Bhupendra K. Gandhi

Indian Institute of Technology Roorkee | University of Roorkee · Department of Mechanical and Industrial Engineering

The present work investigates the effect of the axial water jet nozzle size on the unsteady pressure fluctuations arising from RVR formation in the draft tube of a Francis turbine operating at part load. The results compare two different nozzle diameter jets for their effect on the pressure pulsations and pressure recovery in the draft tube. Simula...

The powerplants in the Himalayan region are generally subjected to hydro-abrasive erosion. The deterioration of components due to erosion causes reduction in performance, changes the fluid flow pattern and even the breakdown of the turbine. In the present work, the Bhilangana-III powerplant Francis turbine is considered a reference turbine for nume...

Time-dependent phenomena in a reaction turbine such as rotor-stator interactions (RSI) and rotating vortex rope (RVR) contribute to pressure fluctuations, vibrations, and even failure of the machine. A small scale test rig is being developed to investigate RSI and RVR and to study RVR mitigation methods. The test rig is designed for a maximum avail...

A large scale vortical structure, i.e., rotating vortex rope (RVR), generally forms at part load (PL) operation of a reaction turbine due to the combined effect of swirling flow at the runner outlet and the adverse pressure gradient in the draft tube. Even with the data analysis through advanced measurement techniques like Laser Doppler velocimetry...

A significant variation in particle size distribution (PSD) is generally encountered in slurry transportation. The goal of this work is to establish the effect of variation in PSD on the centrifugal slurry pump (CSP) performance and particle kinetics. Computational fluid dynamics (CFD) modeling of a CSP with multi-size particulate slurry has been p...

Particle size normally varies over wide ranges in any commercial transportation of solids through the pipeline. In the present study, the three-dimensional numerical modeling of the conventional 90 o bend transporting multi-sized particulate slurry using granular Eulerian-Eulerian model is performed. The mixture of water and six different sizes of...

In the published article [1] there is an error in the listing of the last author. “Dahlhaug G. Ole” should be “Ole Gunnar Dahlhaug” as listed in this erratum.

The Winter-Kennedy (WK) method is used to estimate relative flow rate using the differential pressure between two taps located at a radial section of a spiral casing (SC). It is widely used in index testing, for double regulated turbines optimization and sometimes for continuous discharge measurement in low head plants. This paper explores the poss...

In this study, the flow field over three square cylinders (SCs) arranged side by side is investigated in a low-speed wind tunnel. The experiments are performed with three similar square cylinders for Reynolds number (Re) 295. The influences of spacing ratio on the wake size, drag coefficient and flow interference of the cylinders are reported with...

Increased penetration of intermittent energy resources disturbs the power grid network. The frequency band of the power grid is normally controlled by automatic opening and closing of the guide vanes of hydraulic turbines. This has increased the number of shutdown cycles as compared to the defined ones for the normal operation of turbines. Turbine...

The Winter-Kennedy (WK) method is a widely used index testing approach, which provides a relative or index value of the discharge that can allow to determine the on-cam relationship between blade and guide vane angles for Kaplan turbines. However, some discrepancies were noticed in previous studies using the WK approach. In this paper, a numerical...

Some unsteady phenomenon such as the formation of dead velocity zone, flow oscillations, and rotating vortex rope (RVR) are observed in the draft tube when a Francis turbine operates at part load (PL). In this paper, such a flow field is visualized by 2D Particle Image Velocimetry (PIV) and pressure measurements. A total of six pressure sensors wer...

Severe pressure fluctuations and vibrations arise in the draft tube of a single regulated reaction turbine running at off-design conditions due to the presence of a rotating vortex rope (RVR). Axial jet injection is a novel technique aimed to mitigate the vortex rope and reduce the fluctuations. In the present work, the effect of the axial jet size...

Slurry transportation using long pipelines is a cost-effective means of transporting solids. A numerical study is performed to determine erosion wear of straight pipe due to the presence of suspended solid particles in the carrier liquid. Local changes in the erosion of pipe surface are analyzed with the variation of particle size and flow velocity...

