BIOL606: Fish Locomotion

Viscous properties, boundary layer with more sheer force near the object

Real Fluid Properties

Friction Drag

tangential stress in the boundary layer

Pressure decreases until it gets to the deepest portion of an animal, where a reversal of pressure results in a flow reversal. This destabilizes the boundary layer and generates a wake on the back of the animal. The back eddy from the reversal flow is tighter and more stable

Describe the change in pressure drag over a fishes body in a real fluid

Turbulence flow dominants

High Re

smaller organisms, or animals in low density waters

What type of organisms typically have a lower Re

Fusiform streamlined shape

Alteration of shape to reduce pressure profile. Peak in aspect ratio occurs at the 1-2.4 place along body

Pressure drag DECREASES with higher finess ratio (meaning less depth, more length); when legnth is 4x the depth, drag is fulyl reduced, after which drag increases with length

How does pressure affect the fineness ratio (lenth to depth)

YOY must priotozie feeding by investing in a larger gape size over movement

In YOY and fry, why is it more advantageous to experience laminar flow

Cruising, swimming muscles, sustained swimming

Extends anteroposteriorly into the body of fishes where the contraction pulls into the penducle, helping form the oscillatory muscle

might also keep muscle warm

Function of red muscle blocks

burst swimming

fast swimming

time to fatique increase

Function of white muslce

Anguilliform Movement type

Multiple waves propagate along the fish's body, and the amplitude of the wavelength increases along the body. The wave is displaced; the tail has a large wavelength with lots of wake coming off it.

Morphology of anguilliform motion

lonfg fish that taper off near the tail, low aspect ratio fish

Subcarangiform locomotion

Undulation occurs in less than one wavelength yet more than one-half wavelength (at speeds greater than one body length per second). Wave porpgapted along the back 1/3 of the fish.

Dispalcement does not occur until the caudal peduncle

Subcarangiform morphology

morphology in gadide, slamonidae, centridae

Caraginform

A locomotion type that switches between oscillatory and undulatory movement. A high-aspect-ratio design minimizes frictional drag, maximizes propulsive force, and minimizes energy wasted on lateral water displacement. Vertically lare tail allows greater mass of water to be accelerated faster.

Thunniform movement

Movement is restricted to rigid anal fin. Generates little wake. One big wave is generated throughought the body

Burst glide swimming

fish accelerate then glide through the water Ratio of energy increases in an exponential pattern when mean velocity/ max sustinable swimming spped increases (velocity increases).

Ground effects

Force is pushed back on the pectoral fish of the water, closer to the ground generates more life. Fins of flexible, oscillating foils create unsteady wakes that could increase thrust; thrust of free-swimming foils increases closer to the ground because vortices are compressed.