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INVERTEBRATES AND FLUID DYNAMICS : HOLDING ON

INVERTEBRATES AND FLUID DYNAMICS : HOLDING ON. BOUNDARY LAYER. Mainstream Velocity (U). Boundary layer thickness (90%). Distance from substrate. Boundary layer thickness (99%). Velocity. BOUNDARY LAYER. Using the boundary layer – water pennies ( Psephenidae ). BOUNDARY LAYER.

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INVERTEBRATES AND FLUID DYNAMICS : HOLDING ON

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  1. INVERTEBRATES AND FLUID DYNAMICS: HOLDING ON

  2. BOUNDARY LAYER Mainstream Velocity (U) Boundary layer thickness (90%) Distance from substrate Boundary layer thickness (99%) Velocity

  3. BOUNDARY LAYER Using the boundary layer – water pennies (Psephenidae)

  4. BOUNDARY LAYER Mainstream Velocity (U) Distance from substrate Velocity

  5. BOUNDARY LAYER Using the boundary layer – water pennies (Psephenidae)

  6. Other stream insects Trichoptera Plecoptera Ephemeroptera

  7. Stream animals– Strategies for holding on Baetis Rhithrogena Ancylus

  8. Stream animals– Strategies for holding on Psephenus Bibliocephala Neothremma

  9. Extreme Gradients – Swash Zone

  10. Donax

  11. Swash Surfing

  12. Donax Density Weight distribution Shape

  13. Density 2.0 1.0 0 Macrocallista Chione Donax Spisula Mercenaria Tellina Divaricella Tagellus Density (103 kg/m3)

  14. Weight Distribution Pivot point

  15. Dorsal Posterior Anterior Ventral

  16. Behaviour in a Swash Zone

  17. WAVE STRESS a. Limitation of size Water flow 100% 90% Boundary layer

  18. WAVE STRESS a. Limitation of size Water flow

  19. WAVE STRESS b. Holding on – flow tolerance 3 Flow rate (m/s) 0 Time to dislodge

  20. WAVE STRESS c. Holding on - orientation Keyhole limpet

  21. WAVE STRESS c. Holding on - orientation Water flow

  22. WAVE STRESS c. Holding on - orientation <.5 m/s >.5 m/s Freq -90 0 90 -90 0 90 Orientation (º to flow)

  23. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 1. Testing holding power

  24. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 1. Testing holding power 100 0 Kg required to dislodge 15 Foot area (cm2)

  25. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 1. Suction? Atmospheric pressure ≈ 1 kg/cm2 Patella ≈ 3 - 7 kg/cm2 -can generate a force > atmospheric pressure - No negative pressure under foot

  26. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Patella Mucous layer

  27. WAVE STRESS d. Holding on - tenacity What is “tenacity”? area 2. Adhesion surface tension Thickness of fluid Theoretical adhesion = 600 kg/cm2

  28. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? 2. Adhesion Tenacity (kg/cm2 to detach) Weight of mucous

  29. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Foot rigidity

  30. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Foot rigidity l d

  31. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Foot rigidity High In field - Tenacity Low Low High Flexibility

  32. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Drag Resistance to water movement depends on: 1) Size FLOW 2) Shape 3) Texture

  33. 3. WAVE STRESS d. Holding on - tenacity What is “tenacity”? Drag Drag – not well correlated with density Drag Side Front Rear

  34. Types of Limpets Non-Migratory Migratory -don’t move far -move up shore -often fixed and territorial -high r -low r -high growth -low growth (need high food intake) -react to predators by clamping -flee from predators LESS FLEXIBLE MORE FLEXIBLE

  35. A COMPROMISE OF SEVERAL FACTORS Sea Urchins - Echinoidea lunules

  36. 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

  37. If lunules have a hydrodynamic function -they should grow with the animal observed isometric Log lunule length p < .05 Log test diameter

  38. Burrowing speed 231 sec 230 sec Time to burrow Plugged Not plugged

  39. Flow through a sand dollar

  40. Weight Lift Weight

  41. Burrowing to add weight Lift Weight

  42. Sand Dollar reorientation - Dendraster

  43. Adding weight – incorporate magnetite

  44. Reducing lift and drag Skin drag – important? Pressure drag – depends on shape

  45. Reducing lift and drag Skin drag – important? Pressure drag – depends on shape Very flat

  46. Reducing lift and drag Skin drag – important? Area of lower pressure Pressure drag – depends on shape Rounded

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