# Simultaneous measurement of fluctuating velocity and pressure

### Overview

It is well recognized that velocity-pressure correlation is one of fundamental turbulence statistics including fluctuating pressure, and it well reflects the flow structure. Recent progress of computer technology enables us to simulate the complex turbulence phenomena and pressure-related statistics becomes obtainable. However, it has still been challenging issue for experimentalists to evaluate these statistics because of technical difficulties with accurate measurement of fluctuating pressure.

In the present study, a fluctuating pressure probe was fabricated. It is composed by miniature-static pressure tube shown in the picture below and condenser microphone as a pressure transducer. Fluctuating pressure is captured at small holes on the wall of pressure tube and it is converted electric signal through the vibration of the diaphram. As for velocity measurment, conventional hot-wire anemometry is employed. The hot-wire- and the fluctuating pressure- probes are closely placed, and velocity-pressure correlation is calculated from the result of the simultaneous measurement of velocity and pressure.

So far, a plane turbulent mixing layer was picked up for the test case, and pressure-related statistics were estimated. The results were coincide with DNS result, therefore it is confirmed that the present method is valid.

Currently, we're trying to improve the applicability of our method to more complex flow.

### Related Reports

- Kawata, T., Naka, Y., Fukagata, K, Obi, S., Simultaneous measurement of three velocity components and pressure fluctuation in a turbulent wing-tip vortex, 6th International Symposium on Turbulence, Heat and Mass Transfer (THMT-6), Italy, September, 2009.
- Naka, Y., Obi, S., Velocity-pressure correlation measurements in complex free shear flows, Int. J. Heat Fluid Flow, 30, 3, 411-420, 2009. doi:10.1016/j.ijheatfluidflow.2009.01.002
- Naka, Y., Azegami, S., Kawata, T., Fukagata, K. and Obi, S., 2009, Simultaneous measurement of velocity and pressure in a wing-tip vortex, Journal of Fluid Science and Technology, Vol. 4, No. 1, 107-115.
- Naka, Y. and Obi, S., Velocity-pressure correlation measurements in complex free shear flows, ETMM-7, Cyprus, June, 2007
- Naka, Y., Obi, S., and Masuda, S., Development of a miniature probe for velocity-pressure correlation measurement, Proc. TSFP-5, Garching, Germany, Aug. 28, 2007. 619-624.
- Naka, Y., Omori, T., Obi, S. and Masuda, S., Simultaneous measurement of fluctuating velocity and pressure in a turbulent mixing layer. International Journal of Heat and Fluid Flow, 2006, 27, 737-746
- Naka, Y., Obi, S. and Masuda, S., Measurement of velocity-pressure correlation in a free shear flow., EFMC-6, 2006/6/27-30
- Naka, Y., Omori, T., Obi, S. and Masuda, S., Experimental study on velocity-pressure correlation in turbulent mixing layer out of equilibrium state., TSFP-4, 2005/6/27-29
- Omori, T., Obi, S., Masuda, S., 2003. Experimental study on velocity-pressure correlation in turbulent mixing layer, 4th Int. Symp. Turbulence, Heat and Mass transfer, Antalya, Turkey, 253-260