This corrects the article “Experimental investigations of transient pressure variations in a high head model Francis turbine during start-up and shutdown” in volume 26, issue 2 on page 277. In the published article “Vaginal adhesions in a woman with the history of dystocia. Journal of Hydrodynamics, 2014, 26(2): 277–290. 10.1016/S1001-6058(14)60031...

Increased penetration of solar and the wind impels the designers of the hydroelectric power generation unit to provide more flexibility in operation for the stability of the grid. The power generating unit includes turbine which needs to sustain sudden change in its operating conditions. Thus, the hydraulic turbine experiences more transients per d...

The present work is an experimental investigation of flow control over a square cylinder using an attached splitter plate. The experiments are mainly conducted at a Reynolds number of 485. A splitter plate of varying length from 0 to 6 times of the cylinder width is attached to the rear side of the square cylinder to control the flow. The thickness...

This paper presents the temperature measurement with in-situ calibration check and uncertainty analysis of hydraulic efficiency evaluation by thermodynamic method for two small hydropower plants Baner (3x4 MW), and Binwa (2x3 MW) in Himachal Pradesh, India. The hydraulic efficiency was evaluated with overall uncertainty of less than 1%. The calibra...

On-field optical measurements in Francis turbine are difficult to perform due to insufficient optical access. The scaled model turbine with an optical window of glass or Plexiglas is preferred to perform the optical measurements. Here, the PIV measurements on a scaled (1:5.1) high head model Francis turbine were performed. A draft tube cone made of...

A penstock is a conduit which is normally used to convey water from a reservoir to hydraulic turbines. It is made by joining a number of pieces of pipe whose proper alignments are essential to minimize the flow disturbances and hydraulic losses. This paper experimentally investigates the effect of misalignment of two pipes of the same diameter on h...

Electricity generation from solar and wind has raised a significant concern about the stability of grid networks. Hydroelectricity plays an important role to balance the stability of grid network. In order to improve the stability of presently high loaded grids, hydropower plants are being operated over a wide range of operations and experiencing f...

The flow in the off-design operation of a Francis turbine may lead to the formation of spiral vortex breakdowns in the draft tube, a diffuser installed after the runner. The spiral vortex breakdown, also named a vortex rope, may induce several low-frequency fluctuations leading to structural vibrations and a reduction in the overall efficiency of t...

Hydraulic turbines are operated over an extended operating range to meet the real time electricity demand. Turbines operated at part load have flow parameters not matching the designed ones. This results in unstable flow conditions in the runner and draft tube developing low frequency and high amplitude pressure pulsations. The unsteady pressure pu...

Penetration of solar and wind energy into the grid network has raised the concern for grid stability which is generally balanced by operating the hydropower plants over a wide range. This results in several issues, such as rotor-stator interaction (RSI), vortex breakdown, rotating vortex rope (RVR), pressure shocks, vibration, and noise which may l...

Francis turbines are often operated over a wide load range due to high flexibility in electricity demand and penetration of other renewable energies. This has raised significant concerns about the existing designing criteria. Hydraulic turbines are not designed to withstand large dynamic pressure loadings on the stationary and rotating parts during...

Hydraulic Efficiency Measurement of Two Small Hydro Power Plants in India using Thermodynamic Method in June 2016 under Project: Measurement of Hydraulic Efficiency by Thermodynamic Method

Flow over a square prism with attached splitter plate is investigated at Reynolds number 485. Splitter plate attached on the base of a square prism acts as a control for wake modification. By varying the splitter plate length the wake structure can be manipulated according to the need. In present study, we investigated the effect of splitter plate...

When two cylinders are in proximity with each other the vortex shedding of one cylinder are influenced by the other. The flow field becomes even more complex when one cylinder subjected to an oscillation. In present study flow around two inline square cylinders of aspect ratio 50 at different spacing ratio is investigated experimentally. Experiment...

The increasing demand of energy sometimes forces the hydraulic turbines to operate at high load condition. A Francis turbine operating at high load condition develops a significant amount of pressure fluctuations that can disrupt the turbine operation and may cause subsequent damages to its components. The flow leaving the runner rotates in a direc...

