TAU0 - Revision history

Taylorgasher: category

2019-05-20T11:55:08Z

Taylorgasher: /* Nodal Attributes */ typo

2019-02-19T15:52:15Z

Nodal Attributes: typo

← Older revision		Revision as of 11:52, 19 February 2019
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	*<code>TAU0 >= 0</code>, <math>\tau_0</math> is constant in time and equal to [[primitive weighting in continuity equation]] values		*<code>TAU0 >= 0</code>, <math>\tau_0</math> is constant in time and equal to [[primitive weighting in continuity equation]] values
	*<code>TAU0 = -3, -6, or -7</code>, <math>\tau_0</math> varies in time and based on [[primitive weighting in continuity equation]] values		*<code>TAU0 = -3, -6, or -7</code>, <math>\tau_0</math> varies in time and based on [[primitive weighting in continuity equation]] values
	The [[min and max primitive weighting in continuity equation]] only works with [[TAU0 = -5]], details on it are below.		The [[min and max primitive weighting in continuity equation]] only works with <code>TAU0 = -5</code>, details on it are below.

	=== Positive TAU0 ===		=== Positive TAU0 ===

Taylorgasher: usage notes

2019-02-19T15:50:56Z

usage notes

← Older revision		Revision as of 11:50, 19 February 2019
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	'''<code>TAU0</code>''' is an input in the [[fort.15 file]] that influences the degree of numerical diffusion in ADCIRC's governing equations. Specifically, it influences the weighting factor that determines the relative contribution of the primitive and wave portions of the the Generalized Wave-Continuity Equation (GWCE). The weighting factor, <math>\tau_0</math>, is affected by values in both the [[fort.15 file]] and the [[fort.13 file]], if the [[primitive weighting in continuity equation]] or [[min and max primitive weighting in continuity equation]] nodal attributes are specified. This page addresses both the <code>TAU0</code> value in the fort.15 file and the <math>\tau_0</math> parameter more generally.		'''<code>TAU0</code>''' is an input in the [[fort.15 file]] that influences the degree of numerical diffusion in ADCIRC's governing equations. Specifically, it influences the weighting factor that determines the relative contribution of the primitive and wave portions of the the Generalized Wave-Continuity Equation (GWCE). The weighting factor, <math>\tau_0</math>, is affected by values in both the [[fort.15 file]] and the [[fort.13 file]], if the [[primitive weighting in continuity equation]] or [[min and max primitive weighting in continuity equation]] nodal attributes are specified. This page addresses both the <code>TAU0</code> value in the fort.15 file and the <math>\tau_0</math> parameter more generally.

	== ~~TAU0 Values~~ ==		== Parameter Summary ==
	Because the <code>TAU0</code> value specified in the fort.15 file can be either a flag (indicating how ADCIRC should operate) or the actual <math>\tau_0</math> value used in solving the GWCE, it is important to distinguish between the two. All negative <code>TAU0</code> are flags, all positive <code>TAU0</code> are <math>\tau_0</math>. Furthermore, some values are overridden by the [[primitive weighting in continuity equation]] nodal attribute. The following table is a summary of possible <code>TAU0</code> values and their meaning. Note that for <code>TAU0 = -x.1</code> (where <code>x</code> is an integer), behavior is the same as <code>-x</code>, but the <math>\tau_0</math> values are written to the [[fort.90 file]]. More on this below in [[TAU0#Outputting\|Outputting]].		Because the <code>TAU0</code> value specified in the fort.15 file can be either a flag (indicating how ADCIRC should operate) or the actual <math>\tau_0</math> value used in solving the GWCE, it is important to distinguish between the two. All negative <code>TAU0</code> are flags, all positive <code>TAU0</code> are <math>\tau_0</math>. Furthermore, some values are overridden by the [[primitive weighting in continuity equation]] nodal attribute. The following table is a summary of possible <code>TAU0</code> values and their meaning. Note that for <code>TAU0 = -x.1</code> (where <code>x</code> is an integer), behavior is the same as <code>-x</code>, but the <math>\tau_0</math> values are written to the [[fort.90 file]]. More on this below in [[TAU0#Outputting\|Outputting]].

