Transcription
FE Exam ReviewCivil EngineeringHydraulics, Hydrology, and Fluid MechanicsCary Troy, Lyles School of Civil EngineeringFebruary 11, 2015
Exam Specifications – Civil 3/10/FE-Civil-CBTspecs with-ranges.pdf
Exam Specifications – Civil 3/10/FE-Civil-CBTspecs with-ranges.pdf
Reference ManualExample: If 3” of rain fall on a catchment that has acurve number of 75, what is the total amount of direct runoff?Runoff (Q) Rainfall (P) - LossesRAINFALLRUNOFFGroundLosses(depnds on catchment type, oad-fesupplied-reference-handbook/
Peak runoff (discharge)Rain falls at a maximum rate of 2”/houron a watershed of 77 acres. If the runoffcoefficient is 0.42, what is the expectedpeak discharge?QHydrographFlowTime
Groundwater flowA given soil has hydraulicconductivity K 5 x 10-6 m/s. If thehydraulic grade line falls 1m every100m of distance, what is theaverage seepage velocity? Theeffective porosity is 0.55.
Well drawdown
Well drawdown - unconfined
Well drawdown - confined
Open Channel Flow classifications Uniform vs. non-uniform If Uniform, can use Manning’s equation If not, need to use specific energy to relate points at different locations Critical, vs. super-critical vs. sub-critical Depends on the Froude number Fr 1 : Super-critical Fr 1 : Sub-critical Hydraulic Jump: Flow jumps from super-critical (shallow) to sub-critical (deep)
Key variables Flow rate, Q (m3/s, cfs) Flow rate per unit width, q (m2/s, ft2/s) Average velocity, V Q/A (m/s, ft/s)Flow depth, y (m,ft)Channel width, B (m, ft)Flow area, A (m2, ft2)Wetted perimeter, P (m,ft)Hydraulic radius, RH A/P (m,ft)
Specific EnergyFlow is always somewhere along this curve,for a given flowrate per unit width
Open Channel Flow – Uniform flow Manning’s Equation for Uniform FlowA 20 foot wide rectangular channel has a slopeof 0.0001. If the channel has Manning’s n of0.013, and the depth is 3ft, what is thedischarge? Assume uniform flow.
Open Channel Flow – Froude numberAn open channel flow has discharge 300 cfs. Ifthe channel is rectangular with width 10ft, andthe depth is 3ft, what is the Froude number ofthe flow? How would you classify the flow?
Open channel flow – critical flow/depth For a given flow rate and channel geometry, what is the critical depthof flow?
WeirsRectangularHLV-NotchH
Full (pressurized) pipe flow – Hazen Williams
Head loss in full pipes – H-W
Head loss in pipes – H-W
Partially-full pipeflow (sewers) Calculate totally fulldischarge, velocity Use depth ratio to figureout partially-full: Discharge Velocity Other
Flow in open channelsyB geometry: wetted perimeter, P, and hydraulicradius, Rh A/P uniform flow: Sf S0 , where S0 is channel slope concept of critical flow and importance of Froudenumber for rectangular channels of width, B, and depth, y:q Q / B Vy , yc q / g , Fr V / gy , Frc 121/ 3– subcritical flow (Fr 1 or y yc), supercritical flow(Fr 1 or y yc)
Open channel problems (p. 6, #3) What is the hydraulic radius of a rectangularflume 2 ft high and 4 ft wide, which is running half full?Rh A / P By /( B 2 y )yAns: B DB (p. 6, #12) The critical depth in a rectangular channel 8 ft wide flowing at acritical velocity of 2 ft/s is approximately?Frc 1 Vc / gyc , yc Vc2 / gAns: A
FE Exam Review Civil Engineering Hydraulics, Hydrology, and Fluid Mechanics Cary Troy, Lyles School of Civil Engineering February 11, 2015
