We propose to develop a novel laser velocimetry technique to simultaneously measure multi-component flow velocity at multiple-points. The velocity is measured using diode array velocimetry technique, DAV. Multiple DAV probe volumes are generated simultaneously using a holographic optical element (HOE) lens. The frequency content of a signal generated by a particle is analyzed by a digital signal processor (DSP) using fast Fourier transform (FFT) techniques. The velocity is determined from the product of frequency and laser-to-laser separation. We have demonstrated the feasibility of DAV/HOE technique for measuring a single velocity component at multiple probe volumes [1,2]. Here, we propose to extend DAV to distinguish the direction of the flow velocity, and to develop methods to simultaneously measure two or three components of velocity. Microgravity combustion experiments often require the measurement of the instantaneous velocity vector and its turbulence characteristics at multiple points. Currently microgravity experiments are carried out on one or a combination of several platforms including: drop towers, aircraft, and space scuttle. These platforms have limited available working volume and power. Therefore, the velocity diagnostic technique has to result in a compact, self-aligned, low power consumption, and stand- alone instrument that is safe & reliable and be capable of measuring the velocity at multiple points without any mechanical motion.
Potential Commercial Applications: An inexpensive laser velocity instrument that does not require laser coherence and is capable for multi- point measurements without any mechanically moving parts is in demand for many applications other than microgravity experiments. Large commercial market applications include volumetric flow rate measurements in natural gas custody transfer and/or distribution stations, volumetric flow rate measurements of the flue gases emitted from the smoke stacks, and air intake for jet airplanes. The inexpensive feature of DAV/HOE technique will render it the instrument of choice in wind tunnel and laboratory measurements. The incoherence nature of DAV technique will make it a potential candidate for an optical air data sensor for use aboard aircrafts.
