Bijoy Mazumder

• Ph.D.
• Indian Statistical Institute

Turbulence characteristics in the region of wave-blocking over a submerged forward-facing obstacle is explored, and the results are compared with those of base-flow over the obstacle. Wave-blocking over obstacle is setup, adjusting the strong incoming flow with counter-propagating waves, and confirmed by linear dispersion relation. A variation in t...

The present study illustrates an experimental investigation of flow hydrodynamics in the vicinity of a submerged circular pier across various submergence levels under only current and wave–current combined flow conditions. The instantaneous velocity data are collected using particle image velocimetry for three distinct frequencies of waves to deter...

This study investigates the local scour around the cylindrical pier mounted on a gravel bed for low coarseness ratio (d/d50), which is defined as the ratio of pier diameter d to the median particle size (d50) of the bed material. Experimental study was conducted in a flume with varying pier diameter and flow conditions. Effect of flow depth on the...

This study investigates the turbulent flow properties experimentally in the vicinity of two side-by-side circular cylinders, along with the influence of the third cylinder of the same dimension placed in the upstream and successively in the downstream forming an equilateral triangle. Three-dimensional stereoscopic Particle Image Velocimetry (PIV) w...

Wakes and higher-order turbulence around circular cylinders of different diameters are investigated using particle image velocimetry measurements. The cylinder Reynolds number (Re d) is defined by the depth-averaged velocity, cylinder diameter, and kinematic viscosity. The influence of Re d on third-order moment of velocity fluctuations, turbulent...

The local flow field and wake region over a forward-facing obstacle were experimentally investigated, when the water surface above the obstacle was dipped compared to flow further upstream and further downstream. The obstacle was modelled resembling the shape of an airfoil with a flat top having stoss-side slope 35∘ and downstream lee-side slope 6∘...

Human settlement in Sundarbans deltaic region of India adopted a method of erecting embankments along the riverside to prevent the river water from spilling over to the colonised areas. These embankments develop undercut at toe region that lead to failure by the swirling currents coupled with tidal surges and strong winds. To protect the embankment...

The present study focuses on understanding the bank undercut mechanism under controlled conditions in a laboratory flume, using cohesive sediments collected from the toe region of Ganges River (India). The velocity data were analyzed to determine the turbulence characteristics such as mean velocities, Reynolds stresses, intensities and other higher...

The present paper concerns an experimental study of externally generated turbulence and its impact on the bed load sediment transport in an open channel flow. The external turbulence was generated by vertically oscillating a submerged grid, hereafter referred to as turbulence generator, in the flume with a clearance of 11 cm from the bed. Two kinds...

Experiments are conducted in a laboratory flume on the propagation of a surface wave against unidirectional flow with a sediment bed. This paper presents the spatial variation of bed forms induced by the wave‐blocking phenomenon by a suitably tuned uniform fluid flow and a counter‐propagating wave. The occurrence of wave‐blocking is confirmed by fi...

The paper reports the experimental investigation of free surface turbulent flow under control laboratory flume conditions over a bed artificially roughened by cubes arranged periodically and symmetrically with respect to the channel in a squared configuration. The relative submergence associated with the cube height was 8 which fall into the catego...

Experiments are conducted in a laboratory flume on the propagation of a surface wave against unidirectional flow with a sediment bed. This paper presents the spatial variation of bed forms induced by the wave-blocking phenomenon by a suitably tuned uniform fluid flow and a counter-propagating wave. The occurrence of wave-blocking is confirmed by fi...

The purpose of this research paper is to investigate the third-order moments of velocity fluctuations , turbulent kinetic energy (TKE) fluxes, turbulence dissipation rate, turbulent length scales, and Reynolds stress anisotropy in the wake regions over two artificial upstream-facing bed forms. For the structure having a smaller flow-facing slope (s...

This study explores experimentally the turbulent flow in a laboratory flume, interacting with waves propagated against the flow. It focuses a region of wave-blocking for which there is a streamwise location on the water surface, where the wave propagation velocity vanishes. The observations are corroborated by finding a critical wave frequency for...

This study explores experimentally the turbulent flow in a laboratory flume, interacting with waves propagated against the flow. It focuses a region of wave-blocking for which there is a streamwise location on the water surface, where the wave propagation velocity vanishes. The observations are corroborated by finding a critical wave frequency for...

