Free-swimming kinematics of Artemia

A huge variety of organisms inhabit the oceans, lakes and rivers of the earth. These forms of life differ vastly in shape and size, from the largest mammal, blue whale, with body length of 22-24 m to single bacteria in the size scale of 1-2 mum. This amounts to a 10^14-fold range in Reynolds number;...

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Bibliographic Details
Main Author: Rislakki, Ensio
Other Authors: Ayala Lara, Rafael, Perustieteiden korkeakoulu, Backholm, Matilda, Aalto-yliopisto, Aalto University
Format: Bachelor Thesis
Language:English
Published: 2024
Subjects:
Online Access:https://aaltodoc.aalto.fi/handle/123456789/131288
Description
Summary:A huge variety of organisms inhabit the oceans, lakes and rivers of the earth. These forms of life differ vastly in shape and size, from the largest mammal, blue whale, with body length of 22-24 m to single bacteria in the size scale of 1-2 mum. This amounts to a 10^14-fold range in Reynolds number; the ratio of inertial and viscous forces. This is remarkably large compared to the 10^5-fold range in aerial locomotion. Furthermore, in aquatic locomotion, the Reynolds number is found to have values less than or equal to 1 for the smallest organisms, which never occurs in aerial locomotion. One would certainly expect the physics of the locomotion to be completely different in the extremes of this scale, and indeed, this turns out to be the case. The two extremes, micro- and macroscale, are relatively well understood, since in these regimes one can ignore the inertial or the viscous force, respectively. However, a particular challenge is proposed by the scale in between: the mesoscale. In this regime, characterized by a Reynolds number close to one, modeling swimming becomes exceedingly difficult. Unlike the microscale, where the linear Stokes equation applies, or the macroscale, governed by the quasi-linear Euler equation, locomotion at the mesoscale is described by the full-form Navier-Stokes equation, which is nonlinear and often numerically unstable. This range in Reynolds number is inhabited by the species Artemia salina, which was the subject of the experiments for this thesis. In this thesis, the strategies for swimming in mesoscale are analysed in great detail and some remarks are made on the scaling of the kinematics as the Artemia grow. Swimming kinematics are measured using an inverted microscope and an image analysis software. Much attention is paid to ensure that the Artemia swim undisturbed, allowing the locomotion to be observed as naturally as possible. Additionally, the concept of symmetry breaking area is introduced to assess the significance of non-reciprocal motion in swimmers at intermediate ...