A versatile mechanical engineer with 12 years of experiences including industry and academia, I have worked in various fields such as oil and gas, internal combustion engines, aerodynamics, bio-heat and mass transfer, and pressure vessels. I completed my PhD in mechanical engineering from Louisiana State University in May 2014.
Geological carbon sequestration is a proven method of safely storing carbon dioxide in formations... more Geological carbon sequestration is a proven method of safely storing carbon dioxide in formations, thereby reducing atmospheric carbon imprint and mitigating global warming. The relative permeability to carbon dioxide versus brine/water in geological formations determines flow characteristics of one fluid in the presence of another. The objective of this research is to evaluate the relative permeability to carbon dioxide in both the gas phase and the supercritical state in the presence of water in a Vedder sandstone core sample. The sandstone sample used is medium- to fine-grain arkosic artenite containing primarily quartz, potassium feldspar, plagioclase, and biotite. The effect of the viscosity ratio between the non-wetting phase and the wetting phase, on the relative permeability to the non-wetting phase, is studied. Computational fluid dynamics (CFD) is used for this study. Results show that with the same amount of irreducible water fraction, the endpoint relative permeability t...
Natural gas hydrate formation in subsea pipelines is a major problem in the upstream petroleum in... more Natural gas hydrate formation in subsea pipelines is a major problem in the upstream petroleum industry. Gas hydrates are formed at high pressures and low temperatures when water lattice with cavities trap gas molecules such as methane. Hydrates are solid deposits that clog subsea flowlines and increase pressure drops across the pipeline, and under severe conditions can completely stop flow through pipelines resulting in tremendous production losses. The authors briefly explain the structure and mechanism of gas hydrate formation and provide the audience with an overview of various gas hydrate prevention and mitigation technologies used in the upstream petroleum industry. The manuscript discusses important methods used in the industry, such as chemical injection, depressurization, thermal stimulation, and mechanical removal by summarizing work from over a hundred reports. Relative merits and demerits of these methods are also discussed. In addition, some interesting research results are also reviewed. The authors conclude by providing a table showing the relative technology readiness level for each method. Also, potential areas of future research are discussed.
Abstract In the petrochemical industry, separation of oil from water is a very important process.... more Abstract In the petrochemical industry, separation of oil from water is a very important process. Wells produce mixtures of gas, oil, and water which undergo a primary stage of separation inside horizontal gravity separators. The performance of these vessels is evaluated by measuring mean residence time (MRT) and residence time distribution (RTD). Although many researchers studied flow characteristics in horizontal separators, limited number of articles exist that discuss separator MRT and RTD with varying water-cuts. In this article, the authors study an experiment using a horizontal gravity separator by previous researchers and perform computational fluid dynamics (CFD) simulations on the same geometry under similar conditions. The simulation results show qualitative agreement with the experiments by previous researchers. As shown by experiments before, CFD results showed that MRT of the organic phase increased with increase in water-cut. In addition, the RTD characteristics show very similar trends between CFD and experimental results.
A disk spindown experiment allows measurement of tangential momentum accommodation coefficients o... more A disk spindown experiment allows measurement of tangential momentum accommodation coefficients of different gases and material combinations in a consistent manner. Aluminum is tested for a range o...
Summary Wax or paraffin formation in subsea pipelines is a major problem in the upstream petroleu... more Summary Wax or paraffin formation in subsea pipelines is a major problem in the upstream petroleum industry, accounting for tremendous economic losses. Researchers have reported that approximately 85% of the world's oils encounter problems from wax formation (Thota and Onyeanuna 2016). In this manuscript, the authors briefly discuss the mechanism of wax formation in pipelines. Next, a review of various wax-mitigation technologies is provided. The review includes citations of various thermal, chemical, mechanical, biological, and other innovative methods reported by previous researchers and used in the industry.
