1University of St. Thomas, School of Engineering, St. Paul, MN 55105-1079, USA
2ENEA, UTMAR-OSS, Forte S. Teresa, 19032 Pozzuolo di Lerici, Italy
3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
4Pacific Marine Environmental Laboratory/NOAA, Seattle, WA, 98115-6349, USA
5CNR-ISMAR, Forte S. Teresa, 19032 Pozzuolo di Lerici, Italy
Received: 13 Jun 2011 – Published in Ocean Sci. Discuss.: 02 Aug 2011
Abstract. A new technique for determining the depth of expendable bathythermographs (XBTs) is developed. This new method uses a forward-stepping calculation which incorporates all of the forces on the XBT devices during their descent. Of particular note are drag forces which are calculated using a new drag coefficient expression. That expression, obtained entirely from computational fluid dynamic modeling, accounts for local variations in the ocean environment. Consequently, the method allows for accurate determination of depths for any local temperature environment. The results, which are entirely based on numerical simulation, are compared with the experiments of LM Sippican T-5 XBT probes. It is found that the calculated depths differ by less than 3% from depth estimates using the standard fall-rate equation (FRE). Furthermore, the differences decrease with depth. The computational model allows an investigation of the fluid flow patterns along the outer surface of the probe as well as in the interior channel. The simulations take account of complex flow phenomena such as laminar-turbulent transition and flow separation.
Revised: 17 Oct 2011 – Accepted: 27 Oct 2011 – Published: 08 Nov 2011
Stark, J., Gorman, J., Hennessey, M., Reseghetti, F., Willis, J., Lyman, J., Abraham, J., and Borghini, M.: A computational method for determining XBT depths, Ocean Sci., 7, 733-743, doi:10.5194/os-7-733-2011, 2011.