Symmetrization of a tensor in spherical coordinate

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SUMMARY

The discussion focuses on transforming a symmetric tensor \( S_{ij} = \frac{\partial_i x_j + \partial_j x_i}{2} \) from Cartesian coordinates to spherical coordinates \((\rho, \theta, \varphi)\) for the purpose of calculating the shear stress tensor in fluid dynamics. The reference "Bird, Stewart, and Lightfoot, Transport Phenomena" is highlighted as a key resource, providing components of the stress tensor and relevant equations in various coordinate systems. It is noted that the text employs a unique sign convention where compressive stresses are positive and tensile stresses are negative, which is crucial for accurate interpretation.

PREREQUISITES
  • Understanding of symmetric tensors and their properties
  • Familiarity with spherical coordinate systems
  • Knowledge of fluid dynamics principles, particularly shear stress
  • Proficiency in the Navier-Stokes equations
NEXT STEPS
  • Study the transformation of tensors between coordinate systems, focusing on spherical coordinates
  • Review the components of the stress tensor in "Bird, Stewart, and Lightfoot, Transport Phenomena"
  • Learn about the implications of different sign conventions in stress analysis
  • Explore advanced fluid dynamics topics, specifically the application of the Navier-Stokes equations in spherical coordinates
USEFUL FOR

Fluid dynamics engineers, researchers in continuum mechanics, and students studying tensor calculus and fluid behavior in spherical coordinates will benefit from this discussion.

oliveriandrea
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Hello, i don't know if my question is well posed,

if i have a symmetric tensor Sij = (∂ixj + ∂jxi) / 2
with xi cartesian coordinates, how can i transform it in a spherical coordinates system (ρ,θ,[itex]\varphi[/itex])?
(I need it for the calculus of shear stress tensor in spherical coordinate in fluid dynamics)
 
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oliveriandrea said:
Hello, i don't know if my question is well posed,

if i have a symmetric tensor Sij = (∂ixj + ∂jxi) / 2
with xi cartesian coordinates, how can i transform it in a spherical coordinates system (ρ,θ,[itex]\varphi[/itex])?
(I need it for the calculus of shear stress tensor in spherical coordinate in fluid dynamics)
Bird, Stewart, and Lightfoot, Transport Phenomena, gives the components of the stress tensor for a Newtonian fluid in cartesian coordinates, cylindrical coordinates, and spherical coordinates. They also give the stress equilibrium equations and the Navier Stokes equations for these coordinate systems. One thing to be careful about is that they use an unconventional sign convention for the stress tensor: compressive stresses are considered positive and tensile stresses are considered negative. But once you get past this, they have a wealth of useful information tabulated.

Chet
 
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