Blog
Shark-skin riblets could boost hydropower turbine efficiency
Estimated reading time: 5 minutes · Last updated:
Shark-skin riblets were the focus of BILASURF, a ten‑partner European R&D effort that tested laser-engraved micro-grooves on turbine hardware to see if they reduce hydraulic losses. SuperGrid Institute and GLOBAL Hydro ran scaled experiments under IEC 60193 conditions; laboratory water-tunnel tests recorded lift and drag improvements, and the model campaign functionalised twenty guide vanes. The demonstrator did not texture the runner within the project schedule, so the campaign could not assess the combined textured guide vane and runner configuration. The host page also lists related posts dated 29 September 2026, 15 September 2026 and 8 September 2026.
Key takeaways
- Project and partners: BILASURF brought together ten European partners to develop laser-textured, riblet surfaces for industrial components.
- What was tested: The project applied the chosen laser process to twenty guide vanes on a reduced-scale Francis turbine model supplied by GLOBAL Hydro.
- Lab evidence: Low-flow water-tunnel profiling at SuperGrid Institute showed measurable lift and drag gains for textured hydrofoil profiles.
- Model campaign limits: The runner was not textured within the project schedule, so the full textured guide vane and runner configuration was not tested.
- Cavitation and efficiency: No significant difference in cavitation behaviour was observed, and the full-model tests provided insufficient evidence of a turbine efficiency improvement.
Table of contents
How BILASURF reproduced shark-skin riblets for turbines
BILASURF — Bio-inspired Laser Functionalisation of Complex 3D Industrial Surfaces — set out to reproduce the microscopic, aligned structures that give shark skin its hydrodynamic advantage. The consortium combined expertise across advanced manufacturing, surface engineering and fluid mechanics: Ceit coordinated the initiative while AIMEN, Fraunhofer IWU, Fusion Bionic, Workshop of Photonics and Bionic Surface Technologies provided laser-process and riblet design skills.
The project aimed to engrave riblets directly into metal components rather than add a coating, which led to the technical description 'laser-functionalising complex turbine components' as a central capability to demonstrate. GLOBAL Hydro and ZIEHL-ABEGG produced demonstrator hardware and SuperGrid Institute supplied an IEC 60193‑compliant hydraulic test platform to evaluate hydraulic performance and cavitation under controlled head and flow.
Applying the texture to a complex geometry proved time-consuming: three laser-texturing approaches were trialled and one selected, and the process was completed on the model’s twenty guide vanes but not on the runner within the project schedule. That manufacturing-time constraint is crucial for interpreting the demonstrator results and for planning any industrial rollout.
What the laboratory and model tests actually showed
The clearest experimental signals came from controlled blade profiling in SuperGrid Institute’s low-flow water tunnel, where geometrically similar smooth and textured profiles were tested for lift and drag and observed for flow separation. Those tests showed measurable improvements for the textured profiles, and flow visualisation helped characterise how riblets influence separation under varying incidence angles.
CFD work by Bionic Surface Technologies complemented the experiments: simulations comparing smooth and ribleted configurations produced encouraging indications, particularly when both guide vanes and runner were modelled with textures. However, the full-model campaign tested riblets on guide vanes only, and the tank tests did not provide sufficient evidence that that configuration alone improved overall turbine efficiency.
SuperGrid Institute also compared smooth and textured hydrofoil profiles at scale factors 1 and 1.4 using identical physical riblet dimensions; percentage gains in lift and drag were larger at scale factor 1, confirming that riblet geometry cannot be transposed without considering component scale and operating conditions. Cavitation behaviour showed no significant difference between textured and smooth configurations in the conditions tested.
Industrial gaps: durability, scale and economics to resolve next
BILASURF demonstrated feasibility but left the industrial questions that decide deployment unresolved: manufacturing time per component, abrasion resistance, durability in sediment-laden water and long-term economic value. The project shows a laser process can produce riblets on complex blades, yet the demonstrator’s limited scope means answers on service life and maintenance remain empirical rather than proven.
