A non-obstructive fluid diagnostic technique is described which enables the measurement of different parameters in a fluid. The diagnostic technique includes the steps of focusing a laser (10) in a fluid volume (14) to generate a laser induced breakdown spark (15). The characteristics of the initial laser induced breakdown spark (15) are measured and compared to the characteristics of a delayed image of the spark, formed by light emission due to recombination and excited molecules and ions generated by the laser induced spark (15). The differences between the initial and delayed images being used to diagnose characteristics of the fluid, such as velocity, temperature and pressure.

A method of superficial laser induced fluorescence for measuring film cooling performance within a fluid tunnel apparatus includes the step of introducing a test fluid uniformly dyed with a fluorescent dye into the fluid tunnel apparatus so as to surround a cooling model having a test geometry. The cooling model is positioned adjacent to a laser sheet. A background fluorescent image of the test fluid about the cooling model is recorded. The test fluid is then flushed from the tunnel apparatus. Next, a cooling simulation fluid flow and a hot gas simulation flow are introduced within the fluid tunnel apparatus. The cooling simulation fluid contains the same fluorescent dye concentration as the test fluid and the hot gas simulation fluid contains no fluorescent dye. A data image of the cooling simulation fluid flow is recorded about the cooling model as the cooling simulation fluid flow passes through the cooling model and into the hot gas simulation fluid flow. Finally, the data image is corrected using the background fluorescent image so as to determine superficial flow characteristics of the cooling simulation fluid flow passing through the cooling model.

In the method for measuring the velocity of fluid or visualizing the distribution of fluid by feeding tracer particles to the fluid, irradiating the fluid with light and observing return light from the tracer particles, tracer particles containing a fluorescent substance are fed at least partially to the fluid and the fluid is irradiated with exciting light to cause the tracer particles to output fluorescent emissions. A filter which does not transmit the exciting light is used to substantially selectively observe the fluorescent emissions of the tracer particles. This method results in a remarkable improvement in the accuracy of flow velocity measurement or visualization of fluid distribution. Moreover, in a mixed fluid system consisting of two or more different fluids, the pattern of behavior of each fluid and the intermingled state of the fluids can be observed by using a plurality of different tracer particles.

In the method for measuring the velocity of fluid or visualizing the distribution of fluid by feeding tracer particles to the fluid, irradiating the fluid with light and observing return light from the tracer particles, tracer particles containing a flourescent substance are fed at least partially to the fluid and the fluid is irradiated with exciting light to cause the tracer particles to output flourescent emissions. A filter which does not transmit the exciting light is used to substantially selectively observe the flourecent emissions of the tracer particles. This method results in a remarkable improvement in the accuracy of flow velocity measurement or visualization of fluid distribution. Moreover, in a mixed fluid system consisting of two or more different fluids, the pattern of behavior of each fluid and the intermingled state of the fluids can be observed by using a plurality of different tracer particles.

A multiple-exposure fluorescent image tracking velocimeter (FITV) detects and measures the motion (trajectory, direction and velocity) of small particles close to light scattering surfaces. The small particles may follow the motion of a carrier medium such as a liquid, gas or multi-phase mixture, allowing the motion of the carrier medium to be observed, measured and recorded. The main components of the FITV include: (1) fluorescent particles; (2) a pulsed fluorescent excitation laser source; (3) an imaging camera; and (4) an image analyzer. FITV uses fluorescing particles excited by visible laser light to enhance particle image detectability near light scattering surfaces. The excitation laser light is filtered out before reaching the imaging camera allowing the fluoresced wavelengths emitted by the particles to be detected and recorded by the camera. FITV employs multiple exposures of a single camera image by pulsing the excitation laser light for producing a series of images of each particle along its trajectory. The time-lapsed image may be used to determine trajectory and velocity and the exposures may be coded to derive directional information.