Abstract An experimental technique using spin-down of a disk approaching the free-molecular flow ... more Abstract An experimental technique using spin-down of a disk approaching the free-molecular flow limit is developed to measure the tangential momentum accommodation coefficient σ t . The new technique uses a disk mounted on a shaft supported by gas bearings in vacuum. A differential scavenging system allows disk spin-down experiments in different gases. Representative test results with two different materials in two different gases are shown, demonstrating the method is capable of handling a range of gases, as well as any material that is available as, or can be formed into, a planar disk.
This study evaluates the freezing response of three different cell types, Pacific oyster embryos ... more This study evaluates the freezing response of three different cell types, Pacific oyster embryos (~50 µm in diameter), Jurkat cells and HeLa cells (~12 to 15 µm’s in diameter), using cryomicroscopy. Freezing experiments were performed on oyster embryos at cooling rates of either 5 or 10 °C/min, while Jurkats were cooled at either 1 or 10 °C/min and HeLa cells were cooled at either 1, 15 or 20 °C/min, respectively. The experiments with oyster embryos were primarily designed to investigate the phenomena of intracellular ice formation (IIF) while the experiments for Jurkat and HeLa cells were designed to investigate both cellular dehydration and IIF during freezing. IIF was characterized by the abrupt black flashing during the cooling steps while the cellular dehydration experiments were characterized by the volumetric (projected area) shrinkage of the cells during the cooling steps. Mathematical models were fit to the cellular dehydration data to obtain the Jurkat and HeLa cell membra...
The urban heat island (UHI) effect increases the ambient temperatures in cities and alters the en... more The urban heat island (UHI) effect increases the ambient temperatures in cities and alters the energy budget of building materials. Urban surfaces such as pavements and roofs absorb solar heat and re-emit it back into the atmosphere, contributing towards the UHI effect. Over the past few decades, researchers have identified albedo and thermal inertia as two of the most significant thermal properties that influence pavement surface temperatures under a given solar load. However, published data for comparisons of albedo and thermal inertia are currently inadequate. This work focuses on asphalt and concrete as two important materials used in the construction of pavements. Computational fluid dynamics (CFD) analyses are performed on asphalt and concrete pavements with the same dimensions and under the same ambient conditions. Under given conditions, the pavement top surface temperature is evaluated with varying albedo and thermal inertia values. The results show that the asphalt surface...
A mathematical model has been developed to quantify momentum accommodation coefficient as a funct... more A mathematical model has been developed to quantify momentum accommodation coefficient as a function of ambient pressure, gas density, ambient temperature, mass of the gas molecule, and the angular velocity of a disk. An experimental method is proposed for the ...
SUMMARY The main objective of this work was to be conversant with using cryomicroscopy as an esse... more SUMMARY The main objective of this work was to be conversant with using cryomicroscopy as an essential technique for investigation of cellular behavior under application of given freezing stress. Two different cells namely Pacific Oyster embryos and Jurkat were chosen for study. Oyster embryos were obtained from Oysters bought from several local seafood markets of Baton Rouge. The freezing experiments on Oyster embryos were carried out at defined protocols and freezing rates of 5 and 10 o C/minute. Likewise Jurkat cells were collected from culture and then washed and resuspended in Dulbecco’s Phosphate Buffered Saline (PBS). The freezing experiments were carried out at defined freezing protocols and at various freezing rates of 5, 20, 30 and 50˚C/min. Intracellular ice formation in Oyster embryos were observed at both freezing rates of 5 and 10 o C/minute. In Jurkat cells IIF was observed through two different phenomena namely darkening of cells and twitching at freezing rates of 10...
Natural gas hydrate formation in subsea pipelines is a major problem in the upstream petroleum in... more Natural gas hydrate formation in subsea pipelines is a major problem in the upstream petroleum industry. Gas hydrates are formed at high pressures and low temperatures when water lattice with cavities trap gas molecules such as methane. Hydrates are solid deposits that clog subsea flowlines and increase pressure drops across the pipeline, and under severe conditions can completely stop flow through pipelines resulting in tremendous production losses. The authors briefly explain the structure and mechanism of gas hydrate formation and provide the audience with an overview of various gas hydrate prevention and mitigation technologies used in the upstream petroleum industry. The manuscript discusses important methods used in the industry, such as chemical injection, depressurization, thermal stimulation, and mechanical removal by summarizing work from over a hundred reports. Relative merits and demerits of these methods are also discussed. In addition, some interesting research results...