A series of flume experiments were conducted with varying the flow discharges at the Fluvial Mechanics Laboratory of Indian Statistical Institute (Kolkata) to understand the co-evolution patterns of generating bed forms and the corresponding flow turbulence. Instantaneous bed elevations and velocity components were recorded continuously for suffici...

This paper presents the results of an experimental study carried out in a laboratory to investigate the sediment suspension due to combined wave-current flows over asymmetric dunes placed successively at the flume. The flume base was made by fixing 12 artificial asymmetric dunes. Experiments were performed with current only and combined wave-curren...

This paper presents the spatio-temporal variations in bed elevations and the near-bed turbulence statistics over the deformed bed generated around the submerged cylindrical piers embedded vertically on loose sediment bed at a constant flow discharge. Experiments were carried out in a laboratory flume for three blockage ratios in the range of 0.04–0...

This work presents a study of spatiotemporal changes of scour-holes around sand embedded submerged circular and non-circular cylinders with associated turbulence properties and aims at analyzing the contribution of each quadrant event to the Reynolds shear stress. Experiments were carried out using submerged circular, elliptical, square and triangu...

Flume experiments were carried out to study the turbulence and its impact on suspension and segregation of grain-sizes under unidirectional flow conditions over the sand-gravel mixture bed. The components of fluid velocity with fluctuations were measured vertically using 3-D Micro-acoustic Doppler velocimeter (ADV). The theoretical models for veloc...

The present paper explores the characteristics of turbulent flow and drag over two artificial 2-D forward-facing waveform structures with two different stoss side slopes of \(50^{\circ }\) and \(90^{\circ },\) respectively. Both structures possessed a common slanted lee side slope of \(6^{\circ }.\) Flume experiments were conducted at the Fluvial M...

This paper investigates the phenomena of turbulent bursting events, and to make a comparative study among the events in the scour geometry developed by short circular cylinders of fixed length with different diameters placed on the sand bed transverse to the flow. The distributions of turbulent kinetic energy (TKE), turbulent diffusion in both long...

Mathematical models have been developed to predict the vertical velocity and sediment concentration distributions in a sediment-laden turbulent open channel flow taking into account a modified mixing length based on sediment-induced stratification. The coupled non-linear differential equations for vertical velocity and concentration arising out of...

The purpose of the present paper is to investigate the contributions of turbulent events to the total Reynolds shear stress over artificial waveforms and to make a comparative study of turbulence between two types of isolated wave geometries: the scalene triangular shape (STS) and the isosceles triangular shape (ITS). All three components of veloci...

This paper presents a numerical study on the stream-wise dispersion of settling particles in an oscillatory turbulent shear flow. The dispersion process is formulated in two differential equations, one for suspension and other one for deposition. The exchange of particles between the bed and the flow is permitted. The statistical parameters viz., c...

Experiments were conducted in a laboratory flume to estimate the grain size distributions in suspension at different heights over five heterogeneous sediment beds of different values of bed roughness. The analysis had been performed to study the influences of velocity, bed roughness and ripple height on the size sorting, which developed the specifi...

The longitudinal dispersion of a chemical species released in an oscillatory flow through an annular tube has been studied in presence of two kinds of first order reactions between the species and tube-wall. The species is supposed to undergo kinetic reversible phase exchange with the outer-wall material and irreversible absorption into the wall. D...

The paper concerns with the determination of effective transport coefficients associated with the oscillatory flow through a tube where a solute undergoes nonlinear chemical reactions both within the fluid and at the boundary. Method of homogenization, a multiple-scale method of averaging, is adopted to derive the transport equation that contains a...

The paper presents the results of an experimental study of mean fluid flow and turbulence over bed forms in a unidirectional flow with superimposed surface waves. Experiments were performed with only current and with combined wave-current flows over a series of bed forms under different surface wave frequencies for two different Reynolds numbers. T...

The objective of this research is to examine the turbulent flow characteristics over artificial waveform structures and to compare turbulence between two types of isolated geometries. Measurement of turbulent velocity components have been performed over the respective structures of equal crest height and length at the Fluvial Mechanics Laboratory (...

The grain-size fractions in the bedload transported over the five heterogeneous sediment beds of different values of bed roughness were computed from the flume experiments. The existence of an entrapment factor associated with the sorting observed from the bed to active layer was modeled based on the modified critical shear stress to estimate the g...

