Numerical simulation of drop impingement and bouncing on a heated hydrophobic surface

The heat transfer of a single water droplet impacting on a heated hydrophobic surface is investigated numerically using a phase field method. The numerical results of the axisymmetric computations show good agreement with the dynamic spreading and subsequent bouncing of the drop observed in an experiment from literature. The influence of Weber number on heat transfer is studied by varying the drop impact velocity in the simulations. For large Weber numbers, good agreement with experimental values of the cooling effectiveness is obtained whereas for low Weber numbers no consistent trend can be identified in the simulations

Parametric Study on Ridges Inducing Secondary Motions in Turbulent Channel Flow

A DNS parametric study of streamwise‐aligned rectangular ridges is carried out in a fully developed turbulent channel flow with constant flow rate at $Reb = 18000$. The simulations were carried out systematically varying the ridge height h, width w and structural wavelength $S$. The ridges generate a strong large‐scale secondary motion, which is measured in terms of the integral swirl strength. Of the presented cases, the configuration with the ridge height$h = 0.1 \delta$, $S/w = 4$, $S = 1 \delta$ produces the strongest secondary flow of $4.5\%$ $U_b$. The varying flow topology is discussed as a result of the varying ridge dimensions

Global Friction of Uniform vs. Heterogeneous Sandpaper Roughness

Skin-friction measurements of streamwise aligned sandpaper strips are presented in Nikuradse-type di-agrams obtained in a dedicated experimental facility. These novel results shed light onto the global friction drag of heterogeneous rough surfaces. They indicate the drag-increasing presence of secondary motions known to exist over spanwise heterogeneous roughness. The Reynolds number dependency of the skin-friction coef-ficient appears to be a superposition of the smooth wall and homogeneous rough wall behavior. The results sug-gest that the present heterogeneous rough surface does not reach a fully rough behavior in which the friction co-efficient becomes independent of Reynolds number

Channel flow with large longitudinal ribs

We present data from direct numerical simulations of flow through channels containing large, longitudinal, surface-mounted, rectangular ribs at various spanwise spacings, which lead to secondary flows. It is shown that appropriate modifications to the classical log-law, predicated on a greater wetted surface area than in a plane channel, lead to a log-law-like region in the spanwise-averaged axial mean velocity profiles, even though local profiles may be very different. The secondary flows resulting from the presence of the ribs are examined and their effects discussed. Comparing our results with the literature we conclude that the sense of the secondary flows is largely independent of the particular rib spacing whether normalised by channel depth or rib width. The strength of the secondary flows, however, is shown to depend on the ratio of rib spacing to rib width and on Reynolds number. Topological features of the secondary flow structure are illustrated via a critical point analysis and shown to be characterised in all cases by a free stagnation point above the centre of the rib. Finally, we show that if the domain size is chosen as a ‘minimal channel’ size, rather than a size which allows adequate development of the usual outer layer flow structures, the secondary flows can be affected and this leads inevitably to differences in the near-rib flows so that for ribbed channels, unlike plain channels, it is unwise to use minimal domains to identify details of the near-wall flow

Translation of Anticancer Efficacy From Nonclinical Models to the Clinic

Mouse cancer models have provided critical insights into tumor biology; however, clinical translation of these findings has been challenging. This perspective posits that factors impacting on successful translation start with limitations in capturing human cancer pathophysiology and end with challenges in generating robust translatable preclinical end points. A comprehensive approach that considers clinically relevant mouse models with both an integrated biomarker strategy and a complementary modeling and simulation effort will strengthen the current oncology drug development paradigm