High Viscous Flow in Silk Spinneret

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High Viscous Flow in Silk Spinneret
2004.May.4th
Tetso Asakura Ayano Ino Toshiyuki Suzuki
Tokyo University of Agriculture and
Technology CHAM Japan
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Introduction

• For create silk artificially, it is important to
  application of process of silk spinning.

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Silkworm spinneret
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3D structure silkworm spinneret
Silk Press part
chitin plate
Silk
Silk tube
spigot
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Process of Silk spinning

• Silk spinning
• ? a to ß transition by shear Stress

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Shear rate of Silk fibroin

• Experiment of critical shear rate

• Kataoka at.al
• transition shear rate is
• 1E021E-3 sec-1

Critical shear rate
concentration
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Molecular Dynamics simulations
Tensile stress 0.1GPa Shear stress 0.3,0.5,0.7
,1.0GPa
Conformational probability
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Geometry from Biology
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PHOENICS OBJECTS

• PHOENICS-VR Objects
• ? Dont need BFC meshing Easy to Use
• Complex Geometry
• ?facet data converted from STL format
• Wall friction added automatically on Object face

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STL(Stereo Lithograph) file

• STL file
• Solid model ? triangle patches
• It accepts the un-closed and twist surface
• Many tools can be used to make it

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Graphical tools to Object(Make STL file from
picture)
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Repair STL

• What is required before importing PHOENICS ?
• No Hole or Gap
• Surface vector is the same direction(twist)
• Cut small parts
• Smoothing

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Model (meshing)
152µm (ny78)
156µm (nx78)
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Properties of Silk fibroin

• Density
• 75water 1.075g/cm3
• Viscosity
• Neuton Fluid 6.5E4P
• Ref Water0.01P,Glycerin7.982P

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Boundary Conditions

• Inlet Velocity 0.178cm/sec
• (spinneret velocity1.0cm/s)
• Outlet P0
• Wall Non-Slip

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High Viscosity Flows

• Transport Equations
• ??u0
• ??uu ??p/? µ?2u
• Finite volume equations
• FP(aNFNaSFSetc.)/aP

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Continuity Equations

• Error of continuity
• RcN-cSetc.
• c convective flux
• Pressure correction equation
• aPpP aNpNaSpSetc.R
• by default adc/dp

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Convergence acceleration

• Pressure correction equation at ADDDIF option for
  High Viscosity flow
• aPpPaNpNaSpSetc.R
• ad(cd)/dp
• Diffusion Flux

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Corresponding in MIGAL

• MIGAL Solver ? Velocity-Pressure Coupling
• ApFpSAnbFnbb
• Matrix A included convection and diffusion fluxes

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Convergent test

• Use cut model near chitin plate
• No. of cells
• 94x114x63

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Pressure and Velocity
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Slip velocities(shear rate)

• In PHOENICS, the magnitude of the total rate of
  strain GEN1 is given as,
• GEN12(du/dx)2(dv/dy)2(dw/dz)2
• (du/dydv/dx)2
• (dv/dzdw/dy)2
• (dw/dxdu/dz)2
• Slip velocity is VsSQRT(GEN1)

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Summary Conclusion

• About Simulation Result
• The maximum shear velocities is 451/s at silk
  press part. Where is provided the transition from
  liquid protein to fiber.
• Static Pressure loss is Giga Pascal order in
  spinner. It is as same as the transition stress
  with the molecular dynamics simulation.

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Summary Conclusion 2

• About CFD technique
• With some graphical tools, we can calculate
  easily the case with complex biology geometry by
  PHOENICS.
• A better convergence has been gotten by adding
  the diffusion velocity into pressure correction
  equation for High Viscous Flow, If we desire
  much better performance, we can use MIGAL.

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Summary Conclusion 3

• Future and next step
• PARSOL (Cut cell)
• Pressing at chitin plate (use Moving Grid or
  MOFER).
• Survey for the fibroin properties.