Research On Fluid-structure Coupling Hybrid Stress Element

Shale gas is an important resource,but the exploitation efficiency is not so high that this important resource cannot be fully utilized.Two main difficulties are the important reasons: Firstly,when using hydraulic fracturing as a mining technology,it is inevitable to consider the problem of fluid-solid coupling.Secondly,because the storage environment of shale is in bad condition and contains tremendous pores with fluid,and it is a challenge to simulate the real shale with a large number of pores.The hybrid stress element method is an effective means of simulating and solving engineering problems.Based on this method,this article has made the following work:1.A new fluid-structure coupling element(FCHSE)is derived.On the basis of the hybrid stress element,the surface force balance condition at the fluid-solid interface and between the element are introduced,and a given surface force boundary condition is introduced to obtain a modified complementary energy functional.Four sets of models have been established for comparison with the model in MARC.The accuracy of the model is verified via two different simulation methods,and the stress when the number and distribution of inclusions change is studied.The influence of the distribution law of stress has been studied when the distribution,numbers of inclusions change,and obtained the diagram of pressure change with hole number.2.Four important factors of FCHSE equivalent elastic modulus are studied.Firstly,compare the equivalent elastic modulus calculated by the FCHSE method with MARC to prove the effectiveness of the method.Then,The impact of the variance,the average radius,the volume ratio,and the angle to the equivalent elastic modulus are studied.Both studies have shown that this element has high accuracy and excellent ability to capture stress concentration at the fluid-solid interface.The comparison between a small number of elements and a large number of fine elements in MARC proves the effectiveness of the method in simulation.The study of equivalent elastic modulus can give the basic properties of fluid-solid materials under load and the influence of various factors on their mechanical properties.It has certain guiding significance in the theoretical research of engineering practice.