CFD Prediction and LDV Validation of Liquid and Particle Velocities in a Submerged Jet Impinging a Flat Surface for Different Viscosities and Particle Sizes

Abstract

Solid particle erosion commonly occurs in the oil and gas industry and can cause severe damage to flow lines and equipment. One successful approach to predicting erosion, and mitigating sand erosion damage, is through the application of computational fluid dynamics (CFD) modeling of the fluid flow, sand particle movement within the flow, and erosion resulting from the sand particles hitting the metal surface [1, 2, 3]. A key ingredient to predicting erosion damage is having an equation to represent erosion damage due to sand particles hitting the metal surface. This equation, called the erosion equation, usually includes the properties of the sand, the particle impact speed, and the angle of impact. The particle impact speed is known to be a major factor affecting the severity of erosion and can be found in most erosion equations in the literature. The erosion equation is usually material specific and its validation is very important before being applied in engineering calculations to predict erosion of flow lines, tubing, and equipment. Carrier fluid properties have a substantial effect on particle trajectories. The present studies were performed to examine the effect of fluid viscosity on the particle impacting velocity. Direct impingement tests, which consist of a submerged fluid jet containing aluminum particles impinging on a flat surface, were conducted. Carrier fluids with viscosities ranging from 1 cP to 100 cP and three types of aluminum particles with average diameters of 3 μm, 120 μm, and 550 μm were tested in the experiments. The distance between the nozzle exit and the target surface is 12.7 mm and the nozzle diameter is 8 mm. The flow rate through the nozzle is 8 GPM, which corresponds to an average flow velocity of about 10 m/s. Particle velocities at different locations between the nozzle exit and the target surface were measured using a laser Doppler velocimeter (LDV). CFD simulations for all test conditions were also run using FLUENT 6. The predicted solid particle velocities were compared with the LDV data and good agreement was achieved. Both experiments and simulations indicate that flow in the nozzle and near the target undergoes a transition from turbulent to laminar flow when the fluid viscosity is increased and this greatly affects particle velocities near the target.