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Full Equations Utilities (FEQUTL) Model for the Approximation
of Hydraulic Characteristics of Open Channels and Control
Structures During Unsteady Flow

Purpose: A reasonable estimate of the maximum flow in a closed conduit when the conduit is flowing full is computed in the QCLIMIT command for defining the free-flow limit for the EXPCON command (section 5.7). Critical flow is used in EXPCON to determine the location of a control, but when a closed conduit is flowing full, critical flow is undefined. Therefore, some reasonable flow must be set as the maximum possible so that EXPCON can be used with closed conduits. QCLIMIT should be utilized for each closed-conduit cross section appearing in the EXPCON command.

LINE 1

Variable: TABLE

Format: 7X, I5

Example: TABLE *#=* 291

Explanation:

TABLE is the table number of the cross-section table to be limited by critical flow. This table must already have been input to FEQUTL with the FTABIN command (section 5.13) or have been saved with SAVE22 or SAVE25 on a previous computation for a closed conduit (sections 5.16, 5.17, and 5.19). The table must be of type 22 or 25. |

Variable: FACTOR

Format: A7, F10.0

Example: FACTOR

Explanation:

FACTOR is a multiplying factor to change the limiting value
from that given by the built-in
extrapolation. The limiting value is computed in QCLIMIT
assuming that the logarithm of critical flow and the logarithm
of water-surface height are linearly related. The two
topwidths in the closed conduit that are closest to the
hypothetical slot at the top of the conduit are detected and
utilized for extrapolation. Critical flow is undefined in a
closed conduit. The critical flow produced with the top width
of the hypothetical slot is so large that the computations in
EXPCON will be nonsensical to applications. EXPCON |

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