The present paper concerns with the dispersion process in steady and oscillatory flows through an annular pipe in presence of reversible and irreversible reactions at the wall. Method of homogenization, a multiple-scale method of averaging, is adopted for deriving the effective transport equations. The main objective is to look into the effect of a...

The paper presents the longitudinal dispersion of passive contaminant released in an incompressible viscous fluid flowing between two infinite parallel flat walls, in which the flow is driven by the application of both periodic pressure gradient and the oscillation of upper plate in its own plane with a constant velocity. A finite difference implic...

The present paper examines the stream-wise dispersion of suspended fine particles with settling velocities in an oscillatory turbulent shear flow with or without a non-zero mean over a rough-bed surface when the particles are being released from an elevated continuous source. A finite-difference implicit method is employed to solve the unsteady tur...

This paper addresses the development of a flow region associated with turbulence and stress characteristics over a series of 2-D asymmetric dunes placed successively at the flume surface. Experiments were conducted over twelve asymmetric dunes of mean length 32 cm, crest height 3 cm and the dune width almost as wide as width of the flume, using 3-D...

This paper presents the longitudinal dispersion of passive contaminant released in an incompressible viscous fluid flowing between two infinite parallel plates, where the contaminant undergoes irreversible heterogeneous reaction with the boundary walls. The flow is driven by the oscillation of the upper plate in its own plane with a constant veloci...

This paper presents the results of an experimental study of flow over asymmetric wavy bottom boundary in the presence of surface waves carried out in a laboratory flume. The bottom of the flume is made wavy by fixing 12 asymmetric dunes of mean length 32 cm and mean height 3 cm. Four types of experiments were performed, one with current alone and t...

The paper describes an experimental study carried out in a laboratory flume with a smooth surface to investigate the interactions of gravity waves and unidirectional current. The observations are particularly focused on the changes induced in the mean velocity profiles, turbulent intensity and turbulent shear stress due to superposition of differen...

Longitudinal dispersion of suspended particles with settling velocity in a turbulent shear flow over a rough-bed surface is investigated numerically when the settling particles are released from an elevated continuous line-source. A combined scheme of central and four-point upwind differences is used to solve the steady turbulent convection–diffusi...

The objective of this paper is to analyze statistically the turbulence characteristics of flow over an artificial waveform geometry in an open channel, using velocity data collected by 3-D acoustic doppler velocimeter (ADV). The joint distribution of velocity fluctuations have been studied and modeled using multivariate normal distribution, and its...

Computation of the grain‐size distribution of the suspended load above a sand bed must take into consideration: (1) sorting processes from the bed to the bed layer and (2) sorting between the bed layer and suspension. Grain‐size distributions of the bed layers above sand beds of three different types have been computed in this work, both by the Ein...

Experimental results show that the grain size distribution of suspended material is related to flow parameters and grain size distribution in the bed. A theoretical model has been developed to compute the suspension grain size distribution on the basis of diffusion equations, taking into account the effect of hindered settling due to the increased...

This paper presents a theoretical model for computing the velocity and sediment concentration profiles in a uniform sediment-laden flow carrying all fine, medium and coarse sediments. The proposed model essentially includes the effect of sediment concentration in total turbulent shear stress and eddy diffusivity in addition to the modified mixing l...

A vertical gradient of suspended sediment concentration exists in a turbulent open channel flow, particularly near the bed where sediment erosion and deposition take place. This shows a remarkable effect on the flow dynamics. The density gradient of sediment-mixed fluid may become stably stratified, which results in damping of turbulence fluctuatio...

Longitudinal dispersion of passive tracer molecules released in a pulsatile flow through an annular pipe with a reactive outer wall is studied by employing the method of integral moments. It is shown how the spreading of tracers is influenced by the shear flow due to a periodic pressure pulsation in the pipe and a first-order reaction at the wall....

The paper presents the longitudinal dispersion of passive tracer molecules released in a steady laminar flow through an annular pipe with heterogeneous reaction at the outer wall, which causes a depletion of contaminant in the flow. A finite-difference implicit scheme has been adopted to solve the unsteady advection-diffusion equation for all time...

Flume experiments with five beds of heterogeneous sediment mixtures having different values of bed roughness show that for fixed height and velocity the amount of suspension concentration increases up to a certain value with increase of bed roughness and then decreases with further increase of bed roughness. This indicates depletion of concentratio...

