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Research Interests

  • Experimental, Computational & Analytical Fluid Dynamics
  • Complex Non-Newtonian Fluid Flows
  • Suspensions, Multiphase, Displacements & Buoyant Flows
  • Thin-Film Flow Modelling & Stability Analysis
  • Coating & Co-Extrusion Flows

Current Research

Suspension Schematic
Figure: Schematic of suspension flow in an inclined geometry.

Flow of Suspensions with Non-Newtonian Bed Fluids

Suspension flows frequently occur in both natural phenomena (gravity currents, debris flows, lava flows) and many industries including oil & gas (hole cleaning, transport of cuttings and solids during drilling process, hydraulic fracturing, gravel packing), food processing, paint, mining, pulp and paper processing, etc. Non-Newtonian rheological effects are often prevalent. The geometry in which suspension flows occur are commonly pipe, channel or annulus geometries. We study the flow of suspensions through experimental, numerical and analytical techniques in order to find the most optimum rheological and flow conditions that cause the least amount of sedimentation throughout the process.

Displacement flows in inclined ducts

Displacement of one fluid by another is a fundamental problem widely observed in both nature and industry. Over several years we have been studying this problem in inclined geometries for both Newtonian and non-Newtonian fluids. The industrial motivation for this research comes from the processes present in construction and completion of oil & gas wells. Examples include primary cementing, hydraulic fracturing and gravel packing. Geothermal, Carbon sequestration and domestic water distribution wells are cemented using the very same techniques as in the oil & gas industry. The objective in well primary cementing is to hydraulically seal the newly constructed well to avoid leakage of subsurface fluids into the near-surface ecosystem. We study these flows through joint experimental, numerical and analytical techniques to finally design the displacement processes more efficiently. This in turn will reduce the environmental impacts while increasing the well productivity. The figure shows flow patterns observed in buoyant displacement flows in inclined geometry experimentally and numerically.

Angle Snapshots
Figure: Snapshots of the displacement flow at different inclination angles: a) Experiments in pipe b) Simulations in channel. Flow direction is from left to right.

Fluid invasion into viscoplastic beds

Carbopol Gel
Figure: Experimental snapshot of liquid invasion into a viscoplastic fluid.

We are working on the fundamental topic of fluid (gas/liquid) invasion into viscoplastic beds with intentions to resolve the gas-migration problem in cemented oil & gas wells. Once oil & gas wells are drilled, the annulus space between the production casing and rock formation is filled by cement slurry. The slurry will then be left to set and solidify. During the solidification stage, formation fluids may enter the cemented annulus in the form of gas or liquid. This in turn, can create channels that provide an undesirable flow path of the reservoir fluids including hydrocarbons into the wellbore and near-surface environment. We aim to study this problem experimentally, computationally and analytically in order to finally design the cement slurry fluid such that it minimizes the fluids intrusion from formation into the wellbore. This will in return, decrease the environmental impacts and increase the well productivity. The figure shows the experimental snapshot of a liquid invading a viscoplastic fluid, mimicking the formation liquid migration towards the cement slurry.

Multi-layer coating and extrusion flows

Co-extruxion Schematic
Figure: Schematic of the co-extrusion process.

Two-layer flows are found in both nature and industry, e.g. coating and co-extrusion flows. At high flow rates inertial effects become increasingly important and a long-standing problem has been how to represent these effects simply in a way that remains faithful to the flow stability. Although resolved for single fluid flows years ago, extending the stability analysis methodology to multi-fluid flows has been evolved more slowly owing to the difficulties associated with the interfacial conditions. We aim to overcome these obstacles through flow modelling. The mathematical models developed and their implementation to a two-layer system enables us to predict the behavior of co-extrusion and coating flows more accurately by including the combined effects of surface tension, viscous, gravitational and inertial forces. By properly modelling the co-extrusion one can predict, and thus prevent, defects in the final product which arise due to the flow instability.