Toshiharu Mizukaki

Submicrosecond temperature measurement in liquid water with laser-induced thermal acoustics

Using laser-induced thermal acoustics, we demonstrate nonintrusive and remote sound-speed and temperature measurements in liquid water. Unsteady thermal gradients in the water sample produce fast, random laser beam misalignments, which are the primary source of uncertainty in these measurements. For water temperatures over the range 10 degrees C to 45 degrees C, the precision of a single 300-ns-duration measurement varies from +/-1 to +/-16.5 m/s for sound speed and from +/-0.3 degrees C to +/-9.5 degrees C for temperature. Averaging over 10 s (100 laser pulses) yields accuracies of +/-0.64 m/s and +/-0.45 degrees C for sound speed and temperature, respectively.

Quasi-Real Time Bio - Tissues Monitoring using Dynamic Laser Speckle Photography

AbsractJoint development of a laser monitor for the real-time bio-tissue analysis is presented. The monitor is based on the digital dynamic laser speckle photography and deals with soft and hard bio-tissues. In soft tissues, the dynamic bio-speckles are formed in a scattered from a tissue laser light. An optically transparent model of hard bio-tissue was prepared and preliminary analysis of a stress field in the stressed model was performed using the dependence of the refractive index of transparent solids upon the state of stress and the double exposure speckle photography data. The refractive index of the stressed material was evaluated and the state of stress was reconstructed using the stress-optical law.

Development of Background-Oriented Schlieren for NASA Langley Research Center Ground Test Facilities

This paper provides an overview of recent wind tunnel tests performed at the NASA Langley Research Center where the Background-Oriented Schlieren (BOS) technique was used to provide information pertaining to flow-field density disturbances. The facilities in which the BOS technique was applied included the National Transonic Facility (NTF), Transonic Dynamics Tunnel (TDT), 31-Inch Mach 10 Air Tunnel, 15-Inch Mach 6 High-Temperature Air Tunnel, Rotor Test Cell at the 14 by 22 Subsonic Tunnel, and a 13-Inch Low-Speed Tunnel.

Background-Oriented Schlieren for Large-Scale and High-Speed Aerodynamic Phenomena (Invited)

Visualization of the flow field around a generic re-entry capsule in subsonic flow and shock wave visualization with cylindrical explosives have been conducted to demonstrate sensitivity and applicability of background-oriented schlieren (BOS) for field experiments. The wind tunnel experiment suggests that BOS with a fine-pixel imaging device has a density change detection sensitivity on the order of 10(sup -5) in subsonic flow. In a laboratory setup, the structure of the shock waves generated by explosives have been successfully reconstructed by a computed tomography method combined with BOS.

Visualization of Flow Separation Around an Atmospheric Entry Capsule at Low-Subsonic Mach Number Using Background-Oriented Schlieren (BOS)

This paper presents the results of visualization of separated flow around a generic entry capsule that resembles the Apollo Command Module (CM) and the Orion Multi-Purpose Crew Vehicle (MPCV). The model was tested at flow speeds up to Mach 0.4 at a single angle of attack of 28 degrees. For manned spacecraft using capsule-shaped vehicles, certain flight operations such as emergency abort maneuvers soon after launch and flight just prior to parachute deployment during the final stages of entry, the command module may fly at low Mach number. Under these flow conditions, the separated flow generated from the heat-shield surface on both windward and leeward sides of the capsule dominates the wake flow downstream of the capsule. In this paper, flow visualization of the separated flow was conducted using the background-oriented schlieren (BOS) method, which has the capability of visualizing significantly separated wake flows without the particle seeding required by other techniques. Experimental results herein show that BOS has detection capability of density changes on the order of 10(sup-5).

Visualization of very weak shock waves by digital phase-shift interferometry

In this study, the method of digital phase shift holographic interferometry is applied to accurately measure the density distribution behind a weak shock wave. The goal of this investigation is to visualize and quantitatively evaluate flow fields behind weak disturbances, which are only marginally stronger than sound waves. In the present experiment, the shock Mach number was approximately Ms approximately equals 1.01. The wave was generated by the explosion of a small silver-azide (micro- charge) pellet, which was ignited by an Nd:YAG laser. Using phase shift interferometry, the phase distribution of the region far behind the incident shock could be detected.

Digital phase-shift holographic interferometry for quantitative measurements of weak shock waves and its related phenomena

By applying two-reference beam interferometry together with digital data processing, a correspondingly modified double exposure holographic interferometer has been used to measure the density distribution in flow fields generated by very weak shock waves. The weak shock waves were generated by the explosion of milligram charges of silver azide, which were ignited by a pulsed Nd:YAG laser. With the help of this technique, density variations in a flow field associated with a shock Mach number Ms = 1.0007 were visualized and quantified. Phenomena that generated a sound intensity of 135dB could be resolved.

Measurement of density distribution in a small cell by digital phase-shift holographic interferometry

Using digital phase shift holographic interferometry (DPSHI), the internal density distribution of water which is sealed in a cylindrical cell has been measured under the condition that one of the cylinder end walls is oscillated by a PZT-actuator, which is driven by high frequency: 20kHz. The density distributions concerned with three different end wall pressures have been visualized and analyzed by DPSHI. Carre algorithm is employed for phase interpolation to reproduce phase maps. The absolute density changes in the cell have been demonstrated. The results have indicated that DPSHI can allow us to measure small density changes in narrow space under high frequency oscillation.