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<br />lIlUell larger than the contraction loss, and losses from short abrupt <br />transitions are larger than losses from gradual transitions. The <br />transition loss is computed by multiplying a coefficient times the <br /> <br />absolute difference in velocity heads between cross sections. If <br /> <br /> <br />the values for the coefficients are being redefined to account for <br /> <br /> <br />contraction and expansion through a bridge, the new values are read on <br /> <br /> <br />the NC card prior to the section where the change in velocity head is <br /> <br /> <br />evaluated. Referring back to Figure 6, on a subcritica1 profile the <br /> <br /> <br />new values should be read in just before section 2 and changed back to <br /> <br /> <br />the original values after section 4. Typical values are shown below. <br /> <br />Coefficients <br /> <br />Expans i on <br /> <br />Contraction <br /> <br />No transition loss computed <br />Gradual transitions <br />dr1dge sections <br />Abrupt transitions <br /> <br />0.0 <br />0.3 <br />0.5' <br />0.8 <br /> <br />0.0 <br />0.1 <br />0.3 <br />0.6 <br /> <br />The maximum value for the expansion coefficient would be one (1.0). <br />Special Bridge Coefficients. When using the special bridge <br />routine, coefficients must be read in for the Yarnell equation, the <br />orifice equation, and the weir equation. The follOWing discussion pro- <br />vides suggested values and methods for estimating the required coeffi- <br /> <br />cients. <br /> <br />Pier Shape Coefficient XK is used in Yarnell's energy equation for <br /> <br />computing the change in water surface elevation through a bridge for <br /> <br />29 <br />