{ "metadata": { "name": "", "signature": "sha256:cd2be77f3b9478c6cae134ea907a28e897f525fa56fe0f236e6cf640bce7cb59" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "heading", "level": 2, "metadata": {}, "source": [ "Chapter 5 : Fluid Momentum" ] }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.1 Page no 192" ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Resultant force on the elbow\n", "\n", "from math import *\n", "\n", "# Given\n", "\n", "Q = 0.3 # Water flow rate in m**3/s\n", "\n", "d1 = 0.3 # diameter at inlet in meters\n", "\n", "A1 = pi*d1**2/4 # inlet area in m**2\n", "\n", "d2 = 0.15 # diameter at outlet in m\n", "\n", "A2 = pi*d2**2/4 # area at outlet in m**2\n", "\n", "P1 = 175*10**3 # inlet pressure in kN/m**2\n", "\n", "P2 = 160*10**3 # Pressure at outlet in kN/m**2\n", "\n", "F1 = P1*A1 # Force at inlet\n", "\n", "F2 = P2*A2 # Force at outlet\n", "\n", "rho = 1000 # density of water in kg/m**3\n", "\n", "V1 = Q/A1 # inlet velocity in m/s\n", "\n", "V2 = Q/A2 # Velocity at outlet in m/s\n", "\n", "theta = 45*pi/180 # angle in deg\n", "\n", "# Soultion\n", "\n", "# Applying the X momentum equation we get\n", "\n", "Rx = F1 - F2*cos(theta)-rho*Q*(V2*cos(theta)-V1)\n", "\n", "# Applying the Y momentum equation\n", "\n", "Ry = F2*sin(theta)+rho*Q*(V2*sin(theta)-0)\n", "\n", "R = sqrt(Rx**2+Ry**2)\n", "\n", "print \"Resultant force on the elbow = \",round(R,2),\"N\"\n", "\n", "a = atan(Ry/Rx)*180/pi\n", "\n", "print \"Angle of resultant force = \",round(a,4),\"deg\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Resultant force on the elbow = 9800.58 N\n", "Angle of resultant force = 34.8516 deg\n" ] } ], "prompt_number": 4 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.2 Page no 194" ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Force exerted by the jet on the vane\n", "\n", "from math import *\n", "\n", "# Given\n", "\n", "V1 = 80 # Velocity in ft/s\n", "\n", "A1 = 0.1 # area in ft**2\n", "\n", "g = 32.2 # Acceleration due to gravity in ft/s**2\n", "\n", "rho = 1.94 # density in lb/ft**3\n", "\n", "a = pi/3 # angle of pipe bend\n", "\n", "# Solution\n", "\n", "Q = A1*V1 # Total discharge in m**3\n", "\n", "# Applying bernoullis at point 1 and 2\n", "\n", "V2 = sqrt((2*g*V1**2/(2*32.2))-3*2*g)\n", "\n", "# Pressure at the end of the section are atmospheric and hence 0\n", "\n", "# momentum equation in X direction\n", "\n", "Rx = -(rho*Q*(V2*cos(a)-80))\n", "\n", "# momentum equation in Y direction\n", "\n", "Ry = (rho*Q*(V2*sin(a)-0))\n", "\n", "R = sqrt(Rx**2+Ry**2)\n", "\n", "print \"Resultant force = \",round(R,0),\"lbs\"\n", "\n", "ang = atan(Ry/Rx)*180/pi\n", "\n", "print \"Angle of resultant force = \",round(ang,4),\"deg\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Resultant force = 1232.0 lbs\n", "Angle of resultant force = 59.2396 deg\n" ] } ], "prompt_number": 7 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example no 5.3 Page no 195 " ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Force needed to hold the Y position \n", "\n", "# Given\n", "\n", "from __future__ import division\n", "\n", "from math import *\n", "\n", "Q1 = 0.5 # discharge from pipe 1 in m**3/s\n", "\n", "Q2 = 0.3 # discharge from pipe 2 in m**3/s\n", "\n", "Q3 = 0.2 # discharge from pipe 3 in m**3/s\n", "\n", "d1 = 0.45 # diameter of pipe 1 in m\n", "\n", "d2 = 0.3 # diameter of pipe 2 in