The study of the properties of fluids and gases in motion

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25 views

Is there a jump condition for this PDE? ( Brinkman model , piecewise constant permeability)

The Brinkman equations for steady flow of an incompressible fluid through rigid porous solid are: $-\dfrac{\mu_0}{k}\mathbf{v} - \mathrm{grad}p + \mu_0 \Delta \mathbf{v} =0$ and ...
2
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2answers
66 views

Simulating interaction of Smart Fluids with Solids

Is it possible to simulate interaction of Smart Fluids with Solids? Is there a software capable of doing so? What I Know: The two software that I know of are Autodesk Simulation Mechanical and ...
1
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0answers
51 views

How to get proper parameters of SPH simulation?

I'm implementing basic fluid flow simulator using SPH method basing on e.g. https://www10.informatik.uni-erlangen.de/Publications/Theses/2010/Staubach_BA10.pdf. So far I've implemented: uniform ...
4
votes
2answers
114 views

Projection Method: Boundary condition on intermediate velocity field

I'm trying to solve variable density and viscosity Navier-Stokes equation using lagged pressure projection method. I'm solving for cavity problem as a test case now (once I get projection right, I ...
0
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1answer
48 views

FEM with soil slope

I what to calculate displacements, stress and strain in a soil slope with a FEM script. The slope moves like a laminar flow. Can you suggest me some bibliography on this problem? I've already look on ...
3
votes
1answer
122 views

Finite Elements Weak Formulation generalization

I am struggling with an equation that represents the Weak form of Galerkin method: $ \phi^{T}F(\textbf{u})\sim \int_{\Omega}^{ } \phi.f_{0}(\mathit{u},\nabla \mathit{u}) + ...
2
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1answer
92 views

Organizing a CFD program written in python

I've spent some time writing a spectral element solver aimed at solving fluid flow problems concerning the motion of self-propelled bodies. I've gotten to the point where the code has grown long ...
4
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3answers
147 views

vector PDEs on manifolds

What are the subtleties involved in solving vector PDEs on manifolds? Can someone suggest a reference summarizing the problems involved? Specifically I want to solve a vector Helmholtz equation with ...
2
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2answers
175 views

CFD absractions in Modern Fortran

I'm a novice in object-oriented programming, but this design technique seems very interesting for me. I have a Fortran 90 CFD package , not very complex, but it is already very hard to maintain and to ...
0
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1answer
88 views

MPI_ERR_TRUNCATE appears for no understandable reason

I am developing some parallel CFD code using Fortran 90 and OpenMPI. The processes are structured into two groups such that half perform a certain type of calculations (let's say Velocity, Pressure ...
1
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1answer
70 views

Importance of change the Time Step Value for the Accuracy of a Transient CFD Simulation

I have a transient simulation for a case from 0 to 3 sec , actually i interest the solutions on time range from 2 to 3 sec , as my velocity and mesh size , my time step should be 0.0000000001 sec , my ...
3
votes
2answers
132 views

C - OpenMP, MPI, Serial Program

I'm part of a Computational Science course and come from a non-programming background, so please forgive me my ignorance. I'm working on a set of code in C to numerically solve the Navier Stokes ...
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23 views

Tecplot Span-Wise Loading Visualization

all. I have data from a CFD simulation for a wing, and I need to obtain a visualization of the span-wise load distribution. I'm attempting to do this using Tecplot. I've tried using 'slices' and ...
1
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1answer
107 views

Type of Navier-Stokes equation

What type equation Navier-Stokes is: Elliptic, parabolic, or hyperbolic? Should it give always the same answer no matter what is the initial condition? How these statements could be proved?
0
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1answer
53 views

Regarding streaming operator in Lattice Gas Automata

The classical streaming operator used in FHP lattice gas automata is this: $$n_i(r - c_i, t + 1) = n_i(r, t)$$ However if you think in terms of the streaming itself, it should be something like ...
2
votes
2answers
95 views

Solving Stokes flow with walls using Oseen tensor

Introduction I've developed a code to solve for generalised, incompressible 2D Stokes flow $\eta \nabla^2 \mathbf{v} - \nabla p + \mathbf{S} = 0$ $\nabla . \mathbf{v} = 0$ where $\mathbf{S}$ can ...
2
votes
3answers
118 views

How to get discretization coefficients of matrix A in Finite Volume Method (FVM)?

