ME 322: Instrumentation Lecture 41 April 29, 2016 Professor Miles Greiner Review Labs 11 and 12

Announcements/Reminders Cancel HW 14 Supervised Open-Lab Periods Saturday, Sunday 1-6 PM Please pick up old homework during the open lab times Lab-in-a-box (DeLaMare Library) Lab Practicum Finals Start Monday Guidelines, Schedule http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/Tests/Index.htm Monday Answer questions Reviewing course objectives and asking for feedback Allow time to complete course evaluation at www.unr.edu/evaluate

Opportunities Summer position at the Nevada National Security Site (NNSS) http://www2.nstec.com/job%20opportunities/110723.pdf ME 322 Lab assistant Please let me know if you’re interested greiner@unr.edu

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

Setup Measure PATM, TATM, and cylinder D Find air m from text myDAQ Variable Speed Blower Hot Film Probe VCTA Barometer PATM TATM Plexiglas Tube CTA DTube Cylinder, D Pitot-Static Probe Static Total PP - + 3 in WC IP Measure PATM, TATM, and cylinder D Find air m from text A.J. Wheeler and A. R. Ganji, Introduction to Engineering Experimentation, 2nd Edition, Pearson Prentice Hall, 2004, p. 430 Tunnel Air Density 𝜌= 𝑃 𝐴𝑇𝑀 + 𝑃 𝐺𝑎𝑔𝑒 𝑅 𝐴𝑖𝑟 𝑇 𝐴𝑇𝑀 =𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑅 𝐴𝑖𝑟 =0.287 𝑘𝑃𝑎 𝑚 3 𝑘𝑔 𝐾

Hints When calibrating, Do not center probe behind cylinder Read IP visually while clicking Run on VI to get simultaneous measurement of VCTA Some people are using DVM to measure VCTA Do not center probe behind cylinder Use 1/8 inch cylinder (closer to hot film) May help to not use auto-scale for URMS. Low frequency signals can be large and swamp the Karman Vortex oscillatory amplitude

Calibration Calculations 𝑆 𝑈 , 𝑉 𝐶𝑇𝐴 2 Based on analysis we expect 𝑉 𝐶𝑇𝐴 2 =𝑎 𝑈 +𝑏 𝑈=𝐶 2 𝑃 𝑃 𝜌 𝐴𝑖𝑟 =1 2 𝜌 𝑊 𝑔𝐹𝑆 𝐼 𝑃 −4𝑚𝐴 16𝑚𝐴 𝜌 𝐴𝑖𝑟 Need to adjust transmitter current to be 4 mA when blower is off, or use actual current with no wind (don’t adjust span) 𝜌 𝑊 =998.7 𝑘𝑔 𝑚 3 𝐹𝑆= 3 𝑖𝑛𝑐ℎ 𝑊𝐶 2.54 𝑐𝑚 𝑖𝑛𝑐ℎ 1 𝑚 100 𝑐𝑚 For: 𝑉 𝐶𝑇𝐴 2 =𝑎 𝑈 +𝑏, find: a and b 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 𝑤 𝑈 =2 𝑈 𝑠 𝑈 , 𝑉 𝐶𝑇𝐴 2 (68%) 𝑆 𝑉 𝐶𝑇𝐴 2 , 𝑈

Hot Film System Calibration The fit equation 𝑉 𝐶𝑇𝐴 2 =𝑎 𝑈 +𝑏 appears to be appropriate for these data. To use calibration : 𝑈= 𝑉 𝐶𝑇𝐴 2 −𝑏 𝑎 2 (program into labview)

Need mean voltage for calibration Fig. 2 VI Block Diagram Mean Voltage Starting point VI Need mean voltage for calibration Need mean speed for Strouhal and Reynolds numbers

Fig. 1 VI Front Panel Don’t use frequency of Maximum Use “eyeball” technique

Unsteady Speed Downstream of a Cylinder When the cylinder is removed the speed is relatively constant Downstream of the cylinder The average speed is lower compared to no cylinder There are oscillations with a broadband of frequencies You don’t need to plot this in the report

Fig. 4 Spectral Content in Wake for Highest and Lowest Wind Speed (a) Lowest Speed URMS [m/s] fp = 751 Hz (b) Highest Speed URMS [m/s] fp = 2600 Hz Hint: Don’t use auto-scale for URMS 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 don’t show the highest frequencies. It is not “straightforward” to distinguish fP from this data. Its uncertainty is wfp ~ 50 Hz.

