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Enhancements and Modifications to the Full Equations (FEQ) 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.
Input description update for section
13.6, Network-Matrix Control Block-- Network-Matrix Table, Code5 (Two-node
head-discharge relations), Franz and Melching (1997a), p. 174
Section 13.6 Network-Matrix Control
Block--Network-Matrix Table, Code 5
To
RELEASE.TXT
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If TYPE3
(Variable-speed variable-head pump): |
|
N(5) is
the flow direction: 1 means pumping from upstream
node to downstream node; -1 means pumping from downstream node to upstream
node. The node from which water is being drawn is called the source node
and the node to which water is being pumped is called the destination node. |
|
N(6) is
the table number of table giving the flow through
the pump for each head, that is, a pump performance curve. The speed of
the pump used to define this curve is the base speed to which all
speeds are relative. This should be the highest speed for the pump so that
all other speeds are smaller. For example, if a pump has a speed range
from 0 to 1800 revolutions per minute (rpm), then 1800 rpm should be used
to define the head across the pump. A relative speed of 0.5 then means
that the pump is operating at 900 rpm. The relationship between flow through
the pump and head must be unique. Pumps exist for which this is not true,
that is, they have ranges of flow for which the head increases as the flow
increases followed by a decreasing head with increasing flow. For a given
head, there are two different flows. These pumps could prove to be unstable
if used for pumping in an open channel network. They could also prove unstable
in simulation using FEQ and therefore, the representation of the pump performance
in FEQ requires that their pump curve be modified to render them stable
when used in an open channel network. |
|
N(7) is
the table number of table giving the sum of the
entrance losses at the inlet, friction losses in the inlet conduit, and
friction losses in the outlet conduit. The sum is expressed in terms of
head as a function of flow through the pump. FEQ assumes that these losses
will increase with flow. This table is optional and if omitted, the losses
are assumed to be included in the pump performance curve table given in
N(5). |
|
N(8) is
the table number of table giving the exit loss
coefficient on the velocity head difference between the end of the outlet
conduit and the destination node. This coefficient is given as a function
of the depth of submergence of the outlet conduit. The loss coefficient
must be 1.0 at zero submergence. If this table is omitted, FEQ uses an
exit loss coefficient of 1.0 for all levels of submergence. |
|
N(9)0
gives the table number for the table specifying the pump speed as a function
of time. N(9)0
gives the operation block number controlling the pump. N(9)0
keeps the pump running at its base speed all the time. Water will not be
pumped if the water-surface elevation at the source node is below the inlet
elevation. If N(9)0
and N(9)the
maximum number of operation blocks, then FEQ treats the value of N(9)
as
a table number for selection of the operation block. This permits FEQ to
model operation rules that vary with the season of the year. The operation-block
selection table is a time-series table of type 7. The function value is
a block number. Block numbers are integers but the table treats them as
real numbers in its operations. The result of a table-lookup is rounded
to the nearest integer to yield the current operation block number for
control of the structure. The maximum number of operation blocks is contained
in the value MNBLK
in
the file ARSIZE.PRM.
Its value is also printed near the top of the output file from FEQ. This
number is typically 50 so that any table number greater than 50 will be
treated as if it were an operation-block selection table. |
|
N(10) is
the optional name for the pump. The name can
be four alpha-numeric character at most. The first character should be
alphabetic. A name given for the pump permits having its state printed
in the Special Output file by giving the name in the field as for an exterior
node in the Special Output Block. In this case the state of the pump includes
its relative speed, and the nature of flow: NO H2O-denotes that the pump
is on but the inlet is above water; FP-denotes free flow out of the pump
outlet; SP-denotes submerged flow out of the pump outlet; and OFF-denotes
that the pump is currently not running. |
|
F(1) is
the elevation of the outlet conduit. Point of
reference
for submergence of the outlet. If the water surface elevation at the destination
node is below this elevation, FEQ assumes that the exit velocity head from
the outlet conduit is a loss. If the water surface elevation at the destination
node is greater than this elevation, FEQ looks up a loss coefficient in
the table in N(8),
if it exists, or takes 1.0 if it does not, and uses the loss coefficient
to compute the fraction of the velocity head difference between the exit
and the destination node to use as an exit loss. The argument to the table
is the depth of submergence computed relative to the elevation of the outlet
conduit. |
|
F(2) is
the area of the outlet conduit when flowing full.
FEQ assumes that the pump will keep the outlet conduit flowing full at
all pump speeds. |
|
F(3) is
the elevation of the inlet conduit. Pump flow
is zero if the water-surface elevation is below the inlet. |
|
F(4) is
the factor on the velocity head at the source
node. Usually 0 or 1 to exclude or include the velocity head at the source
node. FEQ will force this factor to 0 if the source node is a free node. |
|
F(5) is
the factor on velocity head at the destination
node. Usually 0 or 1 to exclude or include the velocity at the destination
node. FEQ will force this factor to 0 if the destination node is a free
node. |
|
Discussion: This network-matrix control
option is designed to represent a variable-speed variable-head pump. If
the head on the pump exceeds its cutoff head, the flow through the pump
will reverse if a check valve of some kind does not exist in the outflow
conduit. The pump characteristic table determines if reverse flow is to
be allowed. In most cases check valves are provided, and reverse flows
are not allowed. If this is the case, the table given in N(6),
must be extended to a head higher, and sometimes much higher, than any
expected with flow through the pump set to zero in the extension. |
Back
to Franz and Melching (1997a), section 13.6 Network-Matrix Control Block--
Network-Matrix Table, Code 5, Type 4, p. 175