Controlled experiments have shown that the grain-size distribution of suspended sediments is related to bed material, flow velocity and height of suspension above the sand bed in an open channel flow. A theoretical model has been developed for computation of suspended grain-size distribution on the basis of continuity equations of sediment and wate...

The paper presents the longitudinal dispersion of passive tracer molecules released in an incompressible viscous fluid flowing through a channel with reactive walls under the action of a periodic pressure gradient. A finite-difference implicit scheme is adopted to solve the unsteady advection–diffusion equation based on the Aris–Barton method of mo...

A theoretical model has been developed to determine the maximum saltation layer thickness of sediment particles in water associated with the migration velocity of particle in the bed layer. This is consistent with Owen's (1964) hypothesis for saltation of uniform grain in air. The equation for mean particle velocity at the bed is derived by balanci...

An investigation is made of flow of an electrically conducting falling liquid film over a smooth vertical surface taking Hall effects into account, the liquid being permeated by a transverse magnetic field. Consideration of Hall current into the flow indicates a similarity between the flow of a rotating liquid and that due to the non-rotating syste...

The streamwise dispersion of contaminant molecules due to a turbulent shear flow over a gravel-bed surface is examined when the solute is released from an elevated line source. A finite-difference, implicit method is used to solve the unsteady turbulent convection-diffusion equation, employing a combined scheme of central and four-point upwind diff...

The release of waste materials from chemical plants or industries into a river or the atmosphere over a period of time is a common phenomenon. So the dispersion of contaminants for a time-dependent release is an important problem in controlling pollution. The present paper examines the streamwise dispersion of passive contaminant released from a ti...

The paper presents the longitudinal dispersion of passive contaminant molecules released in an incompressible viscous fluid flowing through a parallel plate channel under the influence of the oscillation of upper plate in its own plane with a constant velocity and an imposed constant pressure gradient in the axial direction. Analytical solution of...

The paper presents an exact analysis of the streamwise dispersion of passive contaminant molecules released in an incompressible viscous fluid flowing through a channel under the influence of a periodic pressure gradient. Using the Aris-Barton method of moments which is valid for all time after the injection of the solute, the dispersion coefficien...

This report summarizes the investigation conducted by the Illinois State Water Survey on the physical changes associated with the movement of navigation traffic on the Illinois and Upper Mississippi Rivers. This research project was partially sanded by the Environmental Management Technical Center of the U.S. Geological Survey and the U.S. Army Cor...

The longitudinal dispersion of passive contaminant molecules released in unsteady viscoelastic fluid flowing through a tube is examined. A finite difference implicit scheme is adopted to solve the Aris integral moment equations arising from the unsteady convective-diffusion equation for all time period. Here it is shown how the injected material sp...

The longitudinal dispersion of a pollutant due to asymmetric flow through a two-dimensional (2-D) channel has been studied for two different inputs: (i) instantaneous uniform line source and (ii) oscillatory source. This study reveals the process whereby the dispersion reaches a stationary state after the release of pollutant as an instantaneous li...

This paper presents the research results of statistical parameters associated with turbulence in a natural river caused by the movement of navigation traffic. Movement of navigation traffic within restricted inland waterways, such as the Illinois, Mississippi, or Ohio Rivers. changes their flow characteristics temporarily in space and time. These s...

This paper examines the streamwise dispersion of passive contaminant molecules released in a time-dependent laminar flow through a tube in the presence of boundary absorption or a catalytic wall reaction, which causes a depletion of contaminant in the flow. A finite-difference implicit scheme has been used to solve the unsteady convective–diffusion...

An exact solution of oscillatory Ekman boundary layer flow bounded by two horizontal flat plates, one of which is oscillating in its own plane and other at rest, is obtained. The effect of coriolis force on the resultant velocities and shear stresses for steady and unsteady flow has been studied.

The paper presents the statistical behaviour of concentration distribution of a reactive solute injected in a laminar flow through a tubular reactor with first-order heterogeneous chemical reaction at the wall. A finite-difference implicit scheme is adopted to solve the Aris-moment equations for all time. The deviations from Gaussianity are examine...

Finite--difference implicit scheme is adopted to solve the Aris-moment equations of dispersion of solute in an oscillatory flow through a pipe for all time. Mean concentration distribution have been calculated from first four central moments by using Hermite polynomials and the deviations from Gaussianity have also been examined for unsteady flow.