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 reference value is from A.J. Wheeler and A.R. Ganji, Introduction to Engineering Experimentation, 2nd Edition, Pearson Prentice Hall, 2004, p. 337. 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

Lab 12 Setup Measure beaker water temperature using a thermocouple/conditioner/myDAQ/VI Use myDAQ analog output (AO) connected to a digital relay to turn heater on/off, and control the water temperature Use Fraction-of-Time-On (FTO) to control heater power

Lab 12 Integral Control Block Diagram

Figure 1 VI Front Panel Plots help the user monitor the time-dependent measured and set-point temperatures T and TSP, temperature error T–TSP, and control parameters

Hint Use Control-U to make wiring easier

VI Components Display using slide indicators Input tCycle, fSampling, TSP, DT, and DTi Measure and display temperature T Plot T, T-TSP (error), TSP, TSP-DT, and log(DTi) Increase chart history length, auto-scale-x-axis Write to Excel file (next available file name, one time column, no headers) Calculate 𝐹𝑇𝑂𝑝= 𝑇 𝑆𝑃 −𝑇 𝐷𝑇 and 𝐹𝑇𝑂𝑖= 𝑖 𝑡 𝑇 𝑆𝑃 −𝑇 𝐷𝑇𝑖 (shift register), Limit FTO = FTOp + FTOi to >0 and <1 Display using slide indicators Write data to analog output within a stacked-sequence loop (millisecond wait)

Figure 3 Measured, Set-Point, Lower-Control Temperatures and DTi versus Time Data was acquired for 40 minutes with a set-point temperature of 85°C. The time-dependent thermocouple temperature is shown with different values of the control parameters DT and DTi. Proportional control is off when DT = 0 Integral control is effectively off when DTi = 107 [10log(DTI) = 70]

Figure 4 Temperature Error, DT and DTi versus Time The temperature oscillates for DT = 0, 5, and 15°C, but was nearly steady for DT = 20°C. DTi was set to 100 from roughly t = 25 to 30 minutes, but the system was overly responsive, so it was increased to 1000. The controlled-system behavior depends on the relative locations of the heater, thermocouple, and side of the beaker, and the amount of water in the beaker. These parameters were not controlled during the experiment.

Table 1 Controller Performance Parameters This table summarize the time periods when the system exhibits steady state behaviors for each DT and DTi. During each steady state period TA is the average temperature TA – TSP is an indication of the average controller error. The Root-Mean-Squared temperature TRMS is an indication of controller unsteadiness

TRMS is and indication of thermocouple temperature unsteadiness Figure 5 Controller Unsteadiness versus Proportionality Increment and Set-Point Temperature TRMS is and indication of thermocouple temperature unsteadiness Unsteadiness decreases as DT increases, and is not strongly affected by DTi.

The average temperature error Figure 6 Average Temperature Error versus Set-Point Temperature and Proportionality Increment The average temperature error Is positive for DT = 0, but decreases and becomes negative as DT increases. Is significantly improved by Integral control.

Process Sample Data Add time scale in minutes Figure 3 Figure 4 http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/Labs/Lab%2012%20Thermal%20Control/Lab%20Index.htm Add time scale in minutes Calculate difference, general format, times 24*60 Figure 3 Plot T, TSP, DT and 10log(DTi) versus time Figure 4 Plot T-TSP, -DT, 10log(DTi) and 0 versus time Table 1 Determine time periods when behavior reaches “steady state,” and find 𝑇 𝐴 = 𝑇 and 𝑇 𝑅𝑀𝑆 = 𝜎 𝑇 during those times Figure 5 Plot 𝑇 𝑅𝑀𝑆 versus DT and DTi Figure 6 Plot 𝑇 𝐴 − 𝑇 𝑆𝑃 versus DT and DTi

VI Block Diagram Modify proportional VI http://wolfweb.unr.edu/homepage/greiner/teaching/MECH322Instrumentation/Labs/Lab%2012%20Thermal%20Control/Lab%20Index.htm

Figure 1 VI Front Panel Plots help the user monitor the measure and set-point temperatures T and TSP, temperature error T–TSP, and control parameters