CFD modelling of pipe erosion under multiphase flow regimes.

Pipe erosion due to sand transport can have an adverse effect on the production efficiency of pipe-lines and other related flow systems. Proper knowledge of the flow characteristics, particle behaviour and geometric effects is very important in the accurate prediction of erosion rates and location. This study focuses on predicting erosion under complex multiphase flow conditions with emphasis on double bend geometries. The Eulerian Multifluid-VOF coupled with the Lagrangian Discrete Phase Model (DPM) has been employed to account for the flow and particle behaviour, RNG k - e model for the effects of turbulence and erosion rate was calculated using the Oka et al. model. A pseudo-single phase model was also evaluated in order to reduce the simulation resources to predict erosion in elbows mounted in series. Results from both modelling techniques were compared. Results show that phase distribution plays a vital role in estimating erosion in complex multiphase flows. The presence of a separation distance results in a change in phase distribution before the first and second elbows, and an increase in the separation distance aides the flow development towards the second elbow. The presence of the second bend has a significant influence on the erosion rate of the first bend compared to a single bend geometry. Furthermore, Elbow 2 is subjected to more erosion than Elbow 1 in churn flow, while Elbow 1 is more erosive in slug flow. The reverse of these were predicted with the pseudo single-phase approach for both flow conditions. Although the pseudo approach reduces computational time, it ignores vital flow features and predicts erosion rates higher than the Eulerian Multifluid-VOF approach in both elbows and flow condition. And, irrespective of modelling technique, the best double bend operating conditions predicted for both flow conditions are the same

Computational fluid dynamics modelling of multiphase flows in double elbow geometries.

This study investigates the effects of elbow on the transition and development of multiphase flow using computational fluid dynamics modelling techniques. The Eulerian - Multifluid VOF model coupled with an Interfacial Area Transport Equation has been employed to simulate air-water two-phase flow in a pipe with two standard 90 degree elbows mounted in series. Turbulence effects were accounted for by the RNG k-ε model. The effects of separation distance on two-phase flow development have been studied for initial slug and churn flow regimes. Computational fluid dynamics simulation results of phase distribution and time series of void fraction fluctuations were obtained and they showed good agreement with available experimental data. The results show that for initial slug flow regime, there is no flow regime transformation upstream and downstream of the two elbows. While at initial churn flow regime, flow regime transformation occurs at different sections of the flow domain before and after the two elbows. It was noticed that irrespective of the flow regime, the amplitudes and frequencies of void fraction fluctuation become smaller as the fluid flows along the pipe. Changes in the separation distance between the two elbows have larger effects on the flow at churn flow regime

Provisioning ecosystem services provided by the Hadejia Nguru Wetlands, Nigeria – current status and future priorities

The Hadejia Nguru Wetlands (HNWs) located in the Sahel zone of Nigeria support a wide range of biodiversity and livelihood activities. Providing strategic management information that aids understanding of the changing values of the wetlands is a key principle for their prudent use. This is even more important in a society where the value of wetlands is not fully appreciated. This study assesses the status (resource users, monetary values, threats to and management options) of the HNWs with a view to providing important information for their sustainable management. Data was collected through questionnaire survey, focus group discussions, informal interviews and field observations. The main services provided by the wetlands include farming (mainly rice, maize, cowpeas and millet in the wet season and sorghum, tomatoes and wheat in the dry season), collection of materials (mainly doum palm - Hyphaene thebaica and fuelwood), fishing, grazing and hunting of water birds. The monetary contribution of fishing to participating households was highest at US$5,864/household/year while that of fuelwood at US$427/household/year was the lowest financial contributor. The study found that the monetary value of doum palm collection has declined by 23% and farming by 45% over a 20 year period, while fuelwood value has increased by 119%. The impacts posed by invasive Typha grass and dam construction were identified as the major threats to the HNWs. These have led to scarcity and competition for resource and hence conflicts. Therefore, we suggest a management approach that designs a resource use calendar especially for farmers and herders as a means of reducing conflicts

Cfd modelling of pipe erosion due to sand transport

Erosion caused by sand particles is a serious problem facing the oil and gas industry. Predicting pipe erosion due to sand transport is a complex process in multiphase flows due to the complex nature of the flow. Existing erosion studies are however focused on single phase flow conditions which are conservative and could lead to under-/over-engineering because actual fluid flow in pipelines is multiphase. There is therefore a need for in-depth analysis of the complex interaction between the multiphase fluid and transported sand particles. Document type: Part of book or chapter of boo

Salvage Autologous Stem Cell Transplantation in Daratumumab-Refractory Multiple Myeloma

Daratumumab, a CD38-targeting monoclonal antibody, has significantly improved survival rates in multiple myeloma (MM), yet patients who progress on Daratumumab have dismal clinical outcomes with an overall median of less than 10 months. While emerging novel modalities have shown promising results, the current study explores the use of high-dose chemotherapy followed by autologous stem cell transplantation (ASCT) in heavily pretreated Daratumumab-refractory MM patients. We retrospectively investigated the outcome of 69 consecutive patients who received upfront ASCT. The median progression-free survival (PFS) for the entire patient cohort was 7.2 months with a median overall survival (OS) of 19.3 months. For patients with ≥very good partial response (VGPR), median PFS and OS improved to 9 months and 34 months, respectively. Achievement of MRD negativity in ≥VGPR did not further improve the outcome. A better performance status, younger age, longer time interval from initial MM diagnosis/initial ASCT to salvage ASCT and low-risk GEP70 were all associated with improved PFS and OS after salvage ASCT. Our results suggest a role for salvage ASCT in selected heavily pretreated and Daratumumab-refractory patients