Measurements in Fluid Mechanics 058:180:001 (ME:5180:0001) Time & Location: 2:30P - 3:20P MWF 218 MLH Office Hours: 4:00P – 5:00P MWF 223B-5 HL Instructor: Lichuan Gui

2 Lecture 10. Fluid mechanical apparatus: producing desired flow

3 Fluid flow systems Controlled flow systems - wind tunnel- water tunnel - others Flow systems beyond control of experimenter e.g. environmental & industrial

4 Components of controlled flow systems - Diffuser Flow generation & management - Settling chamber or plenum - Fluid mover - Contraction Test/work section - Desired flow - Test model - Measurements Controlled fluid flow systems

5 Type of controlled flow systems Controlled fluid flow systems Closed-circuit facility Open-circuit systems - simple and low cost - wasting fluid - wasting energy - dependent on surroundings - complicated and high cost - save fluid - save energy - independent on surroundings

6 Flow generation & management Fluid movers pressure vesselBlowerPump - absolute - relative model towed by carriage in water tank Controlled fluid flow systems

7 Flow generation & management Settling chamber or plenum - upstream fluid container - relatively low-speed region 1 Screens 2 Honey comb 3 Turbulence screens C - Settling chamber Honey comb: - to reduce upstream turbulence w. flow straightener (e.g. honey comb) turbulence screen Contraction (D) - reduce cross-section area to fit test section - increase flow speed to desired value Diffuser (B & F) - increase cross-section area - reduce flow speed to desired value Controlled fluid flow systems Pressure loss coefficient:  p – unexpected pressure loss  – fluid density V – mean flow speed

8 Controlled fluid flow systems Flow in contractions & diffusers Subsonic contraction - second-order small values ignored - contraction ratio (c>1) - upstream turbulence reduced w. c>1

9 Controlled fluid flow systems Subsonic contraction Flow in contractions & diffusers More accurate estimation: Relation between turbulence and density change: Subsonic diffuser - increase cross-section area (A 2 >A 1 ) - reduce flow speed to recover pressure - L large enough to avoid flow separation i.e.   5  - L short enough to avoid large friction

10 Homework - Questions and Problems: 1 & 2 on page Read textbook on page Due on 09/16 ( Question 2 is optional )