Numerical investigation of conjugated heat transfer in a channel with a moving depositing front

This article presents numerical simulations of conjugated heat transfer in a fouled channel with a moving depositing front. The depositing front separating the fluid and the deposit layer is captured using the level-set method. Fluid flow is modeled by the incompressible Navier–Stokes equations. Numerical solution is performed on a fixed mesh using the finite volume method. The effects of Reynolds number and thermal conductivity ratio between the deposit layer and the fluid on local Nusselt number as well as length-averaged Nusselt number are investigated. It is found that heat transfer performance, represented by the local and length-averaged Nusselt number reduces significantly in a fouled channel compared with that in a clean channel. Heat transfer performance decreases with the growth of the deposit layer. Increases in Reynolds, Prandtl numbers both enhance heat transfer. Besides, heat transfer is enhanced when the thermal conductivity ratio between the deposit layer and the fluid is lower than 20 but it decreases when the thermal conductivity ratio is larger than 2

Low cost soft robotic gloves for at-home rehabilitation and daily living activities

Stroke is one of the major reasons which affect the human hand functionality and lead to disability. Different repetitive exercises are used to regain the hand functionality which involves robotic exoskeleton. Soft pneumatic actuators are one of the good alternatives to rigid and fixed exoskeletons for rehabilitation. This paper presents soft robotic gloves fabricated with two different lowcost silicones which can be used in daily living activities and rehabilitation purpose. Soft robotic gloves are light weight and compact. These robotic gloves utilize the pneumatic pressure to flex and extend the human hand. Soft robotic gloves were tested on a healthy object for grasping and rehabilitation ability. Results showed that robotic glove was able to grasping and do the Kapandji test. This work presents an important step toward low cost efficient soft robotic devices for rehabilitation of stroke patients

Satellite image analysis and frozen cylinder experiments on thermal erosion of periglacial fluvial islands

International audienceFrozen islands in the Lena River, Siberia, experience rates of fluvial thermal erosion exceeding 10m/year. The islands erode differentially, with rates of frontal retreat exceeding those on island sides. We define the erosion ratio (ER) between the front and sides to estimate this differential erosion. A GIS‐based study of 19 islands from 1967 to 2010 indicated average erosion rates of 19.7 and 3.7 m/year for the island heads and sides, respectively. The average ER over the period was 4.7. An analytical model of local thermal erosion for a frozen cylinder of sand in a turbulent water flow is proposed, assuming an ablation process. Thermal erosion of 19 frozen cylinders was measured for water flows of different temperature and velocity in a cold chamber. As observed in the field, frontal erosion always exceeded lateral erosion, with an average ER of 1.6. The ER decreased with increasing temperature from 5 to 15°C. The higher value of ER in the field may be due to interactions with neighboring islands and banks. An empirical law including phase change and the process of erosion is proposed, and validates our model compared with previous laws that do not account for erosion. The erosion process enhances heat transfer

Flow pattern and heat transfer past two tandem arranged cylinders with oscillating inlet velocity

Unsteady laminar convective fluid flow and heat transfer past two cylinders in tandem arrangement is investigated. Besides forced mixing by the natural vortex streets, extra imposed oscillating inlet velocity are considered. The lift and drag coefficients and Strouhal number for a single cylinder and their dependence on Reynolds number are also provided to validate the calculations with previous experiments. Different frequencies and amplitudes of the oscillating flows are set as inlet boundary conditions. For the cycle effect, at some specified points of the cycle ratios, the heat transfer enhancement of the upstream cylinder and the downstream cylinder are relatively larger due to the combined-effect of the natural vortex streets and the imposed oscillating inlet flows. The interaction between the natural vortex streets and imposed oscillating inlet flow leads to non-regular shaped vortices with increased flow mixing. For the amplitude effect, Nusselt numbers of the two cylinders are both greatly increased with increased amplitude ratios. With increased amplitude ratios, the vortex street expands and vibrates in a larger region which leads to stronger flow mixing and higher heat transfer. Generally, oscillating inlet flows can efficiently increase the heat transfer of two cylinders in crossflow without increasing the flow rate of the coolants