but ESLNodes.63 file will not be affected, and the elemental slope limiting will not actually occur at the node. A suggested value for this nodal attribute is 0.001.
ADCIRC Variable: elemental_slope_limiter_grad_max
Nodal attribute name: advection_state
Description: The advection_state nodal attribute is used to provide fine grained control over the NOLICA and NOLICAT parameters, so that they can be set on an element-by-element basis. The bathymetric depth at the three nodes of an element are compared to the corresponding nodal attribute values, and if the bathymetric depth at all three nodes is greater than or equal to the corresponding nodal attribute value, the values of NOLICA and NOLICAT will be set to the value indicated in the Model Parameter and Periodic Boundary Condition (fort.15) file. If the bathymetric depth at any of the three nodes of a particular element is less than the corresponding nodal attribute value, the values of NOLICA and NOLICAT will be set to zero on that element.
ADCIRC Variable: AdvectionState
Initial River Elevation
Nodal attribute name: initial_river_elevation
Description: The initial_river_elevation nodal attribute is used to set the initial water surface elevation in inland rivers that have some portion of the river bed above mean sea level as well as an upstream flux boundary condition. ADCIRC assumes by default that vertices that are above mean sea level (i.e., with negative depths) will be dry when the simulation starts. This assumption is violated when the elevation of a river bed is above mean sea level, and there is an upstream flux boundary. This nodal attribute is used in those cases to provide the initial water surface elevation of the river at cold start.
Requirement: Required only if the domain contains a river with an upstream flux boundary condition and a bed elevation above mean sea level.
ADCIRC Variable: Eta2.
Nodal attribute name: internal_tide_friction
Description: Linear friction term that accounts for energy conversion from barotropic modes to baroclinic modes as surface tides flow over steep and rough topography in the deep ocean generating internal tides.
Requirement: Important when simulating tides in computational domains that cover large portions of the deep ocean.
Values: Computed through analytical formulations that are spatially dependent on buoyancy frequencies and topographic gradients.
ADCIRC Variable: IT_Fric
Note: IT_Fric can have 1 (scalar) or 3 (tensor) dimensions. The scalar form dissipates equally in all flow directions. The tensor form dissipates asymmetrically to account for the fact that internal tides are generated as surface tides flow across topographic slopes but not along them.