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Abstract Partial ice covers alter the hydraulic regime of rivers in cold regions. Border ice is a type of partial ice cover that forms on the river banks and grows toward the centre of the channel to form a full ice cover; thereby impacting freeze-up processes. Many studies have been conducted to understand flow characteristics under open channel and full ice cover conditions; however, only a few studies have focused on the effects of partial ice covers on flow characteristics in a rectangular channel. This study goes even further by investigating stream-wise velocity and shear stress distributions in a trapezoidal channel with simulated border ice. This is the very first study to investigate the effects of different border ice coverage ratios and roughness conditions on flow characteristics in a trapezoidal channel. Experiments were conducted under seven different roughness and coverage conditions. High-resolution velocity data were collected using acoustic Doppler velocimeters within the fully-developed region of the flume. The magnitude and shape of the stream-wise velocity contours were significantly altered by the presence of the partial ice and rough boundaries. Moreover, local boundary shear stress distributions were significantly impacted by the coverage and roughness conditions. Generally, stream-wise velocity and local boundary shear stress increased within the open section and decreased within the covered section. For practical purposes, depth-averaged velocity and discharge distributions were investigated for each experiment. Results from this study will improve the current knowledge of the flow in partially covered channels and can be used for design and modelling purposes. Highlights • A novel study was conducted to understand the effects of partial ice covers on flow characteristics in a trapezoidal flume. • Boundary shear stress and stream-wise velocity are significantly impacted by the presence of partial ice covers. • Effects of roughness and ice coverage ratio on flow characteristics were investigated. • Stream-wise velocity could increase up to 32% compared to the open water condition. • Local boundary shear stress could increase up to 20 times more than the open water condition. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate influence of different post-end positions in alveolar bone level on stress distributions in resin-core build-up tooth under different load directions. Three-dimensional mathematical models of a root-filled mandibular premolar tooth were constructed. Resin post and core were built-up with six post lengths: 0, 1, 2, 3, 4, and 6 mm. Finite element analysis calculated stress distributions with oblique load of 400 N to buccal cusp 45 degree from buccal side or from lingual side. The 3 mm-post length (post-end position equal to cancellous bone level) caused highest equivalent stress of post-end compared with the shorter or longer post length. When change of load direction, the direction of maximum shear stress became completely opposite at mesiodistal cervical edge of core-part without a change of the magnitude. Changing shear stress direction would increase risk of debonding at mesiodistal cervical edge. [ABSTRACT FROM AUTHOR]

This study aims at showing that the shear stress distribution on a flat surface in the porous media can be expressed by just one probability density function. It is known that methane hydrate exists in the sand layers off Kii Peninsula in Japan within the turbidite sand-mud alternate strata. One of the concerns about gas production from methane hydrate is mud erosion and consequent reservoir clog caused by skin formation. The erosion rate of mud particles depends on the shear stress distribution on the surface of the mud layer in the alternates. The distribution of shear stress should depend on the flow and reservoir properties. Being able to predict the total mass of the eroded mud in advance would definitely be convenient. The objective of this paper is to propose a mathematical model of shear stress distribution on a flat interface between sand and mud layers, because it is believed that the maximum mud-erosion rate is given at the very beginning of the gas production when the mud surface is almost flat. To obtain the shear stress distribution on a flat surface, we conducted pore-scale numerical simulations using computational domains including numerically generated sand-mud beds. Interestingly, we found that the histograms of the shear stresses fit just one curve by means of proper non-dimensionalization. These consistent histograms of the non-dimensional shear stress were then matched with a Gamma distribution function, to develop a mathematical model. This new finding may make possible to predict the maximum rate of mud erosion if we know water flow velocity and reservoir properties, such as porosity and permeability. [ABSTRACT FROM AUTHOR]

