Dr. Mohd Hafiz bin Zawawi Hydraulic Engineering CEWB222 CHAPTER 1 (INTRODUCTION)What is Hydraulics?Hydraulic may be defined as the science that deals with the mechanical behavior of water at rest or in motion.The mechanical behavior may entail computing forces and energy.The science of fluid at rest is called hydrostaticsThe science of moving fluid is called hydrodynamics2Distinction Fluid echanics ! is the study of fluids itself under all condition. The fluids maybe gaseous or li"uid.Hydraulic ! #rimarily deals with water. $ hydraulic approachis more empirical and emphasis on finding solution of practical value practically %Hydrology ! &tudy of space and time and fre"uency characteristics of the "uality and "uality of water on earth.'Closed conduit fow (Pipe fow) It does not have any free surface.If there is free surface in water fow in pipes, therefore it is classifed as open channel fow.Open channel fow It has a free surface.TYPE AND C!AI"ICATION O" "!O#Two $%&'( of f)ow of wa$'r in a *ond+i$Classifcation based on time criteria(a) Steady fow is for fows with constant depth during the time interval under considerate. The fow is continuous i.e. discharge is continuous throughout the reach of the channel under consideration.Therefore, the discharge at a channel section, Q Q1Q2Q! (where the subscripts denotes dierent!hannel sections)."ote# Q"#$here # % & fow cross sectional area ('()) & 'ean velocity '*s(b) $nsteady fow is for fows with depth that changeswithti'e.+,a'ples are surgesand food fows.Classifcation o% o&en c'annel fows$ni%orm fow is fows wit' t'e same de&t' at e(ery section o% t'e c'annel) $ni%orm fow can be %urt'er classifed into*i) Steady uni%orm fow w'ere t'e de&t' also does not c'ange (constants) during t'e time inter(al)ii) $nsteady uni%orm fow w'ere t'e de&t' c'anges during t'e time inter(al but at t'e same time t'e water sur%ace remains &arallel to t'e c'annel bottom)$ni%orm fow are based on s&ace criteria#aried fow is %or fows wit' t'e de&t' o% fow t'at c'anges along t'e lengt' o% t'e c'annel)#aried fow can be %urt'er classifed into *i)+radually (aried fow (+#,) - w'ere t'e de&t' c'anges gradually o(er a com&arati(ely long distance)ii) .a&idly (aried fow (.#,) w'ere t'e de&t' c'anges abru&tly o(er a com&arati(ely s'ort distance)iii) S&atially (aried fow or discontinuous fow w'ere some fow is added to or abstracted %rom t'e fow system)E/am&le would be li0e fows at roadside gutters and %eeding c'annels in irrigation systems))%-I+. /01$2!0%22I/I!%TI1" 1/ 13+" !4%""+0 /01$2&teady flow(nsteady flow(niform flow )aried flow*apid varied flow+radually variedFlow,lassification of -pen ,hannel FlowsC1"SS2,2C"3245 4, 46E5 CH"55E1 ,14WS$'ad% f)ow, +n($'ad% f)owUnifor- f)ow, .ari'd f)ow&teady&teady&teady&teady(niform flow+radually varied flow*apidly varied flow&patially varied flow(nsteady(nsteady(nsteady+radually varied flow*apidly varied flow&patially varied flow..classificationClassification3'e state is go(erned by*a) 3'e e7ect o% (iscosityb) 3'e e7ects o% gra(ityState o% fowTh' 'ff'*$ of .i(*o(i$% r')a$i.' $o in'r$ia wo+)d *a+(' $h' f)ow $o b' in 'i$h'r on' of $h' fo))owin/ ($a$'( 0State o% fowii) 3urbulent fow * #iscous %orces are wea0 relati(e to t'e inertial %orces Water &articles mo(e in irregular &at's but still re&resent t'e %orward motion o% t'e entire stream .eynolds number 8 .e 9 1:::iii) 3ransitional fow 3'e fow state between laminar and turbulent fows ;:: < .e < 1:::i) !a-inar f)ow 01i(*o+( for*'( ar' (o ($ron/ r')a$i.' $o $h' in'r$ia) for*'(.#a$'r &ar$i*)'( a&&'ar $o -o.' in ($r'a-)in'(R'%no)d( n+-b'r R' 2 344State o% fowb) 3'e e7ects o% gra(ityThe eect of viscosity relative to inertia would cause the fow to be in either one of the following states#i) Subcritical fow * +ra(ity %orce is more &ronounced 3'e fow 'as a low (elocity and o%ten tran=uil and streaming ,roude 5umber 8 ,