A Reynolds stress model for turbulent flows of viscoelastic fluids

A second-order closure is developed for predicting turbulent flows of viscoelastic fluids described by a modified generalised Newtonian fluid model incorporating a nonlinear viscosity that depends on a strain-hardening Trouton ratio as a means to handle some of the effects of viscoelasticity upon turbulent flows. Its performance is assessed by comparing its predictions for fully developed turbulent pipe flow with experimental data for four different dilute polymeric solutions and also with two sets of direct numerical simulation data for fluids theoretically described by the finitely extensible nonlinear elastic - Peterlin model. The model is based on a Newtonian Reynolds stress closure to predict Newtonian fluid flows, which incorporates low Reynolds number damping functions to properly deal with wall effects and to provide the capability to handle fluid viscoelasticity more effectively. This new turbulence model was able to capture well the drag reduction of various viscoelastic fluids over a wide range of Reynolds numbers and performed better than previously developed models for the same type of constitutive equation, even if the streamwise and wall-normal turbulence intensities were underpredicted.

Numerical and experimental investigations of three-dimensional container filling with Newtonian viscous fluids

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Theoretical Analysis and Experimental Validation of the Scholte Wave Propagation in Immersed Plates for the Characterization of Viscous Fluids

This work reports the study of an attractive interfacial wave for application in ultrasonic NDE techniques for inspection and fluid characterization. This wave, called quasi-Scholte mode, is a kind of flexural wave in a plate in contact with a fluid which presents a good sensitivity to the fluid properties. In order to explore this feature, the phase velocity curve of quasi-Scholte mode is experimentally measured in a plate in contact with a viscous fluid, showing a good agreement with theory.

Growth Control of Microbial in Miscible Cutting Fluids Using Ultraviolet Radiation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)