• Campbell Scientific Inc., 2012: CSAT3 three-dimensional sonic anemometer. Campbell Scientific Instrument Manual, 72 pp.

  • Kravchenko, A. G., and Moin P. , 2000: Numerical studies of flow over a circular cylinder at ReD = 3900. Phys. Fluids, 12, 403417.

  • Marks, L. S., 1934: The determination of the direction and velocity of flow of fluids. J. Franklin Inst., 217, 201212.

  • Moller, A. R., 1978: The improved NWS storm spotters' training program at Ft. Worth, Tex. Bull. Amer. Meteor. Soc., 59, 15741582.

  • Prandtl, L., 1952: Essentials of Fluid Dynamics: With Applications to Hydraulics Aeronautics, Meteorology, and Other Subjects. Hafner, 452 pp.

  • Rennó, N. O., 2008: A thermodynamically general theory for convective vortices. Tellus,60A, 688–699.

  • Rennó, N. O., Burkett M. L. , and Larkin M. P. , 1998: A simple thermodynamical theory for dust devils. J. Atmos. Sci., 55, 32443252.

  • Rennó, N. O., Halleaux D. G. , Saca F. , Rogacki S. , Gillespie R. , and Musko S. , 2010: A generalization of Bernoulli's equation to convective vortices. Extended Abstracts, 41st Lunar and Planetary Science Conf., The Woodlands, TX, Lunar Planetary Institute, 1745.

  • Saca, F. A., Rennó N. O. , Halleaux D. G. , Rogacki S. , Gillespie R. , and Musko S. , 2010: A portable instrument for atmospheric measurements. Extended Abstracts, 41st Lunar and Planetary Science Conf., The Woodlands, TX, Lunar Planetary Institute, 1767.

  • Wieringa, J., 1967: Evaluation and design of wind vanes. J. Appl. Meteor., 6, 11141122.

  • Zucrow, M. J., and Hoffman J. D. , 1976: Gas Dynamics. Wiley, 772 pp.

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The Michigan Prandtl System: An Instrument for Accurate Pressure Measurements in Convective Vortices

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  • 1 Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan
  • | 2 Department of Earth and Atmospheric Science, Cornell University, Ithaca, New York
  • | 3 Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan
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Abstract

This article describes a Prandtl tube system developed at the University of Michigan to measure the static pressure, the total (or stagnation) pressure, and the velocity in flows whose direction and intensity change rapidly. The ever-changing wind vectors in convective vortices are a challenge for making accurate measurements on them. Accurate measurements of the static pressure are particularly problematic because they require the sensor air intake to be aligned perpendicular to the wind direction. This article describes calibrations and tests of the Michigan Prandtl System (MPS) and, in particular, the characterization of the errors in the static pressure measurements as a function of misalignments between the Prandtl tube and the wind vector. This article shows that the MPS measures the pressure with a relative error of 3.5% for wind flows whose direction is within about 10° of the MPS tube direction. It also shows that the MPS adjusts to changes in wind direction of 90° in about 1.5 s, the average rate of change expected in a typical dust devil of about 15 m of radius traveling at 10 m s−1 (Rennó et al.). Field tests indicate that misalignments between the MPS and the wind vector are usually smaller than ~30° during measurements in dust devils and that these misalignments always cause increases in the static pressure measured and decreases in the total pressure measured.

Corresponding author address: Douglas G. Halleaux, Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109. E-mail: dgossiau@umich.edu

Abstract

This article describes a Prandtl tube system developed at the University of Michigan to measure the static pressure, the total (or stagnation) pressure, and the velocity in flows whose direction and intensity change rapidly. The ever-changing wind vectors in convective vortices are a challenge for making accurate measurements on them. Accurate measurements of the static pressure are particularly problematic because they require the sensor air intake to be aligned perpendicular to the wind direction. This article describes calibrations and tests of the Michigan Prandtl System (MPS) and, in particular, the characterization of the errors in the static pressure measurements as a function of misalignments between the Prandtl tube and the wind vector. This article shows that the MPS measures the pressure with a relative error of 3.5% for wind flows whose direction is within about 10° of the MPS tube direction. It also shows that the MPS adjusts to changes in wind direction of 90° in about 1.5 s, the average rate of change expected in a typical dust devil of about 15 m of radius traveling at 10 m s−1 (Rennó et al.). Field tests indicate that misalignments between the MPS and the wind vector are usually smaller than ~30° during measurements in dust devils and that these misalignments always cause increases in the static pressure measured and decreases in the total pressure measured.

Corresponding author address: Douglas G. Halleaux, Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109. E-mail: dgossiau@umich.edu
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