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	=== Positive TAU0 ===		=== Positive TAU0 ===
	A positive value is ignored if the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file. For all positive values, the value specified in the fort.15 file is spatially and temporally constant and applied directly, i.e. <code>TAU0 = <math>\tau_0</math></code>. Practical guidance on setting a constant <code>TAU0</code> is provided below in [[#Selecting ~~Tau0~~\|Selecting ~~Tau0~~]]. Mathematically, the GWCE is a pure wave equation for <math>\tau_0=0</math>, and approaches a pure primitive equation as <math>\tau_0\rightarrow\infty</math>, however in practice, it behaves like a pure primitive equation once <math>\tau_0</math> reaches 1 or so.		A positive value is ignored if the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file. For all positive values, the value specified in the fort.15 file is spatially and temporally constant and applied directly, i.e. <code>TAU0 = <math>\tau_0</math></code>. Practical guidance on setting a constant <code>TAU0</code> is provided below in [[#Selecting Values\|Selecting Values]]. Mathematically, the GWCE is a pure wave equation for <math>\tau_0=0</math>, and approaches a pure primitive equation as <math>\tau_0\rightarrow\infty</math>, however in practice, it behaves like a pure primitive equation once <math>\tau_0</math> reaches 1 or so.

	=== Negative TAU0 ===		=== Negative TAU0 ===
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	For <code>TAU0 = -3, -5, -6, or -7</code>, <math>\tau_0</math> is updated (via the <code>CalculateTimeVaryingTau0</code> subroutine) in space and in time. An initial "update" is done when the model starts. After this, updates are done only after a time step in which there is a change in wet/dry state somewhere in the model domain. For use cases that contain large number of nodes near the wet/dry boundary, this can be the equivalent of updating every time step. However, for use cases that have little or no wet/dry changes, '''there may be little or no updating'''. The rules listed above in [[TAU0#TAU0 Values\|TAU0 Values]] are applied during the update. Each node's <math>\tau_0</math> is then spatially averaged with all immediate neighbors. Time-averaging (for <code>TAU0 = -6 or -7</code>) is applied last.		For <code>TAU0 = -3, -5, -6, or -7</code>, <math>\tau_0</math> is updated (via the <code>CalculateTimeVaryingTau0</code> subroutine) in space and in time. An initial "update" is done when the model starts. After this, updates are done only after a time step in which there is a change in wet/dry state somewhere in the model domain. For use cases that contain large number of nodes near the wet/dry boundary, this can be the equivalent of updating every time step. However, for use cases that have little or no wet/dry changes, '''there may be little or no updating'''. The rules listed above in [[TAU0#TAU0 Values\|TAU0 Values]] are applied during the update. Each node's <math>\tau_0</math> is then spatially averaged with all immediate neighbors. Time-averaging (for <code>TAU0 = -6 or -7</code>) is applied last.

	== Selecting ~~Tau0~~ ==		== Selecting Values ==
	For positive values (<code>TAU0=<math>\tau_0</math></code>), a good rule of thumb for setting <code>TAU0</code> is to set it equal to the largest value of an equivalent linear friction factor: for linear friction <code>TAU0 = [[TAU]]</code>; for quadratic friction <code>TAU0 = max(speed*Cd/depth)</code>. Typical values for <code>TAU0</code> are in the range of 0.005 – 0.1.

