Instrumentation for Studies of High Reynolds Number Non-Equilibrium Flows
Abstract
Investigating the behavior and characteristics of high Reynolds number turbulence is of great importance for our ability to understand and predict flows of relevance to the naval applications. Such flows cannot be computed using Direct Numerical Simulations, and so detailed experiments become essential. At Princeton, we have made extensive use of high pressure facilities to generate high Reynolds number flows in the laboratory, and consequently we have helped to advance our knowledge of wall-bounded flows and wakes. Achieving highReynolds number by increasing the pressure, however, brings major challenges in instrumentation. For example, spatial resolution can be a serious obstacle, and so we developed Nano-Scale Thermal Anemometry Probes (NSTAP) with a spatial resolution down to 30 ~m [1, 2]. These sensors enabled unique studies at unprecedented Reynolds numbers. Unfortunately, NSTAP or hot-wire measurements are mostly limited to single point data and they can give only limited information on the structure and organization of turbulence.Equipment is therefore requested that will enable unique measurements of three dimensionalturbulent velocity fields at very high Reynolds number. The equipment isdesigned such that it can be used in all of the Princeton high Reynolds number facilities that use high-pressure air as the working fluid (Superpipe, HRTF, and the new FSUFT) and permit the use of Particle Image Velocimentry (PIV) in these facilities for the first time. The system will be able to operate both as conventional PIV and Particle Shadow Velocimetry, and it will incorporate tunable acoustic gradient index of refraction lenses (TAG lenses), which can change their focal length at MHz rates. This novel approach promises volumetricPIV data with a reduced number of cameras, simplified lighting, and a more compact footprint, which is what is needed in the high pressure environment. The proposed equipment will decisively expand the types of non-equilibrium flows that can be studied, including investigations of separated flows and other non-equilibrium flows at very high Reynolds number, and flows around and behind rotating machinery such as propellers, fans or turbines. This new capability will be in primary support of the work being performed by the PI~s underONR Grant ~Understanding Turbulence on Navy Vehicles~ N00014-17-1-2309 (Joseph Gorski), and in secondary support of the work under ONR MURI Grant (UVA Prime) ~Bioinspired flexible propulsors for fast, efficient swimming: What physics are we missing?~ ONR N00014-14-1-0533 (Robert Brizzolera).This equipment will overcome many limitations on measuring turbulent flows in our high Reynolds number facilities. In addition to our current capabilities to study one point statistics in the field, it will enable investigations of the instantaneous volumetric field, which is essential for detailed investigations of turbulent structure and multi-point statistics. Such studies are especially important for the understanding of non-equilibrium flows, where the flow often cannot be assumed homogeneous. In addition, the equipment requested here will allow a much wider range of studies to be made at high Reynolds number, including flows with pressure gradients and regions of separated flow, primarily by providing a much larger working section that can house moveable models, traversing cameras, and large changes on model geometry. It will support and enhance the ongoing ONR funded research, and it will also enable future research projects at high Reynolds numbers otherwise out of reachexperimentally.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 25, 2019
- Source ID
- N000141912301
Entities
People
- Alexander Smits
Organizations
- Office of Naval Research
- Trustees of Princeton University
- United States Navy