First we have Discretization of the Transport Equation $$ \frac{\partial \rho \phi}{\partial t} + \nabla(\rho U \phi) - \nabla (\rho \Gamma_\phi \nabla \phi) = S_\phi (\phi) $$ In Finite Volume ...
0
votes
4answers
144 views

What scale problem can be simulated on an PC using Smooth Particle Hydrodynamics?

I want to simulate tidal features in a large body of water using was smooth particle hydrodynamics. For a system composed of an incompressible fluid, what general scale of problem can be tackled with ...
4
votes
2answers
126 views

What makes turbomachinery so special in CFD

As my experience with CFD grows, I start to gain the feeling that turbomacinery is kind of special in CFD: there are special tools tailor for it. For example, ANSYS has TurboGrid or Vista TF for ...
11
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2answers
202 views

Do black-box preconditioners for matrix-free methods exist?

Jacobian-Free Newton-Krylov (JFNK) methods, and Krylov methods in general, can be very useful because they don't require explicit storage or construction of a matrix, only the results of matrix-vector ...
3
votes
1answer
169 views

Comparison of Lattice Boltzmann Method vs Traditional Navier-Stokes based Methods

I have a choice of two options, analysing and implementing Lattice Boltzmann methods or traditional Navier Stokes based methods. I'm a CFD newbie and I have a rough idea (though not rigorous enough to ...
1
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1answer
95 views

Is it possible to simulate fluid dynamics in a time-based and deterministic manner?

The Problem Domain I have a number of network-connected PCs. I want to be able to simulate and replicate the same simple fluid dynamics simulation (E.g. Navier-Stokes), in real-time, between them. ...
1
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1answer
119 views

Moving airfoil boundary condtitions

I am trying to simulate a moving airfoil with constant speed (Mach=0.755, aoa=1.25). I solve Euler equations with Roe's method. I have two boundary conditions: Farfield Slip wall (airfoil) For all ...
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vote
2answers
106 views

Computing Kolmogorov/Energy spectrum for turbulent boundary layer

Previously, I have calculated energy spectrum for 3D DNS data obtained for isotropic turbulence which is equally spaced in all three directions and then to compute the energy spectrum, one performs ...
0
votes
2answers
86 views

WENO reconstruction of flux involving derivative terms

I have a set of modified compressible Euler equations that I would like to solve using a WENO method. The issue is that the modified flux function involves derivative and filtering terms and I'm not ...
0
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1answer
54 views

How to model waterflow when only a couple of sample points available

Figure below depicts a cross section of a creek for which I am trying to measure the water flow for that section. What we have as inputs are a bunch of sample points on the river. For each sample ...
0
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1answer
143 views

Dual time stepping for fluid dynamics

I'm attempting to implement the Weiss and Smith preconditioner in an existing finite volume code and I am struggling with the idea of dual time stepping. My inner time steps are predictor-corrector, ...
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0answers
91 views

High-order continuous Galerkin Navier-Stokes solver in deal.II

I looked at the list of publications related to deal.II, but it seems that when it comes to Navier-Stokes equations, everyone speaks about Discontinuous Galerkin solver in their papers. I know there's ...
1
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1answer
172 views

Euler's equations 1d for pipe, Inlet boundary conditions

$\def\rmin{{\mathrm{in}}}$ $\def\l{\left}\def\r{\right}$ $\def\tagl#1{\tag{#1}\label{#1}}$ I am using the one-dimensional finite volume method to calculate the air flow in some tube. For subsonic ...
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0answers
50 views

Turbulence: Suggest research papers similar to this experiment

I am trying to find the effect on turbulence characteristics when flow passes through a converging section. For this experiment I will use a PIV system to gather data about the flow. However, I could ...
3
votes
1answer
111 views

Euler's equations for a tube with varying cross-section

$\def\pd{\partial}$ $\def\l{\left}\def\r{\right}$ $\def\mdot{{\dot{m}}}$ $\def\eps{\varepsilon}$ Consider a tube with longitudinal coordinate $x$ from $0$ to $l$ and varying cross-section $A(x)$. ...
2
votes
1answer
89 views

2d pseudo-spectral turbulence simulation with random initial velocities

I am trying to write a 2d pseudo-spectral DNS code with random initial velocities. This is kind of a classic simulation where the very tiny vortices group together forming larger and larger vortices ...
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0answers
42 views

Numerical strategy to detect the point of detachment over the wall of cylinder in the simulation of unsteady flow over circular cylinder

I am working on unsteady simulation of flow over circular cylinder where we get Kármán vortex street. Kármán vortex street is a repeating pattern of swirling vortices caused by the unsteady separation ...
1
vote
1answer
51 views

“boundary” vs “interface”?

