Effects of diameter, density, and adhesiveness on settling velocity and drag coefficient of two sturgeon species eggs in flow

Abstract

Motion of eggs has received increasing attention because they are different from inanimate particles in physical and biological properties (density, diameter and adhesiveness), which determines their motion mechanism. Settling and drifting experiments were conducted to measure and identify the transport mechanism of eggs of two sturgeon species, Siberian sturgeon and Amur sturgeon. The terminal settling velocities are 4.30 ± 0.19 cm s−1 and 4.85 ± 0.22 cm s−1 for adhesive and de-adhered Siberian sturgeon eggs, respectively, and 5.23 ± 0.16 cm s−1 and 5.46 ± 0.19 cm s−1 for adhesive and de-adhered Amur sturgeon eggs, respectively. Adhesiveness decreases the terminal settling velocity. Meanwhile, the terminal settling velocity increases with increasing fish egg size. We developed a formula for the drag coefficient of sturgeon eggs and verified it via drifting experiments. The drag coefficient of sturgeon eggs is mainly affected by adhesive force when the Reynolds number R e ≤ 700 and by inertial force when R e > 700. The results show that sturgeon eggs differ significantly from other solid particles in their behaviour and an exclusive formula is necessary. This further provides new insights into the movement of adhesive demersal eggs and supports numerical simulation of their transportation in natural rivers.