ME 322: Instrumentation Lecture 34 April 13, 2016 Professor Miles Greiner Lab 11 Calculations, Sample data demo Ran out of time in 2016

Announcements/Reminders HW 11 Due Friday Tutorial: Thursday 7 PM, SEM 321 unless Joseph lets you know otherwise This week: Lab 10 Vibrating Beam Sign up for 45-minute Lab 11 periods with your partner in lab For Lab 11, each lab day will have a required demonstration for all students to learn how to perform the details of the experiment. You must be on time to the demo and your lab time (participation grade) Help wanted (see me greiner@unr.edu) Spring 2016: ME 322 Lab Assistant

Announcements/Reminders Exam solution posted outside PE 213 (my office) Will consider regrading until Friday, 4/15/2016 If you have a Laptop, you may want to load LabVIEW and bring it to class to follow along, especially next week for Lab 12 (complicated VI) Lab-in-a-Box All the equipment for Lab 10 and 12 is in the DeLaMare library basement. LabVIEW also in Library You can use this to See if your VI’s work, and Practice for the final

Internship Opportunities Nevada National Security Site (Las Vegas) Nuclear materials packaging internship Description: http://www2.nstec.com/job%20opportunities/110723.pdf The Orthopedic Implant Company (OIC) Internship (SolidWorks +?) Send resumes to Joseph Bozsik jbozsik@unr.edu

Lab 11 Unsteady Speed in a Karman Vortex Street Nomenclature U = air speed (instead of V) VCTA = Constant temperature anemometer voltage Two steps Statically calibrate hot film Constant Temperature Anemometer (CTA) using a Pitot probe Downstream from a cylinder of diameter D, find frequency fP with largest URMS for a range of air speeds U Compare to expectations: StD = DfP /U = 0.2-0.21

Table 1 Cylinder Diameter and Air Properties Air Viscosity from A.J. Wheeler and A. R. Ganji, Introduction to Engineering Experimentation, 2nd Edition, Pearson Prentice Hall, 2004, p. 430.

Calibration Calculations Based on physical analysis we expect 𝑉 𝐶𝑇𝐴 2 =𝑎 𝑈 +𝑏 𝑈=𝐶 2 𝑃 𝑃 𝜌 𝐴𝑖𝑟 =𝐶 2 𝜌 𝑊 𝑔𝐹𝑆 𝐼 𝑃 −4𝑚𝐴 16𝑚𝐴 𝜌 𝐴𝑖𝑟 𝜌 𝑊 =998.7 𝑘𝑔 𝑚 3 𝐹𝑆= 3 𝑖𝑛𝑐ℎ 𝑊𝐶 2.54 𝑐𝑚 𝑖𝑛𝑐ℎ 1 𝑚 100 𝑐𝑚 𝜌 𝐴𝑖𝑟 = 𝑃 𝐴𝑇𝑀 𝑅 𝐴𝑖𝑟 𝑇 𝐴𝑇𝑀 ; 𝑅 𝐴𝑖𝑟 =0.287 𝑘𝑃𝑎 𝑚 3 𝑘𝑔 𝐾 𝑆 𝑉 𝐶𝑇𝐴 2 , 𝑈 = 𝑎 𝑈 𝑖 +𝑏 − 𝑉 𝐶𝑇𝐴 2 𝑖 2 𝑛−2 𝑆 𝑈 , 𝑉 𝐶𝑇𝐴 2 = 𝑆 𝑉 𝐶𝑇𝐴 2 , 𝑈 𝑎

Hot Film System Calibration The fit equation VCTA2 = aU0.5+b appears to be appropriate for the calibration. The standard estimate of the error of 𝑉 𝐶𝑇𝐴 2 for given 𝑈 is 𝑠 𝑉 𝐶𝑇𝐴 2 , 𝑈 =0.26 𝑉 2 The standard estimate of the error of 𝑈 for given 𝑉 𝐶𝑇𝐴 2 is 𝑠 𝑈 ,𝑉 𝐶𝑇𝐴 2 =0.10 𝑚 𝑠 1 2

Unsteady Karman Vortex Flow Note: Change from before. Do not place the hot film probe directly behind the cylinder. Offset is better Need to remove cylinder to find UA Replace cylinder to find spectral content and fP

Fig. 4 Spectral Content in Wake for Highest and Lowest Wind Speed (a) Lowest Speed URMS [m/s] fp = 751 Hz URMS [m/s] (b) Highest Speed fp = 2600 Hz The sampling frequency and period are fS = 48,000 Hz and TT = 1 sec. The minimum and maximum detectable finite frequencies are 1 and 24,000 Hz. It is straightforward to distinguish fP from this data. Its uncertainty is Wfp = 0.5 Hz.

Dependence on Probe Location Offset Aligned Offset is better than aligned with cylinder

Dimensionless Frequency and Uncertainty UA from LabVIEW VI 𝑤 𝑈 =2 𝑈 𝑠 𝑈 , 𝑉 𝐶𝑇𝐴 2 (68%) fP from LabVIEW VI plot 𝑤 𝑓 𝑃 = ½(1/tT) or eyeball uncertainty Re = UADr/m (power product) 𝑤 𝑅𝑒 𝑅𝑒 2 = 𝑤 𝑈 𝐴 𝑈 𝐴 2 + 𝑤 𝐷 𝐷 2 + 𝑤 𝜌 𝜌 2 + 𝑤 𝜇 𝜇 2 StD = DfP/UA (power product) 𝑤 StD StD 2 = − 𝑤 𝑈 𝐴 𝑈 𝐴 2 + 𝑤 𝐷 𝐷 2 + 𝑤 𝑓 𝑃 𝑓 𝑃 2

Fig. 5 Strouhal versus Reynolds The expected Strouhal range is from A.J. Wheeler and A.R. Ganji, Introduction to Engineering Experimentation, 2nd Edition, Pearson Prentice Hall, 2004, p. 337. The Strouhal numbers are roughly independent of Reynolds number Four of the six Strouhal numbers are within the expected range.

Process Sample Data http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/Labs/Lab%2011%20Karmon%20Vortex/Lab%20Index.htm

Fig. 2 VI Block Diagram Starting point VI

Fig. 1 VI Front Panel