The variable demand of electricity and its limited storage capacity requires a great flexibility in turbine operating range such as part load, best efficiency point, and high load. Francis turbine operating at part load operating condition induces high swirling flow downstream to the runner. This leads to the development of a helical vortex rope in...

Francis turbine working at off-design operating condition experiences high swirling flow at the runner outlet. In the present study, a high head model Francis turbine was experimentally investigated during load rejection, i.e., best efficiency point (BEP) to part load, to detect the physical mechanism lies in formation of the vortex rope. For that,...

Francis-99 is a set of workshop aiming to determine the state of the art of high head model Francis turbine simulations (flow and structure) under steady and transient operating conditions as well as to promote their development and knowledge dissemination openly. The first workshop (Trondheim, 2014) was concerned with steady state operation. The s...

Centrifugal pumps are being extensively used for hydraulic transportation of solids over short and medium distances through pipelines where the requirements of head and discharge are moderate. The performance characteristics and erosion wear of the pump components are the most critical design and selection parameters. An improvement in performance...

Hydraulic turbines are operating at part load conditions depending on availability of hydraulic energy or to meet the grid requirements. The turbine experiences more fatigue during the part load operating conditions due to flow phenomena such as vortex breakdown in the draft tube and flow instability in the runner. The present paper focuses on the...

Francis-99 is a set of workshop aiming to determine the state of the art of high head model Francis turbine simulations (flow and structure) under steady and transient operating conditions as well as to promote their development and knowledge dissemination openly. The first workshop (Trondheim, 2014) was concerned with steady state operation. The s...

Detailed heat transfer and flow field investigations behind a surface mounted slitted-trapezoidal rib have been performed using liquid crystal thermography and particle image velocimetry. In the accomplished experiments, the effects of varying the chamfering angle over the trailing edge of a rib with a centrally placed longitudinal continuous slit...

The disposal of coal ash from thermal power plants in India is a challenging task. The objective of the present study was to investigate the leaching characteristics of the bottom ash disposed in ash pond of thermal power plants. A series of leaching experiments have been performed to analyze the tracing elements of metal at different liquid-to-sol...

For commercial slurry transportation, particle sizes are varied over wide ranges. It is important to analyze their distribution across the pipe cross section in order to enhance the design of slurry pipeline. This paper shows distribution of six particle sizes in a 105 mm diameter horizontal pipeline transporting multisized particulate slurry of zi...

Hydraulic turbines exhibit total load rejection during operation because of high fluctuations in the grid parameters. The generator reaches no-load instantly. Consequently, the turbine runner accelerates to high speed, runaway speed, in seconds. Under common conditions, stable runaway is only reached if after a load rejection, the control and prote...

The accuracy of discharge measurement in open channels using propeller current meters can be improved considerably by optimizing the number and locations of the current meters to be deployed for this purpose. The optimization is possible if the nature of the flow profile in the channel can be assessed. This paper reports development of a mathematic...

In this paper, the fluid flow around two identical square cylinders arranged in tandem has been discussed. The upstream cylinder is oscillated in the transverse direction while the downstream cylinder is held stationary. The experiments are conducted at a Reynolds number of 295. Both the influences of spacing between two cylinders, as well as the e...

An experimental study of flow around triangular prism with effect of apex angle is reported. The focus of the study is towards understanding the effect of apex angle on flow structure and related forces occurring. Four triangular prisms with apex angle 30°, 45°, 60° and 90° respectively are reported at Reynolds number of 520 (based on cylinder diam...

This paper presents an experimental study of flow over a square cylinder oscillating in transverse direction. The Reynolds number selected for present study is 485. Limited study has also been made for two other Reynolds numbers, namely, 295 and 775. The objective of the present study is to modify the near-wake flow structure using actuation of the...

Bassi Hydro Power station with vertical-shaft Pelton-turbine generating units gets its water from the tail-race discharge of Shanan Hydro Power Station in the state of Himachal Pradesh, India. The four generating units were commissioned during the period of 1970-1981. Reduced generation and excessive vibrations of machines let the station owner to...

Water passes freely through a hydraulic turbine in the absence of power requirements or during maintenance of the transmission lines, spillways, or dam. Moreover, the turbine operates under no-load conditions prior to generator synchronization during startup and after the generator disconnection from the grid load for shutdown. High-velocity swirli...

