Analytical Modelling of Flow Behavior and Energy Losses in Tidal Stream Turbines : a CFD-Informed Study
Tamim, Ashraful (2026)
2026
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-202605059342
https://urn.fi/URN:NBN:fi:amk-202605059342
Tiivistelmä
Tidal energy is a predictable and sustainable renewable energy source. Understanding the flow behavior around tidal turbines is essential for improving efficiency and minimizing energy losses. This thesis presents an analytical investigation of turbine performance and wake development using actuator disc theory. The study combines a review of existing Computational Fluid Dynamics studies with original analytical calculations.
The analytical model is based on actuator disc theory. The power coefficient, thrust coefficient, and wake velocity are evaluated as functions of the axial induction factor. The results are compared with findings from CFD studies reported in the literature. The comparison focuses on power coefficient values, wake recovery distances, and energy losses.
The results show that the theoretical maximum power coefficient is 0.59, corresponding to the Betz limit at an axial induction factor of 0.33. Literature values for real turbines range from 0.35 to 0.45, representing energy losses of 24 to 41 percent. The wake velocity decreases linearly with increasing energy extraction. Recovery distances of 10 to 20 rotor diameters are consistent with CFD findings.
The study demonstrates that simplified analytical models provide a valuable theoretical baseline for understanding turbine performance. The results highlight the trade-off between energy extraction and wake deficit, which has important implications for turbine array design. Recommendations for future research include blade-resolved CFD, turbulence modelling, and experimental validation.
The analytical model is based on actuator disc theory. The power coefficient, thrust coefficient, and wake velocity are evaluated as functions of the axial induction factor. The results are compared with findings from CFD studies reported in the literature. The comparison focuses on power coefficient values, wake recovery distances, and energy losses.
The results show that the theoretical maximum power coefficient is 0.59, corresponding to the Betz limit at an axial induction factor of 0.33. Literature values for real turbines range from 0.35 to 0.45, representing energy losses of 24 to 41 percent. The wake velocity decreases linearly with increasing energy extraction. Recovery distances of 10 to 20 rotor diameters are consistent with CFD findings.
The study demonstrates that simplified analytical models provide a valuable theoretical baseline for understanding turbine performance. The results highlight the trade-off between energy extraction and wake deficit, which has important implications for turbine array design. Recommendations for future research include blade-resolved CFD, turbulence modelling, and experimental validation.