scholarly journals Experimental studies of the kinematics flow and bottom’s reformations in the area of bridge pier during the construction of the bridge crossing

2021 ◽  
Vol 2131 (3) ◽  
pp. 032064
Author(s):  
K Morgunov ◽  
G Gladkov ◽  
Yu Ivanovsky
Keyword(s):  
Experimental Studies ◽  
Horseshoe Vortex ◽  
Hydraulic Modeling ◽  
Acute Angle ◽  
Bridge Pier ◽  
Similarity Criteria ◽  
Bottom Relief ◽  
Quantitative Characteristics ◽  
Specific Discharge ◽  
Bridge Crossing

Abstract The results of laboratory modeling of bottom reformations in the area of bridge pier crossing over water barriers are presented. The basics of hydraulic modeling are described taking into account the similarity criteria. The flow around a rectangular box (tongued-and-grooved protection of a constructed pier) is experimentally studied, the pattern of erosion if an ice-cutter device is installed in front of the box in the form of a triangle directed at an acute angle towards the flow is considered. The structure of the bottom relief in the vicinity of the tongued-and-grooved box is experimentally studied under the conditions of the bottom erosion. Two cycles of experiments were performed for different values of the flow depth and specific discharge of water. Localization and quantitative characteristics of washouts and alleviation of sandy soil in the vicinity of the streamlined design are established. It is noted that the main mechanism for the formation of the bottom relief is a horseshoe vortex at the base of the pier. A stagnation zone is formed inside the horseshoe. In the absence of an ice cutter, the main zones of soil erosion occur in the corners of the frontal bezel of the box, alluvium forms in the rear unit of the design. By installing an ice-cutter device in front of the box, the erosion zones move to the vicinity of the corners lying at the base of the triangular ice-cutter facing the box. The alluvium remains in the wake of the box. At the same time, the absolute values of the erosion depth and the height of the alluvium under installing the ice-cutter close to the box are reduced. The data of velocity measurements on the free surface and in the flow thickness are also given.

Self-preservation Effect of Gas Hydrates

2021 ◽  
Vol 23 ◽  
pp. 346-355
Author(s):  
Anatoliy Pavlenko
Keyword(s):  
Gas Hydrates ◽  
Gas Hydrate ◽  
Experimental Studies ◽  
Interphase Surface ◽  
Quantitative Characteristics ◽  
Nonequilibrium Conditions ◽  
Water Simulation ◽  
Gas Loss ◽  
Physical And Mathematical Models ◽  
And Storage

This work was performed to improve the storage and transportation technology of gas hydrates in nonequilibrium conditions. At atmospheric pressure and positive ambient temperature, they gradually dissociate into gas and water. Simulation of the gas hydrate dissociation will determine optimal conditions for their transportation and storage, as well as minimize gas loss. Thermodynamic parameters of adiabatic processes of forced preservation of pre-cooled gas hydrate blocks with ice layer were determined theoretically and experimentally. Physical and mathematical models of these processes were proposed. The scientific novelty is in establishing quantitative characteristics that describe the gas hydrates thermophysical parameters thermophysical characteristics influence on the heat transfer processes intensity on the interphase surface under conditions of gas hydrates dissociation. Based on the results of experimental studies, approximation dependences for determining the temperature in the depths of a dissociating gas hydrate array have been obtained. Gas hydrates dissociation mathematical model is presented.

scholarly journals A Hooked-Collar for Bridge Piers Protection: Flow Fields and Scour

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1251 ◽  
Author(s):  
Su-Chin Chen ◽  
Samkele Tfwala ◽  
Tsung-Yuan Wu ◽  
Hsun-Chuan Chan ◽  
Hsien-Ter Chou
Keyword(s):  
Laboratory Experiments ◽  
Horseshoe Vortex ◽  
Flow Fields ◽  
Bridge Pier ◽  
The Other ◽  
Bridge Piers ◽  
Vortex Strength ◽  
Numerical Tests ◽  
Scour Hole ◽  
New Type

