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<br />Flows less than 5,000 ft'/s (3.6 ft'ls model) were supplied by a portable pump and measured with <br />a Venturi orifice meter and a differential mercury manometer. For t10ws exceeding 5,000 ft'ls, <br />water was delivered to the model by the laboratory control supply and measurement system. <br /> <br />Velocity measurements were taken using Marsh McBirney electromagnetic flowmeters and Ott <br />current meters. Surface velocities and directions were obtained by taking time lapse pictures of <br />model boats traversing the area. <br /> <br />Hydraulic Similitude <br /> <br />Hydraulic similitude must exist between model and prototype to obtain accurate flow measurements <br />in the model. The inertial force is the vector sum of all forces. When gravitational forces <br />predominate, which is the case with most open channel hydraulic structures, a basis for similitude <br />can be established by equating the ratio of gravitational forces to inertial forces and neglecting the <br />other forces. Flow in the model was simulated by using the dimensionless Froude number which <br />relates inertial force to gravity force. <br /> <br />V <br /> <br />(1) <br /> <br />F, = <br />~ <br /> <br />Using the Froude number, model and prototype parameters can be determined from the following <br />similitude equations: <br /> <br />L, = Lp 18 (2) <br /> = <br /> Lm <br /> 2 <br />A, = L, = 324 (3) <br /> <br /> , <br />V" = L, = 5,832 <br /> 1/2 <br />T, = L, = 4.24 <br /> 1/2 <br />V, = L, = 4.24 <br /> 5/2 <br />Q, = (L,) = 1,375 <br /> <br />(3) <br /> <br />(5) <br /> <br />(5) <br /> <br />(7) <br /> <br />3 <br />