k.1.materi mekflu ii pendahuluan

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1. PENDAHULUAN

Aplikasi Aerodinamis dalam bidang engineering, antara lain pada; penukar kalor Cooling Tower, Cerobong, Struktur penyangga anjungan lepas pantai & Pelabuhan, Kapal Laut Gandeng (Kapal Tongkang), Kereta Api &Truk Gandeng, Bangunan Bertingkat, Dsb.

Bila fluida mengalir melalui suatu benda, maka akan kehilangan energi, yang disebabkan : a. Pemisahan aliran (separasi aliran), karena faktor bentuk benda. b. Gaya tahanan karena gesekan dan tekanan.

K.1. PENDAHULUAN

Gambar . Koefisien tahanan (CD) terhadap bilangan Reynolds (Re) pada silinder persegi dengan aspek ratio (B) bervariasi, (Salam Nasaruddin,1999).

Fluid dynamics is the key to our understanding of some of the most important phenomena in our physical world: ocean currents and weather systems.

57:020 Fluid Mechanics4Vehicles

AircraftSubmarinesHigh-speed railSurface ships57:020 Fluid Mechanics5Sports & RecreationWater sportsAuto racingOffshore racingCycling

Surfing6One-, Two-, and Three-Dimensional FlowsA flow field is best characterized by its velocity distribution.A flow is said to be one-, two-, or three-dimensional if the flow velocity varies in one, two, or three dimensions, respectively. However, the variation of velocity in certain directions can be small relative to the variation in other directions and can be ignored.

The development of the velocity profile in a circular pipe. V = V(r, z) and thus the flow is two-dimensional in the entrance region, and becomes one-dimensional downstream when the velocity profile fully develops and remains unchanged in the flow direction, V = V(r).

Flow over a car antenna is approximately two-dimensional except near the top and bottom of the antenna.6

A fluid moving relative to a body exerts a drag force on the body, partly because of friction caused by viscosity.78

The Wright brothers take flight at Kitty Hawk.

The Oklahoma Wind Power Center near Woodward consists of 68 turbines, 1.5 MW each.857:020 Fluid Mechanics9Applications of EFD (contd)

Example of industrial application

NASA's cryogenic wind tunnel simulates flight conditions for scale models--a critical tool in designing airplanes.

Application in teaching

Fluid dynamics laboratory57:020 Fluid Mechanics10Full and model scale

1. Scales: model, and full-scale2. Selection of the model scale: governed by dimensional analysis and similarity57:020 Fluid Mechanics11Commercial softwareCFD software 1. FLUENT: http://www.fluent.com 2. FLOWLAB: http://www.flowlab.fluent.com 3. CFDRC: http://www.cfdrc.com 4. STAR-CD: http://www.cd-adapco.com 5. CFX/AEA: http://www.software.aeat.com/cfxGrid Generation software 1. Gridgen: http://www.pointwise.com 2. GridPro: http://www.gridpro.comVisualization software 1. Tecplot: http://www.amtec.com 2. Fieldview: http://www.ilight.com

57:020 Fluid Mechanics12Hands-on experience using CFD Educational Interface (pipe template)

57:020 Fluid Mechanics13Hands-on experience using CFD Educational Interface (airfoil template)

Fig. 7.1 Comparison of flow past a sharp flat plate at low and high Reynolds numbers: (a) laminar, low-Re flow; (b) high-Re flow.

Fig. 7.2 Illustration of the strong interaction between viscous and inviscid regions in the rear of bluntbody flow: (a) idealized and definitely false picture of blunt-body flow; (b) actual picture of bluntbody flow.