Tagged: 16, fluid-dynamics, General, polyflow, viscoelasticity, Viscous Heating
March 17, 2023 at 8:58 amFAQParticipant
In a shear flow, shear stress is the only stress component that contributes to viscous heating. In other words, having a proper description of the viscosity is enough. Normal stresses in shear do not produce any heat. In a pure extensional flow, viscous heating for a viscoelastic fluid will usually be lower than that of its inelastic counterpart at early deformations while the opposite can be found at large deformations, this originates from the increase of extensional viscosity. In most observed cases, the viscous heating in an extensional flow remains very low as compared to that of a shear flow. The reason is easy: one can have a shear flow involving a high shear rate during a long time while one cannot have an elongational flow involving a high elongation rate during a long time interval. In a shear flow, one can easily get shear rates of 100 s-1 or higher. If one considers at time t=0 a square fluid sample whose side length is 1 cm, after undergoing a shear rate of 100 s-1 during 1 s, two of its sides will have a length of about 100 cm. If one considers the same fluid sample in an extensional flow at strain rate of 100 s-1, it will be stretched up to a length of exp(100) after 1 s! This would never be achieved so that viscous heating in extension can never be significant. If one compares the non-isothermal converging flow for a Newtonian fluid and for a Maxwell fluid, both having the same shear viscosity, the temperature increase will be slightly larger for the Newtonian fluid. Despite the additional elongational stress component of the viscoelastic Maxwell model, the lower temperature increase actually originates from the transient stress build-up. Due to viscoelasticity, the shear stress does not develop instantaneously and its contribution to viscous heating is therefore reduced.
Introducing Ansys Electronics Desktop on Ansys Cloud
The Watch & Learn video article provides an overview of cloud computing from Electronics Desktop and details the product licenses and subscriptions to ANSYS Cloud Service that are...
How to Create a Reflector for a Center High-Mounted Stop Lamp (CHMSL)
This video article demonstrates how to create a reflector for a center high-mounted stop lamp. Optical Part design in Ansys SPEOS enables the design and validation of multiple...
Introducing the GEKO Turbulence Model in Ansys Fluent
The GEKO (GEneralized K-Omega) turbulence model offers a flexible, robust, general-purpose approach to RANS turbulence modeling. Introducing 2 videos: Part 1 provides background information on the model and a...
Postprocessing on Ansys EnSight
This video demonstrates exporting data from Fluent in EnSight Case Gold format, and it reviews the basic postprocessing capabilities of EnSight.
- ANSYS Fluent: Introduction to the GEKO Turbulence Model Part I
- ANSYS System Coupling: Two Way Fluid Structure Interaction – Part 1
- ANSYS Polyflow: Adaptive Meshing Based on Contact
- Delete or Deactivate Zone in Fluent
- Apply Custom Material Properties in Fluent
- How can I create a Cell Register from a Cell Zone?
- Check CPU Time in ANSYS FLUENT
- What is meant by Warning: Flow boundary zone 18 is adjacent to a solid zone?
- Running Python Script from Workbench
- Aero-Mechanical Simulation of Turbomachinery Blading
© 2023 Copyright ANSYS, Inc. All rights reserved.