Scale transposition is also a technical gate. The IEC 60193 standard provides model-to-prototype formulae for isotropic roughness, but textured, anisotropic riblets fall outside those prescriptions. SuperGrid Institute’s comparison at scale factors 1 and 1.4 underlines that a texture tuned for one component size or operating point will likely require redesign for a different prototype.
For procurement and tenders, even modest efficiency gains can be material; the path to those gains runs through runner texturing combined with guide vane changes, durability testing in representative site water containing sediment, and an economic case that weighs manufacturing time and lifecycle maintenance against energy gains. Those steps are what will determine whether riblets move from demonstrator to specification in real projects.
| Item | What was done | Where tested | Main finding |
|---|---|---|---|
| Guide vanes | Laser-engraved riblets applied to twenty guide vanes | IEC 60193 model tests; water-tunnel profiling | Lift/drag gains in profiling; insufficient evidence of turbine efficiency gain |
| Runner | Runner not textured within project schedule | N/A | Combined effect with guide vanes not tested |
| Hydrofoil profiling | Geometrically similar smooth vs textured profiles | Low-flow water tunnel | Measurable lift/drag improvement; scale dependence observed |
Where riblet research could head next
The case for
- Laser engraving of riblets on complex components is feasible and was completed on twenty guide vanes, establishing a production route to test at larger scale.
- Water-tunnel profiling and CFD both showed lift and drag improvements, giving a physical basis for further texture refinement.
The case against
- The demonstrator did not texture the runner, so the combined guide vane and runner configuration that could deliver the strongest efficiency gains remains untested.
- Durability, abrasion resistance and behaviour in sediment-laden water are unresolved and could negate hydraulic gains if maintenance costs outweigh energy benefits.
What to be careful about
- Manufacturing time required to laser-texture complex blade geometry may make adoption uneconomic without faster processes.
- Abrasion resistance of engraved riblets is unknown and could reduce lifetime performance in sediment-bearing flows.
- Durability in sediment-laden water and the need for repair or rework could offset any hydraulic gains.
- Scale-transposition issues mean a riblet geometry that helps one component size may not work on a prototype without redesign.
The bottom line
BILASURF has opened a plausible research path: shark-inspired riblets can be laser-engraved onto complex turbine components and produce measurable hydraulic effects in controlled tests. The demonstrator’s constraints — most notably that the runner was not textured and that scale-dependent responses were observed at scale factors 1 and 1.4 — mean the hydraulic promise has not yet translated into proven model-scale turbine efficiency gains. Resolving manufacturing throughput, abrasion and sediment durability, and running a campaign that textures both guide vanes and the runner are the next practical steps before riblets can be judged for industrial adoption.
What to watch
- Watch for a follow-up test campaign that includes a textured runner alongside textured guide vanes; no date has been set.
- Watch for abrasion and sediment-durability trials on laser-engraved riblets to establish service life; no date has been set.
- Watch for any announced industrial-scale trial or procurement that adopts laser-textured components; no date has been set.
Frequently asked questions
What exactly did BILASURF test?
BILASURF developed a laser process to engrave riblet textures into industrial components and applied that process to twenty guide vanes on a reduced-scale Francis turbine model supplied by GLOBAL Hydro; the consortium comprised ten European partners.
Did the riblets improve turbine efficiency?
Lab-scale water-tunnel profiling at SuperGrid Institute recorded measurable lift and drag improvements, and CFD gave encouraging indications, but the full-model campaign — which only textured guide vanes — provided insufficient evidence of an overall turbine efficiency increase.
What technical barriers remain before deployment?
Key open questions are manufacturing time to functionalise complex geometries, abrasion resistance and durability in sediment-laden water, and the economic case for lifecycle maintenance versus energy gains.
Related reading