This study presents computational fluid dynamics analyses on oil–water flow characteristics in a ... more This study presents computational fluid dynamics analyses on oil–water flow characteristics in a horizontal separator. The performance of these vessels are inferred from mean residence time and cumulative residence time distribution of the hydrocarbon phase inside the separator. The authors model a separator used by previous researchers and evaluate mean residence time of the hydrocarbon phase in a two-phase mixture of oil and water. Three different water-cuts of 21%, 32%, and 57% are used. Additional analyses are done to assess how certain geometric features of the separator influence hydrocarbon mean residence time. The results show that the addition of a second perforated baffle plate does not improve the hydrocarbon mean residence time significantly. However, introducing a downward slanting throat section between the primary zone and the gravity separation zone improves the hydrocarbon mean residence time at 21% and 32% water-cuts. The results suggest oil–water separators with a...
In the petrochemical industry, separation of oil from water is a very important process. Wells pr... more In the petrochemical industry, separation of oil from water is a very important process. Wells produce mixtures of gas, oil, and water which undergo a primary stage of separation inside horizontal gravity separators. The performance of these vessels is evaluated by measuring mean residence time (MRT) and residence time distribution (RTD). Although many researchers studied flow characteristics in horizontal separators, limited number of articles exist that discuss separator MRT and RTD with varying water-cuts. In this article, the authors study an experiment using a horizontal gravity separator by previous researchers and perform computational fluid dynamics (CFD) simulations on the same geometry under similar conditions. The simulation results show qualitative agreement with the experiments by previous researchers. As shown by experiments before, CFD results showed that MRT of the organic phase increased with increase in water-cut. In addition, the RTD characteristics show very similar trends between CFD and experimental results.
Geological carbon sequestration is a proven method of safely storing carbon dioxide in formations... more Geological carbon sequestration is a proven method of safely storing carbon dioxide in formations, thereby reducing atmospheric carbon imprint and mitigating global warming. The relative permeability to carbon dioxide versus brine/water in geological formations determines flow characteristics of one fluid in the presence of another. The objective of this research is to evaluate the relative permeability to carbon dioxide in both the gas phase and the supercritical state in the presence of water in a Vedder sandstone core sample. The sandstone sample used is medium- to fine-grain arkosic artenite containing primarily quartz, potassium feldspar, plagioclase, and biotite. The effect of the viscosity ratio between the non-wetting phase and the wetting phase, on the relative permeability to the non-wetting phase, is studied. Computational fluid dynamics (CFD) is used for this study. Results show that with the same amount of irreducible water fraction, the endpoint relative permeability t...
Natural gas hydrate formation in subsea pipelines is a major problem in the upstream petroleum in... more Natural gas hydrate formation in subsea pipelines is a major problem in the upstream petroleum industry. Gas hydrates are formed at high pressures and low temperatures when water lattice with cavities trap gas molecules such as methane. Hydrates are solid deposits that clog subsea flowlines and increase pressure drops across the pipeline, and under severe conditions can completely stop flow through pipelines resulting in tremendous production losses. The authors briefly explain the structure and mechanism of gas hydrate formation and provide the audience with an overview of various gas hydrate prevention and mitigation technologies used in the upstream petroleum industry. The manuscript discusses important methods used in the industry, such as chemical injection, depressurization, thermal stimulation, and mechanical removal by summarizing work from over a hundred reports. Relative merits and demerits of these methods are also discussed. In addition, some interesting research results are also reviewed. The authors conclude by providing a table showing the relative technology readiness level for each method. Also, potential areas of future research are discussed.
