WS0-Fluid Mechanics Review - Rowan University -...
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Water Resources Engineering Dr. Jagadish Torlapati Spring 2018 1 FLUID MECHANICS REVIEW Learning outcomes 1. List different types of fluid properties 2. Summarize different types of fluid flow 3. Explain the energy considerations in single pipe flow Conceptual questions What are Newtonian fluids? Which fluid property changes with gravity? Fluid Mechanics Fluid properties – density, volume, weight, specific gravity, specific weight, viscosity, surface tension Newtonian fluids – viscosity is constant Non-newtonian fluids – viscosity varies based on the shear stress applied on them. They have apparent viscosity Pressure Absolute pressure – pressure referenced at zero vacuum Gage pressure – pressure referenced at atmospheric pressure Two different types of fluid mechanics • Statics – deals with fluids in stationary state (pressure head = depth) • Dynamics – deals with fluids in motion Continuity equation – flow rate is constant (assuming steady state) Bernouli’s principle – Total head is constant. Total head is the sum of pressure head, velocity head and gravitational head. Only applicable for steady state, incompressible, inviscid fluids, no change in temperature along the streamlines Energy equation – applicable in most cases. Considers losses due to friction and pipe fittings Types of losses – Major (frictional losses) and Minor (due to fittings)
Transcript of WS0-Fluid Mechanics Review - Rowan University -...
Water Resources Engineering Dr. Jagadish Torlapati Spring 2018
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FLUID MECHANICS REVIEW
Learning outcomes
1. List different types of fluid properties 2. Summarize different types of fluid flow 3. Explain the energy considerations in single pipe flow
Conceptual questions What are Newtonian fluids? Which fluid property changes with gravity? Fluid Mechanics Fluid properties – density, volume, weight, specific gravity, specific weight, viscosity, surface tension Newtonian fluids – viscosity is constant Non-newtonian fluids – viscosity varies based on the shear stress applied on them. They have apparent viscosity Pressure Absolute pressure – pressure referenced at zero vacuum Gage pressure – pressure referenced at atmospheric pressure Two different types of fluid mechanics
• Statics – deals with fluids in stationary state (pressure head = depth) • Dynamics – deals with fluids in motion
Continuity equation – flow rate is constant (assuming steady state) Bernouli’s principle – Total head is constant. Total head is the sum of pressure head, velocity head and gravitational head. Only applicable for steady state, incompressible, inviscid fluids, no change in temperature along the streamlines Energy equation – applicable in most cases. Considers losses due to friction and pipe fittings Types of losses – Major (frictional losses) and Minor (due to fittings)
Water Resources Engineering Dr. Jagadish Torlapati Spring 2018
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Energy Grade Line (EGL) – Represents the total energy of the system at any given point using the energy equation (sum of pressure head, velocity head and gravitational head minus the losses) Hydraulic Grade Line (HGL) – Represents the hydraulic head of the systems (sum of the pressure head and the gravitational head minus the losses) Note that the difference between EGL and HGL is the velocity head. How to calculate major losses?
1. Identify the pipe material and get the roughness coefficient (e) 2. Evaluate the relative roughness coefficient of the pipe (e/D) 3. Find the Reynold’s number (Re) 4. Find the friction factor
a. Laminar flow – Use Hagen-Poiseulle substitution b. Turbulent flow – use Moody chart, Colebrook formula or Swamee-Jain formula
5. Find the frictional losses using Darcy-Weisbach formula
PUMPS
• Head increases with increase in impeller size • Flow rate increases as the amount of head that the pump needs to overcome decreases • Net Positive Suction Head (NPSH) available should always be greater than the NPSH
required to prevent cavitation • Cavitation is the processes where the pressure at the eye reduces to the vapor pressure of the
water and causes it boil. This causes water bubbles to form and damages the pump.
Water Resources Engineering Dr. Jagadish Torlapati Spring 2018
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Water Resources Engineering Dr. Jagadish Torlapati Spring 2018
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Pumps in series and parallel
Type of arrangement EGL & HGL Pump curve Single Pump
Series Configuration
Parallel Configuration
