Schlieren Optical Method Research Articles

101 ダブルスロットによる凝縮衝撃波の制御

Since the concept of passive control of shock-boundary layer interaction using a double slot was published in 1984, several papers have been reported on the application of this technique to transonic airfoil flows. In the present paper, this technique is applied to condensation shock wave which is caused by rapid expansion of moist air in a supersonic nozzle. The effects of passive control on condensation shock wave have been experimentally investigated by a schlieren optical method and pressure measurements. As a result, it is found that the passive control is the useful technique to suppress the periodic oscillation of condensation shock wave.

55 キャビティ付多孔壁による凝縮衝撃波の制御

Since the concept of passive control of shock-boundary layer interaction was published in 1983, many papers have been reported on the application of this technique to transonic airfoil flows. In the present paper, this technique is applied to condensation shock wave which is caused by rapid expansion of moist air in a supersonic nozzle. The effects of passive control on condensation shock wave have been experimentally investigated by a schlieren optical method and by pressure measurements. As a result, it is found that passive control is the useful technique to suppress the periodic oscillation of condensation shock wave.

Investigations of transonic diffusers. (1st report Behavior of a shock wave in a two-dimensional circular diffuser)

The behavior of shock waves in a two-dimensional transonic circular diffuser has been experimentally investigated by a schlieren optical method and by pressure measurements. When the overall pressure ratio of the diffuser, φ, increases, a few weak shock waves appear near the throat section before the flow is completely choked at the throat. These weak shocks are not stable but fluctuate in the channel, and the pressure at the throat p* increases with an increasing φ, although it is not in proportion to φ. when the flow is completely choked, these weak shocks coalesce into a single normal shock, and p* increases in proportion to φ. The behavior of the shock waves in diffusers with different geometries can be plotted on a single curve in an x/√(h*R)-φ plane if the position of the shock from the diffuser throat x is non-dimensionalized by the characteristic length √(h*R), where h* and R are the throat height and the radius of curvature of the diffuser, respectively.

Method for the measurement of the sound velocity in metastable liquids, with an application to water

A standard optical Schlieren method has been adapted to the problem of measuring the speed of sound in moderately supercooled and in superheated liquids under atmospheric pressure. The estimated accuracy is ±3 m/s. Results in supercooled water down to −16.75 °C and in superheated water up to 176.5 °C are reported.

Velocity of sound in superheated water

We present the first measurements of the sound velocity of distilled water superheated to 150°C at atmospheric pressure. This was accomplished by using a prepressurization scheme [E. Harvey et al., J. Cell. Comp. Physiol. 24, 1 (1944); 24, 23 (1944)]. This procedure eliminates the microscopic gas prockets which ordinarily prevent a liquid from undergoing significant superheating. A modified all quartz spectrophotometer cell holds the liquid in which an acoustic standing wave of 2.5 MHz has been established. An optical schlieren method has been used to visualize this standing wave, thus allowing an absolute measurement of the acoustic wavelength and thereby the calculation of the sound speed. The error in the data obtained so far is estimated to be less than 0.2%. At the present time we are trying to gather additional data at higher temperatures, to refine the thermal control system, and to reduce the error. [This work supported by U. S. Office of Naval Research.]

Effect of heat conduction on the vibration-translation relaxation time measured by an optical Schlieren method

Quantitative calculations show that heat conduction plays a dominant role in optical Schlieren measurements of vibration-translation relaxation times in liquid O 2 and N 2. Previous experimental results are re-examined on the basis of these calculations.

Schlierenoptical Stress Analysis of Short Duration Pulses in Elastic Plates

Applying a quantitative schlieren optical method, the shape and the stress amplitudes of elastic pulses traveling through a plate are determined experimentally. The short duration pulses are generated by loading an edge of the plate with an exploding wire. The influence of several experimental parameters is shown. The primary dilatational pulse splits up into a train of equally spaced pulses.

Very long vibrational lifetimes in liquid O2 and N2

Abstract Via stimulated Raman scattering the first vibrational energy level is excited above the thermal equilibrium value. Using an optical Schlieren method the vibration-translation relaxation times are measured to be 50 μs and 1 ms in liquid O 2 and N 2 , respectively.