Hot Wire Anemometry Laboratory

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Henry Dickerson
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1 Lab # 2 Hot Wire Anemometry Laboratory Objectives:. To get hands-on experiences on how to conduct flow velocity measurements by using hot wire anemometry technique. 2. To learn how to determine the ensemble-averaged velocity, turbulent intensity and turbulent spectrum for the instantaneous measurement results of a hot wire anemometer. Technical Background:. Calibration experiments to determine the relationship between the in coming flow velocity, U, and the voltage output, v, from the electric circuit of the CTA. The relationship between the in coming flow velocity, U, and the voltage output, v, from the electric circuit of the CTA usually can be expressed as a polynomial function, U = Co + Cv + C2v + C3v + C4v, where C o, C, C2, C3 and C4 are the coefficients to be determined by the calibration experiments. Since it is quit time consuming to do the calibration experiments, the result of calibration experiment is provided for you use in order to save your time. The calibrated relationship for the hotwire probe used for your experiment will be provided by the TA. An example of calibration curve is: U = v v v v The studied flow field. The flow field to be measured is a wake flow of a circular cylinder. The students will be divided into 4 groups to measure the mean velocity and turbulence intensity profiles across the wake flow at different Reynolds number levels. 3. Calculation of the ensemble-averaged parameters based on the instantaneous flow velocity measurement results.

2 The ensemble-averaged parameters such as mean velocity U and turbulent intensity RS (u) can be determined based on the instantaneous flow velocity measurement results u (t). U = u i i=, 2 ( ui U ) i= RS( u) =. Identify the vortex shedding frequency The power spectrum of the flow velocity can also be determined by transferring of the instantaneous measurement data to frequency domain through FFT transformation. The shedding frequency of the vortex structures in the wake of the circular cylinder can be identified for the power spectrum of the velocity measurements results.

3 Requirements for the Lab Report. You are required to prepare a formal lab report with following results included: a. A plot of the ensemble-averaged velocity profile across the wake flow ( at least measurement points). b. A plot of the turbulence intensity profile across the wake flow ( measurement points). c. Plots of the power spectrum of the flow velocity at two interested points (the locations of the interested points to be decided by yourself) 2. Report requirement: a. Calculations for all the steps leading up to the final answers. b. Representative raw data shown as spreadsheet. c. A brief discussion about the measurement error estimation of your results.

4 The Experimental Data eeded for the Lab #2. Atmosphere pressure in the lab, P 2. The temperature in the wind tunnel lab, T 3. The density of air in the wind tunnel lab, ρ 4. The voltage outputs of the CTA system at the interested points v v atm 5. The flow velocity corresponding to the voltage outputs of the CTA system at the interested points. u u ote: For the instantaneous velocity measurements, it is recommended to run the CTA with the data acquisition of about 2000Hz for about 0 seconds for each measurement point in order to calculate the ensemble-averaged velocity and the power spectrum of the flow velocity.

5 The parameter setting for the experiments: First ame Last ame motor speed Sunil Arolla 70Hz Daniel Dvorak 70Hz Daniel Garrick 70Hz Xuan Ge 70Hz Christopher Karstens 60Hz eng Lo 60Hz John eyer 60Hz Katrine ilsen 60Hz Ahmet Ozbay 50Hz Suganthi Selvaraj 50Hz Jason Ryon 50Hz Spencer Pack 50Hz Lei Shi 40Hz Hephzibah Thampi 40Hz Kai Zhang 40Hz

Module 3: Velocity Measurement Lecture 16: Validation of PIV with HWA. The Lecture Contains: Hotwire Anemometry. Uncertainity

Module 3: Velocity Measurement Lecture 16: Validation of PIV with HWA. The Lecture Contains: Hotwire Anemometry. Uncertainity The Lecture Contains: Hotwire Anemometry Hotwire Measurements Calibration Methodology Curve Fitting Directional Probe Senstivity Data Reduction Uncertainity Validation of Experiments Comparision of Hot