Schlieren Flow Visualization and Analysis of Synthetic Jets

This work explores several low-cost methods for the visualization and analysis of pulsed synthetic jets for cooling applications. The visualization methods tested include smoke, Schlieren imaging, and thermography. The images were analyzed using Proper Orthogonal Decomposition (POD) and numerical methods for videos. The results indicated that for the specific nozzle studied, the optimal cooling occurred at a frequency of 80 Hz, which also corresponded to the highest energy in the POD analysis. The combination of Schlieren photography and POD is a unique contribution as a method for the optimization of synthetic jets.

Visualization of the gas flows that formed above the thin-film coatings under VUV radiation influence

The plasma focus of a magnetoplasma compressor is a unique source of high-brightness broadband VUV (with photon energy of 5 to 100 electron volt) radiation. When such radiation affects on the surfaces of materials, it is possible to generate rather complex gas-dynamic structures due to the evaporation of the material and ionization of its vapors. A separate task is to study the processes of a gas-dynamic response to the exposure of the specified radiation fluxes on the surface of interference antireflection and reflective multilayers, which are used in modern laser technology, high-power optoelectronics, etc. In this report, we used schlieren photography for studying the features of gas-dynamic structures that arise at irradiation of coatings. Radiation resistant (in the visible and near IR ranges) HfO2/SiO2 and ZrO2/SiO2 multilayer structures (with a total thickness of 140–3700 nanometers and a number of layers of from 2 to 24) were used as prototypes for testing their stability under the VUV exposure.

A Novel Concept for Air Removal in Two-Phase Immersion Cooling Systems

A 10 kW scale model of a decoupled immersion cooling rig is constructed in order to serve as a testbed for immersion cooling, using 3M FC3284 dielectric cooling fluid. A species separator is constructed and demonstrates an ability to remove air from the flowfield before the condensable gases enter the condenser vessel, verified with Schlieren photography. The condenser underperformed significantly compared to initial sizing calculations using the NTU method, and film thickness of FC3284 liquid on the surface of the condenser was determined to be the cause due to low thermal conductivity of the liquid. The average film thickness on the surface of the condenser is calculated. In addition to the performance detriment of the film, air is also shown to reduce the condenser’s performance. The height of a transient stratification line is measured and compared against condenser power. Condenser efficacy losses are large and variable based on the concentration of air in the condenser vessel. A low vs high-mounted boiler is investigated. The mounting of the boiler has an effect on how much vapor is lost during a maintenance event. Finally, a comparison of the test rig’s overall cooling efficiency is made with various air-cooled datacenters by tracking energy consumption to cool a given IT load. This also translates to a reduction in carbon emissions.

On the Synchronization of Candle Oscillators

In this study we will investigate an interesting collective behavior of candles. It has been observed that when several candles burn close to each other they form a common flame that exhibits oscillations in size and brightness. If two such oscillators burn together, they interact and the oscillations of the resultant system depend on the distance between them. The aim of this investigation, inspired by Problem 5 of the International Young Physicists Tournament in 2021, is to theoretically explain the phenomenon through overlapping of hot gas flows and radiation, as well as to check our understanding and measure additional parameters experimentally using advanced techniques, such as high speed schlieren photography.

A corpus of Schlieren photography of speech production: potential methodology to study aerodynamics of labial, nasal and vocalic processes

This report presents a corpus of articulations recorded with Schlieren photography, a recording technique to visualize aeroflow dynamics for two purposes. First, as a means to investigate aerodynamic processes during speech production without any obstruction of the lips and the nose. Second, to provide material for lecturers of phonetics to illustrates these aerodynamic processes. Speech production was recorded with 10 kHz frame rate for statistical video analyses. Downsampled videos (500 Hz) were uplodad to a youtube channel for illustrative purposes. Preliminary analyses demonstrate potential in applying Schlieren photography in research.

Schlieren Imaging of Single-Fin Missile models in a De-Laval Nozzle Test Section

The experimental study (Schlieren photography) to characterize the flow behavior around a semi-cylindrical missile model having a single planar and wrap-around fin surface is performed inside a modified De-Laval nozzle test section capable of sustaining an airflow at Mach number ~1.7M. The images obtained from this schlieren technique is compared with flow field contour images of the similar missile models at similar flow conditions. The experiments are performed on a modified two-walled glassed section to assist the Schlieren imaging. The test section is calibrated preliminary to the experiments to assure the supersonic fluid flow. A comparison of flow images around the two types of fins further helps in characterizing the flow in their vicinity.