Hydraulic turbines are widely used to meet the real-time electricity demand at moderate to low cost. Intermittency in the power grid due to high penetration of wind and solar power has raised significant concerns for grid stability and reliability. The intermittency results in an increase of the start–stop cycles of hydraulic turbines. Each cycle i...

Discharge Measurement in Small Hydropower Stations using Acoustic Doppler Current Profiler

The penetration of intermittent wind and solar power to the grid network above manageable limits disrupts electrical power grids. Consequently, hydraulic turbines synchronized to the grid experience total load rejection and are forced to shut down immediately. The turbine runner accelerates to runaway speeds in a few seconds, inducing high-amplitud...

Laser cladding of Colmonoy-5 (a nickel base alloy) and Metco-41C (an iron base alloy) on AISI type 316L stainless steel (SS316L) and their wear behaviors were investigated to establish Co-free clad layers for potential applications in nuclear industry. A 3.5 kW CO2 laser-based system was used to optimize the laser cladding on SS316L substrate. The...

The present study reports on the performance characteristics of the centrifugal slurry pump with multi-sized particulate slurry of bottom ash and fly ash mixtures. The performance characteristic of the pump was experimentally evaluated at rotational speed 1450 rpm for bottom ash slurries with and without the addition of fly ash in the concentration...

In the present work, numerical simulation has been carried out to investigate the effect of an inclined rib with a gap on the performance of a solar air heater duct. The geometry is numerically modelled and three-dimensional Navier-Stokes equation has been solved using a commercial code Ansys Fluent 14. 5 for the Reynolds number range of 3500 to 19...

Penetration of the power generated using wind and solar energy to electrical grid network causing several incidents of the grid tripping, power outage, and frequency drooping. This has increased restart (star-stop) cycles of the hydroelectric turbines significantly since grid connected hydroelectric turbines are widely used to manage critical condi...

Hydraulic turbines are frequently used to maintain electrical grid parameters. An angular movement of the guide vanes (GVs) during transients such as load acceptance and rejection within short time raised significant concerns for increased wear and instabilities. The present work focuses on the pressure variations in a high-head Francis turbine dur...

Experimental and numerical studies on a high head model Francis turbine were carried out over the entire range of turbine operation. A complete Hill diagram was constructed and pressure-time measurements were performed at several operating conditions over the entire range of power generation by installing pressure sensors in the rotating and statio...

Experimental and numerical studies on a high head model Francis turbine were carried out over the entire range of turbine operation. A complete Hill diagram was constructed and pressure-time measurements were performed at several operating conditions over the entire range of power generation by installing pressure sensors in the rotating and statio...

This paper explores the effect of two orientations (0° and 180°) on near wake region of an equilateral triangular prism at intermediate Reynolds number. The paper also investigates the effect of Reynolds number on the near wake region at intermediate regime. Two orientations are defined such that the apex of the equilateral triangle is pointing ups...

The present work is an experimental investigation inside a rectangular duct for flow behind a trapezoidal type of rib with chamfering angle α (toward the direction of flow) at different Reynolds numbers. Chamfering angle α has been varied in between 0° and 20° with an increment of 5° and subsequently detailed fluid flow and heat transfer experiment...

The present electricity market and the injection of power generated using intermittent energy sources have brought instability in the operation of the power grid. This has resulted in frequent load variations, emergency shut-down and restart, total load rejections, and off-design operation of grid connected hydraulic turbines. The present paper rev...

In this paper three-dimensional fluid flow behavior of centrifugal slurry pump has been studied using commercial Computational Fluid Dynamics (CFD) code FLUENT at design and off-design conditions. Steady state simulation with Moving Reference Frame (MRF) model is used to consider impeller-volute interaction. Different turbulence models namely, stan...

Disposal of bottom ash is a major concern for thermal power plant operations. The objective of the present study was to investigate the possibility of disposal of bottom ash at higher solid concentrations. As rheology of the slurry plays a major role in flow, the rheological behavior of the bottom ash in the concentration range of 10-50% (by weight...