m\n", "\n", "d3 = 0.15 # diameter of pipe 3 in m\n", "\n", "A1 = pi*d1**2/4 # area in m**2\n", "\n", "A2 = pi*d2**2/4 # area in m**2\n", "\n", "A3 = pi*d3**2/4 # area in m**2\n", "\n", "P1 = 60*10**3 # Pressure at point 1 in kPa\n", "\n", "gma = 9810\n", "\n", "g = 9.81 # acceleration due to gravity in m/s**2\n", "\n", "rho = 1000 # density in kg/m**3\n", "\n", "# Solution\n", "\n", "V1 = Q1/A1\n", "\n", "V2 = Q2/A2\n", "\n", "V3 = Q3/A3\n", "\n", "P2 = gma*((P1/gma) + V1**2/(2*g) - V2**2/(2*g))\n", "\n", "P3 = gma*((P1/gma) + V1**2/(2*g) - V3**2/(2*g))\n", "\n", "F1 = P1*A1\n", "\n", "F2 = P2*A2\n", "\n", "F3 = P3*A3\n", "\n", "Rx = rho*(Q2*V2*cos(pi/6)-Q3*V3*cos(pi/9)-0)+F3*cos(pi/9)-F2*cos(pi/6)\n", "\n", "Ry = rho*((Q2*V2*sin(pi/6)+Q3*V3*sin(pi/9)-Q1*V1))+F3*sin(pi/9)-F2*sin(pi/6)-F1\n", "\n", "R = sqrt(Rx**2+Ry**2)\n", "\n", "a = atan(Ry/Rx)*180/pi\n", "\n", "print \"Resultant Force = \",round(R,0),\"N\"\n", "\n", "print \"Angle with horizontal = \",round(a,1),\"deg with horizontal\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Resultant Force = 12489.0 N\n", "Angle with horizontal = 69.2 deg with horizontal\n" ] } ], "prompt_number": 10 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.4 Page no 199" ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Normal force on the plate\n", "\n", "# Given\n", "from math import *\n", "\n", "d = 2 # diameter in inches\n", "\n", "A = pi*d**2/(4*144) # Area of jet\n", "\n", "V = 100 # velocity of jet in ft/s\n", "\n", "Q = A*V # dischargge in ft**3/s\n", "\n", "gma = 62.4 # mass\n", "\n", "g = 32.2 # acceleration due to gravity in ft/s**2\n", "\n", "# Solution\n", "\n", "Rx = (gma*Q*V)/g # horizontal force required to keep plate in position\n", "\n", "print \"Normal force on the plate = \",round(Rx,0),\"lbs\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Normal force on the plate = 423.0 lbs\n" ] } ], "prompt_number": 11 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.5 Page no 202" ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Force on the plate ; work doen per second; efficiency\n", "\n", "# Given\n", "\n", "from math import *\n", "\n", "D = 0.075 # diameter in m\n", "\n", "A =pi*D**2/4 # area of jet\n", "\n", "V =15 # velocity of jet in m/s\n", "\n", "w = 9810 # specific weight\n", "\n", "g = 9.81 # acceleration due to gravity in m/s^2\n", "\n", "# Solution\n", "\n", "Q =A*V # Discharge in m**3/s\n", "\n", "Vp = 10 # velocity of plate in m/s\n", "\n", "Rx = w*Q*(V-Vp)/g # force in X direction\n", "\n", "print \"Force on the plate = \",round(Rx,2),\"N\"\n", "\n", "W = Rx*Vp\n", "\n", "print \"Work done per second = \",round(W,1),\"N.m/s\"\n", "\n", "Eff = 2*(V-Vp)*Vp/V**2\n", "\n", "E = 100*Eff\n", "\n", "print \"Efficiency = \",round(E,1),\"%\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Force on the plate = 331.34 N\n", "Work done per second = 3313.4 N.m/s\n", "Efficiency = 44.4 %\n" ] } ], "prompt_number": 12 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.6 Page no 204" ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Force exerted on the plate\n", "\n", "# Given\n", "from math import *\n", "\n", "d = 3 # diameter in inches\n", "\n", "A = pi*d**2/(4*144) # Area of jet\n", "\n", "Q = 2 # discharge in ft**3/s\n", "\n", "rho = 1.94 # density in lbs/ft**3\n", "\n", "# Solution\n", "\n", "V = Q/A # velocity in ft/s\n", "\n", "alpha = pi/6 # inlet