INVERTEBRATES AND FLUID DYNAMICS: HOLDING ON. BOUNDARY LAYER Mainstream Velocity (U) Boundary layer...
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Transcript of INVERTEBRATES AND FLUID DYNAMICS: HOLDING ON. BOUNDARY LAYER Mainstream Velocity (U) Boundary layer...
BOUNDARY LAYER
Mainstream Velocity (U)
Boundary layer thickness (99%)
Boundary layer thickness (90%)
Dis
tanc
e fr
om s
ubst
rate
Velocity
Density
2.0
1.0
0
Density(103 kg/m3)
DonaxChione
Mercenaria
Spisula
Macrocallis
ta
Divaric
ella
Tellina
Tagellus
WAVE STRESS
c. Holding on - orientation
<.5 m/s
-90 0 90 -90 0 90
>.5 m/s
Freq
Orientation (º to flow)
WAVE STRESS
d. Holding on - tenacity
What is “tenacity”?
1. Testing holding power
Kg required to dislodge
100
0
Foot area (cm2)15
WAVE STRESS
d. Holding on - tenacity
What is “tenacity”?
1. Suction?
Atmospheric pressure ≈ 1 kg/cm2
Patella ≈ 3 - 7 kg/cm2
-can’t generate a force > atmospheric pressure
- No negative pressure under foot
WAVE STRESS
d. Holding on - tenacity
What is “tenacity”?
2. Adhesion area
surface tension
Thickness of fluid
Theoretical adhesion = 600 kg/cm2
3. WAVE STRESS
d. Holding on - tenacity
What is “tenacity”?
2. Adhesion
Tenacity(kg/cm2 to detach)
Weight of mucous
3. WAVE STRESS
d. Holding on - tenacity
What is “tenacity”? Foot rigidity
Tenacity
Flexibility
High
HighLow
Low
In field -
3. WAVE STRESS
d. Holding on - tenacity
What is “tenacity”? Drag
FLOW
Resistance to water movement depends on:
1) Size
2) Shape
3) Texture
3. WAVE STRESS
d. Holding on - tenacity
What is “tenacity”? Drag
Drag
Side Front Rear
Drag – not well correlated with density
Types of Limpets
Non-Migratory Migratory
-don’t move far
-often fixed and territorial
-low r
-low growth
-move up shore
-high r
-high growth
(need high food intake)
-react to predators by clamping -flee from predators
LESS FLEXIBLE MORE FLEXIBLE
WHAT IS THE FUNCTION OF LUNULES?
1) Aid in burrowing
2) Removal of feces
3) Maintain a “communication” with the surface if buried
4) Maintain inclined posture
5) Feeding
Log lunule length
Log test diameter
p < .05
If lunules have a hydrodynamic function-they should grow with the animal
isometric
observed
Reducing lift and drag
Skin drag – important?
Pressure drag – depends on shape
Rounded
Area of lower pressure