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Computational Fluid Dynamics (CFD) modeling is effectively coupled with the experi-

Recent progress in the development of a miniature Laser Doppler Anemometer (LDA) and a micro optical shear stress sensor is described. Miniaturization of these sensors has been achieved with the use of integrated optics and micro fabrication techniques. This paper describes the fabrication of the two sensors and presents an experiment for the evaluation of the sensors. The results show perfect agreement between the boundary layer velocity gradient performed with the LDA, and the measurements obtained with the shear stress sensor. The range of experimental conditions suitable for the wall shear sensor is reported. Finally, we describe the application of the sensors in a series of tests performed at the William B. Morgan Large Cavitation Channel of the Navy's Carderock Division, in Memphis, Tennessee.

In an effort to extend wall shear stress measurements to high Reynolds number flows, a new MEMSbased optical shear stress sensor was fabricated and tested in the 2 feet wind tunnel at the California Institute of Technology for Reynolds numbers of up to 5.6 x 10 6. The description of this sensor and the test results are reported in this paper. The sensor, the Dual Velocity sensor, designed using recent developments in diffractive and integrated optics, was small enough to be embeddable in test models. The sensor measured the average flow velocity at two probe volumes located within the first 110 micrometers above the flush-mounted sensor surface. The velocity gradient at the wall was estimated by fitting the Spalding formula to the average velocity measurements, once mapped using the inner-law variables u+ and y+. The results obtained with the Dual Velocity sensor were in excellent agreement with measurements obtained in the same tunnel using other techniques such as the oil film interferometry technique and with another MEMS-based optical shear stress sensor, the Diverging Fringe Doppler sensor. All wall shear stress measurements were also in agreement with those calculated from boundary layer surveys obtained with a miniature LDV.

Quantitative flow visualization has many roots and has taken several approaches. The advent of digital image processing has made it possible to practically extract useful information from every kind of flow image. In a direct approach, the image intensity or color (wavelength or frequency) can be used as an indication of concentration, density and temperature fields or gradients of these scalar fields in the flow (Merzkirch, 1987). For whole-field velocity measurement, the method of choice by experimental fluid mechanicians has been the technique of Particle Image Velocimetry (DPIV). This paper presents a novel approach to extend the DPIV technique from a planar method to a full three-dimensional volume mapping technique useful in both engineering and biological applications.