A new type of collar, the hooked-collar, was studied through experiments and numerical methods. Tests were conducted using a hooked collar of a width of 1.25b and a height of 0.25b, where b is the bridge-pier width. The hooked-collar efficiency was evaluated by testing different hooked-collar placements within the bridge-pier, which were compared to the bridge-pier without any collar. A double hooked-collar configuration, one placed at the bed level and the other buried 0.25b, was the most efficient at reducing the scour hole. In other cases, a hooked-collar positioned 0.25b above the bed slightly reduced the scour hole and had similar scour patterns when compared to the pier without the hooked-collar. The flow fields along the vertical symmetrical plane in the experiments are also presented. Laboratory experiments and numerical tests show that maximal downflow is highly reduced along with a corresponding decrease in horseshoe vortex strength for the experiments with the hooked-collar, compared to cases without the hooked-collar. The flow fields reveal that the maximum turbulent kinetic energy decreases with the installation of the hooked-collar.

scholarly journals Effect of Slam Force Duration on the Vibratory Response of a Lightweight High-Speed Wave-Piercing Catamaran

2015 ◽  
Vol 59 (02) ◽  
pp. 69-84
Author(s):  
Jason John McVicar ◽  
Jason Lavroff ◽  
Michael Richard Davis ◽  
Giles Thomas
Keyword(s):  
High Speed ◽  
Bending Strength ◽  
Experimental Studies ◽  
Bending Moment ◽  
Higher Order ◽  
Acute Angle ◽  
Beam Model ◽  
Higher Order Modes ◽  
Hull Structure ◽  
Vertical Bending Moment

When the surface of a ship meets the water surface at an acute angle with a high relative velocity, significant short-duration forces can act on the hull plating. Such an event is referred to as a slam. Slam loads imparted on ships are generally considered to be of an impulsive nature. As such, slam loads induce vibration in the global hull structure that has implications for both hull girder bending strength and fatigue life of a vessel. A modal method is often used for structural analysis whereby higher order modes are neglected to reduce computational effort. The effect of the slam load temporal distribution on the whipping response and vertical bending moment are investigated here by using a continuous beam model with application to a 112 m INCAT wave-piercing catamaran and correlation to full-scale and model-scale experimental data. Experimental studies have indicated that the vertical bending moment is dominated by the fundamental longitudinal bending mode of the structure. However, it is shown here that although the fundamental mode is dominant in the global structural response, the higher order modes play a significant role in the early stages of the response and may not be readily identifiable if measurements are not taken sufficiently close to the slam location. A relationship between the slam duration and the relative modal response magnitudes is found, which is useful in determining the appropriate truncation of a modal solution.

scholarly journals Application of Riblets on Turbine Blade Endwall Secondary Flow Control

2014 ◽  
Author(s):  
X. Miao ◽  
Q. Zhang ◽  
H. Jiang ◽  
H. Qi
Keyword(s):  
Secondary Flow ◽  
Experimental Studies ◽  
Surface Texturing ◽  
Horseshoe Vortex ◽  
Laser Surface Texturing ◽  
Small Scale ◽  
Large Space ◽  
Readiness Level ◽  
Laser Manufacturing ◽  
Manufacturing Readiness

Within the past ten years, significant improvements have been achieved in the laser manufacturing process. It is feasible now to obtain various small-scale surface features (such as dimples, riblets, grooves, etc.) with the current manufacturing readiness level of laser surface texturing techniques. In this paper, the aerodynamic impact of the employment of riblets on turbine endwall has been investigated through combined CFD and experimental studies in a low speed linear cascade environment. Detailed comparisons of the flow structures have been made for cases with and without riblets on the endwall. The results show that endwall riblets can effectively reduce the strength of the pressure side leg of the horseshoe vortex, lower the cross passage pressure gradient, and alleviate the lift up of the passage vortex. A test section with seven passages and eight blades was used to validate the CFD observations. Both numerical and experimental results indicate that, the addition of riblets can be an effective approach to reduce the endwall secondary flow, and there is a large space for further optimization.

scholarly journals Scour around Bridge Piers: Numerical Investigations of the Longitudinal Biconcave Pier Shape