	<code>TAU0 = -3</code>, paired with the [[primitive weighting in continuity equation]] nodal attribute is generally the most popular formulation. In this case, <code>TAU0Base</code> nodal attribute values can be generated with the ADCIRC utility program tau0_gen.f. The program bases generation on the following logic applied to each node individually:		<code>TAU0 = -3</code>, paired with the [[primitive weighting in continuity equation]] nodal attribute is generally the most popular formulation. In this case, <code>TAU0Base</code> nodal attribute values can be generated with the ADCIRC utility program tau0_gen.f. The program bases generation on the following logic applied to each node individually:
	*<code>If the avg. dist. to neighboring nodes < 1750 m; then TAU0Base = 0.03</code>		*<code>If the avg. dist. to neighboring nodes < 1750 m; then TAU0Base = 0.03</code>
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	**<code>If depth < 10m; then TAU0Base = 0.02</code> (<code>TAU0</code> is constant in time)		**<code>If depth < 10m; then TAU0Base = 0.02</code> (<code>TAU0</code> is constant in time)
	**<code>If depth > 10m; then TAU0Base = 0.005</code> (<code>TAU0</code> is constant in time)		**<code>If depth > 10m; then TAU0Base = 0.005</code> (<code>TAU0</code> is constant in time)
			<math>\tau_0</math> needs to be smaller in deeper water where there is little dissipation, and can also be sensitive to mesh resolution. The spatial variation, spatial smoothing, and physics-driven time-updating typically allow for a good balance between stability and conservation.

			For manually-specified positive values (<code>TAU0=<math>\tau_0</math></code>), a good rule of thumb for setting <code>TAU0</code> is to set it equal to the largest value of an equivalent linear friction factor: for linear friction <code>TAU0 = [[TAU]]</code>; for quadratic friction <code>TAU0 = max(speed*Cd/depth)</code>. Typical values for <code>TAU0</code> are in the range of 0.005 – 0.1.

	== Outputting ==		== Outputting ==
	For <code>TAU0</code> formulations that vary spatially or temporally, ADCIRC can output the internally-calculated nodal <math>\tau_0</math> values. They are written to the [[fort.90 file]], which has the same format and output frequency as the water surface elevation output file ([[fort.63]]). fort.90 output is activated by placing a 1 in the tenths place of <code>TAU0</code> in the fort.15 file. For example, if <code>TAU0 = -3.1</code>, the calculation of <math>\tau_0</math> is still carried out according to the description of <code>TAU0 = -3</code> above, and the fort.90 output file will also be produced.		For <code>TAU0</code> formulations that vary spatially or temporally, ADCIRC can output the internally-calculated nodal <math>\tau_0</math> values. They are written to the [[fort.90 file]], which has the same format and output frequency as the water surface elevation output file ([[fort.63]]). fort.90 output is activated by placing a 1 in the tenths place of <code>TAU0</code> in the fort.15 file. For example, if <code>TAU0 = -3.1</code>, the calculation of <math>\tau_0</math> is still carried out according to the description of <code>TAU0 = -3</code> above, and the fort.90 output file will also be produced.

Taylorgasher: Even more done

2019-02-19T14:47:17Z

Even more done

← Older revision		Revision as of 10:47, 19 February 2019
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	\|-		\|-
	! style="font-weight:bold;" \| Varies in space		! style="font-weight:bold;" \| Varies in space
	\| style="background-color:#fffc9e;" \| no		\| style="background-color:#fffc9e;" \| no (mostly)
	\| style="background-color:#ffce93;" \| yes		\| style="background-color:#ffce93;" \| yes
	\| style="background-color:#ffce93;" \| yes		\| style="background-color:#ffce93;" \| yes

Taylorgasher: Done

2019-02-19T14:44:20Z

Done

← Older revision		Revision as of 10:44, 19 February 2019
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	\|-		\|-
	! style="font-weight:bold;" \| [[min and max primitive weighting in continuity equation]]		! style="font-weight:bold;" \| [[min and max primitive weighting in continuity equation]]
	\| ~~discouraged~~		\| no
	\| ~~discouraged~~		\| no
	\| ~~discouraged~~		\| no
	\| ~~discouraged~~		\| no
	\| yes		\| yes
	\| ~~discouraged~~		\| no
	\| ~~discouraged~~		\| no
	\|-		\|-
	! style="font-weight:bold;" \| Minimum		! style="font-weight:bold;" \| Minimum
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	*<code>TAU0 >= 0</code>, <math>\tau_0</math> is constant in time and equal to [[primitive weighting in continuity equation]] values		*<code>TAU0 >= 0</code>, <math>\tau_0</math> is constant in time and equal to [[primitive weighting in continuity equation]] values
	*<code>TAU0 = -3, -6, or -7</code>, <math>\tau_0</math> varies in time and based on [[primitive weighting in continuity equation]] values		*<code>TAU0 = -3, -6, or -7</code>, <math>\tau_0</math> varies in time and based on [[primitive weighting in continuity equation]] values
			The [[min and max primitive weighting in continuity equation]] only works with [[TAU0 = -5]], details on it are below.

