The ESEF complex contains several independent laboratories for experiments and advanced diagnostics in the fields of thermodynamics, heat transfer, fluid mechanics, multiphase flows, adhesion, surface rheology, material characterization, X-Ray CT, and material decomposition. Our experimental research activities are focused on both advanced diagnostics and fundamental experiments. We seek to improve our understanding of phenomena in areas of fluid flow, heat transfer, and aerodynamics. We develop state-of-the-art diagnostic techniques for application to benchmark experiments aimed at understanding the fundamental nature of complex systems. This understanding is used to develop and validate the theoretical and computer models necessary for system design and analysis.
Laser-Based Diagnostics
The ESEF is engaged in development of advanced laser-based diagnostics to support multiple Sandia missions. Laser capabilities include multiple cw sources as well as nanosecond, picosecond and femtosecond pulsed-laser capabilities with wavelength tenability. Current capabilities and development efforts include: a cw diffusing-wave spectrometer (DWS); particle-image velocimetry (PIV); planar-laser induced fluorescence (PLIF) for flow visualization in the hypersonic wind tunnel; ultrafast shock interferometry (USI) and transient absorption for characterization of shock waves in energetic materials; laser-induced incandescence (LII) for soot measurements in hydrocarbon flames and fires; nanosecond and femtosecond coherent anti-Stokes Raman scattering (CARS) for temperature and species measurements in fire, energetic materials and heat-transfer applications.
Multi-Phase Flow
Multiphase flow experiments are performed over a wide range of length scales and applications. Gas-solid, gas-liquid, liquid-solid, and combinations including immiscible liquids are being studied. One ongoing project involves the generation and motion of bubbles in liquids under vibration, which leads to unusual bubble motion and breakup. Other areas of interest include liquid sprays which are commonly used in fire suppression and combustion engines. Available measurement techniques include high-speed visualization, phase Doppler anemometery, particle image velocimetry, and digital holography. In addition to this, unique diagnostic techniques are often developed to meet the measurement needs of a wide variety of customers.
Heat Transfer
In the area of heat transfer, thermal transport across rough interfaces is being investigated. The thermal contact resistance measurement system shown in the figure to the left is capable of measuring interface resistance under loads up to 20 atm in nitrogen, argon and air with gas pressures ranging from 10-4 to 1 atm. Additional thermal diagnostic capabilities available include infrared thermography, thermocouple data acquisition, and heater control systems to support environmental testing of large assets.
Multiphase Material and Interface Characterization
We characterize fluids, solids and everything in between at temperatures up to 600°C including flow, adhesion and electrical properties under controlled stress or strain. We also have a vessel that can perform rheology measurements under pressure up to pressures of 330bar and temperatures up to 425°C. Traditional and confocal microscopy, velocimetry and spectroscopy are used to investigate the impact of microstructure on flow and transport properties of multiphase materials. The rheology of air-liquid and liquid-liquid interfaces can be investigated using ring and bicone attachments for our rheometers, or a magnetic needle rheometer for measurements that require more sensitivity. To measure material properties that influence multiphase flow we also have instruments to measure surface/interfacial tension (ring or plate tensiometry and pendant/sessile drop) as well as a goniometer that can measure static contact angle and also measure dynamic contact angles as a function of the contact-line velocity in controlled atmospheres at temperatures up to 1000°C.
Material Decomposition
We have a variety of capabilities to examine the decomposition and flow of organic materials under oxygen-poor environments at temperatures up to 900 °C and pressures up to 330bar. We have developed techniques and obtained equipment to look at electrical conductivity, mass change versus temperature (TGA), off-gas analysis (FTIR), and enthalpy of reactions (DSC).