2018 ◽  
Vol 62 (4) ◽  
pp. 298-304 ◽  
Author(s):  
Bouabdellah Guemou ◽  
Abdelali Seddini ◽  
Abderrahmane Nekkache Ghenim
Keyword(s):  
Shear Stress ◽  
Flow Direction ◽  
Basic Mechanism ◽  
Horseshoe Vortex ◽  
Local Scour ◽  
Bridge Pier ◽  
Bed Shear Stress ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
The Rich

The flow pattern around a bridge pier and the scouring phenomenon are very complicated. The basic mechanism causing local scour is the down-flow at the upstream face of the pier. It is understood that the horseshoe vortex is the key mechanism that leads to the local scour around pier; existing literature revealed that the strength of the down-flow, horseshoe vortex and the wake vortex are greater in the case of square piers compared to circular piers. In this paper we have investigated a new longitudinal biconcave bridge pier shape that reduces better the bed shear stress. For that purpose, a number of numerical simulations have been carried out using a Finite Volume Method (FVM) and for the turbulence model we have chosen the Detached Eddy Simulation (DES) for its capability to capture the rich dynamics of the horseshoe vortex at the upstream junction between the pier and the bed.The present study shows that the new longitudinal biconcave bridge pier shape reduces 10 % to 12 % the bed shear stress at the junction between the pier and the bed in other hand this shape increases the bed shear stress about 20 % but at a distance of D downstream the bridge pier in the flow direction.

scholarly journals RESULTS OF MULTIVARIATE EXPERIMENT TO DETERMINE DEPENDENCE OF THE MAXIMUM PRESSURE OF TRACTOR WHEELS ON THE SOIL FROM TRACTOR’S PARAMETERS AND PHYSICAL AND MECHANICAL PROPERTIES OF SOIL. STATISTICAL ANALYSIS

2017 ◽  
pp. 94-98
Author(s):  
Хафизов ◽  
Kamil Khafizov ◽  
Хафизов ◽  
Ramil Khafizov
Keyword(s):  
Mechanical Properties ◽  
Similarity Theory ◽  
Experimental Studies ◽  
Similarity Criterion ◽  
Statistical Processing ◽  
Physical And Mechanical Properties ◽  
Multiple Correlation Coefficient ◽  
Similarity Criteria ◽  
Maximum Pressure ◽  
Regression Equations

A similarity criteria were reveled to determine the dependence of maximum pressure of the tractor wheel on the soil on the basis of the use of similarity theory. Each similarity criterion includes several parameters, characterizing the tractor, its propeller and physical and mechanical properties of the soil. The similarity criteria is taken as factors in the multivariate experiment. Multifactorial experimental studies were planned and carried out. We used Statistics Toolbox subsystem of Matlab computer mathematics system for processing the results of experiments. As a result of statistical processing of the experimental data by the equation we obtained a dependence of maximum pressure of the tractor wheel on the soil from tractor parameters, and physical and mechanical properties of the soil. Statistical data on the equations, such as - multiple correlation coefficient, Fisher’s criterion, Student’s criterion, indicate the significance of equations of the experiments variants, as well as the significance of the coefficients of the regression equations.

scholarly journals Experimental research of the process of shock pulse transformation through biological objects of fixed geometric shape

1970 ◽  
pp. 30-35
Author(s):  
V Yakovlev
Keyword(s):  
Raw Materials ◽  
Experimental Studies ◽  
Geometric Shape ◽  
Agricultural Products ◽  
Successful Implementation ◽  
Biological Objects ◽  
Quantitative Characteristics ◽  
The Relationship ◽  
Qualitative Characteristics ◽  
Qualitative And Quantitative Characteristics

