Effect Of Pressure Forces Research Articles

Investigation of Air Flow Characteristics in Air Intake Hoses using CFD and Experimental Analysis based on Deformation of Rubber Hose Geometry

In this study, the pressure loss value of air intake hose of FIAT 1.3 E6D type engine, located between intercooler and inlet manifold of the engine, was examined using computational fluid dynamics, considering geometrical deformation in a rubber material. The rubber material modelling was performed by the verification of the data - obtained through the experimental method- with ANSYS software using Mooney-Rivlin method. The rubber material modelling was performed with the aim of correctly determination of the increase in the hose diameter when subjected to pressure, since the material has the feature of elasticity. In this study, ANSYS Fluent v.18.0 software and a static pressure machine were used. The air intake into the hose took place at the pressure of 123,5 kPa and flow rate of 0,087 kg/s. A solution, independent of the number of element, was obtained in the analysis. The turbulence model used in the study is standard k-e type. As a result, the deformation-oriented pressure loss in the last geometry was found 1,85 kPa. The analyses were repeated for non-deformed geometry, and a pressure loss of 2,04 kPa was determined. At the result of the test, the geometry was seen to become actually deformed, and the pressure loss was found 1,9 kPa. The lowness of pressure loss in the deformed geometry was seen as the removal of the sharp bends that would cause local losses with the effect of pressure forces. In this study, it was determined that geometrical deformation changes the geometrical features that causes pressure loss, and leads to less pressure loss.

Notes on a PDE system for biological network formation

We present new analytical and numerical results for the elliptic–parabolic system of partial differential equations proposed by Hu and Cai, which models the formation of biological transport networks. The model describes the pressure field using a Darcy’s type equation and the dynamics of the conductance network under pressure force effects. Randomness in the material structure is represented by a linear diffusion term and conductance relaxation by an algebraic decay term. The analytical part extends the results of Haskovec et al. (2015) regarding the existence of weak and mild solutions to the whole range of meaningful relaxation exponents. Moreover, we prove finite time extinction or break-down of solutions in the spatially one-dimensional setting for certain ranges of the relaxation exponent. We also construct stationary solutions for the case of vanishing diffusion and critical value of the relaxation exponent, using a variational formulation and a penalty method.The analytical part is complemented by extensive numerical simulations. We propose a discretization based on mixed finite elements and study the qualitative properties of network structures for various parameter values. Furthermore, we indicate numerically that some analytical results proved for the spatially one-dimensional setting are likely to be valid also in several space dimensions.

Mathematical Analysis of a PDE System for Biological Network Formation

Motivated by recent physics papers describing rules for natural network formation, we study an elliptic-parabolic system of partial differential equations proposed by Hu and Cai [13, 15]. The model describes the pressure field thanks to Darcy's type equation and the dynamics of the conductance network under pressure force effects with a diffusion rate D ≥ 0 representing randomness in the material structure. We prove the existence of global weak solutions and of local mild solutions and study their long term behavior. It turns out that, by energy dissipation, steady states play a central role to understand the network formation capacity of the system. We show that for a large diffusion coefficient D, the zero steady state is stable, while network formation occurs for small values of D due to the instability of the zero steady state, and the borderline case D = 0 exhibits a large class of dynamically stable (in the linearized sense) steady states.

A linear resonant compressor model based on a new linearization method of the gas pressure force

In this paper, the resonant compressor is studied and one new method for modeling using the gas pressure force's effects is presented. The gas pressure force is nonlinear and variable throughout the operation. Therefore, it is a very difficult task to calculate the resonance frequency with the necessary accuracy to optimize the compressor efficiency. Thus, the design of a high performance controller for linear compressor drive presents a challenge since the system is highly nonlinear. This new method proposes to deal with this problem through linearization of the gas pressure force. This new approach is based on the effects that this force causes in the compressor operation. From the use of this approach, it is possible to model and to analyze the compressor's behavior as a linear time varying system.

Simulating galactic outflows with kinetic supernova feedback

Feedback from star formation is thought to play a key role in the formation and evolution of galaxies, but its implementation in cosmological simulations is currently hampered by a lack of numerical resolution. We present and test a sub-grid recipe to model feedback from massive stars in cosmological smoothed particle hydrodynamics simulations. The energy is distributed in kinetic form among the gas particles surrounding recently formed stars. The impact of the feedback is studied using a suite of high-resolution simulations of isolated disc galaxies embedded in dark halos with total mass 10^{10} and 10^{12} Msol/h. We focus in particular on the effect of pressure forces on wind particles within the disc, which we turn off temporarily in some of our runs to mimic a recipe that has been widely used in the literature. We find that this popular recipe gives dramatically different results because (ram) pressure forces on expanding superbubbles determine both the structure of the disc and the development of large-scale outflows. Pressure forces exerted by expanding superbubbles puff up the disc, giving the dwarf galaxy an irregular morphology and creating a galactic fountain in the massive galaxy. Hydrodynamic drag within the disc results in a strong increase of the effective mass loading of the wind for the dwarf galaxy, but quenches much of the outflow in the case of the high-mass galaxy.

Numerical Method for 2D and 3D Viscous Flows

A numerical method is presented that offers rapid solutions to the Navier-Stokes equations for even the most complicated geometries. It is based on separating the momentum and continuity equations into coupled elliptic and parabolic groups. A rapid iteration occurs between equations. Examples are presented for 3D flow in turbine stators. Good agreement is obtained for experimental loss and heat-transfer coefficients. NTERNAL flow devices currently in use in turbomachinery are among the most complicated fluid dynamic devices to analyze. In the past, the lack of fundamental predictive methods has led to reliance on experiments. However, recent progress in numerical methods is now leading towards the substitution of analysis for experimentation. Nevertheless, methods for solutions to equations, complete enough to include the significant viscous and pressure force effects have been too time-consuming to prove practical. Until recently, effort has been concentrated on the use of simplified forms of the Navier-Stokes equations. One of the early significant efforts in this light was that of Wu,l where inviscid equations in three dimensions are reduced to coupled sets of two-dimension al solutions. The radial equilibrium portion of this solution can be cast essentially as subsonic by specifying the swirl as one coupling term. A numerical method for this particular equation, utilizing curvature of streamline methods, was developed by Smith.2 Subsonic blade-to-blade solutions were developed by Katsanis and McNally.3 Transonic solutions utilizing timedependent methods were developed by Gopalakrishna n and Bozzola,4 and McDonald.5 Transonic relaxation solutions have been developed by Dodge. 6 Inviscid solutions to fully three-dimensional flow in turbomachine components have been developed by Denton,7 utilizing time-dependent methods. Viscous solutions have taken one of three directions. The first is that of boundary-laye r techniques such as those of Hirsch.8 The second is that of following the kinematic transport of vorticity, such as applied by Lakshminarayana.9 The third is to parabolize the Navier-Stokes equations by restricting or eliminating upstream influence. A most recent example of this is the work of Pratap, Majumdar, and Spalding.10 All of these methods suffer from inadequacy in describing the flow processes in turbomachinery. The inviscid methods, although useful, do not begin to provide predictions of loss and heat transfer and the effects of these on the mainstream flow. The parabolic methods allow no recognition of upstream influence. Serious and substantial effects of surface curvatures and downstream blockages are ignored. Timedependent solutions to the Navier-Stokes equations, although theoretically possible, are beyond current computer hardware capabilities. The following discussion describes the development of a method that overcomes many of the objections to past techniques. This method will allow efficient solution of the Navier-Stokes equations in complete enough

The large-scale structure of homogenous turbulence

The large-scale structure of homogenous turbulence