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S�® Citi 9s ENGINEERING REFF-RCNCE MANUAL <br /> Tabla 19.10 Minor Entrance Loss Coefficients D. Type-4 Flow <br /> i As in type-3 flow, the backwater elevation is the Coo- <br /> k' condition of entrance trolling factor in this case. Critical depth cannot occur <br /> and the upstream water surface elevation for a given <br /> 0.08 smooth, tapered discharge is a function of the tailwater elevation. Dis- <br /> 0.10 flush concrete groove <br /> 0.10 flush concrete bell charge is independent of barrel slope. The culvert is <br /> 0.15 projecting concrete groove submerged at both the headwater and the tailwater. No <br /> �. II 0.15 projecting concrete bell differentiation between low head and high head.is made <br /> 0.50 flush, square-edged for this case. If the velocity head at section 1 (the en- <br /> 0.90 projecting, square-edged trance), the entrance friction loss, and the exit friction <br /> I� loss are neglected, the discharge can be calculated. Ar) <br /> +� A. Type-i Flow is the culvert area. <br /> Water passes through the critical depth near the culvert <br /> f entrance, and the culvert flows partially full. The slope <br /> of-the culvert barrel is greater than the critical slope, Q—CdAo 2 hl —h4 i9 104 <br /> and the tailwater elevation is less than the elevation of g 29Cdn2L <br /> the water surface at the control section. 1 R4/3 <br /> The discharge is <br /> The complicated term in the denominator corrects for <br /> ave friction. For rough estimates and for culverts less than <br /> i Q =CdA �29 + hl —z+ 29 —d.—h,f,1_21 19.101 50 ft long, the friction loss can be ignored. <br /> t Q=CdA,, 2g(hl —h4) 19.905 <br /> The area, A, used in the discharge equation is not the <br /> culvert area since the culvert does not flow full. A, is <br /> the area in flow at the critical section. E. Type-5 Flow <br /> B. Type.2 Flow Partially full flow under a high head is classified as <br /> As in type-1 flow,flow passes through the critical depth type-5 flow. The flow pattern is similar to the flow <br /> at the culvert outlet, and the barrel flows partially full. downstream from a sluice gate, with rapid flow near <br /> The slope of the culvert is less than critical, and the the entrance. Usually, type-5 flow requires a relatively <br /> tailwater elevation does not exceed the elevation of the square entrance that causes contraction of the flow area <br /> Nvater surface at the control section. to less than the culvert area. In addition, the barrel <br /> length, roughness, and bed slope must"be sufficient to <br /> w2 f,l-2— f�2-3J <br /> l keep the velocity high throughout the culvert. <br /> Q— d l +1 <br /> C A, 2g (h -do—h h It is difficult to distinguish in advance between type- <br /> 2g <br /> 19.102 5.and type-6 flow. Within a range of the importaait <br /> t parameters, either flow can occur.2e A. is the culvert, <br /> The area, A, used in the discharge equation is not the area. <br /> culvert area since the culvert does not flow full. A, is Q= CdAa 2g(hl —z) 19.106 <br /> the area in flow at the critical section. <br /> C. Type-3 Flow F Type-6 Flow <br /> I When backwater is the controlling factor in culvert flow, Type-6 flow, like type-5 flow, is considered a high-head <br /> i the critical depth cannot occur. The upstream water- flow. The culvert is full under pressure with free outfall. <br /> surface elevation for a given discharge is a function of The discharge is <br /> the height of the tailwater. For type-3 flow, flow is <br /> subcritical for the entire length of the culvert,with the C 19.107 <br /> flow being partial. The outlet is not submerged,but the Q= dAo 2g(hl —h3—h f 2_3) <br /> tailwater elevation does exceed the elevation of critical <br /> depth at the terminal section. Equation 19.107 is inconvenient because h3 (the true <br /> piezometric head at the outfall) is difficult to evaluate <br /> ave without special graphical aids. The actual hydraulic. <br /> Q=CdA3 2g hl+i_h3 —h f i-2 —hf,_3 head driving the culvert flow is a function of the Froude <br /> 2g number. For conservative first approximations, h3 can <br /> 19.103 be taken as the barrel diameter. This will give tl)c <br /> The area, A, used in the discharge equation is not the 2oIf the water surface ever touches the top of the culvert, the <br /> culvert area since the culvert does not flow full. A3 is passage of air in the culvert will be prevented and the culvert Will <br /> I the area in flow at numbered section 3 (i.e., the exit). flow full everywhere. This is type-6 flow. <br /> PROFESSIONAL PUBLICATIONS, INC. <br /> i <br /> ! I <br />