Novel viscoplastically lubricated pipeline flow

As mentioned earlier, in this novel method triple-layer configuration is used. But, there is still one unresolved problem about the density mismatch, i. e., due to density differences, the core can levitate and it will eventually touch the pipeline, so the system will stall. Consequently, we proposed shaping the skin layer to generate lubrication force (similar to slipper bearings) to counterbalance the density difference. Initially, we studied the problem for fully developed periodic triple-layer flow to examine the feasibility of the method. Detailed information and results can be found here. Explicit advantage of his method can be found here.

Flow development and interface sculpting

In Sarmadi et.al. (2017) we introduced a novel methodology for efficient transport of heavy oil via a triple-layer core-annular flow. Pumping pressures are significantly reduced by concentrating high shear rates to a lubricating layer, while ideas from Visco-plastic lubrication are used to eliminate the possibility of interfacial instabilities. Specifically, we purposefully position a shaped unyielded skin of a visco-plastic fluid between the transported oil and the lubricating fluid layer. The shaping of the skin layer allows for lubrication forces to develop as the core settles under the action of transverse buoyancy forces: adopting an eccentric position where buoyancy and lubrication forces balance. We address the equally important issue of how in practice to develop a triple layer flow with a sculpted/shaped viscoplastic skin, all within a concentric inflow manifold. First, we use a simple 1D model to control layer thickness via flow rates of the individual fluids. This is used to give the input flow rates for an axisymmetric triple-layer computation using a finite element discretization with the augmented Lagrangian method to represent the yield surface behaviour accurately and a Piecewise Linear Interface Calculation (PLIC) method to track the interface motion. This establishes that these flows may be stably established in a controlled way with the desired interface shape. The shaped interface induces extensional stresses in the skin layer. We study this directly by developing a long-wavelength/quasi-steady analysis of the extensional flow. This allows us to predict the minimal yield stress required to maintain the skin rigid, for a given shape, all while maintaining a constant flow rate of the transported oil. Detailed information and results can be found here.

Investigation of the inertial and turbulent lubricating layer in triple layer core-annular pipeline flow

Here, we extend the feasibility of this method to large pipes by considering the effect of inertia and turbulence of the lubrication layer flow. Essentially, the method can generate enough lubrication force to balance the buoyancy force for a wide range of density differences and pipe sizes if the proper shape is imposed on the unyielded skin layer. Detailed information and results can be found here.

3D simulations of multi-layer flow with application in VPL

In this study, we present three dimensional (3D) triple-layer computations and the buoyant motion of the core to reach its equilibrium position. The 3D computations are performed using a finite element discretization with the regularization method to represent the yield stress fluid and adaptively aligned meshes to track dynamically the interfaces which are benchmarked against axisymmetric computations from Sarmadi et.al. (2018). Here, the study shows that these flows may stably establish with the control over interface shape. The desirable shaped interface generates sufficient lubrication force to balance the buoyancy force due to density mismatch. We present a simplified analytical model using lubrication approximation and equations of motion for the lubricating layer and rigid skin layer, respectively. this model allows us to estimate the balanced configuration for a given shape and initial conditions. This work is prepared in collaboration with Prof. Stefan Turek from TU Dortmund. Detailed information and results can be found here.