Hydrodynamic characteristics of a partitioned recirculating aquaculture pond

Research Hypotheses
We hypothesize that modular functional zoning with physical baffle guidance can create a spatially heterogeneous flow field in partitioned recirculating aquaculture ponds (PRAP). This design will achieve efficient water circulation, match biological requirements across zones, and enable passive directional transport and graded collection of aquaculture particles, synergistically improving hydrodynamic efficiency and ecological purification. Specifically: (1) Physical baffles eliminate stagnant dead zones by forming closed recirculation zones, and flow uniformity jumps sharply when inlet velocity exceeds the system structural resistance threshold; (2) Zoned design independently regulates hydrodynamic parameters to meet the distinct needs of fish culture, aeration, and water purification; (3) Particle escape rates are negatively correlated with diameter and density, with large/dense particles depositing in low-velocity vortex cores for energy-free solid-liquid separation.
Data Content
A horizontal flow model was established for a 300m×100m PRAP using the SST k-ω turbulence model and Discrete Phase Model (DPM, for dilute particle flow <10% volume fraction). Mesh independence was verified with 40,000–160,000 elements, and 90,000 elements were selected for optimal accuracy-efficiency balance. Transient simulations used the SIMPLE algorithm (convergence 10⁻⁶) with an inlet velocity of 0.25m/s (28.27m³/h). Nine full-pond and six culture-zone monitoring lines collected velocity, vorticity, and particle data at 1s intervals. Experimental validation used Tian et al.’s (2017) PRAP physical model and an LS20B current meter (error ≤1.5%). Vertical integration of measured velocities showed overall simulation error <10%. Key results: quasi-steady state at 90–100s; high-density culture zone 0.03–0.05m/s; flow uniformity index 0.78; total particle escape rate 78% at 1100s.
Significant Findings
Physical baffles form clear S-shaped closed flow channels, eliminating stagnant zones. Flow uniformity jumps from 0.64 to 0.78 when inlet velocity exceeds the 0.20m/s resistance threshold; Hydrodynamic parameters perfectly match functional requirements: 0.04m/s average velocity in culture zones suits fish growth, while high vorticity in aeration zones achieves both propulsion and oxygenation; Vorticity gradients between zones form natural hydraulic barriers, enabling passive solid-liquid separation without extra energy; Inertia dominates particle motion: low-density particles have high escape rates requiring centralized treatment, while large/dense particles deposit for in-situ purification.
Data Interpretation
Interpretation principles: (1) Data reflect large-scale horizontal circulation; 3D models are needed for vertical flow analysis. (2) 0–90s transient data optimize startup, while post-90s steady-state data evaluate long-term performance. (3) Multiple indicators must be interpreted synergistically.