A Surrogate Model for Evaluation of Maximum Normalized Dynamic Load Factor in Moving Load Model for Pipeline Spanning due to Slug Flow

Abstract

Understanding the problem of slug-flow-induced fatigue damage is of particular importance to the reliable operation of pipelines. Slug flow, across unsupported pipeline spans, produces dynamic vibrations in the pipeline resulting in cyclical fatigue stresses. These dynamic effects will cause the pipeline to fail at a point of stress concentration if proper design procedure is not followed. The response of a pipeline span, under the passage of slug flow, can be represented by dynamic load factors that are functions of the speed ratio and damping characteristics of the span. The aspects of these functional relationships are investigated, in this paper by conducting multiple simulations at different speed ratios and damping factors. The data obtained from the steady state Fourier expansion will, consequently, be used to produce a surrogate model with a level of accuracy that adequately qualifies it for use in determining dynamic loading of pipelines. The closed-form surrogate model can be used to eliminate the need to employ costly mathematical procedures or finite element packages for the analysis. The model will also provide a solid ground for optimization studies and help designers gain an insight into how various model parameters impact the system response. This paper will demonstrate the aspects of a proposed surrogate model and endeavor to obtain parameter domains within which the model’s reliability is ensured. A numerical example will be demonstrated to prove the concepts presented in the paper and confirm the validity of the proposed model.