U. C. Kothyari F.Ish

Bio: U. C. Kothyari F.Ish is an academic researcher from Indian Institute of Technology Roorkee. The author has contributed to research in topics: Reynolds stress & Pier. The author has an hindex of 2, co-authored 3 publications receiving 65 citations.

Temporal, variation of scour around circular bridge piers

Abstract: Extensive research has been carried out in the field of scour around bridge piers in past, which resulted in development of various mathematical expressions for computation of equilibrium scour depth. The modern trend in scour investigations is to study the temporal variation of scour rather than the equilibrium scour because the equilibrium scour occurs after a very long period of time. In this paper method of Kothyari et al. (1992) for computation of temporal variation of scour around circular pier has been modified with aid of experimental data of present study and data of various investigators. The mathematical model presented herein has potential of application for computation of temporal variation of scour depth around prototype circular bridge during the passage of the flood hydrograph.

Incipient motion characteristics of cohesive sediments

Abstract: Results of an experimental study on incipient motion characteristics of cohesive sediments are presented. Cohesive sediments used consisted of medium sand mixed with Illite clay in different proportions. Incipient motion condition of thus formed cohesive sediment bed was identified through visual observations. Antecedent moisture content, clay content, plasticity index and void ratio/dry density are found to be significant parameters affecting the incipient motion characteristics in these cohesive sediments. A functional relationship between shear stress for incipient motion and sediment characteristics has been proposed based on dimensional considerations which account for both the plastic as well as non-plastic sediments. An empirical relation is also proposed for computation of Critical Shear Stress (CST) with certain limitations related to the type of clay used for experimentation and other factors.

Velocity, discharge and turbulence characteristics in a straight compound channel

Abstract: Flow characteristics of a compound channel are not the same as that of a channel of simple cross-section Therefore, assessment by use of traditional equations for the discharge carrying capacity of these channels produces inaccurate results The flow characteristics of a compound channel are therefore, investigated experimentally by using an Acoustic Doppler Velocimeter (ADV) Velocity components, turbulence intensities and Reynolds stresses in the main channel, the flood plains and at their interface are measured with the help of the ADV Results obtained from present investigation are reported herein

Bridge Scour: Prediction, Modeling, Monitoring, and Countermeasures—Review

Abstract: Scour is one of the main causes of bridge failures. It accounts for about 60% of bridge failures in the United States. Scour failures tend to occur suddenly without prior warning and are very difficult to monitor during flood events. This paper presents a comprehensive review of the up-to-date work on scour at bridge piers and abutments. First, a general introduction of bridge scour including the current situation of bridge scour problems and different types of bridge scour is given. Then, different approaches developed for predicting bridge scour are reviewed. Numerical and laboratory models established for bridge scour studies are also presented. Moreover, laboratory experiments and field tests conducted for bridge scour are reviewed. Different techniques and instruments developed for bridge scour monitoring are also presented with their advantages, disadvantages, and relative cost summarized in a table. Finally, various mitigation countermeasures developed for bridge scour are discussed.

Field Measurements and Simulation of Bridge Scour Depth Variations during Floods

Abstract: An understanding of bridge scour mechanisms during floods in a fluvial river is very important for cost-effective bridge foundation design. Reliable bridge scour data for flood events are limited. In this study, field experiments were performed at the Si-Lo Bridge in the lower Cho-Shui River, the longest river in Taiwan, to collect scour-depth data using a sliding magnetic collar, a steel rod, and a numbered-brick column. By separating each scour component, a methodology for simulating the temporal variations of the total scour depth under unsteady flow conditions is proposed. The proposed total-scour model integrates three scour components, namely general scour, contraction scour, and local scour. The collected field data, comprising both general scour and total scour depths, are used to validate the applicability of the proposed model. Based on the peak flow discharges during floods, a comparison of the local scour depths calculated using several commonly used equilibrium local scour formulas indicates that most equations may overestimate the local scour depth.

Temporal scour evolution at bridge piers: effect of wood debris roughness and porosity

Abstract: Large wood debris transported by floods affects the scour morphology at bridge piers, thus increasing the bridge failure potential. The characteristic size and shape of the riparian vegetation includes various roughness and permeability conditions of the debris surface. The interaction between two-dimensional flow and rough debris accumulations increases the shear stress, the turbulence and consequently affects the scour evolution process at bridge piers. An experimental study on the bridge pier clear-water scour evolution in the presence of wood debris was conducted at the PITLAB research centre, University of Pisa, Italy. A debris accumulation is characterized by roughness, shape and porosity. Flow intensities range from 65 to 100% of the threshold velocity and included up to 18% of the total flow area. Flow depths were varied from 2.67 to 5.67 times the pier diameter. The effects of wood debris roughness and porosity were analysed in terms of scour temporal evolution and scour morphology.

Equilibrium scour depth at offshore monopile foundation in combined waves and current

Abstract: Unlike the pier scour in bridge waterways, the local scour at offshore monopile foundations should take into account the effect of wave-current combination. Under the condition of wave-current coexistence, the water-soil interfacial scouring is usually coupled with the pore-pressure dynamics inside of the seabed. The aforementioned wave/current-pile-soil coupling process was physically modeled with a specially designed flow-structure-soil interaction flume. Experimental results indicate that superimposing a current onto the waves obviously changes the pore-pressure and the flow velocity at the bed around the pile. The concomitance of horseshoe vortex and local scour hole around a monopile proves that the horseshoe vortex is one of the main controlling mechanisms for scouring development under the combined waves and current. Based on similarity analyses, an average-velocity based Froude number ( Fr a) is proposed to correlate with the equilibrium scour depth ( S / D ) at offshore monopile foundation in the combined waves and current. An empirical expression for the correlation between S/D and Fr a is given for predicting equilibrium scour depth, which may provide a guide for offshore engineering practice.

A model of bridge pier scour during flood waves

Abstract: The time-dependent bridge pier scour during flood waves is analysed. Scour experiments were conducted in a novel installation able to produce complex hydrographs with high precision. Experimental data were used to test scour formulas including a new mathematical model. Results confirm the reliability and superior performance of the proposed dimensionless, effective flow work based model under steady and unsteady hydraulic conditions. Analyses highlight the impact of different hydrographs on scour, demonstrating the strong control by the hydrograph shape of the temporal evolution of scour depth and scour rate, although final scour after a flood only depends on the total effective flow work exerted by the hydrograph on the sediment bed. Hysteresis between flow discharge and scour rate is reported and explained. Flow acceleration is shown to play a minor role in scouring. The proposed model is a promising alternative for computation of local scour under highly unsteady hydraulic conditions.