Dynamic Response and Reliability Analysis of Buried Steel Pipes Under Blast Load

Comprehensively considering the influence of multiple load factors involved in the stress of buried pipelines, the dynamic response model and failure function of buried pressurized pipelines under explosive loads are established, and the formula for calculating the stresses of buried pressurized pipelines is proposed. Design and carry out dynamic response model experiment of buried steel pipe under explosive load, and extract relevant model parameters according to experimental data. For the buried pressurized steel pipes under extreme experimental conditions, the reliability analysis was carried out by Monte Carlo method, and the limit proportional distance of pipeline failure under experimental conditions was obtained. To determine the degree of influence of various parameter changes on the reliability of buried steel pipes. The research results can provide a certain reference for the quantitative risk assessment and safe operation analysis of the adjacent buried pipelines in blasting construction.

2D CFD Modeling of Rapid Water Filling with Air Valves Using OpenFOAM

The rapid filling process in pressurized pipelines has been extensively studied using mathematical models. On the other hand, the application of computational fluid dynamics models has emerged during the last decade, which considers the development of CFD models that simulate the filling of pipes with entrapped air, and without air expulsion. Currently, studies of CFD models representing rapid filling in pipes with entrapped air and with air expulsion are scarce in the literature. In this paper, a two-dimensional model is developed using OpenFOAM software to evaluate the hydraulic performance of the rapid filling process in a hydraulic installation with an air valve, considering different air pocket sizes and pressure impulsion by means of a hydro-pneumatic tank. The two-dimensional CFD model captures the pressure evolution in the air pocket very well with respect to experimental and mathematical model results, and produces improved results with respect to existing mathematical models.

Effects of Surge Tank Geometry on the Water Hammer Phenomenon: Numerical Investigation

A surge tank, as one of the most common control facilities, is applied to control head pressure level in long pressurized pipelines during the water hammer occurrence. The cost-effective operation of surge tank is highly affected by its characteristics (i.e., surge tank diameter and inlet diameter of surge tank) and can effectively reduce the repercussion of water hammer. This investigation utilized the method of characteristics (MOC) in order to simulate the behavior of transient flow at surge tank upstream and head pressure fluctuations regime for hydraulic system of a hydropower dam. The various types of boundary conditions (i.e., sure tank, reservoir, branch connection of three pipes, series pipes, and downstream valve) were applied to numerically investigate the simultaneous effects of the surge tank properties. In this way, all the simulations of water hammer equations were conducted for nine various combinations of surge tank diameter (D) and inlet diameter of surge tank (d). Results of this study indicated that, for the surge tank design with D=6m and d=3.4m, head pressure fluctuations reached minimum level in the large section of pipeline here is surge tank upstream. Additionally, occurrence of water hammer phenomenon was probable at the initial section of pipeline.

Wireless Battery-Free Harmonic Communication System for Pressure Sensing

In this paper, an efficient passive wireless harmonic communication system is proposed for the real-time monitoring of the pressurized pipelines. A pressure sensor is fabricated using the additive manufacturing technique and a harmonic radio frequency (RF) tag is designed to operate at the fundamental frequency (fo) of 2 GHz that shifts the phase of the back reflected RF signal according to the applied pressure ranging from 0 to 20 psi. A power efficient phase modulation with virtually no losses is achieved using a hybrid coupler-based phase shifter that efficiently reflect back the incoming signal using an end coupled reactive impedance element/sensor. The phase delay introduced by the reactive element gets doubled with the second harmonic communication, which increases the sensitivity by a factor of two. The concept of harmonic backscattering is exploited to reduce the effects of multi-path interference and self jamming, as well as improving the signal-to-noise ratio (SNR).