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SUMMARY:Controlling tip vortices\, cavitation\, and wakes through permeabl
 e tip treatment - Yabin Liu\, CUED
DTSTART:20250507T130000Z
DTEND:20250507T140000Z
UID:TALK231181@talks.cam.ac.uk
CONTACT:Anna Walczyk
DESCRIPTION:Wind and tidal energy are essential to the global transition t
 owards net-zero emissions. In 2024\, wind energy contributed 30% to the UK
 ’s electricity generation\, underscoring its significance\, while tidal 
 power has the potential to supply up to 11% of annual electricity demand. 
 Despite the considerable promise of renewable energy\, vortex-induced phen
 omena\, such as turbine wakes\, cavitation\, unsteady loads\, and noise\, 
 remain significant obstacles to the full realisation of these resources. A
 mong these\, tip vortices\, a long-standing challenge in wing- and blade-b
 ased systems\, play a key role in cavitation formation\, wake generation a
 nd propagation\, noise emission\, and delayed wake recovery.\n\nTo address
  these challenges\, I have proposed and developed a passive\, cost-effecti
 ve solution: permeable tip treatment. Both CFD simulations and PIV measure
 ments have been conducted on a wing and a model-scale horizontal-axis turb
 ine\, in a water tunnel and at the FloWave facility in Edinburgh. At the i
 nitial stage\, a porous zone was modelled at the blade tip using Darcy’s
  law\, revealing an optimal permeability that significantly reduces the in
 tensity of tip vortices and the associated pressure drop\, thereby decreas
 ing the risk of cavitation. Notably\, even with a spanwise extent of only 
 0.1% of the turbine diameter\, the design can lead to an increase of up to
  63% in the minimum pressure coefficient at the vortex core\, at a Tip Spe
 ed Ratio (TSR) of 6. In addition\, this approach shows great promise in en
 hancing wake recovery in both wind and tidal turbines. By expediting the b
 reakdown and destabilisation of tip vortices downstream of the rotor\, the
  wake recovery distance can be reduced by up to 20%\, delivering a conside
 rable improvement in the efficiency and energy output of turbine arrays in
  wind and tidal farms.\n\nBuilding upon the above\, we have developed and 
 tested an innovative grooved-tip design\, consisting of multiple grooves a
 long the tip chord to generate an equivalent local 2D permeability. This c
 onfiguration achieved approximately half the effect of a full 3D porous st
 ructure\, presenting a practical alternative. We also examined the chordwi
 se scope of the permeable region and found that the most effective suppres
 sion of tip vortices occurred when the grooved section was placed between 
 the vortex detachment point and the blade’s trailing edge.\n\nFuture wor
 k will focus on developing refined permeable structures with targeted 3D p
 ermeability to more effectively control wake and cavitation\, as well as s
 imultaneously mitigating blade-tip noise through acoustic experiments and 
 simulations. Through high-fidelity simulation and data-driven modal analys
 is\, we will also characterise the influence of permeability on vortex bre
 akdown and wake recovery across a representative range of Reynolds numbers
  and TSRs and understand the underlying physics.\n
LOCATION:JDB Seminar RM
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