A High-Speed Digital Holocamera for the 3-D Analysis of Flow Interaction with High Speed Flows

In hypersonic flight, airborne particles such as water or ice can penetrate and alter the bow shock and flow field, enhance erosion mechanisms and alter aerodynamics. Particles break up as they pass through the shock wave, impact the surface, erode and increase surface roughness, increase turbulence and heat transfer, and augment heating that can destroy heat shields prematurely. Many tests and theoretical analyses, conducted to examine such effects, have yet to a produce a complete understanding and quantification of the processes because of limitations with existing diagnostics. This proposal addresses the need for improved, high-quality, experimental data that captures both the spatiotemporal evolution of the hydrometeors during aero breakup and the effect of the aero breakup on the surrounding flow field. Such data will enable development and validation of improved numerical tools.  Particle field holography has proven itself to be one of the most powerful tools for the study of dynamic 3D fields. Digital holography raises the technique to even higher levels, and its many variations can provide, high speed, 3D video of dynamic, microscopic particle and flow field events over a large volume. The MetroLaser team, which includes Caltech, Aerospace Department, will develop and apply the latest digital holography technology to develop and demonstrate a tool that can track particles in a relatively large volume as they pass through shock waves, break up, and alter the flow field. In addition to quantifying particle size, shape, and velocity, we will also apply holographic interferometry in the same system to quantify and observe the dynamics of the flow field.  The proposed research will build upon our extensive experience employing digital holography in fuel injection and combustor development, enabling a microscopic examination of formation and break up phenomena in fuel injectors showing dynamic particle and ligament formation and break up in extreme conditions, including high pressure and optically dense environments that can be almost opaque.  We propose in Phase I and its option to conduct analyses, bread board and shock tunnel experiments, and design work to establish and demonstrate that all the U.S. Navy requirements can be met in an affordable instrument. We will examine the many possible digital holography configurations, measurement requirements and scenarios they must satisfy, and candidate laser and camera and laser combinations for the specified application. We will produce a preliminary design for a prototype system to be constructed, tested, and demonstrated during Phase II for deployment in U.S. Navy specified facilities or in other candidate test facilities to be evaluated during Phase I option.  This work is expected to provide the U.S. Navy and its contractors with an extremely important tool and capability to aid in future developments of hypervelocity missile technology.