Validation of CFD and Simplified Models With Experimental Data for Multiphase Flow in Bends

Abstract

In this paper details of the measurement results of the forces on the bends in a 4″ setup are compared to two models. The first model is a simple analytical model and is used to estimate the forces. In the second model, CFD is used. In the experiments only resulting forces, including upstream and downstream bends and mechanical resonance and interaction is measured. The goal of the CFD was to discriminate between flow and mechanics and to evaluate the influence of a flow disturbance as a result of a bend on the force on a downstream second bend. For the simplified analytical model the amplitudes are underestimated, but the frequency spectra look very reasonable in case of the slug flow regime. The main advantage of the simplified analytical model is that the computational time is in the order of seconds, but the accuracy is still reasonable for the use in an engineering approach of determining the structural integrity of the complete pipe system. For the CFD the shape of the force function is similar to the experiments. The CFD results indicate that the forces on the second downstream bend are also measured on the first upstream bend. The accuracy of the CFD simulation is the advantage of this model, but the computational time is very long, especially if the multiphase flow simulation is coupled to the structural model.

Investigation of the effects of pipe diameter of internal multiphase flow on pipe elbow vibration and resonance

“…Belfroid et al 10 summarised the results of all the test cases that were investigated by Nennie and Belfroid. 5 Their findings on the relationship between the non-dimensional force fluctuation and Weber number compared fairly to the model by Riverin et al 11 and data from Liu et al 3…”

“…Experimental studies on MFIV in large pipes are few. The most relevant of such studies were conducted by Nennie and Belfroid 5 and Belfroid et al 6 These experiments were also used to validate computational fluid dynamics (CFD) studies that were conducted in a subsequent phase of the project. 7–9 These studies concluded that the fluctuations of liquid hold-up resemble the multiphase flow induced force fluctuations at pipe elbows.…”

Stochastic mechanistic modelling of two-phase slug flow forces on bends in horizontal piping

“…Both 𝐶 = 10 and 𝐶 = 25 have been proposed to fit the measurements. Nennie et al (2013) used slug tracking and a zone-specific density to predict slug forces on bends. A stochastic time dependency was introduced by a normally distributed slug frequency.…”

Vibrations of a vertical 90° pipe bend under two-phase flow conditions

“…The peak frequencies decline as the flow transitions from slug to churn flow. Nennie et al (2013) investigated the influence of pipe entry length on the fluctuating forces of a slug flow at pipe bend with I.D and bend radius of 0.1016 m. It was discovered that when the entry length before the pipe bend is short (1.5 m), the predicted forces were lower than when the entry length was longer (3 m). This flow characteristic was associated with the fact that a shorter pipe did not allow the slug flow velocity at the bend to match with the theoretical slug flow velocity.…”