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-   -   Shear stress induced on fluid in centrifugal pump (http://www.cfd-online.com/Forums/cfx/107891-shear-stress-induced-fluid-centrifugal-pump.html)

MechKim October 8, 2012 21:31

Shear stress induced on fluid in centrifugal pump
 
Hi,

Im completing a study on an artificial heart pump. I have completed a CFD model in CFX, however i am confused as to how to determine the shear stress induced on the blood. Predefined expressions gives Wall Shear Stress, but i dont think this is what i need.
Do i need to define my own expression? And does TauZY = viscosity * (dv/dz + dw/dy) be the correct expression for shear stress on the fluid?

Any insight much appreciated :)

kastarkas September 30, 2016 02:20

Its alomost 4 years old..but still ...i hope you might have solved the problem and travelled way beyond that...

Opaque September 30, 2016 11:39

In CFD-Post, you can create user defined variables, and write expressions for the different components of the stress tensor, say: sigma_xx, tau_xy, ...

Keep in mind CFD-Post provides the gradient of the velocity field, and you can use them as in Velocity u.Gradient X (du/dx).

Also, to clarify the confusion between Wall Shear Stress and tau_yz.

Wall Shear Stress is the tangential force per unit area on the surface, i.e. the tangential component of the product between the stress tensor and the normal unit vector.

tau_yz is the component in yz plane of the stress tensor which only defines the state of stress in space, and a surface must be defined to compute the force per unit area on such surface.

For more information, https://en.wikipedia.org/wiki/Stress_(mechanics)

Hope the above helps,


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