I am working with biofilm and there are many documents talking about boudary conditions while others talks about interface or both of boundary and interface. So, boundary and interface are the same ...
1
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0answers
179 views

A Simple Standard Test Case for Pipe Flow

Original Question I am familiarising myself with OpenFOAM and want to run a simple pipe flow case. I would like to be able to compare my computational pipe-flow results to a well established case ...
3
votes
2answers
121 views

Darcy Flow - Solution by Finite Difference

I'd like to model the fluid flow through a porous medium using finite differences. Since I am new to this numerical technique, I have a simple question. I use the following set of equations to ...
3
votes
0answers
117 views

Transport Equation in a Tube: Source Term on Boundary

I'm modeling mass transport in a flow reactor. The flow reactor is a tube, which allows me to use cylindrical symmetry in solving the Convection-Diffusion-Reaction (CDR) Equation, which governs the ...
1
vote
2answers
283 views

Reconstructing fluxes

Given a standard advection equation, we write the update as $$ q_i^{n+1}=q_i^n+\frac{\Delta t}{\Delta x}\left(F_i^{n+1/2}-F_{i+1}^{n+1/2}\right) $$ with $F_i^{n+1/2}=F\left(q_i^n,\,q_i^*\right)$ and ...
2
votes
0answers
49 views

When a flow changes its character from time-periodic to chaotic?

In this simple benchmark describing the flow around a disc in the plane with stationary bc, for low Reynolds numbers the solution is stationary and for higher RN it is periodic in time. Is there a ...
6
votes
2answers
136 views

Simulating advection over a network of 1D pipes

I am trying to create a simulation to help visualize how different chemical components flow through a network of pipes with associated valves, pumps, and chemical inputs. In this simulation, the pipes ...
5
votes
2answers
134 views

Inverting a pressure matrix for fluid simulation

I am implementing a fluid simulator as my numerical methods course project and I have to compute pressure at each simulation step. Basically, that means solving an equation $Ap = b$, where $A$ is a ...
3
votes
1answer
155 views

Problem in Discretizing Convection-Diffusion-Reaction equation

I'm trying to solve the Convection-Diffusion-Reaction (CDR) equation on a rectangular domain, using cylindrical coordinates and Finite Difference Methods (FDM) (this approximates a flow reactor). ...
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0answers
95 views

Anyone knows why surface-to-ambient radiation is not applicable to interior boundaries in comsol?

I have a 2D model consisting of a square piece of electrical insulator and in the middle I have a thin rectangle acting as a wire. I'm running a current through it so I heat it up to 500 K. Clearly it ...
0
votes
1answer
70 views

zero pressure gradient flat plate CFD++

I'm trying to perform a trasient simulation of a subsonin flow over a flat plate in CFD++. I want to impose a ramp profile on the velocity at the inlet, like for instance a smooth step, and look at ...
3
votes
0answers
301 views

Immersed boundary method

I'm trying to use immersed boundary method for the 3D flow problem (Navier-Stokes equations), but I'm maybe misunderstood something in this method. Main principles I took from this book. I use the ...
2
votes
0answers
134 views

can we calculate y+ apriori?

perhaps the most idiotic question I ever asked. people throw around the parameter $y^+$, as if it is the be all and end all of CFD parameters and use it as if everyone and their dog know how to ...
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2answers
160 views

openFOAM RAS to LES

I successfully ran a RANS simulation of industrial fan with all wall BCs, pimpleDyMFoam solver and spallart-almaras RAS model. I got results upto some time, I would like to continue that simulation ...
0
votes
0answers
119 views

how to visualize velocity from Lagrangian particle tracking method

I have few particle's position and velocity information as a function of time. Particle is following a trajectory path, while doing so, one particle may disappear, other particle may appear. Particle ...
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vote
1answer
279 views

Lid driven cavity flow problem to solve with the help of projection method and use coding in fortran 90 [closed]

I want to solve Lid driven cavity flow with the help of projection method i want to make own fortran program to solve two dimensional unsteady flow. I propose to solve the equations in the following ...
0
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1answer
302 views

how to specify an arbitrary surface for field average in openfoam?

So, I am running this openfoam simulation and I need areaAverage velocity and pressure on a surface,currently the entire plane is being read, I wan't to specify my own in sampleSurfaceDict, ...