Pulse flow of liquid in flexible tube

Abstract

The simulation of liquid flow in significantly deformed elastic material is one of the more challenging tasks. Tube wall motion prediction implemented directly into CFD software can noticeably reduce the computational and time demands of such problems. The FSI simulation of a liquid-flowed flexible plastic tube was analyzed on the FEA and CFD solvers coupling basis. The flexible tube is the basic symmetric test body that could be appropriately tested on the experimental stand. A comparison of experimental data and FSI problem using commercial code and one-dimensional tube models was made by evaluating the tube wall deformation magnitudes at defined flow ratios. The type of tube material, which can be understood as a nonlinear from the stress and deformation point of view, was considered. The paper shows several possibilities of tube modeling using the main constitutive relations of linear and nonlinear mechanics. The hyperelastic material models such as neo-Hookean and Mooney-Rivlin were tested. The results represent differences in impacts on the tube liquid flow and differences in the magnitudes of the wall tube deformations. Based on these findings it should be possible to simulate the problems of liquid flow in more complicated shape flow zones, such as arteries affected by various defects, in our future research.

FSI Computation and Experimental Verification of Fluid Flow in Flexible Tubes

“…However, since experimental data is missing for obvious reasons, the corresponding stresses will not be plotted. Indeed, stress analysis of rotationally symmetric bodies is well described in literature [5], [17], [18]. Other works [3], [7], [19], which were carried out at this topic, show that the link between the static pressure in the tube and the actual or simulated deformation of the tube is less prone to possible inaccuracies than is the case with purely hydraulic parameters.…”

Methods for Simplification of the Mathematical Model for the Calculation of Flows in the Flow Path of Hydraulic Turbines

“…Differentiating continuity equation ( 5) with respect to time yields Application of a procedure similar to that used for ( 12)-( 14), gives (15) Integral equations ( 13) and ( 14) can also be written in vector form (16) The physical concept of equations ( 16) can be very useful for describing unsteady vortex structures inside the region V [18][19][20][21]. Obviously, local acceleration within the volume V depends only on the boundary conditions.…”

“…Further, this equation is used to calculate the forces acting on the body, and the influence of boundary conditions on unsteady vortex structures is analyzed. Substituting (11) and ( 15) into the Navier-Stokes equations (8), yields (20) Equation ( 20) is a new form of the Navier-Stokes equations for incompressible fluid. To analyze equation (20) further, a new tensor is introduced (21) Let us introduce a coordinate system meeting the conditions (22) We can then write (23) and, therefore, (…”

“…It follows from this equation that the force can be calculated without a knowledge of the pressure and velocity fields [20,21]. Therefore, equation (27) may be helpful not only for calculating the acting forces.…”