Inhomogeneous drag models for gas-solid suspensions based on sub-grid quantities

Abstract Particle drag models, which capture macro viscous and pressure effects, have been developed over the years for various flow regimes to enable cost effective simulations of particle-laden flows. The relatively recent derivation by Maxey and Riley has provided an exact equation of motion for spherical particles in a flow field based on the continuum assumption. Many models that have been simplified from these equations have provided reasonable approximations; however, the sensitivity of particle-laden flows to particle drag requires a very accurate model to simulate. To develop such a model, a 2D axisymmetric Navier-Stokes direct numerical simulation of a single particle in a transient, shock-driven flow field was conducted using the hydrocode FLAG. FLAG's capability to run arbitrary Lagrangian-Eulerian hydrodynamics coupled with solid mechanic models makes it an ideal code to capture the physics of the flow field around and in the particle as it is shock-accelerated -- a challenging regime to study. The goal of this work is twofold: to provide a validation for FLAG's Navier-Stokes and heat diffusion solutions, and to provide a rationale for recent experimental particle drag measurements.

Download Full-text

Buoyancy Force on a Plain or Perforated Portion of a Pipe

10.2118/204025-ms ◽

2021 ◽

Author(s):

Eric Cayeux ◽

Sigmund Stokka

Keyword(s):

Buoyancy Force ◽

Construction Operations ◽

Drilling Operation ◽

Drill Stem ◽

Shallow Wells ◽

Plain Tube ◽

End Caps ◽

Drag Models ◽

The One ◽

Perforated Tube

Abstract Torque and drag models have been used for many decades to calculate tensions and torques along drill-strings, casing strings and liner strings. However, when applied to sand-screens, it is important to check that all the initial hypotheses used for torque and drag calculations are still valid. In particular, it should be checked whether the buoyancy force on a perforated tube may differ from the one applied to a plain tube. The buoyancy force applied on a pipe, contributes to the sum of efforts at the contact between the pipe and the borehole and therefore influences torque and drag calculations. This contact force is local and should account for localized effects as well as the material internal forces, torques and moments on each side of the contact. As the buoyancy force is the result of the gravitational component of the pressure gradient on the surface of the pipe that is in contact with the fluid, the presence of holes in the pipe also influences the buoyancy force. When applied to a portion of a pipe, buoyancy does not have contributions at the end caps of that portion of the drill-stem since these end caps are not in contact with the fluid, except at positions with a change of diameter. Therefore, one shall be cautious when calculating the local buoyancy force either on a plain or a perforated tube. The paper describes how to calculate the local buoyancy force on a portion of a drill-stem by application of the Gauss theorem accounting for the necessary corrections arising from the end caps not being exposed to the fluid. An experimental setup has been built to verify that the tension inside a pipe subject to buoyancy does follow the derived mathematical calculations. With complex well construction operations, for instance during extended reach drilling or when drilling very shallow wells with high kick-off rates, the slightest error in torques and drag calculations may end up in jeopardizing the chance of success of the drilling operation. It is therefore important to check that all initial calculation hypotheses are still valid in those contexts and that for instance, sand-screens may be run in hole safely after a successful drilling operation.

Download Full-text

Numerical Modelling of Multiphase Flow With Application to Industrial Processes

10.23889/suthesis.58693 ◽

2021 ◽

Author(s):

◽

Ashutosh Bhokare

Keyword(s):

Numerical Modelling ◽

Multiphase Flow ◽

Multiphase Flows ◽

Oil And Gas ◽

Fresh Concrete ◽

Industrial Applications ◽

Fluidised Bed ◽

Bingham Model ◽

Drag Models ◽

Concrete Flow

Multiphase ﬂows are witnessed often in nature and the industry. Simulating the behaviour of multiphase ﬂows is of importance to scientists and engineers for better prediction of phenomena and design of products. This thesis aims to develop a multiphase ﬂow framework which can be applied to industrial applications such as placement of concrete in construction and proppant transport in oil and gas. Techniques available in literature to model multiphase ﬂows are systematically introduced and each of their merits and demerits are analysed. Their suitability for diﬀerent applications and scenarios are established. The challenges surrounding the placement of fresh concrete in formwork is investigated. Construction defects, the physics behind these defects and existing tests used to monitor fresh concrete quality are evaluated. Methods used to simulate fresh concrete ﬂow as an alternative to experiments are critically analysed. The potential beneﬁts of using numerical modelling and the shortcoming of the existing approaches are established. It is found that the homogeneous Bingham model is currently the most widely used technique to model fresh concrete ﬂow. Determining the Bingham parameters for a given concrete mix remains a challenge and a novel method to obtain values for them is demonstrated in this work. The Bingham model is also applied to a full-scale tremie concrete placement procedure in a pile. Knowledge on the ﬂow pattern followed by concrete being placed using a tremie is extracted. This is used to answer questions which the industry currently demands. The need for a more sophisticated model is emphasised in order to obtain an even greater understanding of fresh concrete ﬂow behaviour. A CFD-DEM framework in which the multiphase nature of concrete is captured is developed. To validate this framework a new benchmark test is proposed in conjunction with the ﬂuidised bed experiment. A comparative study of the drag models used in CFD-DEM approaches is performed to systematically assess each of their performances. CFD-DEM modelling is then applied to model fresh concrete ﬂow and its potential to model defect causing phenomena is demonstrated. A model to capture more complex behaviours of concrete such as thixotropy is introduced and demonstrated.

Download Full-text