Uncertainty Quantification for the Flow of Nanofluids in Converging/Diverging Channels

In mathematical models, parameters are one of the most important input factors that affect the model outputs. In this work, the effects of parameters in complementing their interaction effects on nanofluids' output variables in converging and diverging channels have been studied. The mathematical model is solved numerically by using Matlab's built-in solver bvp4c. Global sensitivity analysis (Sobol's method) quantifies the effects of input parameters and their interactions on model outputs. The results showed that the channel opening (α) is the most influential model parameter for the velocity profile. Simultaneously, Eckert number (Ec) becomes the most influential parameter for temperature distribution in diverging and converging channels. The least sensitive parameters and interaction effects of involved parameters are identified on velocity and temperature profiles in converging and diverging channels.

PIV Study of Turbulent Flow in Asymmetric Converging and Diverging Channels

An experimental investigation of turbulent flow subjected to variable adverse and favorable pressure gradients in two-dimensional asymmetric channels is reported. The floors of the diverging and converging channels were flat while the roofs of the channels were curved. Adverse pressure gradient flows at Reh=27,050 and 12,450 and favorable pressure gradient flow at Reh=19,280 were studied. A particle image velocimetry was used to conduct detailed measurements at several planes upstream, within the variable section and within the downstream sections. The boundary layer parameters were obtained in the upper and lower boundary layers to study the effects of pressure gradients on the development of the mean flow on the floor and roof of the channels. The profiles of the mean velocities, turbulence intensities, Reynolds shear stress, mixing length, eddy viscosity, and turbulence production were also obtained to document the salient features of pressure gradient turbulent flows in asymmetric converging and diverging channels.