TITLE:

Pressure PIV: An Optics-Based Pressure Measurement Technique and Its Applications

DATE:

Friday, October 10th 2014

TIME:

3:30 PM

LOCATION:

GMCS 214

SPEAKER:

Dr. Xiaofeng Liu. Department of Aerospace Engineering at SDSU

ABSTRACT:

Motivated by the fact that there was a lack of an appropriate means for measurement of the

instantaneous spatial pressure field in fluid dynamics research, a novel system and technique

capable of performing such a measurement in a non-intrusive manner in turbulent flow fields

was developed (Liu and Katz, Exp Fluids 2006, Phys. Fluids 2008, JFM 2013). Originally

utilizing four-exposure PIV, and later on a time-resolved version with a high-speed camera

and a high repetition rate laser, the system measures the distribution of material acceleration

by comparing the velocity of the same group of particles at different time, and then integrates

to obtain the pressure field. In order to minimize the error in the pressure field measurement,

an efficient algorithm featuring virtual boundary omni-directional integration over the entire

flow field was introduced and the corresponding code was developed. With this system, the

instantaneous velocity, material acceleration, and pressure field can be measured simultaneously.

In addition to the principles, procedures and development history, in this presentation I will also

show example applications of the pressure measurement technique in unsteady fluid dynamics,

acoustics and turbulence research. A central theme of several research initiatives currently

being carried out at SDSU is focused on establishing a time-resolved 3D velocity and pressure

measurement technique and system, which couples the tomographic PIV together with the

extension of the 2D pressure reconstruction method to 3D. As will be discussed, this opens up

the prospect of direct measurement of all components of the fluctuating pressure-strain rate

tensor in turbulent flows for the first time, and subsequently enabling experimental data-based

improvement in pressure-strain turbulence models.

HOST:

Dr. Satchi Venkataraman

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