Successful implementation of agricultural products requires compliance with the requirements of standards to ensure its high quality, ensuring the technological process (production, processing, storage) with a sufficient level of quality characteristics of the initial raw materials, product quality control at intermediate and final operations. Such qualitative characteristics of products, particularly a fixed geometric shape, the degree of ripeness, presence and depth of the damage, it is not always possible to determine the external condition of the product (e.g., melons) without its destruction. To assess the qualitative and quantitative characteristics of agricultural products, various physical methods are used, of which a special place is occupied by the method of acoustic sensing, which consists in the fact that the properties of products (as biological objects) that determine the excitation and propagation of elastic vibrations are closely related to their anatomical structure and physical and biochemical characteristics, which in turn change during their vegetation when reaching the appropriate degree of ripeness. This material presents the results of experimental studies to establish the relationship between the parameters of the aftereffect of shock excitation of biological objects of plant origin of a fixed geometric shape with their qualitative characteristics, to determine the characteristics and their quantitative values, which in turn makes it possible to implement technical devices Express nondestructive control of qualitative characteristics of agricultural products.

scholarly journals IMPROVEMENT OF THE STRUCTURAL LAYOUT OF POTATO PLANTERS’ COULTER GROUP

2021 ◽  
pp. 81-90
Author(s):  
Alexey Semenovich Dorokhov ◽  
Andrey Grigoryevich Ponomarev ◽  
Vitaly Nikolaevich Zernov ◽  
Sergey Nikolaevich Petukhov ◽  
Alexander Gennadievich Aksenov ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Acute Angle ◽  
Sharp Angle ◽  
Maximum Extent ◽  
Automatic Maintenance ◽  
Potato Planter ◽  
Growing Conditions ◽  
The Stability ◽  
The Impact

Structural layouts of coulters and their groups in potato planters are justified in the article based on the morphological features of the potato plant, its requirements for growing conditions and ensuring the quality of the planting process. The purpose of coulter groups is to form a bed for placing tubers with a loose layer of soil in 5-8 cm and sealing them with loosened soil to a certain depth. To substantiate the type of potato planter coulters that meet the requirements for potato growing conditions to the maximum extent possible, optimize the parameters of coulter groups that automatically ensure the stability of the coulter travel depth when imitating irregularities of the field microrelief. A comparative analysis of the impact on the soil of the most common anchor coulters with a blunt angle of soil entry and a sharp angle with an individual floating suspension is given, and indicators of the quality of their operation are described. It was found that coulters with an individual floating suspension and an acute angle of soil entry meet the requirements for potato growing conditions to the maximum extent possible. In order to ensure travel stabilization of such a coulter at a given depth when imitating field irregularities, a version of the coulter group has been developed that provides automatic correction of the coulter's angle of attack when changing its travel depth. Experimental studies have optimized the parameters of the coulter suspension that ensure automatic imitation of field microrelief irregularities up to 20 cm deep within the initial requirements for potato planting machines. Coulters with an individual floating suspension and a sharp angle of soil entry most fully meet the requirements for potato growing conditions to the maximum extent possible. A coulter group with a suspension aspect ratio of 150:200:400:400 cm and an acute angle of coulter entry into the soil provides automatic maintenance of the set coulter travel depth within the initial requirements (±2 cm) for irregularities in the field microrelief of up to 200 mm. In this case, the bottom and walls of the furrow are not compacted.

scholarly journals Scaling of Scour Depth at Bridge Pier Based on Characteristic Dimension of Large-Scale Vortex

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2458 ◽  
Author(s):  
Nian-Sheng Cheng ◽  
Maoxing Wei
Keyword(s):  
Large Scale ◽  
Horseshoe Vortex ◽  
Bridge Pier ◽  
Theoretical Formula ◽  
Scour Depth ◽  
Flow Depth ◽  
Flow Conditions ◽  
Hydraulic Radius ◽  
Vortex System ◽  
Large Scale Vortex

By examining the variations in the dimensions of a horseshoe vortex system in front of a pier, the present study proposes a new length scale, called pier hydraulic radius, for the scaling of the maximum scour depth at a bridge pier. It is shown that, in comparison with other length scales, the pier hydraulic radius is more effective for quantifying combined effects of pier width and flow depth on the local scour for both low and high flow conditions. A theoretical formula is finally derived, which agrees well with experimental data reported in the literature.

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