Synchronous measurement system of fluctuating pressure and noise

[marketing]

Contact Information

Competition Year: 2015

University: The University of Tokyo

Team Members (with year of graduation): Noriaki KOBAYASHI (M.Eng Grad 03/2015, Ph.D Grad 03/2018), Yasumasa SUZUKI (M.Eng Grad 03/2001, Ph.D Grad 01/2006)

Faculty Advisers: Chisachi KATO

Email Address: noriaki@iis.u-tokyo.ac.jp

Submission Language: English

Project Information

Title: Synchronous measurement system of fluctuating pressure and noise

Description: In wind tunnel tests such as measurement of airfoil noise and flow field around airfoil, long time, high accuracy performance, multi-point and synchronous measurement are important. Using LabVIEW and NI Compact DAQ, it is possible to create the measurement and process system.

Products: LabVIEW 2014 (32 bit), LabVIEW 2014 (64 bit), Sound and Vibration Toolkit 2014, cDAQ-9172, NI 9215

The Challenge: In this study of airfoil noise with inflow turbulence, we need to have measurement of airfoil noise and flow field around airfoil in wind tunnel tests. In addition, for the purpose of high accuracy performance, multi-point and synchronous measurement is required in these tests. Moreover, a longtime measurement, over 10 minutes, is also important. But temperature of the laboratory is changed, for very long time measurement, within 2 hours. Therefore, measurement system which developed in LabVIEW must satisfy these conditions, multi-point, synchronous and longtime measurement.

The Solution:

In our wind tunnel tests, we use measuring instruments such as sound level meter, hot wire anemometers, pitot tubes, a pressure sensors, and thermocouples. The analog signals from the measuring instruments are connected to NI Compact DAQ (NI9215 in cDAQ-9172). And we have the multi-point synchronous measurement using programs of LabVIEW.

The measurement system is divided into three parts, which are Control section and Test section at Laboratory room, and Processing section at Office room shown in Fig.1.

               Fig.1 Overview of the measurement system

First, in Test section, there are some models such as cars, airfoils, and cylinders, and measuring instruments and a traverse device. In addition, Test section is in an anechoic chamber for increasing accuracy of noise measurement. Therefore, only cables, BNC and RS-232c, are out of the anechoic chamber and instruments are controlled from the outside of the anechoic chamber.

Second, in Control section, there are NI Compact DAQ (NI 9215 in cDAQ-9172) and a PC that LabVIEW (32 bit version) has been installed. Cables of BNC from test section are connected to NI 9215, and cables of USB 2.0 from cDAQ-9172 and RS-232c from traverse device are connected to the PC. In tests, we can get analog signal from measuring instruments using Compact DAQ and LabVIEW, and save in TDMS format files on the PC. In addition, it is capable of continuous automatic measurement by interlocking control of traverse device and measurement of Compact DAQ. Furthermore, it can calculate average and fluctuation value, and FFT analysis at the same time of measuring.

Finally, in Processing section, there is a PC that LabVIEW (32 and 64 bit version). TDMS files are sent to the PC of Office room from the PC of Laboratory room by Ethernet. It can be a fledged calculation of average and fluctuation value, and FFT and cross-correlation analysis in simultaneously process. Therefore, on the system, it is possible to read and process of some TDMS files at the same time.

In our experience, it is possible to synchronize measurement of 10 minutes at 16 channels and we get surface pressure and noise waveform of the airfoil model as a TDMS file, whose size is 4 GB. In 1 day, we have about 30 times measurements. Therefore total size of 30 files is 120 GB. And it takes 24 hours in processing section to process 30 files. And results of cross-correlation analysis of pressure fluctuation and airfoil noise and pressure fluctuation distribution of airfoil are shown in Fig.2 and Fig.3.

               Fig.2 Cross-correlation analysis of pressure fluctuation and airfoil noise

               Fig.3 Pressure fluctuation distribution of airfoil

In our study, high accuracy performance, multi-point, synchronous measurement and continuous automatic measurement are required in these tests and we need to get a lot of data and files. Using LabVIEW and NI Compact DAQ, we can easily create the measurement and process system. In addition, we can consistently run from measurement until the process because LabVIEW also play as two roles of instruments control and process.

Video

VI Code

Level of completion:

Beta.

Time to build:

3 days (24 hours = 8 hours in 1 day)

Additional revisions that could be made:

Using the system, it is possible to have high accuracy performance, multi-point, synchronous measurement and continuous automatic measurement.

Next, we want to add some functions such as automatic determination of measurement error, transfer and processing of measurement files to the system.