Abstract In the petrochemical industry, separation of oil from water is a very important process.... more Abstract In the petrochemical industry, separation of oil from water is a very important process. Wells produce mixtures of gas, oil, and water which undergo a primary stage of separation inside horizontal gravity separators. The performance of these vessels is evaluated by measuring mean residence time (MRT) and residence time distribution (RTD). Although many researchers studied flow characteristics in horizontal separators, limited number of articles exist that discuss separator MRT and RTD with varying water-cuts. In this article, the authors study an experiment using a horizontal gravity separator by previous researchers and perform computational fluid dynamics (CFD) simulations on the same geometry under similar conditions. The simulation results show qualitative agreement with the experiments by previous researchers. As shown by experiments before, CFD results showed that MRT of the organic phase increased with increase in water-cut. In addition, the RTD characteristics show very similar trends between CFD and experimental results.
A disk spindown experiment allows measurement of tangential momentum accommodation coefficients o... more A disk spindown experiment allows measurement of tangential momentum accommodation coefficients of different gases and material combinations in a consistent manner. Aluminum is tested for a range o...
Summary Wax or paraffin formation in subsea pipelines is a major problem in the upstream petroleu... more Summary Wax or paraffin formation in subsea pipelines is a major problem in the upstream petroleum industry, accounting for tremendous economic losses. Researchers have reported that approximately 85% of the world's oils encounter problems from wax formation (Thota and Onyeanuna 2016). In this manuscript, the authors briefly discuss the mechanism of wax formation in pipelines. Next, a review of various wax-mitigation technologies is provided. The review includes citations of various thermal, chemical, mechanical, biological, and other innovative methods reported by previous researchers and used in the industry.
Abstract An experimental technique using spin-down of a disk approaching the free-molecular flow ... more Abstract An experimental technique using spin-down of a disk approaching the free-molecular flow limit is developed to measure the tangential momentum accommodation coefficient σ t . The new technique uses a disk mounted on a shaft supported by gas bearings in vacuum. A differential scavenging system allows disk spin-down experiments in different gases. Representative test results with two different materials in two different gases are shown, demonstrating the method is capable of handling a range of gases, as well as any material that is available as, or can be formed into, a planar disk.
This study evaluates the freezing response of three different cell types, Pacific oyster embryos ... more This study evaluates the freezing response of three different cell types, Pacific oyster embryos (~50 µm in diameter), Jurkat cells and HeLa cells (~12 to 15 µm’s in diameter), using cryomicroscopy. Freezing experiments were performed on oyster embryos at cooling rates of either 5 or 10 °C/min, while Jurkats were cooled at either 1 or 10 °C/min and HeLa cells were cooled at either 1, 15 or 20 °C/min, respectively. The experiments with oyster embryos were primarily designed to investigate the phenomena of intracellular ice formation (IIF) while the experiments for Jurkat and HeLa cells were designed to investigate both cellular dehydration and IIF during freezing. IIF was characterized by the abrupt black flashing during the cooling steps while the cellular dehydration experiments were characterized by the volumetric (projected area) shrinkage of the cells during the cooling steps. Mathematical models were fit to the cellular dehydration data to obtain the Jurkat and HeLa cell membra...
The urban heat island (UHI) effect increases the ambient temperatures in cities and alters the en... more The urban heat island (UHI) effect increases the ambient temperatures in cities and alters the energy budget of building materials. Urban surfaces such as pavements and roofs absorb solar heat and re-emit it back into the atmosphere, contributing towards the UHI effect. Over the past few decades, researchers have identified albedo and thermal inertia as two of the most significant thermal properties that influence pavement surface temperatures under a given solar load. However, published data for comparisons of albedo and thermal inertia are currently inadequate. This work focuses on asphalt and concrete as two important materials used in the construction of pavements. Computational fluid dynamics (CFD) analyses are performed on asphalt and concrete pavements with the same dimensions and under the same ambient conditions. Under given conditions, the pavement top surface temperature is evaluated with varying albedo and thermal inertia values. The results show that the asphalt surface...
