Study Of Drag Reduction Fluid Pipe Flow On CFD Simulation Of Viscoelastic Model

Adding a small amount of polymer or surfactant in the water can effectively reduce the turbulent flow resistance of the fluid,which can reduce the energy consumption in long distance fluid transportation.The technique of additive drag reduction has huge engineering application value.The research on additive turbulent drag reduction technology focuses on the study of drag reduction mechanism and its applications in engineering.Studying of numerical methods that meet engineering requirements has gradually become an important research topic in this field.This paper chooses CFD software FLUENT to achieve the purpose of numerical simulation of water and viscoelastic drag fluid’s pipe flow,combined with the function of user-defined functions(UDFs).Firstly,the rheological properties of medium and low concentration surfactant fluid CTAC were studied by rheological experiments.The experiments revealed the change of shear viscosity with shear rate of CTAC drag-reducing fluid,it can be the divided into three stages,shear-thinning,shear-thickening and secondary shear-thinning.The shear viscosity of solution decreases with the increasing temperature,and shear thinning and viscoelastic properties of the CTAC can be well simulated by Giesekus model.The experiment also obtained rheological parameters under different conditions.Based on the calculation logic of FLUENT,this paper introduced the specific forms and numerical calculation methods of simulation control equations.It also introduced the divisions of the domain grid and calculation parameters’ settings.At the same time,the specific method to realize the definition of Giesekus viscoelastic constitutive relations has been given,through functions of UDF.Laser Doppler Velocimetry is used in the measurement of velocity vectors in the pipe flow with water.Comparing the results of LDV measurement experiment and numerical experiment,it can be considered that the numerical calculation method in this paper has good accuracy and feasibility.The Giesekus viscoelastic model was used to simulate the properties of three different concentrations CTAC solutions’ pipe flow in numerical experiment.Compared with the simulation results of Newtonian fluids,CTAC fluids exhibited turbulent drag reduction characteristics,and its drag reduction efficiency increased with solution concentration.The peak value of the Reynolds shear stress distribution curve of each concentration drag reducing fluid is closer to the central area of the pipe.Finally,based on the Giesekus viscoelastic model,numerical calculations were performed for the pipe flow of viscoelastic drag reducing with under different Wessenberg number We and solvent viscosity ratio β.By analyzing the average velocity distribution,normalized mean streamwise velocity distribution and the variation law of friction coefficient with Reynolds number,the feasibility of using FLUENT’s UDF function to simulate drag reduction fluid is further verified qualitatively and quantitatively.Viscoelasticity changes the turbulent flow structure of the CTAC solution.The drag reduction rate increases with the increase of the We number and β.From the distribution of radial turbulent kinetic energy,it can be seen that the larger We number and β have a stronger inhibitory effect on the turbulent pulsation.