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[FEQUTL Update Contents]
Enhancements and Modifications to the Full Equations Utilities (FEQUTL)
Model, March 1995 to August 1999.
Note: This document is separate from the U.S. Geological Survey report by Franz and Melching (1997). This description of enhancements and modifications to the Full Equations Utilities Model has not been approved by the Director of the U.S. Geological Survey.
New subsection for section
5. Input Description for the Full Equations Utilities Model: Version 4.0,
Franz and Melching (1997b), p. 136
Section 5.17a ORIFICE Command
To
RELEASE.TXT
ORIFICE COMMAND
Purpose:
ORIFICE computes a 2-D table of Type 13 for flow
through a vertical orifice using the basic principles of orifice and weir
flow as outlined in Section 4.0, Approximation of Hydraulic Characteristics
of Control Structures.
LINE 1
Variable:
TAB |
|
Format:
7X, I5 |
|
Example:
TABLE#= 527 |
|
Explanation: |
Gives the table number of the type
13 table to be created. |
LINE 2
Variable:
LABEL |
|
Format:
6X, A50 |
|
Example:
LABEL= Bleed down at Alligator
Lakes Dam
Explanation: |
Gives a descriptive label for the
table of type 13. |
LINE 3
Variable: |
HEAD |
Format: |
A80 |
Example: |
Numbr Shape Edge
VertD HoriD Invrt OrifC WeirC |
Explanation: |
Provides descriptive heading for information
to follow. The example heading given should be used without change to provide
compatibility with any future changes. |
LINE 4
Variables: |
Numbr, Shape, Edge,
VertD, HoriD, Invrt, OrifC, WeirC |
Format: |
I6, 2A6, 5F6.0 |
Example: |
1 CIRC SHARP
2.0 2.0 5.0 0.60 0.58 |
Explanation: |
All input fields are 6 columns wide
and COLUMNS ARE IMPORTANT. No part of any input item should fall outside
of its field. Note that the headings define the field width. For example,
the first column of the field for the vertical diameter of the orifice,
VertD,
starts in the column following the heading word, Edge,
and ends in the column under the D
in
VertD. |
|
Numbr is
the number of identical barrels that are to be
included in the computations. |
|
Shape is
the
shape of the orifice opening. CIRCLE,
CIRC,
and ROUND designate
a circular orifice. RECT designates
a rectangular opening. INVTRI or
TRI
designate
a symmetrical triangular opening with the apex of the triangle forming
the invert of the opening. OTHER
or
ODD
designates
shapes defined by a user supplied function table. The number of this table
appears in the field, OriTb.
The table gives the width of the opening relative to the vertical diameter
and at distances from the invert expressed relative to the vertical diameter.
An example appears below. |
|
Edge gives
the nature of the edge on the orifice. Currently the only option is SHARP
to
indicate a sharp-edged orifice. All the computations are done using equations
related to a sharp-edged orifice. However, none of the coefficients are
built into the command so that the user can effectively represent any edge
configuration by selecting the correct coefficient. For example, if the
edge of the orifice is rounded, a coefficient of 0.9 for the orifice flow
might be a better value than the sharp-edged value of about 0.6. |
|
VertD is
the vertical diameter for the orifice, that is,
the maximum vertical distance in the orifice opening. |
|
HoriD is
the horizontal diameter for the orifice, that
is, the maximum horizontal distance from one edge of the opening to the
other. May be omitted if Shape is any one of CIRC,
ROUND,
or CIRCLE. |
|
Invrt is
the elevation of the invert of the orifice, that
is, the lowest point in the opening. |
|
OrifC is
the effective discharge coefficient for orifice
flow. Values close to 0.6 apply approximately to wide range of shapes when
the edge of the orifice is away from any boundary by more than the half-diameter
of the orifice and the edge is sharp and has no rounding or beveling of
its upstream edge. |
|
WeirC is
the coefficient for weir flow expressed in dimensionless
terms. A value of 0.58 is a good estimate for both rectangular and triangle
weirs. Values close to 0.60 are good estimates for a circular weir. See
Chapter 4 of the FEQUTL documentation for references. |
LINE 5
Variable: |
HEAD |
Format: |
A80 |
Example: |
AppTb OriTb MxZup MnHup
MxPFD MnPFD LIPrc |
Explanation: |
Provides descriptive heading for information
to follow. The example heading given should be used without change to provide
compatibility with any future changes. |
LINE 6
Variables: |
AppTb, OriTb, MxZup,
MnHup, MxPFD, MnPFD, LIPrc |
Format: |
10F6.0 |
Example: |
20.0 0.100 0.980 .0050
0.020 |
Explanation: |
AppTb is
the identification number for the cross section
function table that describes the approach channel for the orifice. This
input item is optional and can be left blank as in the example above. It
is only needed if the orifice opening is a large fraction of the approach
channel flow area. The correction for velocity head is only an approximation
and may not be adequate if the velocity head is large. The orifice relationships
are intended to approach Froude numbers less than about 0.5 and usually
much less than this value. |
|
OriTb is
the identification number for the function table
of type 2, 3, or 4 that gives the relative width of the opening as a function
of the relative height in the opening. The width is taken relative to the
vertical diameter given on line 4 and the height is taken relative to the
vertical diameter as given on line 4. |
|
MxZup is
the maximum elevation that will not be exceeded
by the water level upstream of the orifice. Determines the maximum head
used in creating the 2-D table of type 13 describing the flow through the
orifice. |
|
MnHup is
the minimum positive head to use at the orifice
for computing flows. This value should not be too small nor too large.
A value of 0.01 feet is too small and 1.0 foot is too large. A value in
the range of .05 to 0.1 of the orifice vertical diameter is suitable. The
minimum positive head must not be greater than 0.125 of the vertical diameter.
If it is, the ORIFICE
command
replaces it with 0.125D, where D is the vertical diameter of the orifice. |
|
MxPFD is
the maximum partial free drop that is less than
1.0. This value should be in the range of 0.9 to 0.99. This value is used
to define the spacing of points for interpolation of submerged flows for
a given upstream head. |
|
MnPFD is
the minimum positive partial free drop. This
value is used with MxPFD
andLIPrc
to
define the spacing of points for interpolation of submerged flows. Values
in the range of 0.005 to 0.01 are generally adequate. |
|
LIPrc is
the linear interpolation precision that defines
an approximate relative error when interpolating a power function with
a piecewise linear continuous function, that is, a linear spline. See page
A-65 in the FEQUTL input description for more details. Values are in terms
of relative error. Values in the range of 0.001 to 0.10 are defined by
special tables in the file, TYPE5.TAB,
read by FTABIN above.
Values in the range of .01 to .06 probably are adequate. |
Notes: The above cards with the command, ORIFICE,
are repeated for each orifice. If there are 100 orifices then there will
be 100 occurrences of the ORIFICE
command
in the input, each followed by the six lines of input as described above.
Each orifice must have a unique id number for its 2-D table.
Back
to Franz and Melching (1997) p. 91, for CULVERT command section 5.5
To
update for new section 4.7a, Flow in Orifices