With the aid of 174 laboratory data sets, Extreme Learning Machine (ELM) and decision tree (M5) models were investigated in predicting the shear stress distribution in circular channels. To evaluate the sensitivity of the input variables, 15 different input combinations were applied to each model. The calculation results show that the Re andy/Pparameter values greatly affect ELM method performance, whiley/Pandh/Dare sensitive to shear stress distribution modeling with M5. The best models among ELM and M5 were compared with an equation based on the Shannon entropy. According to the comparison results, the two proposed models outperform the Shannon entropy equation. Moreover, the ELM method’s function is superior in estimating the shear stress distribution and more adapted to experimental data with average Root Mean Square Error (RMSE) of 0.0236 compared to the M5 method withRMSEof 0.0364. [ABSTRACT FROM PUBLISHER]

Knowledge of the boundary shear stress distribution in channels is important because it is a key factor affecting on erosion and sedimentation rates. The presence of sediment deposits in sewers is often reported during operation, and circular channels are frequently used in sewer networks. Gene expression programming (GEP) is applied in this study to determine an equation for evaluating the shear stress distribution along the wetted perimeter of a circular channel with a flat bed, because of the presence of sediment on the bed. In view of the parameters affecting the shear stress distribution, five dimensionless parameters are applied to develop six GEP models to be used with 905 experimental data. The impact of the shear stress parameters is studied using the six GEP models and by dividing the wetted perimeter into wall and bed sections. Two equations are extracted from the GEP models’ output to estimate wall and bed shear stresses. The best model results are compared with a well-known equation based on the entropy concept. The GEP model predictions of wall and bed shear stresses are very similar to the experimental outcomes, whereas the entropy-based model overestimates the shear stress distribution. The proposed GEP models demonstrate superior performance in estimating the shear stress distribution with a mean absolute percentage error ( MAPE ) of 3.79% compared to an existing equation with MAPE of 9.52%. [ABSTRACT FROM AUTHOR]

Bonded sleeve joints formed by telescoping a steel tube connector for bolt-fastening are effective means for assembling tubular fibre reinforced polymer (FRP) members into more complex structures such as planar or space frames. A theoretical formulation is developed in this paper to estimate the capacity of such joints in axial loading and the predictions are validated by experimental results covering various section geometries and bond lengths. The formulation is based on the bilinear bond-slip constitutive relationship considering elastic, softening and debonding behaviour at the adhesive bonding region. Finite element (FE) analysis is also conducted to estimate the joint capacity and to describe shear stress distribution in the adhesive layer, validating the reliability of the theoretic results. The theoretical formulation is therefore further used to study the effects of design parameters including bond length and adherend stiffness ratio, again validated by FE results. An effective bond length can be accurately predicted by the theoretical formulation for the joint capacity at both the elastic limit and the ultimate state. Given a bond length, an optimal adherend stiffness ratio can be identified to achieve the maximum joint capacity at the elastic limit or the ultimate state. [ABSTRACT FROM AUTHOR]

Flow perfusion bioreactors have been extensively investigated as a promising culture method for bone tissue engineering, due to improved nutrient delivery and shear force-mediated osteoblastic differentiation. However, a major drawback impeding the transition to clinically-relevant tissue regeneration is the inability to non-destructively monitor constructs during culture. To alleviate this shortcoming, we investigated the distribution of fluid shear forces in scaffolds cultured in flow perfusion bioreactors using computational fluid dynamic techniques, analyzed the effects of scaffold architecture on the shear forces and monitored tissue mineralization throughout the culture period using microcomputed tomography. For this study, we dynamically seeded one million adult rat mesenchymal stem cells (MSCs) on 85% porous poly(l-lactic acid) (PLLA) polymeric spunbonded scaffolds. After taking intermittent samples over 16 days, the constructs were imaged and reconstructed using microcomputed tomography. Fluid dynamic simulations were performed using a custom in-house lattice Boltzmann program. By taking samples at different time points during culture, we are able to monitor the mineralization and resulting changes in flow-induced shear distributions in the porous scaffolds as the constructs mature into bone tissue engineered constructs, which has not been investigated previously in the literature. From the work conducted in this study, we proved that the average shear stress per construct consistently increases as a function of culture time, resulting in an increase at Day 16 of 113%.