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Seawater desalination is increasing due to the global water crisis, and velocity caps are widely used at intake entrances to protect marine life and facilitate the required flow. Despite various investigations of seawater intake, a lack of precise research on the discharge coefficient of these structures is evident. The discharge characteristics of seawater intake are investigated both analytically and experimentally. Results show that the circle velocity caps have higher capacity than square ones, about 2% to 3.5%. Also, the Froude number of approach flow and the area of the velocity caps are the two parameters with the greatest impact on discharge coefficients. However, the height of caps and the number of separator blades have the least effect. Furthermore, some equations of discharge coefficients are developed based on machine-learning techniques with appropriate accuracy. Additionally, the Taguchi method, evaluated as an economical approach, significantly reduces the number of tests while the accuracy of results decreases. [ABSTRACT FROM AUTHOR]

The objective of this investigation is to obtain a more profound understanding of the effective parameters of the velocity caps for bottom intake systems, utilizing particle image velocimetry (PIV) and OpenFOAM. Observations indicate a higher probability of surface vortex formation in square types compared to circular ones, with the vortex being formed downstream of the caps. Additionally, the flow pattern reveals that the flow whirls in a more favorable path into the circular caps as opposed to the square ones. Through both experimental and numerical comparisons of three shapes (rhombus, square, and circle), it becomes evident that the circular type outperforms the other types in terms of discharges through the intake, showing an improvement of about 8%. The results indicate that flow depth and height of the velocity caps are positively effective parameters for the flow rate, with respective influences of 90% and 30%. In contrast, the interaction between the flow and caps intensifies with an increase in the distance of the intake opening from the bed, which plays a negative influence on the flow rate. Enhancing the number of blades in caps proves to be the optimal approach for generating a smoother flow with minimal impact on the flow rate. Numerical simulations show a 50% reduction in cap height leads to a significant 33% decrease in flow rate. Additionally, rotating the square cap by 45° into a rhombus aligned with the flow direction results in a 7% discharge flow rate increase. [ABSTRACT FROM AUTHOR]

Abstract The objective of this investigation is to obtain a more profound understanding of the effective parameters of the velocity caps for bottom intake systems, utilizing particle image velocimetry (PIV) and OpenFOAM. Observations indicate a higher probability of surface vortex formation in square types compared to circular ones, with the vortex being formed downstream of the caps. Additionally, the flow pattern reveals that the flow whirls in a more favorable path into the circular caps as opposed to the square ones. Through both experimental and numerical comparisons of three shapes (rhombus, square, and circle), it becomes evident that the circular type outperforms the other types in terms of discharges through the intake, showing an improvement of about 8%. The results indicate that flow depth and height of the velocity caps are positively effective parameters for the flow rate, with respective influences of 90% and 30%. In contrast, the interaction between the flow and caps intensifies with an increase in the distance of the intake opening from the bed, which plays a negative influence on the flow rate. Enhancing the number of blades in caps proves to be the optimal approach for generating a smoother flow with minimal impact on the flow rate. Numerical simulations show a 50% reduction in cap height leads to a significant 33% decrease in flow rate. Additionally, rotating the square cap by 45° into a rhombus aligned with the flow direction results in a 7% discharge flow rate increase.

The primary environmental impact caused by seawater intake operation is marine life impingement resulting from the intake velocity. Environmental Protection Agency (EPA) of United State has regulated the use of velocity cap fitted at intake structures to reduce the marine life impingement. The engineering design parameters of velocity cap has not been well explored to date. This study has been set to determine the fundamental relationships between intake velocity and design parameters of velocity cap, using computational fluid dynamic (CFD) model. A set of engineering design criteria for velocity cap design are derived. The numerical evidence yielded in this study show that the velocity cap should be designed with vertical opening (Hvc) and horizontal shelf (ℓvc). The recommended intake opening ratio (Or) shall be 0.36 Vr−0.31, where Or = Hvc/ℓvc and Vr =V0/Vpipe. Vo is the velocity at the intake window and Vpipe is the suction velocity at the intake pipe. The volume ratio (ωr) between the velocity cap (ωvc) and intake tower (ωIT) is recommended at 0.11 Vr−1.23. The positive outlooks that yielded from this study can be served as a design reference for velocity cap to mitigate the detrimental impacts from the existing intake structure.

The primary environmental impact caused by seawater intake operation is marine life impingement resulting from the intake velocity. Environmental Protection Agency (EPA) of United State has regulated the use of velocity cap fitted at intake structures to reduce the marine life impingement. The engineering design parameters of velocity cap has not been well explored to date. This study has been set to determine the fundamental relationships between intake velocity and design parameters of velocity cap, using computational fluid dynamic (CFD) model. A set of engineering design criteria for velocity cap design are derived. The numerical evidence yielded in this study show that the velocity cap should be designed with vertical opening (Hvc) and horizontal shelf (ℓvc). The recommended intake opening ratio (Or) shall be 0.36 Vr−0.31, where Or = Hvc/ℓvc and Vr =V0/Vpipe. Vo is the velocity at the intake window and Vpipe is the suction velocity at the intake pipe. The volume ratio (ωr) between the velocity cap (ωvc) and intake tower (ωIT) is recommended at 0.11 Vr−1.23. The positive outlooks that yielded from this study can be served as a design reference for velocity cap to mitigate the detrimental impacts from the existing intake structure. [ABSTRACT FROM AUTHOR]