This study developed an IBM (individual-based model) to model fish movement trajectories integrating hydraulic stimulus variables (turbulent kinetic energy (TKE), velocity (V) and strain rate (SR)) to which fish responded, and the rules for individual fish movement. The fish movement trajectories of the target fish, silver carp (Hypophthalmichthys molitrix), were applied to model fish trajectories in a 1% vertical slot fishway at a discharge of 13.5 L/s. Agreement between measured and simulated trajectories implied the plausibility of the movement rules, which illustrated that the fish movement trajectories model has the preliminary ability to track individual fish trajectories for this fishway.

In this experiment, we analyzed live fish (silver carp) trajectories recorded in an experimental vertical-slot fishway. Combined with a numerical simulation, we demonstrated that randomness shown in fish trajectories might not merely be attributed to the fish’s random choices in its swimming, but could also be a consequence of adaption to the bulk unsteady turbulent flow structures. Simple superposition of a fish trajectory on the time-averaged flow field obtained either by interpolating on discrete point measurements or numerical simulation data is not an ideal method for description of fish movement. How to model the fish paths in transient flow and the necessity of simultaneous recording of the flow field and the fish locomotion are challenging topics. We also discussed the possible integration of currently existing methods to promote the development of fish trajectory modeling.

Perturbations are very common in the transition and heat transfer of thermal convection in nature and industry. Accordingly, thermal convection on a top-open cavity subjected to periodic and random perturbations is investigated using three-dimensional numerical simulation. A great number of numerical experiments are performed at various Rayleigh numbers and a fixed Prandtl number of 0.71 by introducing periodic and random numerical perturbations. Numerical results demonstrate that there exists the effect of periodic perturbations on the transition route over 3.5 × 103 ≤ Ra ≤ 8.5 × 104. That is, the transition route to chaos is sensitive to the amplitude of random perturbations for, e.g., 0.01 ≤ Ar ≤ 0.05, which is also characterized. Furthermore, heat transfer enhancement under periodic and random perturbations is quantified with the scaling law. This study sheds new light on the influence of periodic and random perturbations on thermal convection on the top-open cavity below heating. The possibility to control heat transfer is revealed by introducing random perturbations on the bottom of the top-open cavity.