Prediction of Boundary Shear Stress Distribution in Converging Compound Channel Using Gene Expression Programming

The computation of the boundary shear stress distribution in an open channel flow is required for a variety of applications, including the flow resistance relationship and the construction of stable channels. The river breaches the main channel and spills across the floodplain during overbank flow conditions on both sides. Due to the momentum shift between the primary channel and adjacent floodplains, the flow structure in such compound channels becomes complicated. This has a profound impact on the shear stress distribution in the floodplain and main channel subsections. In addition, agriculture and development activities have occurred in floodplain parts of a river system. As a consequence, the geometry of the floodplain changes over the length of the flow, resulting in a converging compound channel. Traditional formulas, which rely heavily on empirical approaches, are ineffective in predicting shear force distribution with high precision. As a result, innovative and precise approaches are still in great demand. The boundary shear force carried by floodplains is estimated by gene expression programming (GEP) in this paper. In terms of non-dimensional geometric and flow variables, a novel equation is constructed to forecast boundary shear force distribution. The proposed GEP-based method is found to be best when compared to conventional methods. The findings indicate that the predicted percentage shear force carried by floodplains determined using GEP is in good agreement with the experimental data compared to the conventional formulas (R2 = 0.96 and RMSE = 3.395 for the training data and R2 = 0.95 and RMSE = 4.022 for the testing data).

An Enhanced Treatment of Boundary Conditions for 2D RANS Streamwise Velocity Models in Open Channel Flow

A 2D streamwise velocity model based on the Reynolds Averaged Navier–Stokes (RANS) is a useful approach to predict the boundary shear stress and the streamwise velocity in a free surface stream where secondary flows are not relevant. Boundary conditions treatment is a key aspect implementing these models. A low computational cost and fully predictive numerical model with a novel treatment of boundary conditions is presented. The main features of the modified model are the employment of a modified law of the wall valid for any roughness condition, the estimation of the boundary shear stress is done only focusing on the near-contour region, the use of a full-predictive physical based model for the eddy viscosity distribution and the incorporation of the free surface shear stress due to water–air interface. The validation of the proposed changes was performed with a substantial number of experimental cases available in the literature using different cross-section shapes (circular, rectangular, trapezoidal and compound section) and roughness condition with quite good agreement. Preliminary results suggest that the influence of the free surface boundary layer has a significant impact on the results for both the streamwise velocity and boundary shear stress in windy conditions. The proposed approach allows its considerations in practical applications.

An affordable and reliable device for direct bed shear stress measurements

<p>The entrainment and transport of sediment by hydrodynamic mechanisms is strongly related to bed shear stress exerted by flow. Therefore, to quantify sediment transport and to determine sediment incipient motion conditions, accurate estimations of bed shear stress are required. Most of the existing methods used in hydraulics and river engineering to determine bed shear stress are indirect, and are mostly restricted to limited flow conditions or contain a large degree of uncertainty. Although devices to perform direct measurements of boundary shear stress exist, they are normally based on expensive technology. We developed a shear plate for direct shear stress measurements, using relatively low cost components. In this work we present preliminary results of measurements performed with the new shear plate, to characterize the bottom shear stress generated by a ship propeller. The data result in the expected quadratic relation between bed shear stress and jet velocities, and also give evidence of a good reproducibility. We show that the new shear plate appears to be a promising device for reliable measurements of submerged boundary shear stress under a wide range of environments and flow conditions.</p>

Use of Multidimensional Models to Investigate Boundary Shear Stress through Meandering River Channels

Three-dimensional hydraulics were simulated through a wide range of synthetically generated meandering river channels to determine how channel curvature and width would correlate with the maximum boundary shear stress. Multidimensional models were applied, similar to a computational flume to simulate a wide range of 72 meandering channels, developed from sine-generated curves. Cannel sinuosity ranged from 1.1 to 3.0 and included five consecutive meander bends. Longitudinal slopes of the various channels spanned four orders of magnitude, while bankfull discharges spanned three orders of magnitude. Using results from one-half of the simulation sets, an empirical correlation was found to predict the maximum boundary shear stress as a function of dimensionless ratios of channel curvature and width. The remaining simulation sets were used for verification. Multidimensional models were used to simulate channel hydraulics to efficiently investigate a wide range of channel sinuosity, width/depth ratios, bankfull discharges, and valley slopes. When simulating such a wide range of channel conditions, multidimensional models offer a more efficiency method of generating consistent datasets than either field studies or physical modeling. This paper demonstrates how multidimensional models can be used to identify important hydraulic relationships that are otherwise difficult to determine.

IMPROVEMENT OF THE TECHNOLOGY OF FISH PUDDING FOR INFANT NUTRITION

The article deals with the improvement of the technology of fish pudding for infant nutrition. The current state and innovative developments of domestic and foreign scientists have been analyzed, perspective directions of enrichment of the fish puddings range and development of the market of products for infant nutrition have been defined. It is established that the main leaders in the production of this type of product are: Italy, England, Germany, Norway, Bulgaria, which specialize in vegetable and fish products. The effectiveness of combining fish, vegetable and animal raw materials in order to perform the nutritional value of fish puddings, in accordance with the requirements of baby food products, is theoretically substantiated and experimentally confirmed. Through the experimental research, the ingredient composition has been optimized and recipes for new fish puddings for infant nutrition based on fish (hake, pike-perch), vegetable (pumpkin) and animal raw materials (butter, milk, eggs) have been developed in the following ratio: sample 1 ( hake – 50, pumpkin – 16, butter – 4, milk – 13,4, eggs – 16,2); sample 2 ( pike-perch – 50, potato –16, butter – 4, milk – 13,4, eggs – 16,2). The results of researches of structural and mechanical indicators, namely – boundary shear stress, are given in the study. Studies have shown that adding pumpkin to the pudding reduces this indicator. This can be explained by the increase in moisture retention capacity, which makes the finished product susceptible to mechanical impact, ie more soft and juicy. To ensure the warranty period of storage, the patterns and dynamics of changes in quality indicators during the storage have been studied. The results of studies of acid and peroxide values of fat showed that with increasing duration of storage, these indicators increase within acceptable limits, which confirms the possibility of the selected raw materials usage in the recipes of new fish puddings. Based on the obtained results, the prospects of further research are determined - to develop a technological scheme for the production of fish puddings based on representatives of freshwater fish, namely grass carp and silver carp