vane angle\n", "\n", "bta = pi/6 # outlet vane angle\n", "\n", "Rx = rho*Q*(V*cos(bta)+V*cos(alpha)) # force in X direction\n", "\n", "Ry = rho*Q*(V*sin(bta)-V*sin(alpha)) # force in Y direction\n", "\n", "print \"Force exerted in X direction = \",round(Rx,1),\"lbs\"\n", "\n", "print \"Force exerted in Y direction = \",round(Ry,1),\"lbs\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Force exerted in X direction = 273.8 lbs\n", "Force exerted in Y direction = 0.0 lbs\n" ] } ], "prompt_number": 13 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.7 Page no 207" ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Angle of blade tips at inlet and exit ; work done on the vane; efficiency of the vane\n", "\n", "# Given\n", "\n", "from math import *\n", "\n", "V1 =40 # velocity in m/s\n", "\n", "Vp = 20 # velocity of the plate in m/s\n", "\n", "alpha = pi/6 # inlet vane angle\n", "\n", "bta = pi/9 # outlet vane angle\n", "\n", "g = 9.81\n", "\n", "# Solution\n", "\n", "V1x = V1*cos(alpha)\n", "\n", "Vw1 = V1x;\n", "\n", "V1y = V1*sin(alpha)\n", "\n", "dV = V1x - Vp\n", "\n", "theta = atan(V1y/dV)*180/pi\n", "\n", "Vr1 = V1y/sin(theta*pi/180)\n", "\n", "Vr2 = Vr1\n", "\n", "# from trial and error we get the blade tip angle at inlet and outlet\n", "\n", "print \"a ) Angle of blade top at inlet and Outlet, Phi = 4 deg\"\n", "\n", "phi = 4*pi/180 \n", "\n", "V2 = Vr2*sin(phi)/sin(bta)\n", "\n", "V2w = V2*cos(bta)\n", "\n", "W = (V2w+V1x)*Vp/g\n", "\n", "print \"b ) Work done per N of fluid per second = \",round(W,2),\"N.m\"\n", "\n", "Eff = (1 - (V2/V1)**2)*100\n", "\n", "print \"c ) Efficiency = \",round(Eff,2),\"%\"\n" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "a ) Angle of blade top at inlet and Outlet, Phi = 4 deg\n", "b ) Work done per N of fluid per second = 80.31 N.m\n", "c ) Efficiency = 98.4 %\n" ] } ], "prompt_number": 15 }, { "cell_type": "heading", "level": 3, "metadata": {}, "source": [ "Example 5.8 Page no 211" ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Thrust on the plane; propeller efficiency ; theoretical horsepower ; pressure difference acros the blades\n", "\n", "# Given\n", "\n", "from math import *\n", "\n", "v = 220 # velocity in ft/s\n", "\n", "d = 6 # diameter of the propeller\n", "\n", "Q = 12000 # discharge in ft**3/s\n", "\n", "mf = 0.0022 # mass flow rate in slugs/ft**3\n", "\n", "# Solution\n", "\n", "V1 = v*5280/3600 # velocity in ft/s\n", "\n", "V = Q/(pi*d**2/4) # velocity in ft/s\n", "\n", "V4 = 2*V-V1\n", "\n", "F = mf*Q*(V4-V1) # thrust on the plane\n", "\n", "print \"a - Thrust on the plane = \",round(F,1),\"lbs\"\n", "\n", "Eff = V1/V # efficiency \n", "\n", "E = Eff*100\n", "\n", "print \"b - Theoretical efficiency = \",round(E,0),\"%\"\n", "\n", "Thp = F*V1/(500*Eff)\n", "\n", "print \"c - Theoretical horsepower required = \",round(Thp,0),\"hp\"\n", "\n", "dP = mf*(V4**2-V1**2)/2\n", "\n", "print \"d - Pressure difference across blades = \",round(dP,2),\"lbs/ft**3\"" ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "a - Thrust on the plane = 5372.2 lbs\n", "b - Theoretical efficiency = 76.0 %\n", "c - Theoretical horsepower required = 4560.0 hp\n", "d - Pressure difference across blades = 190.0 lbs/ft**3\n" ] } ], "prompt_number": 16 }, { "cell_type": "code", "collapsed": false, "input": [], "language": "python", "metadata": {}, "outputs": [] } ], "metadata": {} } ] }