G. T. Roberts

Bio: G. T. Roberts is an academic researcher from University of Southampton. The author has contributed to research in topics: Heat flux & Heat transfer coefficient. The author has an hindex of 1, co-authored 1 publications receiving 37 citations.

Liquid Crystal Thermography for Heat Transfer Measurement in Hypersonic Flows: A Review

Abstract: Nomenclature substrate specific heat capacity, Jkg^K" fin leading-edge diameter, 10 mm hue;Eq. (7) heat transfer coefficient, Wm~K" intensity; Eq. (10) substrate thermal conductivity, Wm^K" mean refractive index of liquid crystal pitch of helical structure, m convective heat flux, Wm~ red, green, and blue coordinates red, green, and blue chromaticity coordinates saturation; Eq. (9) model surface temperature, K adiabatic wall temperature, K model initial temperature, K time, s semi-infinite penetration depth, m thermal diffusivity, k/ pc, ms~ c D H h / k n P qu) R,G, B r, g, b S T Ta 7} t x* a y A = wavelength of reflection, m p = substrate density, kgm~ (/) angle of illumination

Liquid crystal measurements of heat transfer and surface shear stress

Abstract: Liquid crystals have become an accurate and convenient means of measuring surface temperature and heat transfer for the gas turbine and heat transfer research communities. The measurement of surface shear stress using liquid crystals is finding increasing favour with aerodynamicists and developments in these techniques ensure that liquid crystals will continue to provide key thermal and shear stress data in the future. The increasing use of three-dimensional finite element computational models has allowed industry to capitalize on the advantages of the full surface data generated. The paper reviews the use of these complex materials in research with a special emphasis on recent developments in the field. The aim is to provide the reader with an up to date background in this measurement technology and allow the researcher to decide whether liquid crystals would be suitable in specific applications.

Digital particle image thermometry/velocimetry: a review

Abstract: Digital particle image thermometry/velocimetry (DPIT/V) is a relatively new methodology that allows for measurements of simultaneous temperature and velocity within a two-dimensional domain, using thermochromic liquid crystal tracer particles as the temperature and velocity sensors. Extensive research has been carried out over recent years that have allowed the methodology and its implementation to grow and evolve. While there have been several reviews on the topic of liquid crystal thermometry (Moffat in Exp Therm Fluid Sci 3:14–32, 1990; Baughn in Int J Heat Fluid Flow 16:365–375, 1995; Roberts and East in J Spacecr Rockets 33:761–768, 1996; Wozniak et al. in Appl Sci Res 56:145–156, 1996; Behle et al. in Appl Sci Res 56:113–143, 1996; Stasiek in Heat Mass Transf 33:27–39, 1997; Stasiek and Kowalewski in Opto Electron Rev 10:1–10, 2002; Stasiek et al. in Opt Laser Technol 38:243–256, 2006; Smith et al. in Exp Fluids 30:190–201, 2001; Kowalewski et al. in Springer handbook of experimental fluid mechanics, 1st edn. Springer, Berlin, pp 487–561, 2007), the focus of the present review is to provide a relevant discussion of liquid crystals pertinent to DPIT/V. This includes a background on liquid crystals and color theory, a discussion of experimental setup parameters, a description of the methodology’s most recent advances and processing methods affecting temperature measurements, and finally an explanation of its various implementations and applications.

Aerothermodynamic measurement and prediction for a modified orbiter at Mach 6 and 10 in air

Abstract: Detailed heat-transfer rate distributions measured laterally over the windward surface of an orbiter-like configuration using thin-film resistance heat-transfer gauges and globally using the newly developed relative intensity, two-color thermographic phosphor technique are presented for Mach 6 and 10 in air. The angle of attack was varied from 0 to 40 deg, and the freestream Reynolds number based on the model length was varied from 4 x 10(exp 5) to 6 x 10(exp 6) at Mach 6, corresponding to laminar, transitional, and turbulent boundary layers; the Reynolds number at Mach 10 was 4 x 10(exp 5), corresponding to laminar flow. The primary objective of the present study was to provide detailed benchmark heat-transfer data for the calibration of computational fluid-dynamics codes. Predictions from a Navier-Stokes solver referred to as the Langley aerothermodynamic upwind relaxation algorithm and an approximate boundary-layer solving method known as the axisymmetric analog three-dimensional boundary layer code are compared with measurement. In general, predicted laminar heat-transfer rates are in good agreement with measurements.

Advances in temperature measurement

Abstract: The need for temperature measurement is ever present in science and industry from requirements for monitoring processes, in the management of quality control and research. Temperature can be measured by means of direct contact between the medium of interest and the measuring device or by remote observation of a temperature-dependent parameter. The range of devices with which temperature can be measured is extensive, not surprisingly because most physical parameters exhibit a dependency on temperature. In recent years the dominant position of liquid-in-glass and bimetallic thermometers, thermocouples, and resistant temperature detectors has been challenged as the common choice for temperature measurement by infrared thermometers and an increasing array of other noninvasive techniques. This chapter outlines the principal techniques available for the measurement of temperature, describing the physical phenomena exploited, the temperature range of use, equipment required, and typical applications. Recent trends in requirements for traceability and quantification of uncertainty, as well as developments in the areas of instrumentation capability and technique, are described.