A stratified wake of a hydrofoil accelerating from rest

Hadar Ben-Gida*, Alex Liberzon, Roi Gurka

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Wakes of towed and self-propelled bodies in stratified fluids are significantly different from non-stratified wakes. Long time effects of stratification on the development of the wakes of bluff bodies moving at constant speed are well known. In this experimental study we demonstrate how buoyancy affects the initial growth of vortices developing in the wake of a hydrofoil accelerating from rest. Particle image velocimetry measurements were applied to characterize the wake evolution behind a NACA 0015 hydrofoil accelerating in water and for low Reynolds number and relatively strong stable stratified fluid (Re= 5000, Fr~ O(1)). The analysis of velocity and vorticity fields, following vortex identification and an estimate of the circulation, reveal that the vortices in the stratified fluid case are stretched along the streamwise direction in the near wake. The momentum thickness profiles show lower momentum thickness values for the stratified late wake compared to the non-stratified wake, implying that the drag on an accelerating hydrofoil in a stratified medium is reduced at the acceleration stage. The findings may improve our ability to predict drag due to maneuvering of micro-air/water-vehicles in stratified conditions.

Original languageEnglish
Pages (from-to)366-380
Number of pages15
JournalExperimental Thermal and Fluid Science
StatePublished - 1 Jan 2016


FundersFunder number
Statens Naturvidenskabelige Forskningsrad#2008051


    • Acceleration
    • Hydrofoil
    • PIV
    • Stratification
    • Turbulence
    • Wake


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