Stratified flow past a prolate spheroid

Jose L. Ortiz-Tarin, K. C. Chongsiripinyo, and S. Sarkar
Phys. Rev. Fluids 4, 094803 – Published 25 September 2019

Abstract

The effect of ambient stratification on flow past a prolate spheroid is investigated using large-eddy simulation. The aspect ratio of the body is L/D=4 and the major axis (L) is aligned with the incoming flow. The Reynolds number based on the minor axis (D) and the incoming velocity (U) is Re=104. The stratification is set using a linear density background with constant buoyancy frequency (N). Three simulations with stratification levels, Fr=U/ND=0.5,1,3 and one unstratified simulation, Fr=, are performed. The influence of the body slenderness ratio is assessed by comparing the present results with previous work on a sphere. An overall result is that the flow past a slender body exhibits stronger buoyancy effects relative to a bluff body. At FrO(1), there is a strong interaction between the body-generated internal gravity waves (IGW) and the flow at the body. This interaction gives rise to a critical Froude number, Frc=L/Dπ, which is proportional to the aspect ratio. When FrFrc boundary layer separation is delayed and wake turbulence is strongly suppressed. If FrFrc, wake turbulence is only partially suppressed and, when FrFrc, boundary layer separation is promoted and turbulence reappears. To elucidate the effect of body slenderness on stratification effects, the IGW field, the boundary layer evolution and separation are studied. Analysis of the wake reveals the strong influence of the type of separation, and therefore the body shape, on the dimensions and the energetics of the near and intermediate wake. However, the decay rate of the stratified wake in the nonequilibrium region is the same as that of a sphere.

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  • Received 23 April 2019

DOI:https://doi.org/10.1103/PhysRevFluids.4.094803

©2019 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Jose L. Ortiz-Tarin1, K. C. Chongsiripinyo2, and S. Sarkar1,*

  • 1Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California 92093, USA
  • 2Department of Mechanical Engineering, Chulalongkorn University, Bangkok 10330, Thailand

  • *sarkar@ucsd.edu

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Vol. 4, Iss. 9 — September 2019

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