	=== Positive TAU0 ===		=== Positive TAU0 ===

Taylorgasher: Reorganizing againagainagainagainagain

2019-02-19T14:31:25Z

Reorganizing againagainagainagainagain

← Older revision		Revision as of 10:31, 19 February 2019
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	\| style="background-color:#ffce93;" \| yes		\| style="background-color:#ffce93;" \| yes
	\|-		\|-
	! style="font-weight:bold;" \| ~~Expects nodal attribute~~		! style="font-weight:bold;" \| [[primitive weighting in continuity equation]]
	\| ~~style="background-color:#fffc9e;"~~ \| no		\| yes
	\| ~~style="background-color:#fffc9e;"~~ \| no		\| discouraged
	\| ~~style="background-color:#fffc9e;"~~ \| no		\| discouraged
	\| style="~~background~~-~~color~~:~~#ffce93~~;" \| ~~yes~~		\| yes
	\| ~~style="background-color:#ffce93;"~~ \| ~~yes~~		\| discouraged
	\| ~~style="background-color:#ffce93;"~~ \| yes		\| yes
	\| ~~style="background-color:#ffce93;"~~ \| ~~yes~~		\| yes
			\|-
			! style="font-weight:bold;" \| [[min and max primitive weighting in continuity equation]]
			\| discouraged
			\| discouraged
			\| discouraged
			\| discouraged
			\| yes
			\| discouraged
			\| discouraged
	\|-		\|-
	! style="font-weight:bold;" \| Minimum		! style="font-weight:bold;" \| Minimum
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	=== Nodal Attributes ===		=== Nodal Attributes ===
	The [[primitive weighting in continuity equation]] nodal attribute permits a spatially variable <math>\tau_0</math>~~. Whether or not~~ the ~~value varies in time depends on <code>TAU0</code>~~.		The [[primitive weighting in continuity equation]] nodal attribute permits a spatially variable <math>\tau_0</math> that is (at least initially) set equal to the nodal attribute values.
	*<code>TAU0 >= 0</code> and ~~the~~ [[primitive weighting in continuity equation]] ~~nodal attribute is specified in the fort.15 file~~, <math>\tau_0</math> ~~is set equal to the nodal attribute~~ values.		*<code>TAU0 >= 0</code>, <math>\tau_0</math> is constant in time and equal to [[primitive weighting in continuity equation]] values
			*<code>TAU0 = -3, -6, or -7</code>, <math>\tau_0</math> varies in time and based on [[primitive weighting in continuity equation]] values

	=== Positive ~~values~~ ===		=== Positive TAU0 ===
	A positive value is ignored if the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file. For all positive values, the value specified in the fort.15 file is spatially and temporally constant and applied directly, i.e. <code>TAU0 = <math>\tau_0</math></code>. Practical guidance on setting a constant <code>TAU0</code> is provided below in [[#Selecting Tau0\|Selecting Tau0]]. Mathematically, the GWCE is a pure wave equation for <math>\tau_0=0</math>, and approaches a pure primitive equation as <math>\tau_0\rightarrow\infty</math>, however in practice, it behaves like a pure primitive equation once <math>\tau_0</math> reaches 1 or so.		A positive value is ignored if the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file. For all positive values, the value specified in the fort.15 file is spatially and temporally constant and applied directly, i.e. <code>TAU0 = <math>\tau_0</math></code>. Practical guidance on setting a constant <code>TAU0</code> is provided below in [[#Selecting Tau0\|Selecting Tau0]]. Mathematically, the GWCE is a pure wave equation for <math>\tau_0=0</math>, and approaches a pure primitive equation as <math>\tau_0\rightarrow\infty</math>, however in practice, it behaves like a pure primitive equation once <math>\tau_0</math> reaches 1 or so.