An extension of the Aris-Barton method of moments is presented for the study of statustucal behaviour of dispersion of contaminant molecules in oscillatory flows inside uniform conduits. The main idea is to replace the constant pressure gradient which causes the flow simply by the time-dependent one, and then investigate the effects of the amplitud...

The paper is concerned with the statistical study of the dispersion of a cloud of solute injected into a combined free and forced convective laminar flow through a parallel plate channel under the action of a uniform linear axial temperature variation along the channel walls, including the buoyancy forces. The main idea is to study the effect of th...

Flume experiments with heterogeneous sediment mixtures show that all the grain sizes present in suspension are involved in the process of formation of a bed when the flow velocity is decreased. The size distribution deposited closely reflects the one present in suspension. It should also be possible to work out paleoflow velocities of suspension cu...

The paper is concerned with the dispersion of a solute in combined free and forced convective flow through a channel in the presence of uniform axial temperature variation along the walls. Using a generalised dispersion model, we have evaluated the longitudinal diffusion coefficients which are valid for all time after the injection of the slug in t...

Dispersion of a solute in natural convective laminar flow through a vertical channel is investigated when there is a uniform axial temperature variation along the walls. It is observed that the effective Taylor diffusion coefficient is oscillatory in nature for small and moderate values of Rayleigh number r and it increases gradually with increase...

Dispersion of a solute in combined free and forced convective laminar flow through a parallel plate channel has been considered, when there is a uniform axial temperature variation along the channel walls. It is observed that the effective Taylor diffusion coefficient increases with increase in Grashof number and also the interesting fact that it i...

Hydromagnetic free convective flow of an electrically conducting liquid past an infinite porous vertical flat plate is considered when the liquid is permeated by a transverse magnetic field and the Hall effects are taken into account. An approximate solution is obtained by using the regular perturbation method. It is observed that with increase in...

An exact solution has been obtained for the problem of combined effects of Hall current and rotation on the hydromagnetic flow due to non-torsional oscillation of a porous plate. The structure of the steady and the unsteady velocity field and the associated multiple boundary layers are investigated. It is observed that in the initial stages there i...

Diffusion of a solute in a laminar film of an Eyring liquid down a vertical plate is considered. The Taylor diffusion coefficient for this film increases with the model parameter.RésuméOn considère la diffusion d'un soluté dans un film laminaire de liquide d'Eyring qui tombe le long d'une plaque verticale. Le coefficient de diffusion selon Taylor c...

An exact solution for the MHD Couette flow and heat transfer of a conducting liquid in a rotating system has been obtained. It is found that at the moving plate the resultant shear stress increases and the rate of heat transfer decreases with increase in either magnetic parameter or rotation parameter.

Wall conductance effects on the hydromagnetic flow and heat transfer between two parallel plates in a rotating frame of reference has been studied when the liquid is permeated by a transverse magnetic field. An exact solution of the governing equations has been obtained. It is found that the velocity, current density and the temperature depend only...

The hydromagnetic flow of a viscous incompressible fluid due to the uniformly accelerated motion of an infinite porous flat plate in the presence of a magnetic field fixed relative to the fluid is analyzed in a rotating frame of reference. A solution is obtained with the aid of the Laplace transform technique. It is observed that the primary and se...

Hydromagnetic free and forced convection in a parallel plate channel permeated by a transverse magnetic field has been considered taking Hall effects into account. When there is a uniform axial temperature variation along the walls, the primary flow shows incipient flow reversal at the upper plate for an increase in temperature along that plate. Si...

Flow in the Ekman layer of a conducting liquid past an infinite porous plate is investigated when the liquid is permeated by a transverse magnetic field and the Hall effects are taken into account. It is found that asymptotic solution exists both in the presence of suction or blowing at the plate. For fixed magnetic and suction parameters, the skin...

Free convection in a conducting liquid past an infinite porous vertical flat plate is investigated when the liquid is permeated by a transverse magnetic field and the Hall effects are taken into account. It is found that the primary shear-stress decreases and the secondary shear-stress increases with the Hall parameter whereas the rate of heat tran...

The steady slow flow of a viscous incompressible electrically conducting fluid is investigated together with heat transfer in a diverging and converging channel under an azimuthal magnetic field. It is found that the effect of the magnetic field on the velocity profiles is to flatten them at the central line. The profiles of the induced magnetic fi...