50cm 0

.30cm

20º

150N

UNIVERSITI TEKNIKAL MALAYSIAMELAKA FAKULTI KEJURUTERAANMEKANIKAL

BMCG 2613 – MEKANIK BENDALIR I

TUTORIAL1FLUID AND ITSPROPERTIES

1. (a)Calculatetheweightofareservoirofoilifithasamassof825kg.[8.093kN](b)Ifthereservoirhasavolumeof0.917m3,computethedensity,specificweight,andthe specificgravityoftheoil.[900kg/m3;8.83kN/m3;0.90]

2. Acylindricalcan,150mmindiameter,isfilledtoadepthof100mmwithafueloil.Theoil hasamassof1.56kg.Calculateitsdensity,specificweight,andspecificgravity.[883kg/m3; 8.659kN/m3;0.883]

3. Aplate,0.5mmdistantfromafixedplate,movesat0.25m/sandrequiresaforceperunit areaof2Patomaintainthisspeed.Determinetheviscosityofthesubstancebetweenthe plates.[0.004kg/ms]

4. Ashaft80mmindiameterisbeingpushedthroughabearingsleeve80.2mmindiameter and0.3mlong.Theclearance,assumeduniformisfloodedwithlubricatingoilofviscosity0.1 kg/ms.(a)If theshaftmoves axiallyat0.8m/s,estimatethe resistanceforceexertedbytheoilontheshaft,(b)Iftheshaftisaxiallyfixedandrotatedat1800rpm,estimatetheresisting torqueexertedbytheoilandthepowerrequiredtorotatetheshaft.[60.32N;22.74Nm;4.29kW]

5. Averylargethinplateiscentredinagapofwidth0.06mwithdifferentoilsofunknown viscositiesaboveandbelow:oneviscosityistwicetheother.Whentheplateispulledata velocityof0.3m/stheresultingforceon1m2ofplateduetotheviscousshearonbothsides is29N.Assumingviscousflowandneglectingallendeffects,calculatetheviscositiesofthe oils.[0.97kg/ms]

6. A50-cmx30-cmx20-cmblockweighing 150Nistobemovedataconstantvelocity of 0.8 m/s on an inclined surface with a friction coefficient of 0.27. (a)Determinethe forceF that needs to beappliedin F horizontaldirection.(b)Ifa0.4-mm-thickoil filmwithadynamicviscosityof0.012Pa.sisappliedbetweentheblockandinclined surface,determinethepercentreductionin therequiredforce.[105.5N;45.8%] Figure1

8m/s

7. Athin20-cmx20-cmflatplateispulled at1m/shorizontallythrougha3.6-mm- thickoillayersandwichedbetweentwo plates, one stationary and the other moving ata constantvelocityof 0.3m/s, as shown in Figure 2. The dynamic viscosityofoilis0.027Pa.s.Assumingthe velocityineachoillayertovarylinearly,

(a) plot the velocity profile and findthe locationwheretheoilvelocityiszeroand(b) determinetheforcethatneedstobe applied on the plate to maintain this motion.

[0.6-mmfromthebottomplate;1.62N]

h1=1mm

h2=2.6mm

0.3m/s

Fixedwall

Figure2

1m/s

Drivenshaft

30cm3mmSAE30Woil

h Oil

θ

h

Figure3

8. TheclutchsystemshowninFigure3isused totransmittorquethrougha3-mm-thickoil film with µ = 0.38 N.s/m2 betweentwoidentical 30-cm-diameter disks. Whenthe driving shaft rotates at a speed of1450 rpm, the driven shaft rotates at a 1398 rpm.Assumingalinearvelocityprofilefor the oil film, determine the transmitted torque.[0.55Nm]

9. Theviscosityofafluidistobemeasuredbyaviscometerconstructedoftwo75-cm-long concentriccylinders.Theouterdiameteroftheinnercylinderis15cm,andthegapbetween thetwocylindersis0.12cm.Theoutercylinderisfixedwhiletheinnercylinderisrotatedat 200rpmandthetoqueismeasuredtobe0.8Nm.Determinetheviscosityofthefluid.

[0.231N.s/m2]

10.A1.9-mm-diametertubeisinsertedintoanunknownliquidwhosedensityis960kg/m3,andit isobservedthattheliquidrises5mminthetube,makingacontactangleof15º.Determine thesurfacetensionoftheliquid.[0.0232N/m]

11.ThebeltinFigure4movesatasteadyvelocityV=2.5m/sandskimsthetopofatankofoil of dynamicviscosityµ= 0.29kg/ms,asshown.DistancebetweenrollersL = 2 m, widthofthebeltb=60cmanddepthoftheoilh=3cm.Assumingalinearvelocityprofileintheoil, determine(a)theresistingforceexertedonthebeltbytheoil,and(b)thepowerPrequired todrivethebelt.(Given,P=Tw)(FinalExamSem1Session06/07)[29N;72.5watt]

LV

Driving torqueT

Figure4

12.Two square plates (15 mm x 15 mm) are dipped into a fluid of density ρ = 1000 kg/m3

parallel to each other, as shown in Figure 5. If distance between the plates W = 2 mm, determinethecapillaryriseh.Given,surfacetensionσ=0.073N/mandcontactangleis negligible,i.e.θ=0º.(Test1Sem1Session06/07)[7.44mm]

W

Figure5