A mathematical model has been developed to quantify momentum accommodation coefficient as a funct... more A mathematical model has been developed to quantify momentum accommodation coefficient as a function of ambient pressure, gas density, ambient temperature, mass of the gas molecule, and the angular velocity of a disk. An experimental method is proposed for the ...
SUMMARY The main objective of this work was to be conversant with using cryomicroscopy as an esse... more SUMMARY The main objective of this work was to be conversant with using cryomicroscopy as an essential technique for investigation of cellular behavior under application of given freezing stress. Two different cells namely Pacific Oyster embryos and Jurkat were chosen for study. Oyster embryos were obtained from Oysters bought from several local seafood markets of Baton Rouge. The freezing experiments on Oyster embryos were carried out at defined protocols and freezing rates of 5 and 10 o C/minute. Likewise Jurkat cells were collected from culture and then washed and resuspended in Dulbecco’s Phosphate Buffered Saline (PBS). The freezing experiments were carried out at defined freezing protocols and at various freezing rates of 5, 20, 30 and 50˚C/min. Intracellular ice formation in Oyster embryos were observed at both freezing rates of 5 and 10 o C/minute. In Jurkat cells IIF was observed through two different phenomena namely darkening of cells and twitching at freezing rates of 10...
Natural gas hydrate formation in subsea pipelines is a major problem in the upstream petroleum in... more Natural gas hydrate formation in subsea pipelines is a major problem in the upstream petroleum industry. Gas hydrates are formed at high pressures and low temperatures when water lattice with cavities trap gas molecules such as methane. Hydrates are solid deposits that clog subsea flowlines and increase pressure drops across the pipeline, and under severe conditions can completely stop flow through pipelines resulting in tremendous production losses. The authors briefly explain the structure and mechanism of gas hydrate formation and provide the audience with an overview of various gas hydrate prevention and mitigation technologies used in the upstream petroleum industry. The manuscript discusses important methods used in the industry, such as chemical injection, depressurization, thermal stimulation, and mechanical removal by summarizing work from over a hundred reports. Relative merits and demerits of these methods are also discussed. In addition, some interesting research results...
This study presents computational fluid dynamics analyses on oil–water flow characteristics in a ... more This study presents computational fluid dynamics analyses on oil–water flow characteristics in a horizontal separator. The performance of these vessels are inferred from mean residence time and cumulative residence time distribution of the hydrocarbon phase inside the separator. The authors model a separator used by previous researchers and evaluate mean residence time of the hydrocarbon phase in a two-phase mixture of oil and water. Three different water-cuts of 21%, 32%, and 57% are used. Additional analyses are done to assess how certain geometric features of the separator influence hydrocarbon mean residence time. The results show that the addition of a second perforated baffle plate does not improve the hydrocarbon mean residence time significantly. However, introducing a downward slanting throat section between the primary zone and the gravity separation zone improves the hydrocarbon mean residence time at 21% and 32% water-cuts. The results suggest oil–water separators with a...
In the petrochemical industry, separation of oil from water is a very important process. Wells pr... more In the petrochemical industry, separation of oil from water is a very important process. Wells produce mixtures of gas, oil, and water which undergo a primary stage of separation inside horizontal gravity separators. The performance of these vessels is evaluated by measuring mean residence time (MRT) and residence time distribution (RTD). Although many researchers studied flow characteristics in horizontal separators, limited number of articles exist that discuss separator MRT and RTD with varying water-cuts. In this article, the authors study an experiment using a horizontal gravity separator by previous researchers and perform computational fluid dynamics (CFD) simulations on the same geometry under similar conditions. The simulation results show qualitative agreement with the experiments by previous researchers. As shown by experiments before, CFD results showed that MRT of the organic phase increased with increase in water-cut. In addition, the RTD characteristics show very similar trends between CFD and experimental results.
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Papers by Tathagata Acharya