	=== Negative ~~Values~~ ===		=== Negative TAU0 ===
	Unexpected behavior may arise if a mismatching nodal attribute is specified alongside one of these values, and this is discouraged. <br/>		Unexpected behavior may arise if a mismatching nodal attribute is specified alongside one of these values, and this is discouraged. <br/>
	''Spatially varying, temporally constant''<br/>		''Spatially varying, temporally constant''<br/>

Taylorgasher: temp2

2019-02-19T14:18:07Z

temp2

← Older revision		Revision as of 10:18, 19 February 2019
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	\|}		\|}

	~~'''Positive values'''~~<br/>		=== Nodal Attributes ===
			The [[primitive weighting in continuity equation]] nodal attribute permits a spatially variable <math>\tau_0</math>. Whether or not the value varies in time depends on <code>TAU0</code>.
			*<code>TAU0 >= 0</code> and the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file, <math>\tau_0</math> is set equal to the nodal attribute values.


			=== Positive values ===
	A positive value is ignored if the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file. For all positive values, the value specified in the fort.15 file is spatially and temporally constant and applied directly, i.e. <code>TAU0 = <math>\tau_0</math></code>. Practical guidance on setting a constant <code>TAU0</code> is provided below in [[#Selecting Tau0\|Selecting Tau0]]. Mathematically, the GWCE is a pure wave equation for <math>\tau_0=0</math>, and approaches a pure primitive equation as <math>\tau_0\rightarrow\infty</math>, however in practice, it behaves like a pure primitive equation once <math>\tau_0</math> reaches 1 or so.		A positive value is ignored if the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file. For all positive values, the value specified in the fort.15 file is spatially and temporally constant and applied directly, i.e. <code>TAU0 = <math>\tau_0</math></code>. Practical guidance on setting a constant <code>TAU0</code> is provided below in [[#Selecting Tau0\|Selecting Tau0]]. Mathematically, the GWCE is a pure wave equation for <math>\tau_0=0</math>, and approaches a pure primitive equation as <math>\tau_0\rightarrow\infty</math>, however in practice, it behaves like a pure primitive equation once <math>\tau_0</math> reaches 1 or so.

	~~'''~~Negative Values~~'''<br/>~~		=== Negative Values ===
	Unexpected behavior may arise if a mismatching nodal attribute is specified alongside one of these values, and this is discouraged.		Unexpected behavior may arise if a mismatching nodal attribute is specified alongside one of these values, and this is discouraged. <br/>
	''Spatially varying, temporally constant''<br/>		''Spatially varying, temporally constant''<br/>
	*<code>TAU0 >= 0</code> and the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file, <math>\tau_0</math> is set equal to the nodal attribute values.
	*<code>TAU0 = -1</code>, <math>\tau_0</math> is computed as follows:		*<code>TAU0 = -1</code>, <math>\tau_0</math> is computed as follows:
	**<code>If depth >= 10; then <math>\tau_0</math> = 0.005</code>		**<code>If depth >= 10; then <math>\tau_0</math> = 0.005</code>

Taylorgasher at 14:00, 19 February 2019

2019-02-19T14:00:10Z

← Older revision		Revision as of 10:00, 19 February 2019
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	'''Negative Values'''<br/>		'''Negative Values'''<br/>
			Unexpected behavior may arise if a mismatching nodal attribute is specified alongside one of these values, and this is discouraged.
	''Spatially varying, temporally constant''<br/>		''Spatially varying, temporally constant''<br/>
	~~Unexpected behavior may arise if nodal attributes are specified alongside one of these values, and this is discouraged.~~
	*<code>TAU0 >= 0</code> and the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file, <math>\tau_0</math> is set equal to the nodal attribute values.		*<code>TAU0 >= 0</code> and the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file, <math>\tau_0</math> is set equal to the nodal attribute values.
	*<code>TAU0 = -1</code>, <math>\tau_0</math> is computed as follows:		*<code>TAU0 = -1</code>, <math>\tau_0</math> is computed as follows:

Taylorgasher at 13:59, 19 February 2019

2019-02-19T13:59:08Z

← Older revision		Revision as of 09:59, 19 February 2019
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	'''Negative Values'''<br/>		'''Negative Values'''<br/>
	''Spatially varying, temporally constant''		''Spatially varying, temporally constant''<br/>
	Unexpected behavior may arise if nodal attributes are specified alongside one of these values, and this is discouraged.		Unexpected behavior may arise if nodal attributes are specified alongside one of these values, and this is discouraged.
	*<code>TAU0 >= 0</code> and the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file, <math>\tau_0</math> is set equal to the nodal attribute values.		*<code>TAU0 >= 0</code> and the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file, <math>\tau_0</math> is set equal to the nodal attribute values.

Taylorgasher: Added vague info about weird nodal attribute interactions with TAU0

2019-02-19T13:58:38Z

Added vague info about weird nodal attribute interactions with TAU0

← Older revision		Revision as of 09:58, 19 February 2019
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	'''Negative Values'''<br/>		'''Negative Values'''<br/>
	''Spatially varying, temporally constant''		''Spatially varying, temporally constant''
			Unexpected behavior may arise if nodal attributes are specified alongside one of these values, and this is discouraged.
			*<code>TAU0 >= 0</code> and the [[primitive weighting in continuity equation]] nodal attribute is specified in the fort.15 file, <math>\tau_0</math> is set equal to the nodal attribute values.
	*<code>TAU0 = -1</code>, <math>\tau_0</math> is computed as follows:		*<code>TAU0 = -1</code>, <math>\tau_0</math> is computed as follows:
	**<code>If depth >= 10; then <math>\tau_0</math> = 0.005</code>		**<code>If depth >= 10; then <math>\tau_0</math> = 0.005</code>

← Older revision		Revision as of 10:47, 19 February 2019
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	\|-		\|-
	! style="font-weight:bold;" \| Varies in space		! style="font-weight:bold;" \| Varies in space
	\| style="background-color:#fffc9e;" \| no		\| style="background-color:#fffc9e;" \| no (mostly)
	\| style="background-color:#ffce93;" \| yes		\| style="background-color:#ffce93;" \| yes
	\| style="background-color:#ffce93;" \| yes		\| style="background-color:#ffce93;" \| yes

← Older revision		Revision as of 07:55, 20 May 2019
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	== Outputting ==		== Outputting ==
	For <code>TAU0</code> formulations that vary spatially or temporally, ADCIRC can output the internally-calculated nodal <math>\tau_0</math> values. They are written to the [[fort.90 file]], which has the same format and output frequency as the water surface elevation output file ([[fort.63]]). fort.90 output is activated by placing a 1 in the tenths place of <code>TAU0</code> in the fort.15 file. For example, if <code>TAU0 = -3.1</code>, the calculation of <math>\tau_0</math> is still carried out according to the description of <code>TAU0 = -3</code> above, and the fort.90 output file will also be produced.		For <code>TAU0</code> formulations that vary spatially or temporally, ADCIRC can output the internally-calculated nodal <math>\tau_0</math> values. They are written to the [[fort.90 file]], which has the same format and output frequency as the water surface elevation output file ([[fort.63]]). fort.90 output is activated by placing a 1 in the tenths place of <code>TAU0</code> in the fort.15 file. For example, if <code>TAU0 = -3.1</code>, the calculation of <math>\tau_0</math> is still carried out according to the description of <code>TAU0 = -3</code> above, and the fort.90 output file will also be produced.

			[[Category:nodal attributes]]