 Ch 4. Fundamental Laws (Integral Anal.) Multimedia Engineering Fluids ConservationMass LinearMomentum Moment ofMomentum ConservationEnergy
 Chapter 1. Basics 2. Fluid Statics 3. Kinematics 4. Laws (Integral) 5. Laws (Diff.) 6. Modeling/Similitude 7. Inviscid 8. Viscous 9. External Flow 10. Open-Channel Appendix Basic Math Units Basic Equations Water/Air Tables Sections Search eBooks Dynamics Fluids Math Mechanics Statics Thermodynamics Author(s): Chean Chin Ngo Kurt Gramoll ©Kurt Gramoll FLUID MECHANICS - EXAMPLE Questions Problem Diagram Rain falls at a uniform rate of 2 cm/hr over a 1 km x 1 km field, the water infiltrates into the soil at a rate of 1 cm/hr. At the downstream end of the field, the small channel carries a flow of 0.01 m3/s. If all rates remain constant, determine if ponding occurs. Solution Rain falls at: i = 2 cm/hr = 0.02 m/hr over an area of A = 1 km2 = 1,000,000 m2 Infiltration rate: 1 cm/hr = 0.01 m/hr A small channel causes runoff = 0.01 m3/s = 36 m3/hr For ponding, rainfall must exceed infiltration plus runoff (conservation of mass for a constant density fluid)      rainfall volume      = (rainfall intensity)(area) = iA      = (0.02)(1,000,000) = 20,000 m3/hr      infiltration volume + runoff volume      = (0.01)(1,000,000) + 36      = 10,036 m3/hr Since rainfall volume > (infiltration volume + runoff volume), ponding will occur at a rate of (20,000 - 10,036) = 9,964 m3/hr Note: system is not at steady state. For it to be at steady state, the outflow would need to increase to 10,000 m3/hr, at which point there would be zero ponding.

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