Various rib turbulator geometries have been used earlier to investigate the heat transfer and fluid flow characteristics owing to its vast industrial applications. Permeable ribs are reported to provide better performance in terms of heat transfer enhancement and pressure penalty. The trapezoidal rib with variable downstream chamfering and a centra...

Rib turbulators are the most intensively studied passive technique, which promotes near wall turbulence in the internal cooling passages of heat transfer devices. However, there exists the tradeoff between the pressure penalty and heat transfer enhancement. For suggesting a correct rib configuration for particular application, it is necessary to un...

Material loss due to erosion is a serious problem associated with the flow of solid-liquid mixtures. In the present work, erosion wear tests have been carried out in a slurry pot tester for seven different ductile type materials namely aluminum alloy (AA6063), copper, brass, mild steel, AISI 304L stainless steel, AISI 316L stainless steel, and turb...

This paper presents the effect of artificial surface roughness on flow through a rectangular duct having bottom wall roughened with repeated transverse ribs of wedge shaped cross-section. Experimental and numerical investigations have been carried out for a range of Reynolds number from 5000 to 21000 for a smooth duct and a roughened duct of relati...

Artificial roughness in the form of repeated ribs is generally used for enhancement of heat transfer heated surface to the working fluid. In the present work experimental investigations has been carried out to study the effect of a gap in the inclined rib on the heat transfer and fluid flow characteristics of heated surface. A rectangular duct of a...

The use of artificial roughness in a solar air heater duct has been proposed to be an excellent option to enhance the heat transfer from absorber plate to the air. This paper presents an experimental investigation on heat transfer and friction characteristics of solar air heater ducts with integral repeated discrete square ribs on the absorber plat...

This article presents the computational flow analysis of an axial—centrifugal flow system used for transformer oil cooling in WAP-5 and WAP-7 electric locomotives of Indian Railways. The commercial computational fluid dynamics code ‘FLUENT’ was used for the numerical simulation of the flow system. A standard k—ε turbulence model was employed for tu...

The effect of particle size on erosion wear of aluminium alloy (AA 6063) has been investigated in a slurry pot tester. Eight different sized quartz particles with mean size varying between 37.5 and 655μm have been used. The wear specimens are rotated inside the pot at 3m/s velocity with orientation angle of 30° and 90° in a sand–water mixture of 20...

Austenitic steel surfaces are laser cladded using a 4 kW continuous wave CO2 laser with coaxial powder feeding nozzle to investigate the improvement in slurry erosion characteristics. Colmonoy-6 and Inconel-625 are cladded on AISI 316L steel and AISI 304L steel, respectively by laser cladding. Initially, single-pass clad track is overlaid to optimi...

Wear resistance of austenitic steels is low and needs to be improved for applications in abrasive and erosive environments. In the present work, the powders of chromium carbide (Cr3C2), tungsten carbide (WC) and molybdenum (Mo) were laser cladded on AISI 304L steel. The laser processing parameters have been optimized to fabricate sound metallurgica...

Artificial roughness in the form of repeated ribs has been proposed as a convenient method for enhancement of thermal performance of solar air heaters. This paper presents the experimental investigation of heat transfer and friction factor characteristics of a rectangular duct roughened with repeated square cross-section split-rib with a gap, on on...

The phenomenon of erosion wear at normal impact of solid–liquid mixture has been studied in a slurry pot tester. The erosion wear tests have been carried out using seven different ductile type materials namely aluminium alloy (AA6063), copper, brass, mild steel, AISI 304L stainless steel, AISI 316L stainless steel, and turbine blade steel using thr...

The present work reports the effect of erodent properties on slurry erosion. Experiments have been performed in a pot tester to evaluate the wear of two ductile materials namely, AA6063 and AISI 304L steel. Solid–liquid mixtures of similar particle sizes of three different natural erodents namely, quartz, alumina and silicon carbide have been used...

Experimental investigation on the heat transfer and friction characteristics of rib-grooved artificial roughness on one broad heated wall of a large aspect ratio duct shows that Nusselt number can be further enhanced beyond that of ribbed duct while keeping the friction factor enhancement low. The experimental investigation encompassed the Reynolds...