A Fluid Dynamics Approach for Assessing the Intelligent Geomorphic Design of the Japanese Pufferfish Nest

Abstract

Research into the geometric nests built by white-spotted pufferfish indicated the nest’s potential for flow control and reduction in flow velocity. However, studies to date have only focused on the construction process and behaviour of the male pufferfish. Hence, the form and functions of the unique features of the nest remain unclear. The present study aims to explore the flow features most useful in understanding the habitat conditions of the nest through a combination of photogrammetric reconstructions of the nest features and two-dimensional (2D) computational fluid dynamic simulations. The findings show the role of the nest structure in reducing the flow velocity and shear stress within the nesting site. Analysis of shear stress indicates that male pufferfish build the outer zones of the nest with coarser material that improves the overall shear strength of these areas. The study identified the function of the nest structure in the protection of the eggs through reduction in flow variations and improved aeration. The addition of shell fragments to the nest peaks by the male pufferfish contributes to the resiliency of the nest structure and ensures a stable bed surface at the central zone.

CFD analysis of the complex japanese pufferfish nest

“…Digital photogrammetry techniques allow accurate modeling of 3D space from 2D images [9]. Based on existing images, digital photogrammetry techniques are used for the 3D reconstruction of nest images [7]. After comparing the data and information, it is found that the results of this modeling technique are satisfactory.…”

“…Based on the exciting research [7,9], the entire outer circular radius of the nest is set at 918 mm, and the radius of the center region (living area) is set at 306 mm (one-third of the outer circular radius). As the center region is lower than the seabed, a reference plane is set below the seabed by 40 mm.…”

“…The circular shape guides water flow and accumulates fine sand for egg deposition [6]. Previous research has shown that pufferfish nests reduce flow velocity and enhance shear strength [7]. However, most studies have used smooth and streamlined nest models, leaving the investigation of nest-building behavior with different materials open.…”

3D model of the geometric nest structure, the “mystery circle,” constructed by pufferfish

“…Shameem et al . reconstructed a 3D model of a mystery circle to explore the flow features with 2D computational fluid dynamic simulations 8 . Since our model has already been quantified as 3D data, computational fluid analysis can be immediately performed using this data, and the structural features of the mystery circle are expected to be applied in a wide range of fields, such as architecture and engineering, via biomimetics.…”

“…Shameem et al . reconstructed a 3D model of a mystery circle for computational fluid dynamic simulations 8 ; however, the 3D data is not published anywhere. They used a commercially available video and obtained a sequence of 23 images for the 3D reconstruction, where estimated values of the global scale were used.…”