Modeling and Simulation of Pigging for a Gas Pipeline Using a Bypass Pig

The pipeline inspection gauge (PIG, lowercase pig is commonly used) with a bypass valve is widely used in pipeline inspection because it operates at a low speed without reducing the flow rate. Understanding the dynamics of a bypass pig in a gas pipeline would contribute to the design of the pig and the control of pig speed. This paper deals with the dynamic model for the process of a bypass pig travelling through a hilly gas pipeline. The method of characteristics (MOC) is used to solve the equations of unsteady gas flow. The backward flow of the gas in the bypass valve and pipe is shown by a simulation of pigging for a hilly gas pipeline. Parametric sensitivity analysis of pigging in the horizontal gas pipe using a bypass pig is then carried out. The results indicate that the speed of a bypass pig is most sensitive to the gas speed in the pipe followed by the bypass area and the friction of the pig. A formula, obtained from the results of the simulations using response surface methodology (RSM), is presented to predict the steady speed of a bypass pig in the horizontal gas pipeline.

Haar wavelets scheme for solving the unsteady gas-flow in 4-D

The system of unsteady gas-flow of 4-D is solved successfully by alter the possibility of an algorithm based on collocation points and 4-D Haar wavelet method. Empirical rates of convergence of the Haar wavelet method are calculated which agree with theoretical results. To exhibit the efficiency of the strategy, the numerical solutions which are acquired utilizing the recommended strategy demonstrate that numerical solutions are in a decent fortuitous event with the exact solutions.

Analysis of the Unsteady Flow in Compressor Cascade With POD Method

The leading edge vortex’s frequency characteristics and flow separation due to adverse pressure gradient are found to be dominant in the determination of compressor performance. For deep understanding of the unsteady gas flow in compressor cascade, the numerical study with Proper Orthogonal Decomposition (POD) reconstructed method is performed in the present study. And, the Fast Fourier Transform (FFT) is implemented to get the vortex fluctuation frequency to fully understand flow separation. Furthermore, the comparisons between the baseline results and the reconstructed flow field by POD method are conducted for investigating the feasibility of POD method. It demonstrated that a few POD modes are adequate to reconstruct main flow field and higher POD modes reflect more detailed flow structure. And also, the characteristic of mode coefficient is analyzed with the detailed explanations of POD. Then, the POD method, which decouples flow field in space and time, is found to be effective in the depiction of the vortex structure and the representation of the flow mechanism. The present study can be regarded as the first step to determine the number of POD modes and evaluates the error of reconstructed flow field.